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Discussion Starter #1
When using REW simply to test speaker response, I don't need the impulse test at the start of the measurement sweep. It seems to cause an unusual bump in the sub-30Hz range, probably caused by reflections in the room. (I intend to test in the open air later anyway to get rid of room effects.)

Is there a way (or can there be one added) to disable the impulse test at the start of a sweep?

Thanks in advance.
 

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There is no "impulse test", only the sweep. If you are using a loopback connection for soundcard correction there is a connection check on that channel (1kHz tone), but nothing else. If you are getting clicks before or during the sweep it may be a problem with something causing the soundcard buffers to underflow, try a shorter sweep or altering the buffer size on the soundcard settings and make sure nothing else is running.
 

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Discussion Starter #3
Thanks. I'm definitely getting two clicks out when using the MacBook Pro internal audio system. This happens even if I just run a sweep with the built-in speakers/microphone.

Because it happens on the internal sound I/O, there's no buffer or other settings (aside from volume, which is set in Audio Midi Setup). So that eliminates that from the equation.

If the program is doing an open() of the sound output device at the start of the sweep, it could be a driver issue---they may be configuring the sound output during the open and causing the click. Just a guess.
 

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There are replay and record buffer settings on the REW soundcard settings tab, try setting both to 16k if they are not already set that way.
 

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Discussion Starter #5
Aha. New information now. Still using just the internal speakers and mic on the MBPro. I'm changing

Set to 32k, I get two clicks at the start of the sweep. Tick-tick-sweep.

Set to 16k, I get one click. Tick-sweep

Set to 64k, I get three (the third is quite low, but it's there). Seems like tick-tick-----tick-sweep, where time to the third tick is twice the time as between the first two.

The playback buffer is what makes the difference. Record buffer doesn't affect things. It's definitely an output artifact.

Hopefully you've got something to go on.
 

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Discussion Starter #6
I'm gonna run another test with the FireWire MOTU 828MkII, now that I understand REW better. Maybe my original problems were operator error.
 
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