REW and time delay from active speakers - Home Theater Forum and Systems - HomeTheaterShack.com

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post #1 of 4 Old 03-19-17, 06:24 PM Thread Starter
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REW and time delay from active speakers

I have been playing with REW and also some other room correction software like Dirac (test version).

However I never was really happy with the results so I stopped using oder buying something in that direction.

No I have heard that active speaker often have digital amps and they would produce some time delay which is exactly what >I observed trying to run my active speakers as "front" within a 5.1-System where the rest of the channels would be provided by a regula AVR.

I have a time delay of about 80 ms in my rememberance, but I am not exactly sure. (Will have to re-do the measurement).

NOW my question: Will a delay between the sweeping source and the output from the speaker influence my measurement results???

Running REW involves these frequency-sweeps. As I understand REW, the mic picks up the signal and provides data in form of a time-Intensity diagramm which is then fouriertransformed in a frequency-Intensity diagramm.
If there is a delay, the Mic may "think" it is measuring a 400 Hz-Signal, meanwhile it is still the 390Hz-Signal, which just comes along a little later....

Thanks for hints on this topic in advance.

System: ADAM Tensor full active Speakers, audiolab pre-amp and CD-player, also USB-Input (which would benefit from some room correction done in the computer).
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post #2 of 4 Old 03-20-17, 09:50 AM
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Re: REW and time delay from active speakers

REW is measuring acoustical output, so any delay introduced electronically by an active speaker in front of the drivers will be accounted for. (That said, I don’t know why any speaker would be generating 390 Hz delayed compared to 400 Hz.)

Ultimately it’s no different than the distance of speakers close to the measurement mic (i.e. surrounds) compared to speakers farther away (i.e. front speakers). If your active speakers are delayed, REW will merely “see” them as farther away.

Regards,
Wayne
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post #3 of 4 Old 03-20-17, 12:35 PM Thread Starter
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Re: REW and time delay from active speakers

Thank you for your answer, which is very informative. Indeed, the effect would be the same as if the speakers would be far away (about 20 to 30 meters).

My assumtion was, that REW starts the sweep, begining with the low frequencies, and that the question which f is in the room is taken from the f-t-table. In this case the mic may have "thought" that the incomming signal is 400 Hz wheresas due to delay just the 390 Hz are at the speakers.

If you say that REW figures out the frequency from the input signal - than delay does not matter.

However, the sweep is quite fast. Is there a way to have it running slower?
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post #4 of 4 Old 03-20-17, 01:29 PM
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Re: REW and time delay from active speakers

It can be run slower, but there is no real benefit to that (at least as far as this issue is concerned). Once the sound emanates from the speaker, that is “ground zero,” not any delay that might have happened in front of it.

Regards,
Wayne
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