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Author Topic: Using music or other signals as source for Dual Channel FFT Analysis  (Read 6554 times)

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jfont

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I note that the Dual Channel FFT Analyzer will only run when the its own excitation signal generator is enabled. Also, it does not "see" any other signals sent to the selected Output device, not even those generated by FEAT's own Signal Generator. So the only way to measure transfer function is by using the its excitation signals. This seriously limits its functionality for sound system evaluation, which sometimes has to be conducted during actual performances. Is there a method to do this?. Any ideas how to get around this limitation?. It would be nice to be able to measure system response with any excitation source without having to physically patch the computer audio output to an input, thus losing an input channel.

FaberAST

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Re: Using music or other signals as source for Dual Channel FFT Analysis
« Reply #1 on: November 30, 2009, 09:27:13 AM »
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I note that the Dual Channel FFT Analyzer will only run when the its own excitation signal generator is enabled.
That is only the case if you have selected an output channel for your source or reference signal, and you don't have any Signal Generator tools using that same output channel. If you select an output channel for your measurement, there won't be any measurement made, unless there is some signal being applied to that output channel.

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Also, it does not "see" any other signals sent to the selected Output device, not even those generated by FEAT's own Signal Generator.
That's not correct. You can use the Signal Generator tool rather than the DFFT's built-in generator. You just need to be sure you are using the same output device and selecting the same output channel(s) on that device.

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This seriously limits its functionality for sound system evaluation, which sometimes has to be conducted during actual performances. Is there a method to do this?
You can measure the transfer function between any two input channels of your selected I/O device. Perhaps, I don't understand exactly what your concerns are. If that's the case, please clarify, and I'll try to do a better job of addressing them.

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It would be nice to be able to measure system response with any excitation source without having to physically patch the computer audio output to an input, thus losing an input channel.
Internal excitation sources must come from within the Toolbox. As indicated, you can use the DFFT's built-in excitation, or an excitation from a Signal Generator tool (which includes audio files played back via the AUAudioFilePlayer Audio Unit plug-in). Obviously, any external excitation will require an input channel of your I/O device.

Ben