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Re: resonant frequencies in mic systems

Subject: Re: resonant frequencies in mic systems
From: "Rob Danielson" danielson_rob
Date: Thu Aug 24, 2006 12:29 pm (PDT)
At 10:21 AM -0700 8/24/06, Dan Dugan wrote:
<snip>
>
>  >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.

"Controlled" monitoring is probably the weakest link in the recording 
chain after mic placement and mic/pre.  The end-user controls 
monitoring and this shapes everything.

I used headphones, Sony MDR-V600's mostly (for web discussions like 
this).  I have two other pair, sony 7502, and Senn 280's that I pop 
on at the end to see if there are some discrepancies. They're usually 
pretty much in agreement.

I used to fear that the qualities I was discriminating were 
"monitor-specific." They are, of course, "monitor-centric," but with 
more and more fringe applicability as I learn use the tools. Its all 
we have to work with. The technique helps we understand what the 
mics' prejudices are at the very least.

I'd be curious if you can detect (by ear) some common tones in the 
sound clips from the varied locations:
http://ad2004.hku.nl/naturesound/NielsonSchoepsMSnips7Locs.wav
.

>
>>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.

Higher >1600Hz as a rule and the character varied with amplitude. I'd 
bring up the mid and there would be spots where everything would 
cancel-out and then kick back in. Very odd.  I messed with all of the 
obvious variables, simplifying the chain and some peculiarity was 
always there. As all three plugs did this. I tend to think that 
encoding MS in the field  and decoding in post is probably not the 
best of options. Rob D

>
>-Dan Dugan
>






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