Walt--
I agree, the measurements may not be ideal for uses where
considerable gain (micing distance) is required but putting self
noise and sensititivity together does seem to reveal the more
transparent mics. I found the below website handy when trying to
weigh self noise and sensitivity at once. Note you can change the
sorting criteria.
http://www.microphonereview.com/miclist.asp?F_Sensitivity=&F_Noise=&F_SPL=&F_LLF=&F_ULF=&order=Microphones.%5BNoise+Level%5D%2C+
Wouldn't it be great to see a spec list ranking mics by transparency
and cost-- the best mics for nature recording under $200, $500, $800?
Of course, they'd have to be ear tested but one might be able to
narrow it down to a couple dozen mics with the numbers.
Rob D.
= = = = = =
Walt wrote:
>Rob Danielson wrote:
>>
>> Thanks for the clear explanation Walter!
>
>Just remember it was pretty simplistic, I don't claim to be a expert on
>mic spec measurements. Just some rough rules I've worked out in trying
>to read specs. Once I have a mic in hand, I work out different rules for
>using it without worrying about the numbers too much. Practical ones
>from what I get when it's hooked up in my system.
>
>> Number-wise, my simplistic understanding is that mics capable of
>> excellent transparency (especially in low sound level environments
>> where high-gain is common) will almost always possess sensitivity
>> ratings higher than their self noise ratings. For example, the
>> Sennhesier MKH-20 has 10 dB Equivalent Noise Level (A-weighted) with
>> a Sensitivity of 25 mV/Pa+/- 1dB. The AKG 414 is 14/12-- only 4dB
>> more inherent noise but ~13dB less output. The difference in
>> transparency in field recordings made with the two mics is dramatic.
>> Walter, know how sensitivity is measured? Something to do with the
>> gain required to achieve a certain output,..?
>> Rob D.
>
>I had not thought about that relationship, but I suppose it might be so.
>Or maybe the two specs just relate to other aspects of the mics.
>
>I'm not near as clear on all the methods of sensitivity measurement.
>Every time I think I understand it, some specs throw a wrench in that.
>Most of the sensitivity measurement systems are giving you some idea of
>the output of the mic when exposed to some calibrated sound level.
>Generally for most of it higher numbers are better. Though that may be
>too simplistic. You have to be real careful you are comparing the same
>measurement between two mics.
>
>Here's a few links I've got in my bookmarks connected to the subject,
>none really cover all of it:
>http://www.shure.com/support/technotes/app-sensitive.html
>http://www.audio-technica.com/using/mphones/guide/charact.html
>http://www.cs.columbia.edu/~hgs/rtp/microphone.html
>http://members.aol.com/mihartkopf/index.htm
>
>There's plenty more can be gleaned using web searchers. A lot of it
>about as clear as mud. Or incomplete. Part of the problem is that
>manufacturers consider those specs as selling points or ad copy. And
>will choose measures to show their mics of in the best light. Another
>problem is there are regional differences in testing mics. The Japanese,
>for instance will test and report in different ways from the Europeans.
>
>One thing to note is that the measurements are mostly related to the
>sound levels of voice at close distances. I'd really like to see some
>other measures, like say, how many feet out the mic could pick up a
>standardized sound signal in a usable manner. Or even just do the same
>tests but at a much lower sound level. Which would be more use for us.
>It would be much harder to standardize such a test. And would take a
>whole bunch of discussion to even agree what to test there.
>
>Probably the best source (at least by the sound of it) is the newly
>released Microphone Book which has tried to provide standardized specs
>for a large number of mics. I've not gotten a copy as it's pretty
>expensive, but it's tempting:
>http://www.microphone-data.com/
>
>Walt
>
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