K47 vs K67 Capsule Type Mics

And What is Wrong with Many K67 Capsule Type Mics

I often use the phrase “Neumann-esque” to describe my work. Here’s what I mean: a mid-focused mic with a present, but not peaked top end and a usable, but not excessive proximity effect.

In large diaphragm Neumann mics, the basic “Neumann family sound” is achieved through either the K47 capsule / flat response circuit topology or the K67 capsule / HF de-emphasized topology (there are a few exceptions, but I’m mainly taking about the K47 capsule mics like the U 47 and M 49 and the K67 capsule mics like the U 67 and U 87).

A quick backstory regarding the U 67 and U 87 -

Neumann answered a need for a mic that could be used for close-up rock and roll vocals by developing the U 67. This mic was designed to have more headroom, less bass and less top end sibilance compared to the earlier U 47. These benefits were achieved by using a two-part topology – a K67 capsule with a peaked HFoutput followed by a high frequency de-emphasis circuit.

This combination created a pre-emphasis / de-emphasis system within the mic that increased headroom, lowered noise and sibilance while providing a means of shaping the overall timbre balance from bottom through top end. The basic two-stage pre-emphasis / de-emphasis topology was carried through to the U 87 FET mic from the tube-based U 67.

I mention this backstory because I was recently searching through Matt McGlynn’s Recording Hacks microphone database. I was amazed to find so many K67-type capsule mics listed. But so few of them incorporate the second stage of the U 67 / U 87 topology: HF de-emphasis! And that's a problem...

...When a K67 type capsule with its 8 dB @ 8 kHz peak is followed by a flat response circuit (no HF de-emphasis in other words) the result is a mic with a strong HF peak at 8kHz that is out of balance with the octave below and octave above.

As a side note – part of the reason the C12 sounds “right” to many folks is that its smoothly rising HF response offsets the naturally occurring decline of HF energy in most acoustic sources (and also counters the Fletcher-Munson effect: our hearing is less sensitive to bass and extreme treble as volume decreases).

But a non de-emphasized K67 type capsule has a big 8 KHz peak that jumps out – I hear it as too bright, unbalanced and often sibilant (sibilance reduction in the U 67 and U 87 occurs through the use of negative feedback in the mic to notch-out those sibilant frequencies and restore the proper timbre balance – the “Neumann-esque” sound).

When you’re thinking about filling out your mic locker you may want to think in terms of basic capsule types – K47, K67 or AKG CK12. While I have a preference for the “Neumann-esque” sound, I do respect the sonic achievement of the C12 mic and its value in a broadly appointed mic locker (I just don’t make those kind of mics).

But within the Neumann family sound you can ask – “Do I have the K47 / flat response circuit sound covered?, Do I have the K67 / de-emphasized HF circuit sound covred? "Are my K67 type capsule / flat response circuit mics too bright and sibilant - perhaps just wrong-sounding?

best, Michael