Neumann u87 vintage circuit frequency response

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kingkorg

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Joined
Apr 15, 2017
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1,252
Location
Norway
Hi mates.

I just got an u87 with ruined capsule to try to fix. The first thing i did was to measure frequency response of the circuit to compare it to my clones, and some other mods, and i kind of got shocked. I used several different inject points suggested by people, and the result was the same. -3 to -4 db attenuation at 20KHz.

Nowhere near -10db at 20KHz suggested by a lot of people. However these -10db work great on my mics with 797 capsules, and few other. They match well with u87 takes. I am also puzzled as i have read that original Neumann capsule is actually even brighter than chinese replicas.

The mic i have is an old, black u87 with isolated backplates. That one should have even stronger HF de emphasis than newer ones. 

I would have solved this puzzle immediately by putting original capsule into a flat mic, but it's unfortunately ruined. 
 

RuudNL

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Joined
Apr 26, 2009
Messages
2,486
Location
Haule / The Netherlands
This is the original Neumann U87 specification:

Voltage gain (1 KHz, 1 Kohm termination) -4 dB
Rel. gain 40 Hz.  -3 dB  (+/- 1 dB)
at 16 KHz.  -4 dB

Measured through the 'messeingang'.

I think -10 dB at 20 KHz is a bit too much...
 

Khron

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Joined
Apr 8, 2010
Messages
2,041
Location
Finland
Sounds about right.

http://audioimprov.com/AudioImprov/Mics/Entries/2014/2/7_Mic_Electronic_Eq_Pt.1.html
 
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