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R/E/P => Klaus Heyne's Mic Lab => Topic started by: klaus on August 09, 2018, 05:17:08 pm

Title: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on August 09, 2018, 05:17:08 pm

Neumann U67 Reissue: Complete Tear Down and Analysis


In the spring of 2018, Neumann reissued the U67, a three-pattern, large diaphragm tube microphone first introduced in 1960.

To simply review build features, response curves, and component quality of the Reissue, in order to determine how faithful it is to the original, would be pointless. I’ve invested much of my adult life chasing after good sounds in microphones, therefore I put much emphasis in evaluating the Reissue with my ears, my senses, and the response from my pleasure center. Unlike the original U67, the new Reissue does not touch that pleasure center, at least not out of the box.

My impressions and opinions will inevitably clash with those who bought the mic and hear (and feel) differently. But reports from happy U67 Reissue customers should not be discounted as less credible or erroneous. (I will address the seeming contradiction.)

With access to fine examples of original U67, and having restored and optimized close to a hundred of them over the years, I have a pretty good idea of the performance range of a well-working U67- what it is capable of, and why it became an icon.

The 9dB high-frequency emphasis of the dual-backplate K67 capsule with its phase-inducing offset ports, and its low-frequency proximity effect have been elegantly tamed through a combination of transformer feedback, feed-forward and shunt capacitors in the amp; the 4dB drop@16kHz prevents an overly thinned-out top; the U67’s mid range ranks among the most authoritative of any mics ever made, and the low end, while more choked than in the velvety M49 or the reedy U47, still has enough heft to convince as a mic of choice even for a bass-baritone.
With other words, the curtailments engineered into the U67 did not damage its sex appeal; using modest application of eq, engineers have learned to compensate for these limitations.

But the complex sound processing in the U67 is balancing on a precariously narrow ridge. And when the design or its execution is even moderately off, the whole structure collapses into a mediocre-sounding end result.
This was the case with a brand-new Reissue U67 #712xx I was able to test for several weeks, courtesy of Keith Banning who operates Grange Recorders in Sisters, Oregon: the mic sounded lifeless in the highs, choked and hard in the midrange, congested and unable to process complex information in time, resulting in sibilance. The bass region was starved, with the lowest octave severely under-represented.

The Gestalt of the Reissue (the sound stage) was oddly anemic and small, compared to the original. So, to me, the mic lacked sensual excitement, with an overall character best described as pedestrian, and only the faintest hint that this was the tube mic from the distinguished House of Neumann meant to revive the aura of one of the Big Five.

 With access to quite a few excellent examples of original U67, their cables, NU67 supplies and NOS tubes from a variety of manufacturers, I was intrigued and committed to finding out where the bottleneck was that prevented this mic from pushing through to the lofty reaches of the original. Substituting one Reissue component at a time, I found the culprit(s), and was eventually able to get the Reissue to sound exactly like some of the best vintage originals. No, this is not a pitch to buy my services; you too can have at it, at reasonable cost, and without a technician’s involvement.

I already had an idea where the Reissue’s shortcomings might lie. I had read impressions by new owners online, most of which characterized the mic’s sound in more forgiving terms than I would- that it had a “modern” sound (whatever that means), was bright, pointy, midrange aggressive, and lacked low-end and warmth. But there were also some reports of owners who compared the Reissue to the vintage original, and found absolutely no difference.
What could account for these contradictory opinions?

First, let’s take a closer look and dissect the beast.


Visual Inspection


On all pictures with two items, the Reissue is are always shown on the left. Click image to enlarge photos.

The assembled Reissue, from head to tail, looks and measures identical to the original (which also looks identical to a U87 of any vintage).



(http://repforums.prosoundweb.com/photos/Mics-front-sm.jpg) (http://repforums.prosoundweb.com/photos/Mics-front-lg.jpg) (http://repforums.prosoundweb.com/photos/Mics-rear-sm.jpg)
 (http://repforums.prosoundweb.com/photos/Mics-rear-lg.jpg)
The complete head - K870/67 capsule, mount, grill, and switch assembly - is the same as used on the current U87Ai, except the safety key (a slotted stalk acting as third head screw that fits into a hole in the amp’s head) is replaced with a regular slot screw as found on the U67 and older U87.
(U87Ai head assembly pictured on right)

(http://repforums.prosoundweb.com/photos/Head-pins-sm.jpg) (http://repforums.prosoundweb.com/photos/Head-pins-lg.jpg)

Side note: You can readily swap head baskets, bottom bells, frame supports, and housing tubes between any U67, M269, U87, and U87Ai without modification; but you cannot replace a defective pattern or attenuation switch on an original U67 with one from the Reissue. The new switches connect via magnetic reed, not mechanical pressure.
As with current U87Ai, the surface sheen of the Reissue’s housing components is slightly courser and shinier than the originals were. The Reissue’s badge is black, indicating it’s a tube Neumann, and the decal on the bell identifies the model and its recommended supply.

Electronic component layout on the four amp boards is pretty much duplicated from the original U67.

(http://repforums.prosoundweb.com/photos/amp-front-sm.jpg) (http://repforums.prosoundweb.com/photos/amp-front-lg.jpg) (http://repforums.prosoundweb.com/photos/Amp-rear-sm.jpg) (http://repforums.prosoundweb.com/photos/Amp-rear-lg.jpg)

Capacitor and resistor values and positioning also seem identical with the 1960s version.

(http://repforums.prosoundweb.com/photos/Circuit-close-up-new-sm.jpg) (http://repforums.prosoundweb.com/photos/Circuit-close-up-new-lg.jpg) (http://repforums.prosoundweb.com/photos/Circuit-close-up-old-sm.jpg) (http://repforums.prosoundweb.com/photos/Circuit-close-up-old-lg.jpg)

Side note: Original and Reissue come stock with low-cut wire switch S2 on the amp connected. That cuts bass response (capsule included) a max. of 6dB @ 40Hz. The price for low-end eq in mics and elsewhere is phase anomalies and other artifacts. Proximity and room issues should therefore be mitigated at the source. The U67 processor retains best low-end fidelity with S2 open. All listening tests were done with S2 open.

Capsule.

For the Reissue, Neumann uses stock K870 capsules found in current products U87Ai, TLM67 and USM69. In the Reissue, the capsule sits 6mm higher in the basket than in the original.

(http://repforums.prosoundweb.com/photos/Capsules-sm.jpg) (http://repforums.prosoundweb.com/photos/Capsules-lg.jpg)

As I found out during listening tests, these capsules are not tweaked or especially selected for one of the most expensive mics in Neumann’s line-up. Contrary to common assumption, front sides are also not selected or marked. Neumann believes that any capsule whose response falls within a pre-determined tolerance range will be good enough for installation in any mic.


Tube.


One significant factor that can contribute to the sound quality of tube audio processors is the quality of tubes. And nowhere is that more apparent than with tubes used in microphones; their unique impedance-converting task puts a strong magnifying glass on quality.

Since the demise of U.S. and European tube factories, Russia, Slovakia, and China are the only current suppliers of microphone tubes. When comparing historic quality standards from manufacturers who had their tube chemistry and metallurgy down, all modern tubes suck. It’s beyond this article’s scope to explain the technical reasons why modern miniature triodes and pentodes sound inferior in high-end mics, and most of them don’t last long.

Judging from the choice used in the Reissue - a short-plate Russian EF86, re-branded by New Sensor as Tung-Sol EF806SC* this tube behaved flawlessly under stress: I ran it in the mic for three weeks straight, and it held up and stayed as quiet as the best NOS European EF86 versions. Neumann affixes a silver “select” banderole to pre-sorted tubes, including hand- written serial number.
*Tung-Sol, a long-defunct U.S. tube manufacturer, never made EF86 or EF 806S tubes. New Sensor Corp. acquired the rights to an illustrious brand name.

(http://repforums.prosoundweb.com/photos/Tubes-sm.jpg) (http://repforums.prosoundweb.com/photos/Tubes-lg.jpg)

Lacking affordable high quality EF86 alternatives, there really was no other choice for a company like Neumann with a goal to revive a high-end tube mic and sell it in numbers, than to choose the best of the current Russian crop.

This then is the answer to the question most often brought up about current tube quality: Why don’t mic manufacturers use a better tube? To search the internet for NOS Amperex, Mullard, Telefunken, etc., paying several hundred dollars/per, then discard a good half or more that don’t hold up, would be a logistical and financial nightmare for any manufacturer. Such efforts are best transferred to discriminating mic owners with time and money to select and stock up on NOS.



Cable and Connectors


The company which makes the Reissue cable is not identified. Its rather small diameter looks familiar from cables supplied with M147 and M149. Termination and isolation of the ultra-thin conductors is flawless.

(http://repforums.prosoundweb.com/photos/Connector-wiring-sm.jpg)
 (http://repforums.prosoundweb.com/photos/Connector-wiring-lg.jpg)
Neumann used Binder IP-40 connectors throughout. Since the demise of Tuchel, Binder is now the only choice for mic systems requiring 7-pin broadcast connectors, as used for Neumann’s M2xx mics.

To duplicate the original U67 pin orientation, and to avoid connecting to AC701-powered mics, the Binder connectors for the Reissue needed to be re-keyed: a new channel was cut at the pin #1 position, and the original channel between pins #6 and #1 was filled with epoxy (see picture). A bit primitive, but it works, and is hardly visible. (The original Tuchel-made U67 connector with its unique pin #1 key position mold, was mechanically and electrically superior, but has been obsolete for decades.)

(http://repforums.prosoundweb.com/photos/Mic-connector-sm.jpg) (http://repforums.prosoundweb.com/photos/Mic-connector-lg.jpg)


Power Supply.


Lifting the lid from the Reissue NU67V, its high build quality is apparent: no more Chinese step-down transformers, as used in M147/149 supplies. Lid and frame are solid and heavy; component layout is meticulous.

(http://repforums.prosoundweb.com/photos/Power-supply-sm.jpg) (http://repforums.prosoundweb.com/photos/Power-supply-lg.jpg)

Wiring sizes are substantial and perfectly routed, with the exception of the anemic audio wiring between mic and XLR connectors.

(http://repforums.prosoundweb.com/photos/PS-audio-wiring-sm.jpg) (http://repforums.prosoundweb.com/photos/PS-audio-wiring-lg.jpg)

Circuit board layout and labeling was done logically and intelligently. It took some engineering brains to make this a “no adjustment option” supply, and still nail B+ and heater voltages, no matter the cable length or EF86-type used. I had never seen this before in a commercially available supply.

----------------

Listening Tests


Let’s investigate the sound of the Reissue, and whether it is comparable to that of the vintage original. And if not, what factors might stand in the way, and whether it would be possible to make the Reissue sound as good as a perfect vintage original.

In a high-end condenser mic, the effect of components that determine the quality of sound is cumulative; even a preponderance of well-selected components cannot overcome or neutralize the presence of even one badly chosen part: capsule, tube, transformer, passive components, circuit traces, wiring, mic cable, power supply... each will affect parameters like noise, frequency response, dynamic behavior, timbre, resolution and emotional attraction. (In my opinion, nothing short of a positive emotional response matters for a mic at that price.)

But when we substitute items that only have a subtle impact on a mic’s sound, like a cable or a power supply, we may not hear it in a system whose sound may be compromised elsewhere by more significant roadblocks, like a deficient capsule or tube.

Therefore, the better method of finding out what component of the Reissue has what influence on the sound, and how it may deviate from that of the original, I started out with a well-maintained, therefore representative, vintage U67, then gradually substituted one component after the next in the vintage system. This way, even a subtle deterioration of the mic’s character or sound, say, from the choice of cable, would show up.

And it did: removing one component after another from the characterful, highly authoritative vintage U67 I had selected as the ideal candidate for comparisons, and substituting these parts with ones from the Reissue eventually turned the original’s sound exactly into that of the Reissue. Replacing one original part after another from the vintage U67 to the Reissue confirmed the theory in reverse: after capsule, tube, cable, power supply were transferred into the Reissue, it sounded as elegant, emotionally attractive and musical as the original.
Here are the substitutions, in the order taken, from the most subtle to the most noticeable effect, and the options Reissue owners have if they want to make that mic as compelling sounding as a well-maintained vintage U67:

1. Reissue: NU67V Power Supply

Test: Vintage U67, Telefunken EF86 chrome plate, original cable, but replaced vintage NU67u (1963) power supply with Reissue NU67V (2018) power supply.

DC output @ 120VAC nominal: 207 B+, 6.3VDC Heater.

(These voltages are very close to ideal, considering that there are no adjustment options)

The Sound: against expectations* a small reduction in sound stage width; the formerly robust lower mids are affected and so is the dynamic behavior; everything sounds a bit smaller, slightly distant, a bit listless, with an onset of high-mid smear; a small but noticeable step down in resolution. It’s subtle, but I had no doubt after repeating the test 10 times over several days.

*confirmation bias? I was previously incredulous of the impact a power supply could have on a tube-condenser mic’s sound. I used to discount ‘Golden Ears’ who claimed to “hear the power supply”. No longer.

2. Reissue: Microphone Cable


Back to the all-original vintage U67/NU67u set-up, but tested three different cable types against the Reissue version.

With four cable choices, this test was more extensive than just A and B. For the American market, Neumann supplied the vintage U67 with a Belden 3344 cable with traditional cross-braided shield and conductors with low strand-count.

Around 1964 the 3344 was replaced with a Dörfler-made cable with Reussen-shield (96-count conductor stranding, and two multi-stranded bare copper layers cork-screwed in opposite direction around the cable’s signal conductors).

I was also curious how a current-generation Gotham GAC7 (similar construction as Dörfler’s) would sound, as this option is used by high-end boutique mic manufacturers (I used it for the KHE).

The Sound:

a. Original Belden 3344 cable (ca. 1963): In a word, a match made in heaven. Despite its unsophisticated construction, there is magic and emotion and music: clear, yet richly textured, with fast mids, and excellent high frequency follow-through that never dominates. This is the cable that translates the U67‘s emotional power and connects best with the listener*

b. Doefler-made German Broadcast cable (ca. 1965): rich bass, authoritative lower mids, but with a slight, dark, not strident, sibilance; lacking in upper register clarity.

c. Gotham GAC 7 (from current production, after 2 week burn-in, terminated with NOS Tuchel broadcast connectors): tight bass, pleasant dry, woody low-mid reediness (a term I use for high resolution and speed in that range), and a sound signature similar to Gotham’s 3-conductor GAC3. Sound with this cable was not strident or congested, but using it for the U67, I missed upper register follow-through and clarity. Disappointing, considering its excellence when matched with other high-end mics.

d. Reissue cable: good frequency balance, good bass, reasonably fast, a little bit of mid-range congestion, lacking the high-frequency thrill and dimensional expansion of the Belden. Coming in second best, that skinny cable is good enough to be used in a pinch even with a vintage U67, and is certainly the right choice for the Reissue, given that the Belden 3344 is no longer available, as far as I know.

* it’s worth pointing out that the response and dynamic behavior of a cable is not static or fixed, but audibly changes, depending on the mic (specifically its output transformer) it is connected to: a 4-conductor Belden 3344-style cable was supplied during the U47‘s final years by Neumann’s U.S. importer, but there, it was the wrong choice, sounding too hard and edgy, compared to the earlier “rubber hose” version.

3. Reissue Tung-Sol EF806SG Tube

Back to my all-original vintage U67/NU67u set-up, including original Belden cable, but replaced NOS Telefunken EF86 (chrome plate), with Reissue’s Russian “Tung-Sol EF806SG” tube.

The best way to describe the difference in sound of the Russian tube: Imagine you add a triple-layer pop screen between mic and sound source; everything sounds a bit more distant, slower, less lively, with a bit of mid-range congestion, and lack of an airy layer up top.
 
Side note: As much as I can rely on a Tele EF86 to deliver superb resolution, especially in the high frequencies, and to last forever, I am partial to the mid range texture and sex appeal of Amperex meshplate EF86. To me, that’s another match for the U67 made in heaven.

4. Reissue: K870/67 Capsule

Back to my all-original vintage U67/NU67u set-up, including original Belden cable, but replaced original K67 capsule with Reissue K67/870.

The compromised K67/870 capsule is easily the biggest obstacle to good sound in the Reissue I tested. Many owners of U87Ai (same capsule) made after 2000 have complained about stridency, sibilance, and lack of full bottom in their mics. I have written about my own dissatisfaction with these capsules since the early 2000s on my forum and others. While the design dimensions are unchanged since 1960, (with minor substitutions of materials), the diaphragm tension is now too high on too many of them, and this certainly was the case in the Reissue K67/870 I tested.

The sound of this capsule can only be described as ugly; and none of the vintage mic’s excellence of circuitry, tube, cable, power supply, etc. could overcome such severe bottleneck at the entrance to the conversion and processing of acoustic energy.

Mid-heavy to the point of pinched, hyper sibilant, choked in the bass, lacking any smooth transition between mids and highs-all, because the mids are so dominant and harsh due to the stiff membrane* which chokes off any subtly of response.

* How do I know it’s too much diaphragm tension that causes all this trouble? Because eventually I “relaxed” the honky K67/870 installed in the Reissue, as I had done with several recent U87Ai capsules, and it ended up with full bass, frequency balance, and similar timbre as the K67 from the vintage mic.

Initial impressions were confirmed when I removed that capsule and installed several K870 from a few new U87Ai I had available. They all sounded different, but most trended in the direction of the pinched, honky mid-dominance of the capsule that came in the Reissue.
But to demonstrate how unpredictable Neumann’s capsule manufacturing has become: Among the ten capsules I tested for this occasion (actually: twenty sides, as no two sides ever sound the same, with some sides deviating significantly from each other) were two never-used K67/870 extracted from virgin 2008 TLM67. These sounded every bit as sexy, frequency-balanced and robust in the bass as the original brass-ring K67 from the vintage U67 I used throughout these tests.

This, then explains the contradictory reports from new owners of Reissue 67: some obviously got lucky with balanced capsules, others not so much.



4. Reissue: Complete Circuitry


Rather than picking off each resistor, capacitor, or the transformer from the Reissue at a time, and soldering these components one by one onto the original board, I conducted a reverse test to determine whether any of these components had any audible effect at all: equipping the Reissue with the capsule, tube, cable, and power supply from the original, and all at once, I could not hear the slightest difference between that assembly and the original vintage U67 system. That meant that the Reissue’s passive components, wiring and circuit traces were of high enough quality to be interchangeable with those on the original U67, with no cumulative or ill effect.

Because the mic amp (tube aside) had zero influence on the sound, by deduction, the transformer choice in the Reissue could not be detrimental to the sound of the mic, but must be of the same high quality and characteristic timbre as the original BV12.

Five Final Take-Aways.


One.
If you disagree with my methodology or assessment, please forgive me. I listen to and evaluate the sound of high-end microphones on an emotional level, first and foremost. I am experienced in analyzing, judging, and tuning microphones that way, and as long as enough people continue to agree with my assessments, I am confident with that approach professionally. But it’s naturally subjective. You think differently? Fine, let’s leave it at that.

Two.
By far the biggest audible difference between Reissue and Vintage is the capsule. But as I reported, it’s not as straight forward as simply replacing the stock capsule with, say, an exquisite one from a vintage U67. As with current K870, some, but not many, capsules installed in Reissues will be perfectly frequency balanced, with good low end and little congestion or sibilance. I attribute the glowing reports from some owners to the presence of a well-rounded capsule in their Reissue. This was not the case with the one I had for testing. It was just awful. I ended up installing the K67 from the TLM67 for the owner. It sounded glorious.

Three.
Capsule substitution or re-tuning will get you far. Far enough and good enough for many owners, I suspect. But if you want to get the exact same ultra-high level of performance of a fine vintage U67 from the Reissue, you need to do all of the following:

* replace or modify the capsule, to add highs, reduce sibilance and mid-range congestion, improve low-mid texture and low frequency extension
* replace the Russian tube with a well-selected European old stock Telefunken, Amperex, Valvo, Mullard or similar EF86, to improve fidelity and resolution. OLD stock is the key. No currently-manufactured EF86/806 are any good if you want three-dimension-like resolution
* replace the power supply with an original NU67 or any intelligently-designed modern type, to improve dynamic behavior and fidelity
* replace the stock cable with a Belden 3344 for its unique sex appeal and high frequency clarity
Addressing these items in a Reissue U67 will cost less than $2000 in 2018 dollars. After that investment, you would then have a microphone with the exact same sound signature of a superb-sounding vintage U67.

Four.
I had mentioned that it is sometimes hard to distinguish between slightly better or worse components in a microphone system when you have more significant sonic bottlenecks to contend with. An analogy: when vision is obliterated by heavy fog, you just can’t see whether a layer had just lifted in the distance.

And so it was with the power supply and cable tests: Differences between vintage and Reissue components did not show up at all when substituting these items in the Reissue mic system, because stronger layers of obstruction (capsule, tube) stood in the way to detecting minor ones.

If someone insisted on how much I thought each component was responsible for the Reissue’s compromised sound, I’d assign 70% to the capsule, 20% to the tube and 5% each to cable and power supply. That means, replacing capsule and tube will go very far towards a sensually satisfying U67 Reissue.

I realize, assigning percentages to auditory impressions is unscientific and ridiculous. I am open to a better scaling or weighing method.

Five.
I debated whether or not to publish my impressions of the Reissue U67. My history of support for all things Neumann is long. I ended up in this profession because of my admiration for Neumann’s passion for excellence. And I am impressed that the folks in Berlin try hard to continue Neumann’s heritage under a corporate ownership which would have sent any other legacy mic manufacturer into oblivion or irrelevance.

Though the Reissue U67 is for me a mixed bag, it would be unrealistic to expect much more: nobody makes decent tubes suitable for high-end mics; reviving the historic power supply would have been impossible under current safety and material codes; and choosing a tube mic cable remains too much art than could be guided by science alone.

That leaves the capsule. Put simply: Neumann would make many owners of U67, U87Ai and TLM67 mics very happy if they would relax the capsule’s diaphragm tension to its former range, without the need to change anything else on this legacy product. Why they don’t do it, I can only speculate.

Side note: Neumann knows of my concerns. A few years ago, I had sent them two factory-fresh capsules, one from the pre-2000, frequency-balanced era, the other one from the new crop of bass-starved K870. They ran thorough tests (I have the graphs) and, though the graphs clearly show a bass-roll off of several dB on the bass-starved capsule, Neumann deemed both versions to be within spec.

© Klaus Heyne 2018
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on August 09, 2018, 06:09:10 pm
I want to express my gratitude to Ernie Black, PSW's webmaster, for perfectly formatting my review. It makes for a much better read than I could have managed on my own.
Thanks, Ernie!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on August 22, 2018, 03:00:45 am
Thanks for all the thought and effort you put into this.  One quick question: Is your reference vintage u67 strapped for 50ohm?  And is that your preference?

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on August 23, 2018, 09:38:15 am
It is strapped for 200Ω (the usual studio standard for mics) and so was the Reissue, which came that way from the factory.

I do not like the 50Ω strapping, because it puts the two secondaries in parallel, with a slightly glassier sound and slightly less midrange texture than when the secondaries are connected in series (200Ω).
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Jim Williams on August 23, 2018, 12:06:24 pm
Outside of the subjective evaluations, are there any differences in objective measurements like THD+noise, phase response, noise floor or bandwidth?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on August 23, 2018, 01:20:12 pm
It is strapped for 200Ω (the usual studio standard for mics) and so was the Reissue, which came that way from the factory.

Thank you, Klaus.  I've been diving into my own u67 in attempts to better understand it.  I believe(d) mine was strapped for 200ohm until I saw the photos you posted in this review of your selected vintage u67 which you say is strapped for 200ohm as well. 

Here is a close up of your vintage u67 from your tear down article above.  Is that how it looks when set for 200ohm?  (Mine does not have the two horizontal jumpers, rather one vertical jumper on the right side of the board where it says 200ohm.) 

I've done quite a bit of internet searching on how to configure the strapping for u67, but can't find anything definitive.  (I found a very detailed description from you about the 87 strapping, but that's a different animal...)

Thanks, and please feel free to move this somewhere else if you don't want it cluttering up this tear down thread.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on August 24, 2018, 04:02:57 am
You are correct. I took this photos before restrapping for 200Ω.

This vintage U67 which I used for comparison tests was originally strapped for 50Ω (two wires in parallel, as shown on your photo). 50Ω was the low-output strapping for all Gotham-imported U67. Together with an audio pad network installed in NU67 of the same period, the output was down 12dB, compared to U67 systems sold for European delivery.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on August 24, 2018, 04:10:10 am
Outside of the subjective evaluations, are there any differences in objective measurements like THD+noise, phase response, noise floor or bandwidth?

Aside of the (measurable) output difference between the two secondary strappings, (4-6db), you may be the better source to measure finer points of tranformer strapping choices with your beloved precision analyzers.

I would be curious to know whether different strappings for secondaries would show up on a sophisticated display.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: David Satz on August 24, 2018, 11:38:53 am
There is always a preamp involved. If you try different microphone impedance settings with a variety of different preamps, I think you are likely to get a variety of different impressions.

For example, I imagine that many readers of this forum use preamps that have input transformers. Particularly if those transformers have a high turns ratio (producing a significant voltage step-up within the transformer), the high-frequency response can vary quite audibly as a function of the microphone's impedance. In effect such preamps work properly for only a specific range of driving impedances (generally ~150 Ohms), and anything outside that range produces either a rising or a falling response, with corresponding phase distortion.

Attached is the first part of a 1960s Gotham Audio bulletin showing some aspects of this situation in particular cases (bulletin 10a).

This problem is why, for example, John Hardy's "M-2" and "Twin Servo 990" preamps have switches for use with very low-impedance microphones (e.g. Schoeps and some other transformerless microphones, which can be in the 25 Ohm range). And many other preamps have input transformers with higher turns ratios than the Jensen JT-16-B that Hardy uses, so their potential for having this problem is correspondingly greater.

If your preamp doesn't have this problem (or not enough to worry about), then the choice of 50 vs. 200 Ohms becomes more a matter of practical engineering, e.g. the lower impedance setting helps to isolate the microphone's output circuit from the effects of cable capacitance (high frequency losses, reduced high-frequency headroom); it also decreases the likelihood of overloading the input of the preamp; and if your preamp has a low input impedance, the lower output impedance setting in the microphone will reduce losses due to improper loading, which may well be frequency-selective (as in the Gotham bulletin).

But if you use the microphone with a variety of preamps, the sonic consequences of the different possible settings will be more or less a toss-up, I think. If/when such effects occur, it would be a mistake to attribute them to the microphone alone, out of context.

--best regards
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: soapfoot on September 01, 2018, 08:30:54 am
There is always a preamp involved. If you try different microphone impedance settings with a variety of different preamps, I think you are likely to get a variety of different impressions.

For example, I imagine that many readers of this forum use preamps that have input transformers. Particularly if those transformers have a high turns ratio (producing a significant voltage step-up within the transformer), the high-frequency response can vary quite audibly as a function of the microphone's impedance. In effect such preamps work properly for only a specific range of driving impedances (generally ~150 Ohms), and anything outside that range produces either a rising or a falling response, with corresponding phase distortion.

Attached is the first part of a 1960s Gotham Audio bulletin showing some aspects of this situation in particular cases (bulletin 10a).

This problem is why, for example, John Hardy's "M-2" and "Twin Servo 990" preamps have switches for use with very low-impedance microphones (e.g. Schoeps and some other transformerless microphones, which can be in the 25 Ohm range). And many other preamps have input transformers with higher turns ratios than the Jensen JT-16-B that Hardy uses, so their potential for having this problem is correspondingly greater.

If your preamp doesn't have this problem (or not enough to worry about), then the choice of 50 vs. 200 Ohms becomes more a matter of practical engineering, e.g. the lower impedance setting helps to isolate the microphone's output circuit from the effects of cable capacitance (high frequency losses, reduced high-frequency headroom); it also decreases the likelihood of overloading the input of the preamp; and if your preamp has a low input impedance, the lower output impedance setting in the microphone will reduce losses due to improper loading, which may well be frequency-selective (as in the Gotham bulletin).

But if you use the microphone with a variety of preamps, the sonic consequences of the different possible settings will be more or less a toss-up, I think. If/when such effects occur, it would be a mistake to attribute them to the microphone alone, out of context.

--best regards

This is great, David.

So, a question-- using a mic preamp with a transformer-coupled input, is it better to aim for matched impedance with the microphone, rather than bridged impedance?

I was always operating under the (misconception?) that, as long as the preamp had an input impedance roughly 10x the microphone's source impedance, I'd maximize the microphone's performance  (excepting some special cases). I guess my assumption was based on the idea that we'd be most interested in voltage transfer, and less interested in power transfer in this application.

I'm sure this is incomplete, but if it's actually incorrect I'd appreciate the clarification.

(Mr. Heyne, if this is too far off topic, perhaps a thread split--duplicating Mr. Satz's post--is warranted?)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: David Satz on September 01, 2018, 01:56:14 pm
soapfoot, this board has always seemed to tolerate small amounts of "topic drift" as long as it doesn't get out of hand. Ultimately it's up to Klaus, of course. So I'll just post this one, tiny message (like all my postings), and then we can all return to the topic, OK?

The easy part first: Impedance matching (source impedance = transmission line impedance = load impedance) simply isn't relevant here. Leave that for RF circuitry, where it maximizes power transfer. As you said, we want to maximize voltage transfer, so a "bridging" approach is called for, with the load impedance at least an order of magnitude greater than the source impedance.

The technical problem is that real-world microphones and real-world preamps--especially where transformers are used on one or both sides--don't have purely resistive impedances. Their interactions can lead to audible frequency response variations and other problems. It seems misleading to specify impedance as a single number in such cases; a curve, or at least a numeric range, would be far more appropriate IMO.

The human side of the problem is that circuit designers test their work under certain practical conditions, and can't always anticipate the conditions that might occur when the technology changes in the future. Langevin, for example, may have tested the preamp shown in Temmer's paper only with dynamic microphones, which were far more prevalent in American broadcasting at the time. American studios back then tried to keep equipment running for as long as they could; in the 1960s, consoles from the 1950s were still in widespread use, with input circuits based on the types of microphones prevalent in U.S. studios even earlier.

It's fundamentally problematic to evaluate the "sound" of a component that can't be isolated from the influences of other components. Say you're a studio engineer, and you've always liked the sound of a certain preamp that you have. A client brings his or her own favorite microphone to a session, and you know little or nothing about that type of microphone, but OK, you plug it in. Say that it sounds harsh, or muffled, whatever. Normally you would think that you'd just heard "the microphone" and that you now know "what it sounds like." You would then have an opinion based solidly on first-hand listening experience--exactly what you feel that you can count on. You might never suspect that your impression resulted from an impedance interaction like the ones we're talking about--essentially a malfunction in your trusty preamp. If you're an audiophile, and particularly if the preamp is very expensive, you might even think, "My preamp is so great, it lets me 'resolve' differences between microphones that other people don't hear with their inferior, 'lower-resolution' preamps."

Both reactions are "biased"--by which I don't mean "based on favoritism". People can be 100% fair and open-minded, but when uncontrolled factors skew the outcome, listeners are misled by the very thing we want to trust the most, our own direct experience. Our confidence in our own opinion will then be diametrically opposite to the actual validity of that opinion--but we won't be aware of it.

That's what I think may be going on when people say that the 200 Ohm setting of a microphone sounds different to them (qualitatively) from the 50- or 150-Ohm setting of the same microphone. Basically, if any such difference in sound quality is perceived, rather than drawing conclusions about the "sound" of one impedance setting or another, alarm bells should go off in people's minds; such conclusions aren't likely to be generally valid.

--Back to practical solutions: If your preamp's frequency response depends on the microphone's output impedance as Temmer's paper shows, you might try to find out or figure out what kind of load the secondary winding of the input transformer is "working into" (driving). Those frequency response variations can sometimes be tamed by placing a shunt resistance, or possibly a parallel RC network, across the secondary. Or if you can't (or don't want to) get into the preamp circuitry, you can do what Hardy does when you're going to use a very-low-impedance microphone. That "pads down" the signals coming from the microphone, but not too severely, and it reduces the microphone's self-noise as well as any noise due to interference in the cable, exactly as much as it reduces the wanted signal. So unless your preamp is rather noisy, it won't harm the signal-to-noise ratio of the recording, and it may also help avoid preamp overload.

--best regards
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: soapfoot on September 02, 2018, 09:02:09 am
Thanks, David!

And at risk of continuing the topic drift just a bit too long--what, in your mind, are some practical means of addressing (or circumnavigating) this issue in a methodical, but not-overly-technical way?

Let's say there are several recordists at a studio who have great ears and make great recordings, but whose background is more musical than technical (i.e. they have music degrees, and not EE degrees). How might they be made aware of this problem in a way they might grasp intuitively, and how might they test or control for it if they sense that it's becoming a factor with a given signal chain?

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Jim Williams on September 02, 2018, 12:46:24 pm
An objective analysis will tell "the rest of the story". Load effects on frequency response, THD effects from various loads, peaking of the response and other effects can then be easily documented for those without the time nor test gear to do their own research. This, like many other audio subjects is crying out for answers that can easily be obtained with sufficient effort.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: uwe ret on September 02, 2018, 01:09:11 pm
A few good measurements will always trump multiple opinions...
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: brucekaphan on September 03, 2018, 03:41:00 pm
Klaus, THANK YOU for doing such a thorough job of analyzing and interpreting the U67 reissue—I have to say I would have expected no less, but that doesn't change my appreciation for the obvious amount of time, energy, and thought you put into your analysis. And I am a big fan of using all of one's senses, not just one's intellect, when it comes to judging anything having to do with music/recording. Not being a spring chicken myself, I know how hard fought the battle is to learn how to deeply hear, and even more so to learn to deeply hear and be able to make useful judgements based on hearing deeply. I was one of those foolish folks who bought into the M149 release, before it had been tested and (dis-) proven both by experts such as yourself, and by the marketplace. I wasn't going to make that mistake again! There's a lot of food for thought that you've served up here—so very helpful! Thank you!!!!!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: RuudNL on September 04, 2018, 01:30:30 pm
I was a bit surprised that I didn't read a word about the change in shape of the base below the microphone capsule.
In the 'old' U67 there was a dome shaped piece just below the capsule itself.
In the 'new' U67 the capsule sits higher in the headbasket, but the base where the capsule is mounted on, is flat.
IMHO this could influence the sound. Any opinions?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Jim Williams on September 05, 2018, 11:22:43 am
That will affect the response. I noticed in similar mics with a domed mount that the shape does create reflections, resonances and some nulls too.

Mounting the capsule a few mm higher can overcome some of those reflections. A complete frequency response plot with the differences would also be informative but that isn't likely to happen here.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on September 05, 2018, 05:38:47 pm
That (shape of mounting base) will affect the response.
Whether or not, or if, how much the shape of the base affects the sound of the mic is probably hard, if not impossible, to listeners. Unless all that is done, the statement is speculation.

Quote
I noticed in similar mics with a domed mount that the shape does create reflections, resonances and some nulls too.
Again, speculation, unless proven. I could as well argue (and probably trace) the exact opposite: parallel surfaces - here, a flat base plate, flat capsule sides, flat top of basket- may create standing waves of a higher audible magnitude than the somewhat random reflections off a curved surface (as with the old base).

But the reason I mentioned only the capsule-height differences in my review, and not any acoustical effects of the U87Ai base used in the Reissue vs. the old U67/87 curved one: I did not hear any. And what I heard was the focus of my review.
Quote
Mounting the capsule a few mm higher can overcome some of those reflections
How would you know? It might as easily affect just the wavelength of the reflection, with little decrease in its volume, or may result in nothing audible at all. For me, it was the latter. So I left it out of the review.
Quote
A complete frequency response plot with the differences would also be informative but that isn't likely to happen here.
No, indeed, "here" we listen to detect subtly of sounds, rather than running test tones or protocols.

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Jim Williams on September 06, 2018, 11:42:52 am
I have done some tests that exposed the reflection effects. It was so audible the capsule had to be raised up 5 mm to overcome it. It was on a Rode NT-2 that I designed for Rode back in the mid 1990's.

No, I didn't bother with frequency sweeps as I don't have the anechoic room to do that here.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: duskb on January 04, 2019, 01:48:55 am
Klaus,
Thank you for taking the time to research this mic. I bought a reissue for my employer in October and by and large, in a very unscientific test as compared to an original, I had a hard time hearing any difference. This is not to say that we didn't detect a difference but when blind listening any difference we thought we heard was quickly negated when hearing the next one. If I had more time I suppose I could have dug deeper but it was a moot point. At that point we owned it so we had to accept it for what it was. It is not a bad sounding mic.

This thread made me aware of something though. I personally own three vintage 67s, one with an earlier serial which sounds quite different than the other two. It actually sounds different from any 67 I've heard. I like it better. More creamy in the low end and a bit more soft on the top. Almost like a blend of a 47 and a 67. The finish is different too. It looks as if it was sprayed with a lacquer. I've seen other early 67s with the weird finish before. All serial 19xx and earlier. The reason I ask is I was unaware of impedance strapping for these mics. Maybe the difference has to do with two of them being strapped differently than the other. How do I check to see where the impedance is set and how easy is it to change it? Is the difference I'm describing a version issue or something else?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on January 04, 2019, 02:57:18 am
Hello Dusk,
If any of the three vintage mics were strapped differently, the output would be considerably different as well: 4-6 dB

But you can visually check as well: in the space between connector barrel and the tip of the tube is a rectangular brown circuit sub-board with "200" and two "50" imprinted. It's a bit hard to see because several colored wires are obscuring the board.

If the mic is set to 200Ω, a single wire, usually clear, as in the photo attached, loops between two solder points on the same side of the sub-board.

If the mic is set for 50Ω, there will be two wires soldered in parallel from one end of the board to the other.

But my hunch why your mics sound different: different capsule generations! Take a picture of each and upload it.

P.S.: I am happy that you are happy with your Reissue. As I mentioned in my review, the biggest variable, the current series K67 capsule, is inconsistent, and can range from superb to harsh and unmusical.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: RuudNL on November 07, 2019, 03:20:04 pm
After reading your in-depth analysis of the U67 re-release (my thanks for this!), A question remains: is the U67 reissue worth its money, or are there better alternatives?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on November 08, 2019, 03:26:25 am
At the current street price, I believe the U67 Reissue beats anything comparable in price, and with a few judicious steps it can easily be moved into the world class of the vintage U67.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: ameyerson on November 09, 2019, 04:26:16 pm
As an owner of 2 of the reissues I have to admit I don't disagree. My listening test is not nearly as intricate as yours. Usually when I evaluate a new mic I start by using it as a cello spot mic in an orchestral setting. I feel the cello is a perfect instrument balance wise to give me a clear idea of how the mic responds. I've done it with so many mics now that I have a pretty good sense of how it works. Also there is no instrument that affects me emotionally like the cello. When it sings I feel it in the hairs on the back of my neck
I agree with the pinched upper midrange and the lean low end. It's a subtle shift and took me a while to get it.
On the other hand I really like the way the mic sound set in Omni. It seems to balance out tonally in Omni so when the situation is right I'll do that.
Love to get your hands on these, Klaus.
Best,
Alan

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on November 10, 2019, 01:22:23 pm
(...) I feel the cello is a perfect instrument balance wise to give me a clear idea of how the mic responds.(...) there is no instrument that affects me emotionally like the cello.

I am not the first to note the similar timbre and expression of a cello and the human voice. It's therefore an excellent instrument to judge a mic, as Alan notes. It is enviable to work in a recording environment where cellos are common. The rest of us will have to do with voices, sometimes our own...
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Eddie Eagle on November 11, 2019, 10:22:22 am
The rest of us will have to do with voices, sometimes our own...
I resemble that.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 13, 2020, 02:45:26 pm
Strictly speaking of the 1963 Neumann u67 cable, was there a serial number for this ? like a Neumann ec4 cable ?
I have been searching for a back up cable for my 1963 u67, but when i search a lot of other variables come up.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 13, 2020, 03:33:43 pm
As mentioned in my review, the U67 cable delivered by Gotham for the U.S. market was a U.S.-made Belden product. To my knowledge, it has long been discontinued, but with some luck you can still find it on eBay or Reverb.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 13, 2020, 08:26:02 pm
This cable doesn't have a name ?
I am only speaking of the Neumann cable, not Gotham
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 13, 2020, 10:19:52 pm
That is a great cable, made for Neumann for its 2xx mics. It will not have the particular sound characteristics of the Belden, but it has excellent mechanical properties and  the double Reussen layer shielding with the highest RF rejection possible. This material was widely used by Neumann for delivery to the German Broadcast System.

Just make sure the pin configuration is right for the U67 pin-positions, or transplant your U67 connectors over to that cable material.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 13, 2020, 10:53:18 pm
Good to know Klaus and thank you. Would you happen to have a picture of the Beldon you are talking about ? makes me wonder which cable i have for my u67 ?
Here is my cable which reads neumann made in germany on the cable itself.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 14, 2020, 02:10:42 pm
Maybe a better picture
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 14, 2020, 07:41:04 pm
Yours is the German broadcast cable I had mentioned. Probably made by Gotham/Dörfler, Austria. It's not the Belden material I mentioned in my review.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 14, 2020, 07:59:10 pm
That makes me sad Klaus :-( Of course I'm always going to wonder what the Belden cable sounds like now lol ?
Is there an easy way to find out exactly which cable this is ? and also the date of my cable ?
Ignorance is bliss in this case because this is the only u67 I've ever had and recorded with.
I just received a telefunken EF806s and this tube is beautiful.
Just for fun I've been comparing it with the telefunken EF86 tubes i have, theres not a tremendous difference, but it feels like the EF806s is slightly smoother.
Ive been searching all over the internet for a picture of a 1963 Belden cable and haven't had any luck at all, would you happen to have a pic laying around ?
Thanks again Klaus.

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on April 14, 2020, 11:14:30 pm
These are from my u67’s. (1965 and 64).  I believe one is the Belden and one is the Dorfler...  (Neither have any labelling, but the jackets and the shielding fit the description Klaus offered in this thread: https://repforums.prosoundweb.com/index.php/topic,37359.msg538273.html#msg538273
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 15, 2020, 01:07:40 am
I've been searching all over the internet for a picture of a 1963 Belden cable and haven't had any luck at all, would you happen to have a pic laying around ?
Thanks again Klaus.

In a day or two, I will upload a picture of the Belden cable originally included in U67 sets sold in teh U.S. in the early to mid 1960s.
KH
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 11:34:16 am
These are from my u67’s. (1965 and 64).  I believe one is the Belden and one is the Dorfler...  (Neither have any labelling, but the jackets and the shielding fit the description Klaus offered in this thread: https://repforums.prosoundweb.com/index.php/topic,37359.msg538273.html#msg538273

I have a 1963 u67 I wonder what happened to my original cable ?
I bet this is the Belden, Just a wild guess
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 12:00:04 pm
I’m debating if I should trade my u67 swivel mount for a regular Neumann cable ?
Although I love the way the swivel mount looks, i can hear the low end ruble associated with not having a shock mount.
Just got an original z48 and I’m wondering how strange it’s going to look with the swivel mount on the shock mount.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 15, 2020, 12:33:01 pm
You are actually defeating part of the shock absorption provided by the elastic suspension when you keep the swivel mount connected. The weight of that mount stresses sections of the suspension rubbers and makes it hard to keep the mic centered in the mount.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 12:43:21 pm
You are actually defeating part of the shock absorption provided by the elastic suspension when you keep the swivel mount connected. The weight of that mount stresses sections of the suspension rubbers and makes it hard to keep the mic centered in the mount.
That makes a lot of sense Klaus, so I guess I should sell this and get a proper cable, I’ve been looking everywhere and haven’t had much luck.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on April 15, 2020, 02:13:07 pm
I have a 1963 u67 I wonder what happened to my original cable ?
I bet this is the Belden, Just a wild guess
This looks like the original Dorfler without the swivel mount as far as I understand... (Klaus?) If so, it's great cable! Is this yours? 
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 03:07:47 pm
No this is a pic from the internet, my cable is the swivel mount a few posts up.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 07:28:03 pm
can anyone point me to a site other than reverb and eBay for a neumann u67 cable ? i can't seem to find anything
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on April 15, 2020, 07:39:26 pm
can anyone point me to a site other than reverb and eBay for a neumann u67 cable ? i can't seem to find anything

If your cable is from a m269 as Klaus suggest, then that's great wire.  Just buy a female tuchel connector if you really don't want the swivel mount?
In fact, I'm happy to trade you my u67 female tuchel connector for your u67 female swivel mount conector!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 15, 2020, 07:54:56 pm
Im not sure if my cable fits an m269 ? it came with the u67.
I dont trust my lack of skill to remove the swivel mount and connect something lol
Do you have a picture of your u67 cable ?
and what is the condition, any noise etc :-)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 19, 2020, 02:19:39 pm
That makes a lot of sense Klaus, so I guess I should sell this and get a proper cable, I’ve been looking everywhere and haven’t had much luck.
Hello Klaus, i received my neumann z48 shock mount.
It is so nice but i realized that the diameter of the top ring is larger compared to the bottom ring, i suppose because it contours to the u67 mic body, but the top clasp doesn't hold tightly like the bottom clasp, is that normal ?
Makes me worry as i hang my u67 upside down because of the heat from the tube.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 19, 2020, 02:55:40 pm
With the mic properly fitted, both clasps should have equal tension when closed.
Move the mic up or down inside the mount, to get even contact with the felted rings.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 19, 2020, 03:08:47 pm
With the mic properly fitted, both clasps should have equal tension when closed.
Move the mic up or down inside the mount, to get even contact with the felted rings.
Thats what i did, out of curiosity i held the mic and closed just the bottom clasp and the mic slips out, i tried the same thing with the top clasp and that holds the mic tightly.
Definitely doesn't have equal tension.
Mine almost seems like the top felts just barely hold the mic, more of a guide while the bottom tension is strong.On another note if I position the microphone the proper way meaning the head basket is on top then there is no way for the mic to slip out even with the clasps open because the design of the microphone stops it fr
om falling through where the head basket meets the body :-)
Does the heat from a tube really hurt or damage the capsule over time ?
This is the only reason I hang it upside down.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 19, 2020, 05:11:57 pm
The top felt looks worn. Compare to new.
No heat issues with U67 and K67 capsules. Position the mic as you please.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 19, 2020, 06:59:49 pm
The top felt looks worn. Compare to new.
No heat issues with U67 and K67 capsules. Position the mic as you please.
I compared my z48 to the pictures on the Neumann site and I can’t see a difference personally, but if I don’t have to concern myself with the tube affecting the capsule then I will position my mic right side up, thanks again Klaus problem solved :-)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 20, 2020, 04:59:15 am
Can’t sleep and I’ve been thinking about maybe not selling my swivel mount,
One reason is it’s always nice to have a back up cable and the other thought is that would if I put a small patch of carpet underneath the mic stand to absorb a little low end rumble ? I know carpet can’t compare to the elastic bands in the z48 shock mount but just a thought ?
I think I might do a quick test and compare the low end ruble you get from standing doing a vocal with each and see how much of a difference there is or isn’t :-)
does anyone know if using a z48 shock mount will absorb 3db of noise versus not using one ? there may be some numbers out there lol
Update--
I actually just read a person on this forum saying they did a test using small pieces of foam under the mic legs and that decoupled it better than a shock mount ?
gonna try this.
There is something about this u67 swivel mount that is so strong and secure and makes me feel at ease when recording.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 20, 2020, 12:58:17 pm
..and considering how many seminal recordings have been made with this mic on a swivel mount: has anyone ever noticed the type of mount on any of these recordings, let alone complained about it?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 20, 2020, 05:44:56 pm
I am certainly not complaining Klaus, just my observations :-)
After positioning the z48 I realized that I like to have the option of getting very close to the mic, which the z48 gets in the way, the swivel allows me to get right up on the mic if I need to so I am keeping my swivel mount and ditching the z48.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 20, 2020, 07:05:43 pm
Choices are everything, especially when they are limited to two!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 21, 2020, 06:37:34 am
Choices are everything, especially when they are limited to two!
very true :-)
Klaus is this the Belden cord you mentioned ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 21, 2020, 01:35:05 pm
At least one of them is: the one with the outline of the spiral shielding poking through the silver jacket.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 21, 2020, 05:01:27 pm
At least one of them is: the one with the outline of the spiral shielding poking through the silver jacket.
This picture is such a mess Klaus lol do you mean the left or right swivel ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 21, 2020, 08:40:38 pm
It will be the cable in the cropped section of your picture. I cannot give you further confirmation, as the connector sections are blurry.
As I wrote: only one of the cables has the distinct corkscrew shielding poking through. That's the one.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 21, 2020, 09:37:12 pm
Thank you Klaus I get it now, that corkscrew pattern showing under the wire surface :-)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 21, 2020, 09:59:15 pm
You are welcome. But please please read this forum's ground rules again:

 (" Cross posts. The 'buckshot' approach to placing identical or similar posts of inquiry on several forums is discouraged. Professionals who take time and make efforts answering inquiries placed on my forum deserve the courtesy of undivided attention. With few exceptions (stolen mic alerts) cross posts will be deleted.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 21, 2020, 10:33:55 pm
Are either of these correct?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 21, 2020, 11:18:01 pm
I also saw that  Sommercable Octave Tube makes a cable with connectors for the 67.  Telefunken USA uses this for their 'Diamond' series.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 22, 2020, 03:52:35 am
Are either of these correct?

If by 'correct' you mean like the Belden I mentioned in my review? No. as I wrote: the Belden you can see the cork-screw layer of teh shield through the jacket. I guess, I have to take a picture and post it.

The cable material you show still might be good, though. Listen and compare...
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 10:48:24 am
You are welcome. But please please read this forum's ground rules again:

 (" Cross posts. The 'buckshot' approach to placing identical or similar posts of inquiry on several forums is discouraged. Professionals who take time and make efforts answering inquiries placed on my forum deserve the courtesy of undivided attention. With few exceptions (stolen mic alerts) cross posts will be deleted.

My apologies Klaus, I didn’t realize I couldn’t post elsewhere, won’t happen again.
I think I have finally found the Belden cable :-)
Please tell me this is it ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 11:42:21 am
I have deleted the post in question,
I can see this cable has the outline of the shield pattern poking through the jacket.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 22, 2020, 02:54:22 pm
I think I have finally found the Belden cable :-)
Please tell me this is it ?

Yes, it's the one connected to the swivel mount.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 02:59:21 pm
Yes, it's the one connected to the swivel mount.
Awesome
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 22, 2020, 03:05:15 pm
Klaus the cable you are calling Belden (corkscrew pattern under the wire)
(...) this is what someone told me after speaking to a a person at Neumann Berlin.

Please cite the source for your information. "Someone... speaking to a person" is not good enough. It's hearsay (another no-no in the ground rules), unless it can be traced back to a real person and the source can be confirmed.

FYI: I have here a similar, "Belden"-labeled and numbered cable whose build features are identical to the cable that was used with U67 in the 1960s. The "EMT" cable your source refers to is the famous double Reussen layer shield version, used initially by the German Broadcast Service, its jacket is smooth, and extremely flexible, without any visible print through of the shield layer. Its construction is completely different from Belden's and is easily recognized without opening it up.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 03:21:12 pm
I broke the rules again ? i didn't realize that conversations on a forum would be so strict ? I'm not trying to be difficult i am just trying to understand the famous Belden cable.
So i am now wondering if the last picture i posted is a Belden or double Reussen layer shield version ?
The corkscrew print is visible through the cable.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 22, 2020, 04:06:05 pm
It looked like the Belden cable to me. The silvery color of the jacket is a hint, too. Please read my response again: ONLY (added here, for clarification) the Belden has the outline of the shield pattern poking through the jacket.

As to hearsay: this forum is quite different in trying to maintain a high s/n ratio. Its rules have been copied far and wide on other forums. One way to stay authoritative and trustworthy with information is to read and comply with the ground rules on hearsay:

"...* Posts containing quotes without attribution or original source. These are just hear-say and not good enough for this forum. ("...a trusted engineer-friend thought mic x rocks...") If the engineer thinks it rocks, then ask him to step up and share with us what he knows."...

So, please, back up what you 'heard' with a verifiable source, or delete those statements.

Thanks,
KH
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 04:22:10 pm
I deleted my statements Klaus.
I can see the outline of the shield pattern poking through the jacket so i guess this is a Belden :-)
I found a gentleman who is kindly attaching a swivel mount and male connector with this cable.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 22, 2020, 05:06:37 pm
Great. Make sure that the person who wires up the cable with the connectors follows Neumann's ground/shield scheme, for maximum suppression of noise and RF: cable ground and shield must be connected together and terminated at pins 3 and 7 AND the connector housings.

That scheme has to be executed exactly the same way on both connectors.

And, please report back on how you like the sound of that cable!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 05:24:42 pm
Great. Make sure that the person who wires up the cable with the connectors follows Neumann's ground/shield scheme, for maximum suppression of noise and RF: cable ground and shield must be connected together and terminated at pins 3 and 7 AND the connector housings.

That scheme has to be executed exactly the same way on both connectors.

And, please report back on how you like the sound of that cable!

I am passing along your suggestion and will keep you posted on how it sounds,
And a big thank you again Klaus :-))))
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 22, 2020, 06:34:51 pm
Just a note of caution: Older Belden 8404 cable looks the same as the Belden 3344.  (Gray Exterior with corkscrew outer appearance.) That being said, I don't know if it is similar or not.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 07:05:48 pm
Just a note of caution: Older Belden 8404 cable looks the same as the Belden 3344.  (Gray Exterior with corkscrew outer appearance.) That being said, I don't know if it is similar or not.

Interesting, if it’s the 8404 or the 3344 I’m sure it will be great 👍🏼
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 22, 2020, 11:56:42 pm
I thought this was interesting, a vintage neumann cable in black that looks like the reissue UC 5 cable but isn't ?
It was listed as a Sommer cable without any other information.
Wonder when this was available ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on April 23, 2020, 12:57:11 am
Here’s a good shot of my cable (presumably Belden)..  You can see the “corkscrew” best when looking down along the length of the cable....
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 23, 2020, 01:28:58 am
 Not that I don't want absolute customer satisfaction, or your money back, but... can we now almost be done with this? It has taken up an awful amount of bandwidth.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 23, 2020, 05:39:02 am
Here’s a good shot of my cable (presumably Belden)..  You can see the “corkscrew” best when looking down along the length of the cable....
If your cable is a Belden then mine must be a Shelden because all the other cable I’ve been looking at have a pattern poking through the layer of wire.
I thought the corkscrew patter was underneath the cable not the actual shape of the cable.
I’m not sure what I bought but this is the wire it will have.
Klaus mentioned that the swivel mount picture i uploaded was the Belden cable, to my eyes the swivel mount cable and the guy holding the cable look the same to me which is why i put them together in this photo, but none of my cable pictures look like your cable, in fact if your cable is a Belden
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 23, 2020, 05:59:05 am
Not that I don't want absolute customer satisfaction, or your money back, but... can we now almost be done with this? It has taken up an awful amount of bandwidth.
I am done and i feel like i have not learned anything after a lot of my time has gone into this,
i tried..
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 23, 2020, 12:55:46 pm
Derek,
There is no reason to get upset.
The last picture you uploaded show the same cable construction in both shots, which indicate to me that they are the Belden that was used in the 1960s with U67. No other microphone cable of that era looked remotely close to the two you show in the photo. They both show a silvery, light gray cable with the braided shielding showing through the jacket and the shielding forming a twisted, corkscrew pattern as you look down on the cable.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 23, 2020, 04:45:10 pm
Derek,
There is no reason to get upset.
The last picture you uploaded show the same cable construction in both shots, which indicate to me that they are the Belden that was used in the 1960s with U67. No other microphone cable of that era looked remotely close to the two you show in the photo. They both show a silvery, light gray cable with the braided shielding showing through the jacket and the shielding forming a twisted, corkscrew pattern as you look down on the cable.
I wasn't upset i just felt kind of silly, sometimes you can't hear the emotion that goes with an email or text message :-)
Thank you Klaus for unscrambling my brain, i m happy the Belden is coming and will report back on the sound.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 23, 2020, 05:19:34 pm
Not that I don't want absolute customer satisfaction, or your money back, but... can we now almost be done with this? It has taken up an awful amount of bandwidth.
Last question about mic cables, you have my word.
This Neumann cable i found that has the Neumann logo on the actual cable appears to be a reissue UC 5 but is not.
Could this be from the 1990's era when Neumann reintroduced the u67 or older ?
It was advertised as vintage.
Ok i am totally done and thank you for your patience and answers to my many questions Klaus.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 23, 2020, 06:20:58 pm
The cable in your latest photo is indeed the one that came with the 1992 reissue of the U67. It is a Gotham-Dörfler-(or similar grade) 7-conductor +shield cable of very high quality.
It will not sound the like Belden, if that is what you are after.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 23, 2020, 06:36:12 pm
The cable in your latest photo is indeed the one that came with the 1992 reissue of the U67. It is a Gotham-Dörfler-(or similar grade) 7-conductor +shield cable of very high quality.
It will not sound the like Belden, if that is what you are after.
My hunch was that it was from the 90's era.
When my Belden cable comes i am so excited to compare it to the Gotham-Dorler cable i already have.
If i can't hear a difference can i send you my ears for you to retune, retension or reskin Klaus :-)
Thank you so very much for your time and knowledge.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 25, 2020, 12:02:50 am
I have learned that each element is important, capsule, tube, cable and power supply and obviously all the other components, but i haven't heard any mention of the output section of the power supply ? what Xlr cable should one use coming out of the psu ?
would that also play a role in the sound ?
seems like that would be equally important to bring this beautiful microphone signal to an interface.
My psu output is for an XLR, it does not have a Tuchel socket, so i guess the Tuchel (orange cable) i have in this post would not work.
I have also included a picture of a psu where the Tuchel would work (pic with red arrow) just for reference.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 25, 2020, 06:31:03 am
I wanted to make sure i got your timeline correct Klaus,
The vintage u67 in 1960 shipped with the Belden 3344 cable first, up next would be Around 1964 the 3344 was replaced with a Dörfler-made cable with Reussen-shield, next up was a Gotham GAC 7 and last would be the reissue cable.
Did i get this right ?
I ask because i have seen many people selling their u67's along with a certain cable that was not period correct, but when you ask them they say my 1962 u67 has the original cable it was shipped with and its a Doefler-made German Broadcast cable.
I am pretty sure that the Belden cable was also referred to as an EMT cable ? or no
You didn't mention an EMT cable anywhere in your teardown article.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 25, 2020, 02:38:50 pm
Addressing both issues:

1. All audio cable material used with a tube mic (and transistor mic!) set-up is important and should be of highest quality for RF rejection and sound.

2. I cannot give you a time line or transition years for what cable Neumann used at what point. It seems that the U67 shipped to the U.S. in the mid-1960s came with the Belden this whole discussion has been about. At least all U67 I have had here for service that had the "Gotham" sticker on the bottom of the power supply came with the Belden.

European deliveries of that mic may have used the most widely available cable material at the time- EMT/Gotham/Neumann versions of double Reussen layer 96-strand conductor material.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 25, 2020, 03:57:46 pm
Addressing both issues:

1. All audio cable material used with a tube mic (and transistor mic!) set-up is important and should be of highest quality for RF rejection and sound.

2. I cannot give you a time line or transition years for what cable Neumann used at what point. It seems that the U67 shipped to the U.S. in the mid-1960s came with the Belden this whole discussion has been about. At least all U67 I have had here for service that had the "Gotham" sticker on the bottom of the power supply came with the Belden.

European deliveries of that mic may have used the most widely available cable material at the time- EMT/Gotham/Neumann versions of double Reussen layer 96-strand conductor material.
so is it safe to assume that this EMT is on the same level as the Belden ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: DanDan on April 25, 2020, 08:43:17 pm
Hi Klaus, a very interesting (and to me useful) piece of research. I have an original and one of the reissues from the 90's or whenever that earlier one happened. They measure pretty much identical using REW and a good speaker. But I have always been a bit disappointed by the younger one. Presuming it is high, can the cap tension be reduced to deliver the classic sound?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 25, 2020, 10:34:35 pm
You would need to define "level".

* On the objective and measurable level, the EMT/Gotham double Reussen shielded material is superior to any other construction, and a very neutral, no-offensive overall timbre.

* On the subjective "I like that sound" level, I prefer the Belden. But my experience is limited to just one application: U67.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 25, 2020, 10:38:51 pm
Yes, the diaphragm tension on K67 with tight skins can be reduced, and a mid-1960s tension and timbre can be dialed in in most cases, and pretty reliably.

But before you go off the deep end: switch heads and determine whether the bass-starved impression follows the capsule head, or whether it stays with the mic amp.
In case of the latter, make sure that in both amps S2 is set the same - open or closed.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 10:19:36 am
Here is a picture of my new custom cable :-)
I will let everyone know how it sounds when it arrives.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 11:11:42 am
The special version U67 Tuchel connector, made exclusively for Neumann until the 1970s is no longer available anywhere, so keep that connector healthy! 

Specifically:
Make sure the white rubber buffer washer is seated at the bottom of the female connector, between the 7-pin black plastic insert and the metal housing (second picture, left connector), otherwise the rim of the plastic connector will crack when you screw it into your mic, and the connection becomes wobbly and will fail eventually.
These friction washers are often missing because they have dried off.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 11:42:14 am
Thank you Klaus, i will take very good care of this.
When i look at the swivel mount i have i can not see the rubber buffer washer, is that because it is hidden between the 7 pin plastic insert and the metal housing ?
is there a way for me to see this rubber washer without touching the wires ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 11:46:10 am
If you see just bare metal at the bottom of the channel between black insert and housing you are missing the spacer. Take a close-up picture right into the connector, for confirmation.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 11:58:03 am
My washer is black if that is in fact the rubber washer.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 01:24:36 pm
Someone replaced the buffer spacer with two o-rings. It may work just fine. In any event: Tighten gently and stop when you feel resistance!
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 01:55:46 pm
I guess the original rubber washer went bad then they replaced it.
Can you buy this rubber washer ? also can this washer be installed without disconnecting any wires ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 02:16:01 pm
The original rubber buffer is obsolete. You can always fashion one from high density foam or rubber, and you do not need to disconnect anything to slip it in.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 03:00:15 pm
The original rubber buffer is obsolete. You can always fashion one from high density foam or rubber, and you do not need to disconnect anything to slip it in.
Thats great news, finally something i can do and not be worried lol,
thanks again Klaus.
As far as the power supply goes, my psu has an XLR connection for the output.
Did Tuchel ever make a female (that doesn't have to screw in) XLR to a male XLR ?
that would be so nice to have another strong Tuchel connector for my output stage :-)
Or will i not be able to use a Tuchel connection unless i had the old socket > (picture below)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 05:17:19 pm
Quote
Did Tuchel ever make a female (that doesn't have to screw in) XLR to a male XLR ?

XLR connectors were an American (Cannon) invention, in competition to Tuchel's three-blade audio out, used widely in Europe These were always of the screw-in type.
But I am not understanding the question in relation to your pictures: The upper pic shows an XLR audio out- standard for U.S. deliveries of NU67, and the lower shows the same for European deliveries which were still heavily invested in the Tuchel format.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 06:07:59 pm
Im sorry if my question wasn't clear Klaus, yes i have the XLR psu us version, i wanted to know if Tuchel ever made a female XLR that would fit into my us Psu ?
The reason i added the European psu was because the Tuchel fit that psu, and maybe the Tuchel would only fit a European psu.
Did Tuchel ever make an XLR connection 3 pin that had the same metal casing in this picture ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 26, 2020, 10:23:10 pm
I am not sure whether I got your question right, but I need to state again: an  "XLR" connector has, by definition, a specific shape and pin arrangement that several manufacturers use or used: Cannon, Switchcraft, Neutrik are three of the main ones, with a few Chinese copies to throw in.

Tuchel is a brand of German connectors (the other is Binder) which are normed by the German broadcast institute, and which are not compatible with XLR types, but use the screw-in type form factor and the pin-out system of the RF-tight 2xx connectors, as mounted on U67, M269, etc. Their audio (3-pin) versions are a blade pin type that screws into the power supply-mounted female you pictured. So  no mix and match is possible between the two systems.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 26, 2020, 10:27:51 pm
You answered my question Klaus :-)
So a good quality xlr is all i can have in my situation, thanks again Klaus.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: uwe ret on April 27, 2020, 03:09:02 pm
Suitable adapter cables - DIN (Tuchel or Binder) to XLR are available.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 27, 2020, 03:33:15 pm
Yes, forgot to mention: you can always fabricate or purchase a pigtail that translates from one connector standard to the other.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 27, 2020, 03:44:05 pm
This morning I received a 15ft cannon-ended length of what I think is the old Belden cable. (Gray rigid, corkscrew shielding coming through jacket, with a neat old smell I haven't smelled in years.) Anyway, I hooked it up to the output of a 251 clone power supply and did several A/Bs with two different mic pres, comparing it to Mogami and Canare cable. You could certainly hear a difference. More definition in the lows and smoother highs. Level seemed the same. This was a vocal test of the same repeated musical phrase and counting down from 10. Next I will try acoustic. Quite impressed.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 27, 2020, 04:35:09 pm
What you report and what I experienced, then wrote about at length, is yet another argument for listening over applying "objective" but theoretical considerations.

From the standpoint of cable technology, the Belden cable is inferior in a few aspects to "state-of-the-art" cables: inadequate shielding design, stiff, low strand-count conductors, other mechanical problems...nothing points to such a cable "sounding" preferable, in certain applications to highly-engineered products like the original Swiss EMT material, or its sibling, the Dörfler-made GAC7.

I have experienced a similar phenomenon with U47 cables: the original, thick, first-generation rubber cable with its four course, lamp-cord conductors and atrociously tinned, braided shield somehow sounds more resolved and musical with a U47 than whatever I sometimes need to replace it with (often, the rubber crumbles, and conductor jacket bits dry up and fall off).

I wish someone could reasonably well explain the relation between level of engineering and audible outcome in cables, especially where the audible outcome seems almost impossible, considering the low level of engineering. 
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 27, 2020, 08:13:06 pm
I'm no expert, but maybe it's the quality of the copper. 
Don't know where Mogami or others get their wire from, but there are lots of Chinese copper wire manufacturers and very few US anymore.

I can relate an issue I had with Chinese steel vs. US steel. I had a 1964 Chevrolet that had a hood problem, being that it wouldn't stay up right or hold fast at its detents. The person I bought it from had installed reproduction hood hinges and springs. I called the company that he bought them from and they sent me new ones. I installed them. Same problem. I searched for NOS hinges and springs and found a set. These were GM-made US steel. I installed the first one of two. It's all it needed for the hood to obey my commands. Just one, mind you.

Long story short: the Chinese steel flexes just enough to not hold the hood. The US was solid. Same thickness, same weight (I weighed them) same exact appearance. Any copper experts here?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 28, 2020, 10:21:03 am
Suitable adapter cables - DIN (Tuchel or Binder) to XLR are available.
This sounds great, I've been searching for a suitable cable for the output stage like a Tuchel to Xlr but haven't had any luck ?
but i did find a picture of a cable that looks like it would fit, but it is advertised as for a Beyer microphone.
would you happen to have a link handy ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on April 28, 2020, 10:38:06 am
This morning I received a 15ft cannon-ended length of what I think is the old Belden cable. (Gray rigid, corkscrew shielding coming through jacket, with a neat old smell I haven't smelled in years.) Anyway, I hooked it up to the output of a 251 clone power supply and did several A/Bs with two different mic pres, comparing it to Mogami and Canare cable. You could certainly hear a difference. More definition in the lows and smoother highs. Level seemed the same. This was a vocal test of the same repeated musical phrase and counting down from 10. Next I will try acoustic. Quite impressed.
You said you hooked it up to the “output” of your 251 clone power supply ?
I think Klaus was speaking of connecting the Belden cable from the microphone to the “input” stage of the power supply ?
I am asking because if you hear a significant difference on the output stage, then that tells me that both input and output cables are equally important?
Klaus any thoughts ?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Mannix on April 28, 2020, 12:53:31 pm
I bought the last one off a guy on Ebay. Sorry. Good luck.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on April 28, 2020, 01:18:17 pm
You said you hooked it up to the “output” of your 251 clone power supply ?
I think Klaus was speaking of connecting the Belden cable from the microphone to the “input” stage of the power supply ?

Depends what voltage you are referring to: the power supply's INPUT receives the audio from the mic, its OUTPUT powers the mic. 
As the cable between mic and power supply serves both functions, and electrons flow in both directions, it's best to refer to that  cable as the "microphone cable", in difference to the power supply's "audio-out" cable
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: DanDan on May 01, 2020, 06:57:04 pm
Quote
So, a question-- using a mic preamp with a transformer-coupled input, is it better to aim for matched impedance with the microphone, rather than bridged impedance?

Many traffo output devices were designed with a match in mind. When a modern mismatch is in play, I have seen recommendations to strap a 600 Ohm resistor across say an 1176.

Klause, tx for a very interesting thread and for all the work that went into it.
I have two 67's. One ancient, the other the earlier reissue, in the 90's I think. The FR looks identical but I always find myself preferring the older one. Capsule tension?
Can the newer cap be detensioned?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on May 01, 2020, 07:33:24 pm
Any capsule in the K47/67/870/87 design family can be tension-adjusted. But I doubt very much that you have a tension problem with a 1992 K67. Those were good years, in general.

Please contact me privately if you have specific concerns you wish me to address.
I'd like to keep the forum uncontaminated from business inquires and solicitations.

Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: David Satz on May 02, 2020, 09:51:22 am
DanDan, I'd just like to warn against the risk of over-generalization. Your recent message touches on two such risks that I see:

>> using a mic preamp with a transformer-coupled input, is it better to aim for matched impedance with the microphone, rather than bridged impedance?

I don't immediately see who here asked that question in that way, but anyone who tries to answer it should be a bit careful. To my mind the only valid, neutral answer is "it depends on the operating conditions that the preamp was designed for"--in other words, it depends mainly on the microphones that you're going to use. But microphones designed to be loaded by the equivalent of their own output impedance haven't been made in an extremely long time--so long that they aren't merely "vintage"; they're antique. If you're interested in breaking one of those out of a museum somewhere and trying it, then by all means get yourself an appropriate preamp for the experiment; those microphones won't sound as they were meant to do unless they are loaded as designed. But otherwise, keep away.

To look only at whether a preamp has an input transformer or not, and to assume that this must be the determining factor, is the "streetlight effect" in action. The history of studio practice in the United States, and the loss of Bell Telephone / Western Electric's early dominance over it, are more to the point. 19th-century telegraph systems are where impedance matching comes from; telephone systems were then built onto that infrastructure, which combined balanced signaling with impedance matching. But those two circuit characteristics are really two distinct items.

The only reason anyone gets interested in impedance matching in audio today is that it's been dead so long, hardly anyone alive was there when it died. So the forgetting process has become nearly complete--and those who don't know history start doing what they are proverbially doomed to do.


> The FR looks identical but I always find myself preferring the older one. Capsule tension?

If you change the capsule tension, perhaps you will like the tone better (and perhaps not), but the frequency response and impulse response of the microphone will change as well. Sensitivity, distortion, maximum sound pressure level could all be affected.

A capsule is a complex system with multiple, interdependent parameters. You can't just tweak one and have only one aspect of the system's behavior change, while all its other aspects kindly hold still.

--best regards
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on May 02, 2020, 11:30:01 am

Klause, tx for a very interesting thread and for all the work that went into it.
I have two 67's. One ancient, the other the earlier reissue, in the 90's I think. The FR looks identical but I always find myself preferring the older one. Capsule tension?
Can the newer cap be detensioned?

Could you swap the two head assemblies to see if your “preference” follows the amp or capsule?  Or are there physical (or electrical) differences in the 90’s reissues that prevent that?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: klaus on May 02, 2020, 12:58:51 pm
You can swap without consequences.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: DanDan on May 02, 2020, 07:11:34 pm
Thanks Klaus, that is reassuring.

Tx David, regarding the impedance matching. I might be suffering a little cabin fever and replied in the wrong thread, but somebody did ask about matching vs bridging. 
I note some if not all of my Neuman have adjustable output impedances.
They are probably all set at 150Ω. This seems to work fine with trafoless GML preamps etc. but  I wonder should I drop to 50Ω for my V76 and V78s?
I do strap to 600Ω on the output of my 1176s.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: afterlifestudios on May 03, 2020, 02:28:25 am
I’m curious about 50ohm setting on these mics for v76 as well.  But as far as line level impedance bridging/matching goes, it really matters what kind load you’re output transformer expects, and what kind of load the input of the next piece of gear presents.
 
Instead of strapping loading resistors on the outputs of 1176’s and other outboard, I just put some on the patch bay. That way you can easily patch it independing on the signal chain are currently using.  Sometimes your 1176 output will already be seeing a 600ohm load (patched to tape machine for instance), and sometimes it will be seeing 10k ohm (a/d converters).  You don’t want a 600ohm termination resistor as well as a 600 ohm input of the next device.  So having flexibility is key, which is why I put some loading resistors on the patch bay, not on the unit.

(Sorry if this thread is drifting too far, Klaus.)
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: David Satz on May 04, 2020, 08:53:17 pm
The 150-Ohm setting should be avoided in my opinion. It was meant to work around two defects of older preamps and mixers, but at a definite cost. Meanwhile those defects are far less prevalent today than they were in the late 1950s: [1] input overload (because the particular preamps or mixer inputs had been designed for ribbon and other dynamic microphones) and [2] input impedance below the 1 kHz minimum.

If either of those problems exists in a given case, it is far better to place a resistive pad directly at the input of the equipment that has the problem, rather than to hobble a perfectly good microphone for the sake of equipment that's not up to the demands of modern recording. If you pad the signal "after the cable" rather than "before" it, the microphone signals in the cable will be 6 to 10 dB higher in level depending on what comparison we're making exactly. That's a big advantage when RF interference or hum are a possible concern, e.g. for the type of live concert recording that I do, where there are never any retakes for the recording engineer's sake.

If you expect to use preamps with input transformers, especially if they have a large voltage step-up factor, the 200-Ohm setting may be preferable--but again, we are catering to design limitations here, because in the design of some such preamps, an assumption was made that the microphone's driving impedance would always be in the 150-200 Ohm range, and no allowance was made for a driving impedance as low as 50 Ohms. That's unfortunate in hindsight, but there are some otherwise very good preamps that follow it, unfortunately. They may deviate audibly from flat high-frequency response, and from clean impulse response, if driven by a source impedance much lower than about 150 Ohms. Sometimes this misbehavior can be cured with a benign modification of the preamp's input circuit, but that solution isn't always available.

Since my preamps don't have these restrictions, and are quiet at the gain levels I normally use, I prefer the 50-Ohm setting for my few remaining microphones that have output transformers. It has less chance of clipping the input of any preamp, and it protects the microphone's output stage better from the vagaries of cables--especially long ones which I occasionally have to work with, and/or cables with high capacitance.

--best regards
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on May 06, 2020, 11:58:58 am
Cables do have a sound.
I tested three different cables for my U67.
I first started by listening to each cable over the course of a week by singing and talking.
Then i began recording my results so I can compare them.
This wasn’t scientific i matched three different vocal takes with three different cables and matched the levels the best i could.
Repeating the same few phrases.

Microphone details-
I have a 1963 Neumann U67 with a 1978 K67 capsule which Klaus brought back to life, along with a vintage 1963 NU 67 psu that has been checked by a tech and given a clean bill of health.
I am using a 1968 Telefunken EF806s tube.
My S2 wire on my u67 is not connected.
The u67 was flat (HPF and pad switch Not engaged)

I used the internal mic preamp on an Apogee element 24 interface .
Recorded in Logic X at 24 bit 96 kHz.

Here are the results I heard-
1-Gotham GAC 7 was what came with my u67, rich low frequencies slightly congested mid’s and not enough high frequency presence, a dark sounding cable.

2-1992 reissue also had a rich low end and a nice mid frequency but also lacked in the upper frequencies but i also heard less dimension or width in this cable when compared to the belden and GAC 7

3-Belden was exactly everything Klaus said it was, a match made in heaven.
The low end was tight thick and round and the mid frequencies really had a beauty to them zero congestion,
while the high end frequencies were so silky without being overbearing and no sibilance at all.
Absolutely refreshing.
So I will be selling the GAC 7 and the 1992 reissue cables and most likely purchase another Belden for backup.
Thank you so very much Klaus, because of you I went ahead and bought the Belden and the reissue cable to test and there’s no turning back now.
It was worth my time and money.
Sure you can use eq to get whatever results you want, but for me i wanted the source to be as good as i could possible get it before cutting and boosting.
Ps- the only cable I couldn’t get my hands on was the EMT cable, so I have no idea what that one sounds like.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: RadarDoug2 on May 06, 2020, 05:44:28 pm
How do you get dimension and width from a mono source? I find your conclusions extremely unscientific and unlikely.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on May 06, 2020, 06:41:05 pm
When comparing all three cables, the reissue did not have the same width as the GAC 7 or Belden.
You can hear width on a mono source,
It doesn’t have to be stereo in order to hear how narrow something sounds.
This was my opinion after a week of evaluation, the reissue was the only cable that sounded thinner than the rest.

I mentioned that my test wasn’t scientific, but if you were here listening you would agree.
I’m also not out to try and convince anyone. I am simply reporting my findings and I’m very happy with the results and what I chose :-)
I was going to upload the audio tracks I did but your allowed Only 512kb so I would have to reduce the size which in turn affect quality so what’s the point really.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: RadarDoug2 on May 07, 2020, 04:47:40 pm
In the audio band, cable is cable. If you are using 30 metres or less, in a professional environment, the cable is very unlikely to affect the sound. But dont take my word for it, do the math.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on May 07, 2020, 05:29:09 pm
In the audio band, cable is cable. If you are using 30 metres or less, in a professional environment, the cable is very unlikely to affect the sound. But dont take my word for it, do the math.
I hope Klaus chimes in here lol (I won't! KH)
So you are basically saying that the week of testing I did where I heard differences in each cable was my imagination ?
Or what Klaus has reported in his Reissue tear down article referring to the differences in sound between the four cables he tested was also his imagination ?

Im not sure what math your speaking of, but I can tell you that there is a difference big time.
And if you can't hear width in an audio signal, wether it is acoustic guitar or a human voice, then I question your ears because you said "How do you get dimension and width from a mono source" ?

That tells me: either you are not understanding what I mean, or you can not hear dimension and width in a mono audio signal.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: RadarDoug2 on May 08, 2020, 02:59:14 am
The week of testing you did, how much of it was double blind testing?
Were you in charge of the changeovers?
Did you test on your own?
How long did it take you to change over between cables?
Did you ingest anything between changes?
Was the testing over a period of time more than two hours?
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on May 08, 2020, 10:36:31 am
I stated in my very first paragraph that this was not a scientific test, just a basic vocal recording repeating the same few words with three different cables.
All testing was done by me.
i waited an hour for the mic to warm up, then recording my vocal, power it down and waited an hour before changing cables, i did this for each cable.
I did not eat or drink between vocal takes.
The vocal is 27 seconds each so total time with the mic warming up and cooling down would be 6 hours 1 minute and 35 seconds.

RadarDoug2: this is an easy enough test that you could duplicate very easily, I'm not sure why you are in such disbelief ?
I would have never sold my GAC 7 cable if I didn't hear a difference.
I would suggest that you do your own test, since you remain skeptical.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: gtoledo3 on May 08, 2020, 11:18:18 am
The skepticism comes from the terms being used, which, in my opinion, are not applicable in this context.

When attempting to communicate about these issues, it may be more constructive to work within recognized definitions of terminology, and within what can be explained through real world phenomena. Using that as the foundation, you can have some hope of getting down to real causal factors.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: Derek Samuel Reese on May 08, 2020, 11:43:45 am
Fair enough, i will leave it at this-
I will use other words to describe what i heard- the reissue cable did not sound as full as the other cables, to me it lacked emotion.
I personally chose the Belden cable because it sounded better to my ears.
Title: Re: Neumann U67 Reissue: Complete Tear Down and Analysis
Post by: gtoledo3 on May 08, 2020, 12:01:49 pm
It is a difficult topic for many reasons, but one thing that seems to lead me to some interesting observations is to listen to the quality of the noise floor...bringing it up to a level where it can be easily heard. Be careful with monitor levels, etc.

If the actual sound of the noise floor shifts in a truly discernible way, sometimes it can seem to correlate with perceived differences in the audio output. The frequency distribution of the noise floor can have some interplay with the perceived sound quality of programatic audio. What I personally find interesting about that way of listening, is that sometimes it leads to realizing that certain things can sound cool, but may be inferior in some other way.

I think that aside from that, if you are actually auditioning audio through a given system, it leads to quicker and most solid conclusions to use a constant, looping source, whatever it may be, as opposed to sources that are unique each time, whether it be in performance or minor variances in distance from the mic.

Anyway, these comments aren’t aimed at any particular cable brand, or maybe even particular piece of gear, just general statements.