# How to pick the best volume tradeoff during cal?



## tonyptony (May 20, 2007)

With the movement of some room furniture I felt like I needed to re-do my sweeps and recal my system. I had the following problem before, but I don't think I ever resolved the correct approach...

I'm using an E-mu 0404 USB mic preamp; pretty nice unit for the money. When I first got it I calibrated the inputs to determine just at which point on the input feed volume adjustments (both channels) the preamp would begin to roll off the input signal response. I have those points marked for both the mic input and the comparison signal input.

During sweeps I find that in order to stay at this "optimum preamp volume" point I have to raise my actual stereo preamp volume so that I hit a number of room resonance points during the sweep. So the question I've had is whether it's better to do a sweep that way, or sacrifice some preamp response and raise its volume, so as not to get quite so loud a set room resonances? The actual stereo volume during the sweeps is generally only a click or so louder than what I'd call my average listening volume (really not that loud, but the sweeps come through louder than music)

The output sweeps are used for DRC generation of calibration files.


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## brucek (Apr 11, 2006)

> at which point on the input feed volume adjustments (both channels) the preamp would begin to roll off the input signal response.


Roll off the signal response. It is likely just me, but I can't figure out what this means?

brucek


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## tonyptony (May 20, 2007)

brucek said:


> Roll off the signal response. It is likely just me, but I can't figure out what this means?
> 
> brucek


That is to say, I found the point at which the volume adjustment on the E-Mu started causing the calibration signal (the one in the E-Mu) to begin showing signs where its normal flatness begins to roll off. The calibration signal in the E-Mu shows flat -.2dB or so under a good part of the input volume adjustment range. But beyond that point it starts to roll off pretty rapidly, where maybe an extra notch further along the captured trace is now about .5dB down in the lowest octave and a little over 1dB down in the highest octave. I figured that's the point at which the amplifiers in the E-Mu begin to lose their flat frequency response characteristics. Put the input volume adjust at about the 3:00 position and you're way past capturing anything accurately. So with the mic feed going into one of those inputs, is it better to tradeoff raising the speaker volume and stay in the flat range of the E-Mu - but excite the room modes more - or lower the speaker volume but now maybe lose accurate frequency capture at either end?

It may depend on how well DRC can recognize room mode interactions and maybe take those into account when calculating the correction filters.


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