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 31 
 on: April 05, 2019, 08:48:55 pm 
Started by klaus - Last post by klaus
Microphonics encountered in the use of microphones, especially in sensitive condenser microphones, is still a relatively unexplored and little-understood subject. But their detrimental effect on the sound of a mic is considerable, and should be addressed.

A microphone becomes microphonic when any of its components other than the capsule’s membrane resonates in response to  sound waves, and the parasitic signal thus triggered interferes with the signal captured by the capsule.

Microphonics in microphones can be grouped, in descending order of annoyance, and I give suggestions how to eliminate them:

Tubes. The assumption that tubes selected for microphones are quieter, longer-lasting, or feature other qualities compared to non-selected ones is false. F. ex. Neumann’s EF86, AC701, 13CW4 or VF14 M selected for low-microphonics, and identified as such with a special label or a stamp, are usually identical with the same tube type, except their filament construction went through a ‘pinging’ test. Samples with lower than average microphonic tendencies were then selected out as suitable for use in mics.

Pinging a tube by flicking a finger against its body midway, while you hold the tube to your ear, is an excellent method to pre-select a microphone tube. Nothing fancier is needed to predict whether the tube is likely to be triggered into ringing inside a mic.

All tubes resonate or ring to a degree, due to the various unsecured wire filaments inside, so the goal is to find the specimen with the lowest resonance. If even a light knock will trigger extended ringing, the tube, once installed, will become a serious obstacle to a clean recording.


Passive components.  When resistors, capacitors, switches, wires and other microphone components are not secured from vibrating, they will contribute microphonics to the output signal of the mic. Usually, good mounting and soldering techniques will prevent components from ringing, but sometimes free-standing parts need to be secured with an adhesive that connects them to adjacent components or to the circuit board.

I use Eclectic E6000 to prevent components from vibrating. This Styrene-based glue stays flexible, can be removed completely and without residue, and with one pull, and has an extremely high electrical resistance, preventing any lowering of high impedance circuits in condenser mics.

Other often overlooked causes for microphonics.

* Mono-filament wires. They should not be used as capsule lead-outs. They can hum like a bass guitar string

* Mechanical switch contacts in attenuator and pattern switches. They should not be free-floating, but their contact tongues
   should rest against a firm surface

* Mesh layers of double or triple-layer head baskets.  One of them should be slightly bent inward or outward, so that the layer rests
  firmly against an adjacent one, to prevent resonating                                             

The ultimate test whether you successfully removed all sources of microphonics: hold the mic against your ear and knock its housing with your knuckle. If all you can hear is a dull thud, you are done.

You will appreciate the added clarity the mic delivers once microphonic artifacts are removed from the signal.

© Klaus Heyne 2019

 32 
 on: April 02, 2019, 11:39:42 am 
Started by klaus - Last post by David Satz
A forward-facing cardioid is (1 + cos θ)/2, a backward-facing cardioid is (1 - cos θ)/2, and a figure-eight is simply the cosine function by itself.

If you subtract a backward-facing cardioid from a forward-facing one, the two half-"1"s cancel each other out, while the two half-cosines reinforce one another to become a whole cosine--a figure-8. That assumes that the microphones are well matched and that their directional patterns have a common center point.

 33 
 on: April 01, 2019, 11:23:40 pm 
Started by klaus - Last post by opacheco
That sound interesting set up!

Do exist a method o way in order to simulate the response or the resultant pattern of  an array like this conforming 4 Cardioid Mics for a Blumlein System with the control for each Cardioid??...I mean use a Geometric Angular Graphing in order to get the Directional Pattern in a cylindrical type plot.

What would be the angular equation for something like that mics arrangement?

Thanks


 34 
 on: March 30, 2019, 03:47:42 pm 
Started by Spindrift - Last post by Spindrift
This post is related to the recent thread regarding snipping the jumper on the C414EB to lock it to 48V and ease the load on phantom supplies: 

https://repforums.prosoundweb.com/index.php/topic,37331.msg538131.html#msg538131

Does the AKG C451EB have a similar modification which can be performed which limits it to a 48V supply?  48V is the standard in phantom supplies in this day and age and I'm looking to lessen the load on my phantom supplies when employing these mics. I understand that the C452 was the strict 48V model but I'd like to not have to go hunting down more mic bodies.

Thanks,
Keith Banning

 35 
 on: March 28, 2019, 05:49:57 pm 
Started by mikezietsman - Last post by klaus
Kai,
Can you check your messages. please?

 36 
 on: March 28, 2019, 12:08:02 am 
Started by klaus - Last post by uwe ret
053292 is the correct order number for the K47 capsule (not used in any current microphone model, replacement part for vintage Neumann models)

 37 
 on: March 27, 2019, 06:59:03 pm 
Started by klaus - Last post by afterlifestudios
Whoops! Typo. It’s 053292 they offered...  Sorry.

 38 
 on: March 27, 2019, 02:50:57 pm 
Started by klaus - Last post by uwe ret
Part # 053282 does not show up in the Sennheiser/Neumann data base of part listings for any capsule. It actually is the part # for an obsolete Cheese head screw KB30x6.    
 

 39 
 on: March 26, 2019, 08:36:38 pm 
Started by klaus - Last post by afterlifestudios
Thanks Uwe.  So is this k47 053282 which I was offered by Sennheiser Canada some old stock? (Does Neumann only make k49 now?)   Any thoughts as to which is preferable - since I seem to have a choice?

 40 
 on: March 26, 2019, 08:19:45 pm 
Started by klaus - Last post by uwe ret
053291 - K49      : dual-sided, (dual wires)  - currently used in M149 Tube
053223 - K47fet  : dual-sided, (single wire) - currently used in M147 Tube and U47 fet
514753 - K49fet  : one-sided, (single wire) - currently used in TLM149

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