Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[Avgatzeblouz]

I remember reading on a Neumann forum someone from the company stating these 3 capsules were sonically identical, the only difference being electric. Could that be true ?

[klaus]

Two versions of the acoustically identical capsule, first introduced in the U67 in 1960, exist:

K67/870: no electrical separation between the two backplates. Figure-eight pattern is achieved by doubling the voltage to the rear diaphragm.

K87: electrical separation of the backplates, whereby figure-eight pattern is achieved by only energizing the rear diaphragm, not the rear backplate.

In theory, all K67/87/870 should sound identical because their physical dimensions and operating principle are the same. In practice these double-backplate capsules can vary greatly:

1. Polarization voltage of 47VDC (U87) causes a different electrostatic behavior of the membranes than pulling them with 60VDC (U87Ai, U67)

2. Subtle and not so subtle material and production changes through the years and versions of these capsules cause audible differences (read past threads about this).

3. Even performance differences of same era, same version capsules can be quite large, due to the handmade manufacturing process Neumann uses: build-specifications allow a maximum tolerance, capsule-to-capsule, of 4dB across the frequency spectrum (±2dB @1kHz).

[Avgatzeblouz]

Hi Klaus, and thank you for sharing again your great knowledge. I'm in the process of building a pair of vintage U87 "clones", and contacted sennheiser Canada : a K87 is 1400 $ CAD !!!!! Can I use a K67 instead, or would it require too much a change in the circuit, making it therefore more a degradation than a benefit ?

Thanks again.

[klaus]

The price seems high. U.S, prices are currently at or below $800.-

Yes, you can use a K87 instead of a K67. All you need to do is connect the two backplates.
You can do that by either stripping off the insulation sleeve off one of the four screws which hold the two capsule halved together, or you can simply bridge the backplates with a bare wire held down by screwing a couple of screws into two adjacent backplate threads- one in each backplate half.

[Avgatzeblouz]

Hi Klaus, just to make sure, did you mix it up while typing ? My question was about using a K67 instead of a K87 in a 87 circuit, not the other way around.

[klaus]

Oops, as you Americans would say...

Yes, I described the reverse scenario from yours, which unfortunately does not offer an easy solution: adding a 6µ insulation spacer and four insulation sleeves for the screws is not possible, unless you had these parts left over from a decommissioned K87.

[Avgatzeblouz]

Thanks a lot, you are a great help, as always.

[Derek Samuel Reese]

Old thread I know, but something came to mind..
If you have a healthy 1963 original k67 capsule and a healthy 1973 original k67 capsule  will they sound different from each other ?
Will there be a quality difference or any kind of difference?
I realize that no two u67’s sound the same even when they are both from the same period so did I answer my own question perhaps ?

[klaus]

You can safely assume that, originally in 1973, a 1973 K67 will sound exactly like a K87 would have sounded of that same build era. But time may have done all kinds of numbers on diaphragms and other parts of the mic, (contrary to speculation, diaphragm tension is not among them).

So, you are right, it's hard to get a baseline. But this much is clear: During both eras-the early 1960s, and early 1970s- Neumann produced large diaphragm capsules that had exceptionally good, mediocre, and a few not so good quality (that is on the highly elevated scale of Neumann's quality control!)

[gtoledo3]

You can safely assume that, originally in 1973, a 1973 K67 will sound exactly like a K87 would have sounded of that same build era. But time may have done all kinds of numbers on diaphragms and other parts of the mic, (contrary to speculation, diaphragm tension is not among them).

So, you are right, it's hard to get a baseline. But this much is clear: During both eras-the early 1960s, and early 1970s- Neumann produced large diaphragm capsules that had exceptionally good, mediocre, and a few not so good quality (that is on the highly elevated scale of Neumann's quality control!)

Klaus, are you asserting that capsule manufacturers who indicate that tension loss happens over time, or people who send in mics to be serviced because of the diaphragm losing tension, are simply all incorrect? Interesting hill to stand on. Does it continue to be speculation if it has been measured? It may also be worth remembering that not everyone exerts the caution you advise in mic placement on loud sources or general care. I have no doubt many well cared for specimens should not exhibit much if any perceivable change, but then again this is a forum that seems to flesh out the finest, smallest possible differences in performance of audio equipment.

[Derek Samuel Reese]

You can safely assume that, originally in 1973, a 1973 K67 will sound exactly like a K87 would have sounded of that same build era. But time may have done all kinds of numbers on diaphragms and other parts of the mic, (contrary to speculation, diaphragm tension is not among them).

So, you are right, it's hard to get a baseline. But this much is clear: During both eras-the early 1960s, and early 1970s- Neumann produced large diaphragm capsules that had exceptionally good, mediocre, and a few not so good quality (that is on the highly elevated scale of Neumann's quality control!)

Wow, ok well this is where my brain is going, You repaired and cleaned up my 1978 capsule and brought back to life the sound i heard before sending it to another tech who was incompetent.
I consider myself extremely fortunate to have made your acquaintance and i was blessed to have you work on my 1963 U67.
The moment my microphone came back it sounded like magic all over agin, sensual and robust.
So i ask a ton of question because i am very curious but i am really content when i pull up a chair to record my acoustic guitar or when i sing my little heart out.
Again i take the time to tip my hat to you Klaus because your brilliance brought me to tears when i heard my microphone.

[gtoledo3]

After seeing the very laudatory post - I feel I should add....I also feel Klaus has a depth of knowledge about microphones that is second to none, and has done work that has captivating sonic results.

My scrutiny of fine points of mic technology is only out of a love for the field and the continued pursuit of greater knowledge. Ultimately, sometimes even experts come to disagreement through unrecognized differences in context or more subjective factors.

[afterlifestudios]

Seeing this thread made me want to take a peek at my “pair” of old (non “a”) U87’s capsules.
One head assembly has the “kk 87 a” badge with serial number as expected, and the capsule looks good.  The other U87 has no badge on the head assembly, but a serial number baked into the plastic.  It also has epoxy over one of the fastening screw holes, leading me to believe it’s never been opened.  Not feeling like I should open it just out of curiosity?  (It sounds great!).
Any info to be learned from what’s visible?

[klaus]

The blue seal over one of the mounting screws on the clear plastic switch assembly is not a Neumann seal, but possibly one of mine, which I attach as condition of my warranty. 
The white head is possibly from a late 1970s U87, judging from its serial number. The "A" in the serial number is not related to the U87A.

[afterlifestudios]

Thank you Klaus.  I always favoured that u87 slightly over the other.  Perhaps it was because of your handiwork on the capsule. (Likely a cleaning?)
The one slightly strange thing to me is that the serial number on the non-white head and body is lower (older) but it has the baby blue 50 Ohm impedance dot on it.  The one with the late 70’s white head has the red 50 Ohm dot.  Does that make chronological sense?