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Author Topic: Barking up the right tree?  (Read 6153 times)

Tim McCulloch

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Re: Barking up the right tree?
« Reply #10 on: March 15, 2012, 10:10:45 am »

I think you're not hearing what we're saying. Having your mic not be in a ground plane causes reflections off the floor to interfere with the measurement. Do a ground plane measurement. Use a sheet of plywood over the seats, or a console case lid, anything bigger than say 4'x4'. The tip of the mic should be as close to the surface as you can get, with as much of the flat surface out in front of the mic as possible. I doubt those dips are in the processor. For them to have been in measurements throughout the venue leads me to believe they are part of your measurement technique. Do not use a mic on a stand for venue magnitude response measurements.

Mac

+1.  The screen shot has the tell-tale signs of an invalid measurement.
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Jay Barracato

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Re: Barking up the right tree?
« Reply #11 on: March 16, 2012, 08:37:40 am »

It is easy to discern a dip caused by EQ from a dip caused by cancellation:
A dip by EQ can be filled with EQ, so if you suspect a voicing problem, bring up 1K by about 6dB, if it comes back roughly 6dB, its EQ,
if it comes back only 1dB or less its cancellation

and for the record:
a graph without scaling is worthless


Uwe

Sorry, if this sounds rude, its to late, I should be sleeping

Boosting the eq is also my quick check.

I am not sure the ground plane is always better. If I am doing a quick pre-show check in a theater with installed seats, the ear level measurement is often cleaner. I guess I could use a box cover or something to create a ground plan on top of the seats but that is just one more thing to haul around.
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Jay Barracato

Tom Young

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Re: Barking up the right tree?
« Reply #12 on: March 16, 2012, 03:18:39 pm »


In that line, could one employ a PCC mic for measurement purposes?

No. PCC microphones would be disqualified for measurements because (first of all) they are cardioid, which would skew phase (and frequency) reponse considerably and (secondly) they are not really as close to pressure zone/ground plane as we would like. The capsule is oriented 90-degrees to the ground plane, so there will be a small, but real, bounce. This, of course, would only skew HF's.
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Tom Young
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Re: Barking up the right tree?
« Reply #12 on: March 16, 2012, 03:18:39 pm »


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