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Re: resonant frequencies in mic systems

Subject: Re: resonant frequencies in mic systems
From: "Dan Dugan" dandugan_1999
Date: Thu Aug 24, 2006 10:46 am (PDT)
>Tim Nielsen wrote:
>  >Rob, am curious what software you're using to look at the
>>frequencies, are you using a sonogram or a RTA plugin of some kind?
>
>Hi Tim--
>By ear first. The resonant frequencies in the mic/system are subtle,
>sustained tones. To help me "tune" my ears for your mics/your system,
>I edited quick snippets from each location in your file,
>
>http://www.wildecho.com/Filechute/Schoeps%20MS%20Stereo%20Sample.wav
>
>so that I could listen for the tones that seem to stand out in all of
>the recordings/settings. Here that is:
>
>http://ad2004.hku.nl/naturesound/NielsonSchoepsMSnips7Locs.wav
>
>Then I took the pink noise section about 3.55 in and created a narrow
>band of parametric EQ in Eqium. Next I move a +4dB boost curve and
>slowly up and down the spectrum in the range I believe I'm hearing an
>exaggerated tone. When I think I've found the most pronounced one, I
>see if I can lower its volume until the pitch sounds more in balance
>with the adjacent tones. This process usually reveals another tone
>that seems exaggerated. I repeat the process until only very subtle
>tones stand out when I fade up the volume. To offset subjectivity
>somewhat, I usually perform this step 2 or 3 times from scratch with
>a new Eqium plug to see I'm finding the same notes each time. With
>this pariculat mic rig, there seem to be about 8 resonate tones in
>the mid mic that repeat across the locations  (3 tries) and 5 or 6 in
>the side mic.  This does not include the high Hz hiss/graininess in
>the two mics.

How did you listen? It seems to me that the bumps and valleys in your 
monitor system would dominate over more subtle effects in the mics.

>I hoped to output the EQ'd result but I found that decoding from MS
>to LR and then back from L-R to M-S did not work well with three
>separate plugs designed for this.  There were some fairly pronounced
>phase oddities created.

In what frequency range? M-S theory has to break down at the top end 
where the mic spacing is significant.

-Dan Dugan





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