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Pete Cofrancesco May 9th, 2007 01:01 PM

Microphone Specs
 
What are the most important specs?
How do you read them and what do they mean?
Do they mean that much? (I know in other technologies they can make the numbers appear good no matter what.)
I'm thinking of noise ratio and sensitivity.

Ty Ford May 9th, 2007 09:27 PM

Sensitivity is good.

Lavs are less sensitive than other mics because their diaphragms are smaller.

Selfnoise is important; lower selfnoise is better.

Pattern is important; cardioids, hypercardioids, omnis, figure of eight.

They seldom talk about actual patterns, off-axis frequency response and phase response.

What I'm saying is, you asked a really big question. The answer to which is that specs are frequently written to make the mic look better than it really is.

You can make some silly mistakes by buying a mic based on specs alone.

Regards,

Ty Ford

Pete Cofrancesco May 10th, 2007 09:48 PM

Let me narrow it down. What do the numbers mean? For example here are the specs from two mics I own:

AT822
OPEN CIRCUIT SENSITIVITY -45 dB (5.6 mV) re 1V at 1 P
SIGNAL-TO-NOISE RATIO 70 dB, 1 kHz at 1 Pa

Oktava MK012
Sensitivity 10mV/Pa
No signal to noise ratio listed

Steve House May 11th, 2007 05:14 AM

Quote:

Originally Posted by Pete Cofran (Post 677056)
Let me narrow it down. What do the numbers mean? For example here are the specs from two mics I own:

AT822
OPEN CIRCUIT SENSITIVITY -45 dB (5.6 mV) re 1V at 1 P
SIGNAL-TO-NOISE RATIO 70 dB, 1 kHz at 1 Pa

Oktava MK012
Sensitivity 10mV/Pa
No signal to noise ratio listed

The first spec means that the mic outputs 5.6 millivolts when subjected to a 1kHz tone at a sound pressure level of 1 pascal, which is the equivalent of about 90dB SPL. This voltage corresponds to a signal level of -45dB if the 0dB reference point chosen is 1 volt. At the same time, the mic itself is generating internal noise that is 70dB below the desired output, or -115dB referred to the 1 volt zero level.

The Octava generates a stronger output voltage with the same sound level but the fact that they don't tell you the SN ratio means you have no idea (from the specs) if it's going to be usable or not.

A mic mfgr that doesn't list full specs is one to be suspicious of when plunking down your cash. Not that their products might not be okay but you have to wonder what they're trying to hide.

You can find a lot of info on www.microphone-data.com

Bill Hamell May 11th, 2007 06:46 AM

Something that confuses me is...
"SIGNAL-TO-NOISE RATIO 70 dB, 1 kHz at 1 Pa"

Given equal specs what would be better than the listed spec.

SIGNAL-TO-NOISE RATIO 60 dB, 1 kHz at 1 Pa

or

SIGNAL-TO-NOISE RATIO 80 dB, 1 kHz at 1 Pa

Bill

Pete Cofrancesco May 11th, 2007 07:51 AM

i found this article. i'm still reading through it. i didn't realize all math/science thats behind it.

http://www.dpamicrophones.com/Images/DM00665.pdf

"The signal to noise ratio, or S/N, expresses the relation between a reference sound
pressure level and the A-weighted equivalent noise level (self-noise). The reference
sound pressure level is 94 dB re. 20 μPa. Hence the signal to noise ratio is 94 dB
minus the equivalent noise level."

From that I'd gather that 94 db would be zero noise, so the lower the number the higher the noise. Although, I'm not clear on what S/N would be considered good, average, and bad.


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