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[klaus]

"Eine Schwalbe macht noch keinen Sommer", the saying goes (one swallow does not a summer make), but what I just experienced is quite astonishing, given the sorry state of Neumann K870/K87 capsules of late:

Tonight I installed a brand-new K870 (build date late 2012), and my jaw dropped:

Both sides of the capsule are lush, reedy, frequency-balanced, with a full-figured bass, and are extraordinarily musical. Only the very best K67 from the mid 1960s (the famous 'fibre board' model) could hold a candle to this one. This capsule was so exquisite and similar on both sides (very rare, for any LD dual-membrane capsule, from any period) that I still don't know which of the two sides to make the front side for cardioid operation.

I am hoping and praying that this is a trend, and will report what the next new K870 capsule portends.

Disclaimer: the electronics of the U87Ai which I installed the capsule in are heavily modified; so while this capsule could mitigate some of the stock U87Ai's electronic compromises (which I find especially unsatisfying since circuit diagram 05), it cannot overcome them all.

[soapfoot]

Klaus, this is great news. I really appreciate your sharing of your experiences with things like this-- you see far more of these capsules than most of the rest of us do, so it's good that you keep us abreast of developments. Please let us know if you see evidence of this as a trend (as opposed to an anomaly).

[Jim Williams]

Those '05 SOIC daughter pcb preamps do really sound poor. Best case is to remove that and re-populate the identical pcb with original design components, not too hard to do.

[klaus]

Agreed. And simple enough to do (see previous discussions about how too).

[soapfoot]

I installed a brand new K67/K87 capsule in one of our three U67s yesterday. The old one had a wrinkled rear diaphragm and severe gold loss on both sides (though the front side, interestingly, still sounded fine!)

Once we've used all three for awhile, I'll return to give my impressions of the sound of the new K67 capsule to see if my impressions are positive relative to the other, older K67s in our other two mics.

[soapfoot]

The early 2013 Neumann K67 we installed in our third U67 a couple of weeks ago sounds (so far) very much like our other two U67s (with original capsules).

It's possible that my ear is not as discerning as Klaus's, and it's possible we need even more time to evaluate before an undiscovered subtle difference manifests itself, but... thus far, impressions of this new Neumann capsule are very favorable-- it does not seem inferior in any way to our other U67s.

[NelisB]

Hi Klaus,

Was the capsule you reviewed a K870/K67 (three wires) or K87 (four wires) capsule? My friend just ordered one, he could choose from a 3- and a 4-wire type. I guess that has to do with the isolated backplates?

Thanks, Niels

[klaus]

It's clear from my post you cited that I was referring to a K870/67 (three wires), not a K87 (four wires).

There is no build difference between the two types of Neumann double backplate capsules. They always sounded similar in any given era.

The type of lead-outs or the backplate spacer configuration (aluminum-conductive, or plastic-non-conductive) does not affect the sound, though it could be argued that the lower polarization voltage applied to a K87 will ameliorate the harshness of the capsules of that era I was complaining about.

[NelisB]

Hi Klaus,
About a year ago Ben Sneesby wrote me that one of the reasons for the "inferior' sound of the U87ai, (next to the electronics) is that the diaphragm tension is too high. Do you think it's possible that a lowered tension of the diaphragm causes the renewed sound of your new K870?

Have you used more K870's in the meantime?

Thanks, Niels

[klaus]

It is my opinion that the diaphragm tension causes most of the hardness in the mids and the lack of low end. There are secondary issues with the quality of late model U87Ai sub-boards (starting with circuit #04) but as soon as you pop in a good capsule, even in a brand-new mic, half of the problems are gone.

I have not installed enough recently made capsules to have a firm opinion whether the tension issue has been solved*, but if the trend of the ratio of frequency-balanced capsules to hard-sounding capsules continues, we are on the right track. I will report back when I have enough of a statistical sample to generalize with confidence.

*for those with little time to read on: as of February 2021, the tension problem has not been solved.

[NelisB]

Hi Klaus,

Thanks for your reply.

I have two U87ai's that I hardly ever use because of non-musical sound. Rens Heijnis already changed the electronics what made them better, but still they dont make me smile. I guess your 80% must be the right figure. 

An option I am thinking about is -instead of buying new expensive capsules- is to get my capsules reskined by Thiersch. Can you recommend reskinning? Maybe Thiersch can also get the capsules matched.

Thanks, Niels

[soapfoot]

I've never heard a re-skinned Neumann capsule that actually approached the sound of a good Neumann.
I've heard one of Mr. Thiersch's excellent M7-style rebuilds, and it sounded to my ear very much like Thiersch's excellent new capsules, but (especially being the Mylar version) it did not sound exactly like a good vintage Berlin M7. I've never heard his take on the U87 though.

We once were auditioning some FET 47s, and one had the capsule re-skinned by another very reputable person (not Thiersch-- I won't mention the name). It was so far inferior to the mics with original capsules (despite being in equal or better overall condition) that it was returned despite being significantly lower in price.

By the way, the early 2013 era K67/K870 we installed in our third U67 has been in heavy use, and nobody has once commented that it sounds significantly different (certainly not inferior) to our other U67s (which have original 1960 era capsules). All three have good Telefunken EF86 and are used completely interchangeably-- nobody has picked any of the three as "favorite." This is a testament to the sound of the new capsule, in my mind. Mission accomplished, as far as I'm concerned.

[klaus]

I am in agreement about the uniformly inferior performance of third-party diaphragms mounted on Neumann capsules.
And I can offer first-hand experience with Thiersch-reskinned K870/67: They do not represent the Neumann sound, or even an alternative sonic interpretation that, in its own way, would sound equally or more pleasing than an original Neumann K87/67.

I would also be suspicious when someone offers re-diaphragmed capsules that were restored to supposedly "Neumann specifications" by these third-party providers (Neumann does not offer re-diaphragming services).

[NelisB]

Brad and Klaus,

Thanks a lot for your info!

Best, Niels

[hasbeen]

I've never heard a re-skinned Neumann capsule that actually approached the sound of a good Neumann. I've heard one of Mr. Thiersch's excellent M7-style rebuilds, and it sounded to my ear very much like Thiersch's excellent new capsules, but (especially being the Mylar version) it did not sound exactly like a good vintage Berlin M7.

Then what hope is there for a U47 owner who needs an M7 replacement?

[klaus]

One of the bottlenecks to currently produce a PVC M7 that sounds like a real one (Neumann or Gefell): is the toxic chemical formula that was used until the early 2000s (at least in East-Germany, West-Germany had abolished the material already a decade earlier).

The new stuff has a different, environmentally sound, molecular structure, and somehow that has "colored" the sound differently than the old formula. How else to explain that both MG's and Thiersch's PVC M7 have that same mid-band harshness, no air but a hard ceiling around 7-8 Khz, and inarticulate lows?

I believe both companies do what they can with the PVC they have available. And it's good enough, unless you ever heard a real M7, even only ONCE. Then you can never go back and be satisfied with the current PVC product. And, a consequence of so many people having never heard a real M7 is that they think the current stuff is good and authentic. What a problem to overcome!

[soapfoot]

Then what hope is there for a U47 owner who needs an M7 replacement?

I'll let Klaus weigh in on this, but the Thiersch PVC replacement ("blue line") is an excellent capsule. I used one in a microphone I built for myself and I absolutely love it, and it's captured much of the spirit (to my ear) of the original M7. Probably not identical, but an excellent-sounding capsule in its own right.

[Jim Williams]

China may be an answer to reproducing PVC capsule diaphrams. They don't follow EPA or CE enviromental restrictions there. If Gefell set up a shop there, who knows what could be made? Seems about every other audio company has set up a shop there and if instructed and provided the correct formulas they could be successful.

Mogami is a perfect examle. Their soft, special rubber cable coatings are illegal to manufacture here but not in the far east where enviromental restrictions are not yet in place.

[method1]

I know this thread is old, but I'm wondering if that was a one-off experience or have you experienced a general improvement in k870 capsule quality?

[SergioA]

+1. I feel this deserves some follow up.

[klaus]

China may be an answer to reproducing PVC capsule diaphrams. They don't follow EPA or CE environmental restrictions there.

So their lives and good health are less of a consideration, just because they live far away?

[mikezietsman]

Just a bump for interest.

Klaus - has the post 2012 Era capsule ushered in a step up in consistency of the quality of the k870/k67?

Thanks,
Mike

[klaus]

Thanks for the reminder to update my initial impressions.

As you may know, a constant trickle of factory-new U87Ai come through here- they serve as starting point for my modifications. They also allow me to take the pulse of this model through the years- many tiny changes are continuously introduced in this mic, from the way the attenuation switches are labeled, to the quality of the capsules.

Speaking of capsules: I wish I could report that all is well now, and that an overwhelming percentage of K87/870 capsules is now frequency-balanced and full-bodied in the lower register. They probably all pass Neumann's ±2dB test, but there are still too many of these capsules which take the time-consuming effort to "enrich" their low end far enough, so that the overall sonic impression is no longer harsh, midrange pointy, and congested, i.e. lacking musicality, however you want to define musicality.

The reason why this is so frustrating for me: there are current-production K87/870 capsules which sound extraordinary in their musical and emotional enticement, right out of the box. These capsules are on par with the best that Neumann produced in the early decades of the U87 and its predecessor, U67.

So it's obviously not a systemic issue pointing to a need for a change in design*, but more likely a quality-control or selection issue. I wish I knew how Sennheiser selects and rejects during production, but I don't. But the variable seems to be connected to diaphragm tension, otherwise I would not be able to often dial-in better performance on some of these harsh-sounding capsules by relaxing the diaphragms.

Bottom line: Neumann is still capable of making the absolutely best LD capsules in the world, but it's still too much hit and miss for my taste how individual capsules come out. I wish the company would return to the manufacturing and/or selection methods employed before ca. 2000-whatever they were-when an overwhelming percentage of K87/870/67 was "in the ballpark".

*Stephen Paul once wrote a critique of the new lapping method Neumann started using in the early 1990s (?) which replaced the less-exact gapping between diaphragm and backplate through plastic spacers. I do not believe that that change has anything to do with the quality issues discussed in this thread: Neumann has successfully used backplate lapping for decades without any audible detriment.

[Recording Engineer]

So there is a possibility that this may actually truly be a bean-counting, time is money, kind of issue; be it a sanctioned company policy or simply implemented by a manager?

[klaus]

Yes, that is a possibility, but the general public, me included, would never find out, so I see no purpose in speculating why there is still such range in response from capsule to capsule.

Neumann's Uwe Sattler may chime in here, and remind everyone that his former company still has the tightest tolerance of any capsule manufacturer. That is indeed true. But as I recently posted on another forum, "within spec" is still a 4dB tolerance range from capsule to capsule (±2dB).

I would love more bass in K870, so that most capsules end up on the (+) rather than (-) end of allowable tolerance. Hell, I would even buy Neumann's rejects that fall outside the tolerance on the plus side. Makes my job that much easier.

[Recording Engineer]

I only mention it because it seems everyone always wants to quickly blame everything that's "wrong" on the big-bad-wolf-bean-counter; but here's a real case where it seems to truly be a possibility this time.

[klaus]

The larger picture to keep in mind:
Neumann is the only mic company supplying spare capsules for mics that were first sold in 1951!

So, even if the mercenary aspect may be blamed for the perceived deterioration of some of these capsules, I am grateful that this is not AKG or Schoeps which won't even work on mics that were discontinued only a few years ago. Or try Sony or Microtech Gefell which won't supply parts or service for ANY of its condenser mics-old or new- in the U.S.

[Recording Engineer]

Unless it has changed in the last few years, I believe you can still purchase Sony capsules for C800, 800G, and C38B. I bought a pair of C38B capsules directly from them about 3-years ago. But yes US customer service is absolutely non-existent!

[FoxFoxFox]

Hey Klaus, wondering about buying a 2000's U87. What year were the capsules not sounding right? Thanks.

[klaus]

For the answer please read my opening post #1, and update, #23.

[kamamuri]

Thank you for such invaluable info. Is the capsule in the new U67 reissue the K870/K67? (as far as I know, there is no new capsule available as spare on the Sennheiser site).

[klaus]

Yes, it is. And the U67 Reissue's response, as that of the U87Ai, is largely affected by the individual response of the actual capsule installed.

[kamamuri]

Thank you.
Then my hope is the new batches of capsules of a $7K mic should be better in terms of consistency. I really don't know if I should buy a new K870 for my 1961 U67, wait a little more, or try a vintage second hand and cross fingers (even though, at this point, all choices seems a cross-fingers-matter to me!).

[klaus]

I sympathize with your predicament, and am afraid the news is not good for you and anyone who hopes that the same capsule installed in the $7k U67 will be better or different than when it's installed in the $3.5k U87Ai.

If my complete tear down and analysis of the U67 reissue (permanent article posted on the first page of this forum) is any indication, the ills that plague the K67/870 capsule have not been cured: high diaphragm tension on still too many of them.

There is a way to reduce the tension and, for a balanced response, bring it into a range of past K67/87 generations, but it is laborious and expensive.

[kamamuri]

In any case I'm glad to be here to face the facts (in spite of these disappoint my expectations). Education first. Thank you Mr. Heyne.

[gtoledo3]

So, how do you test the diaphragm tension of an assembled capsule, or do you just listen empirically?

It always seems a little circumspect to me to peg difference down to just that. Small differences in the size of holes in the backplate for instance, etc., could seemingly make as much difference in end frequency response.

It also seems like low tension can be a bad thing... one of the first things to make a capsule sound bad, IMO, is low tension that starts to result in a capsule being overly sensitive to plosives.

[klaus]

So, how do you test the diaphragm tension of an assembled capsule, or do you just listen empirically?

I listen... and I have recently had the resonance frequency of two brand-new, 2021-made K49 capsules tested, to prove the difference (between mid-1960s frequency-balanced tension and current bass-starved performance. I will soon post the data. KH Feb. 2021

It always seems a little circumspect to me to peg difference down to just that. Small differences in the size of holes in the backplate for instance, etc., could seemingly make as much difference in end frequency response.

I know it's the diaphragm tension, because once I relax an overly tight diaphragm, the capsule behaves and sounds just right. If it were something else, relaxing the diaphragm to levels of tension found in former times would not bring the capsule into compliance.

It also seems like low tension can be a bad thing... one of the first things to make a capsule sound bad, IMO, is low tension that starts to result in a capsule being overly sensitive to plosives.

Of course. I speculate that too many K870 were too close to that limit, so they were selected out and rejected, which cost the company too much money, which caused the company to increase diaphragm tension, which reduced the amount of rejects, but which made the capsules sound less pleasing.

I am sure that I will find out some day soon what's behind the change.

[gtoledo3]

Very interesting, thanks for that response!

[RuudNL]

Today I had the opportunity to compare a brand new Neumann TLM67 to my own U87ai microphones.
Although at first I was a bit sceptic about the TLM67 (I am not a real fan of the TLM series), the microphone sounded good.
The TLM67 microphone had a full low end, compared to the (2016) U87ai microphone I compared it with.
Since the capsule heads are exchangeable, I tested the TLM67 capsule assemby on the U87ai.
This resulted in a much better LF response. Measurements confirmed this, the difference at 40 Hz. was more than 4 dB!
So, has Sennheiser/Neumann improved things lately?

[klaus]

So, has Sennheiser/Neumann improved things lately?

I posted a reply on Gearslutz yesterday that sums up my current impression:

Extreme cases of diaphragm hypertension that I encountered in late 2017/18, and in the U67Reissue I tested and wrote about are getting rare.

It's the average that still concerns me: too many people continue to send me current-issue capsules to reduce the tension back to 1960s level. It's time-consuming and not lucrative, but an interesting project I continue to refine and improve.

I have been in communication with Neumann about this for years now, and, who knows, maybe a systematic change has occurred, or it's just a fluke. It will take a few more months to tell which.

[soapfoot]

For what it's worth, we got a pair of U67 reissues and, after replacing the tubes with good NOS Amperex mesh-plate EF86s, they perform very much like our three vintage originals.

Well enough that we use them interchangeably, except on stereo sources, where we actually prefer the reissues as they sound very well identical.

[klaus]

Good for you. As I keep saying: bass-starved K67 are popping up here and there, with no rhyme or reason, and in between perfectly fine samples.

If you find that the Reissue is interchangeable with the vintage U67, it would be interesting to find out what capsule is in the vintage. It may already be a replacement K67, as none of the original K67 made from 1960 to about 1965 was ever lacking in gorgeous bass response.

[soapfoot]

At least one of our vintage U67s does have a replacement Neumann K67--not of extremely-recent vintage, however.