Making Sweeps of Gear with FuzzMeasure Pro
« on: January 29, 2010, 01:53:13 AM »
Hey guys, I figured out a way to use FuzzMeasure Pro to make sweeps of gear and just wrote a quick tutorial.

I put it up on my blog: http://blog.benlindell.com/?p=112

Here's the text version:

The last couple of days I’ve been posting frequency responses of the EQs I’m building at the moment. I used to just use white noise and a Pro Tools plug-in to make estimates of what was going on but I wanted a more accurate idea of what my gear was doing. I’ve used FuzzMeasure Pro before for measuring room acoustics but hadn’t used it for measuring gear yet, I’ve heard it was possible but hadn’t found any specific instructions on how to do it, with some playing around I think I’ve found a good method for testing gear with this awesome piece of software.

My setup is simple, a Digidesign 002r and some TRS to XLR cables. I think the ability to use

96kHz is a huge benefit as it lets you sweep up to 48kHz (see Nyquist). Hopefully you already know how to get your interface working with FuzzMeasure.

  • With my 002 I run CoreAudio and then set the sample rate in Audio Midi Setup.
    IMPORTANT: Set the output level pretty low, FuzzMeasure outputs at or near 0dbFS which means any boost to the signal distorts the results.
  • Launch FuzzMeasure Pro.
  • Audio Capture Settings: I use input and output 5, this way I never have to listen to the sweep and I never use those for anything else but testing gear. Turn off Device Correction, we’re going to calibrate before we start sweeping.
  • Sine Sweep Settings: check out the settings I use. The duration does effect the quality of your sweep.
  • Connect the input to the output and press Measure, this will be our calibration. Go to Frequency>Export Frequency Graph Data. Name the file Calibration.txt. (the .txt is the important part)
  • Now go to Window>Microphone Calibration and press the plus sign. Find that Calibration.txt file you just made and press Open. Now in the top part of that window select Calibration.txt for the Calibration Record.
  • Press Measure again. The resulting Sweep will be pretty darn close to flat. For me it usually drifts a tiny bit below 20hz and a little more so around 40kHz but it’s close enough. You’ll also notice that this puts the magnitude centered around 0dB, making all our measurements even easier to see.
  • Now connect your gear, put everything into bypass and press Measure again. This will give us a baseline for the rest of the tests and you’ll see if the gear is doing anything funny while in bypass.
  • At this point I like to lock down the axis of my graph. Go to Frequency>Set Graph Extents I usually go with 10Hz to 30000Hz and -20dB to 20dB. Be sure to then set Frequency>Lock Graph Extents otherwise it’ll automatically change the scale to fit each measurement.
  • Now tweak your gear and take measurements whenever you want.

Hope this little guide will help you get an accurate picture of what your gear is doing. Also hope you guys don't think this is blogspam, just trying to do my part with helping the community, it's much easier to write and post with pictures in wordpress.


Re: Making Sweeps of Gear with FuzzMeasure Pro
« Reply #1 on: January 29, 2010, 05:39:54 AM »
nice one! thanks ben :)

I use fuzzmeasure 2 though cause I'm still on osx 10.4  ;D
As far as I read fuzzmeasure 3 Pro is 10.5 compatible.
I assume the technique you described can also be applied in version 2.

I also found this (http://www.supermegaultragroovy.com/products/FuzzMeasure/gs/index.html) that also explains how to
measure the impedance, which is a nice thing I believe  :)

w.

Re: Making Sweeps of Gear with FuzzMeasure Pro
« Reply #2 on: January 29, 2010, 11:12:49 AM »
yes it works with version 2 as well, I don't use any features unique to version 3


 

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