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Re: Matching electrets

Subject: Re: Matching electrets
From: "umashankar" umashanks
Date: Sat Apr 6, 2013 6:10 am ((PDT))
I will describe how I have done it, using adobe audition (other editing pro=
grams will also work).
Message: 1. 
Subject: create a 10 second silent file. zoom into the centre of the file till 
yo=
u can see individual samples as dots. drag the dot up to full scale, and sa=
ve the file - this will be very precise click file.
=A0
Message: 2.
Subject: connect your mic to a pip powered circuit (do it so you can change 
capsul=
es easily - I use pigtails which can be twisted) place the mic close to a s=
peaker (a headphone in contact with the mic will do for matching capsules) =
start recording the mic input and play the click. you will now have a recor=
ding of the click.
=A0
Message: 3.
Subject: number your capsules, and produce one recording each.
=A0
Message: 4. 
Subject: bring your recordings into the computer. open one file at a time, and 
se=
lect just the click recording. in Audition, you use "frequency analysis" wi=
ndow. you=A0can open upto four such frequency analysis=A0samples from four =
wave files, super imposed on each other, and in different colors.=A0 you ca=
n compare=A0sensitivities very easily. as bonus you get=A0frequency respons=
e too so you can actually match the capsules for sensitivity and frequency.=
 having only four is not a problem, just drop the outliers, add two more ea=
ch time.
=A0
=A0
umashankar=A0


>________________________________
> From: klangstrand <>
>To: 
>Sent: Saturday, April 6, 2013 2:55 PM
>Subject: [Nature Recordists] Re: Matching electrets
>
>Thanks for excellent input everyone!
>I think I will go for the multimeter-solution.
>I am currently on the EM172=B4s and getting the 470 ohm across the pad 1 a=
nd 3, with a variance of 2-3 (469-472)
>So am I right that the capsules should be within 0.1 of eachother (f.ex 47=
Message: 0.
Subject: 1 and 470.2)? If so, I need a better multimeter.
>Secondly, if this is right, am I right to assume one would be lucky to get=
 a matched pair out of a batch of ten capsules?
>Sorry for my lack of insight BTW, I=B4m working on it:-)
>Best
>-Anders
>
>
>
>--- In  "Mike Rooke" <> wrote:
>>
>> Measure pad 3 to pad 1 note the resistance, sort pairs that match to wit=
hin 0.1R or better.
>> Confirm selection in a 94 dB calibrator once the leads are attached.
>>
>> -M
>>=A0
>>
>> --- In  "rock_scallop" <john_hartog@> w=
rote:
>> >
>> > Hi Anders,
>> > I am not sure what the best or easiest way is but this is what I did t=
o make pairs from ten em172 capsules - the capsules came with leads already=
 soldered on.
>> >
>> > Number each capsule with a marker to keep them straight.
>> > Make a test fixture - stereo cable with screw terminals to easily swap=
 out capsules.=A0
>> > Record a stereo recording of each EM172 capsule beside a single refere=
nce capsule. In this case for the reference capsule I used an EM158 I had l=
ying around.
>> > Open each recording in your audio editing software (I used Adobe Audit=
ion 1.5), run a frequency analysis of a section of each, copy the data to t=
he clipboard, and paste it into a spreadsheet (I used MS Excel.) You may ne=
ed to adjust the frequency analysis resolution to limit frequency divisions=
 to a manageable number of data points. I do not know if "copy to clipboard=
" is a common feature with other editing or analysis software.
>> > In the spreadsheet, subtract the left (reference) channel from the rig=
ht (EM172) of each set to find the differences in frequency response.
>> > Plot the points to make a graph showing the differences from reference=
 of all ten capsules, and use that to decide the best pairing.
>> >
>> > It will be interesting to hear how others have done it.
>> >
>> > John Hartog
>> > oregonsoundscapes.com
>> >
>> > --- In  "kronseth" <anderslangstrand@=
> wrote:
>> > >
>> > > Hi everyone!
>> > > Sorry if/that this question has been raised probably infinite times.=
. So I have received a batch of electrets, both omnis and cardioids.
>> > > The ones I have bought before have come in matched pairs, but this t=
ime I=B4ll have to do it myself.
>> > > I understand there a quite a few ways of doing it. Anyone has a pref=
erred method?
>> > >
>> > > Best
>> > > -Anders
>> > >
>> >
>>
>
>
>
>
>------------------------------------
>
>"While a picture is worth a thousand words, a
>sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
>
>Yahoo! Groups Links
>
>
>
>
>
>








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