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Author Topic: KM84i output level (vs km184)  (Read 297 times)

afterlifestudios

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KM84i output level (vs km184)
« on: December 30, 2019, 03:17:10 pm »

I have a pair of km84i.  Both mics are strapped for 200ohm.  The switchable 10db pad circuit is intact and functioning, but switched off currently.  (ie. no attenuation.)
Both mics are about 10db lower output/sensitivity than my km184.  (20db lower if pad engaged.)
Is this difference in output level/sensitivity between km84 and km184 expected?

(update: I do not think these have the internal resistor pad installed.  photo attached.
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David Satz

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Re: KM84i output level (vs km184)
« Reply #1 on: December 30, 2019, 08:19:11 pm »

The sensitivity of the KM 84 (standard 200 Ohm setting) was specified as 10 mV/Pa. That of the KM 184 is 15 mV/Pa, which is only about 3.5 dB greater--not 10 dB.

--best regards
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klaus

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Re: KM84i output level (vs km184)
« Reply #2 on: December 30, 2019, 10:01:58 pm »

If the output is indeed 10dB higher, the remaining ca. 6dB difference could stem from the inline soldered pad resistors soldered onto the circuitboard of the KM84.

Make sure their solder tabs (backside of the component side of the circuit board) are bridged with solder, not open. In case of doubt, measure the resistance across both 47Ω pad resistors (R11, 12). It should be zero ohms for full, European-delivery output strapping.
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Klaus Heyne
German Masterworks®
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afterlifestudios

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Re: KM84i output level (vs km184)
« Reply #3 on: December 30, 2019, 11:15:37 pm »

Thank you, gentlemen.  The 47ohm resistors have been removed and the traces have been bridged with solder.  But the work is sloppy, and the two traces are actually bridged.  (continuity on DMM)
That can't be right?
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afterlifestudios

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Re: KM84i output level (vs km184)
« Reply #4 on: December 30, 2019, 11:57:13 pm »

Update.  I severed the solder blob between the two traces in the above photo.  Now I have the correct level!  (about 3db down from km184)

BUT...  That's only one of the km84's.  The other mic, the 47ohm pad resistors are gone and the traces are bridged cleanly.  Something else is causing the problem in this one...  Anywhere to start looking?
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klaus

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Re: KM84i output level (vs km184)
« Reply #5 on: December 31, 2019, 12:07:39 am »

Interchange capsules and see whether the lower output of the second KM84 follows the capsule, or stays with the mic amp.
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Klaus Heyne
German Masterworks®
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afterlifestudios

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Re: KM84i output level (vs km184)
« Reply #6 on: December 31, 2019, 01:18:25 am »

Thank you, Klaus.  In the process of swapping capsules I noticed two things.
1. the "pin" from the capsule was quite black on one mic.  (Cleaned it.)
2. On one mic, the two sides of the "female" receptacle for the capsule pin were bent slightly, and the pin was actually not going in between the two sides.  Just pushing up against the outside of one side.  I carefully bent them back into canter so the pin now inserts between them.

The mics are now 3-4db and 4-5 db below the 184.  (the difference follows the capsule.)

This is with fairly crude measurement technique.  (1khz tone from speaker with mics on quick clips on the same mix stand.)
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klaus

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Re: KM84i output level (vs km184)
« Reply #7 on: December 31, 2019, 02:33:48 am »

A ±1dB difference between KM84 heads is well within Neumann tolerances (±2dB). Enjoy!
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Klaus Heyne
German Masterworks®
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