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Discussion Starter #1
How can different Distance settimgs for the Sub be seen with REW ??
Is there a simple way to see the difference

I had the FR of Mains ,... Then did 2 sweeps of Sub alone at different Distance settings 12'and 18' and saw no diff compared to mains ??
 

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Delay settings will not make any difference to the frequency response of the sub alone, it is only in combination with a main speaker that you will see an effect in the response.
 

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Discussion Starter #3
Delay settings will not make any difference to the frequency response of the sub alone, it is only in combination with a main speaker that you will see an effect in the response.
Yes , i took the FR of the Mains alone first then compared to 2 sweeps of the Subs ,one at 12' and the other at 18' , they were identical compared to Mains ??

Maybe something im not doing right ?
 

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You won't see a difference in frequency response unless you measure with both the sub and a main speaker running, the delay changes affect how the sub response and main response add when both are producing sound. If you are looking for timing shifts in the impulse responses you need to provide REW with a timing reference by connecting a loopback between the unused soundcard input and output channels (e.g. the left channels if you are using the right channels for measurement) and ticking the box on the Analysis preferences to "Use loopback as timing reference".
 

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Discussion Starter #5
Ok Thanks John !!
I will try this like u said , 1 sweep with both Sub and mains (sub at 12'),... Then another with sub at 18'
...would the Flattest FR = best delay ?
 

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Discussion Starter #6
One other question ; while my Sub amp SA1000 is powering both identical subs at equal dist to MLP its not using its internal Crossover but Ii am using the Amp's 1 filter (-8db at 51hz ) though does this creat delay ??
 

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Flattest is what you are aiming for. An alternative to making a measurement for each delay setting is to set REW's signal generator to Pink PN, then use the RTA set to:

Mode: RTA 1/48 octave
FFT length: 65536
Averages: None
Window: Rectangular
Max Overlap: 93.75%
Update Interval: 1

to view the response live as you adjust the delay setting. You can ignore the amp's filter setting.
 

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Discussion Starter #8
OK i will try the first method then try to figure out the method u just described.

I' m pretty new to all of this !

Thanks for responding John !!!!
 

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You won't see a difference in frequency response unless you measure with both the sub and a main speaker running, the delay changes affect how the sub response and main response add when both are producing sound. If you are looking for timing shifts in the impulse responses you need to provide REW with a timing reference by connecting a loopback between the unused soundcard input and output channels (e.g. the left channels if you are using the right channels for measurement) and ticking the box on the Analysis preferences to "Use loopback as timing reference".
I am using a USB microphone and my laptop sound card output. Will loop back be effective in this setup as there must be a DAC delay in the mic different from the sound card? Is the RTA analysis you mentioned the best work around?
 

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A loopback cannot be used with a USB mic, but it isn't needed anyway - the aim is to see what effect delay adjustments have on the frequency response when both sub and main are running, delays in the mic path don't affect that. You can either make measurements at various delay settings with sub and main both running or use the RTA approach.
 
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