Correct Speaker Setup for REW Room Measurements

[mattel]

Hi all,
Newbie to REW and forum. I have an Emotiva XMC-1 using Dirac. I want perform a before/after room measurement comparison using REW. In order to take the "before" measurements of the mains and surrounds should I set the processor to one of the Pre-sets and turn off the subwoofer? In reading REW 101 HTS under measurements, the example uses L+R+Sub. Or did I misunderstand?

 

[Matthew J Poes]

Hi all,
Newbie to REW and forum. I have an Emotiva XMC-1 using Dirac. I want perform a before/after room measurement comparison using REW. In order to take the "before" measurements of the mains and surrounds should I set the processor to one of the Pre-sets and turn off the subwoofer? In reading REW 101 HTS under measurements, the example uses L+R+Sub. Or did I misunderstand?

You don’t want to turn the sub off. What you can do with REW is use the ASIO driver and then just measure the respective speakers. If you have never used it, ASIO with HDMI and Windows 10 is a serious PITA.

Another option is to just sweep the left or right speaker using the java sound instead as that include the software as well. IF all you want to do is see the before and after measurements of the mains and subs, this is fine.

To see the flatness that you see in DIRAC you will need to remeasure exactly where you did with Dirac. Then average all of those. A lot of people thought DIRAC was not working because they ran Dirac with 8 measurement points that were very far apart. Then measured at just one point, the primary listening position, and found the corrected response still looked quite bad. In fact If you average you will find a disturbingly flat response with DIRAC.

I hope this helps.

 

[mattel]

You don’t want to turn the sub off. What you can do with REW is use the ASIO driver and then just measure the respective speakers. If you have never used it, ASIO with HDMI and Windows 10 is a serious PITA.

Another option is to just sweep the left or right speaker using the java sound instead as that include the software as well. IF all you want to do is see the before and after measurements of the mains and subs, this is fine.

To see the flatness that you see in DIRAC you will need to remeasure exactly where you did with Dirac. Then average all of those. A lot of people thought DIRAC was not working because they ran Dirac with 8 measurement points that were very far apart. Then measured at just one point, the primary listening position, and found the corrected response still looked quite bad. In fact If you average you will find a disturbingly flat response with DIRAC.

I hope this helps.

Matthew, thanks so much for the info.

When taking REW measurements, bass management and the cross-over (80Hz in this case) are bypassed? So, if I select the mains for measurement in REW, only the mains will be swept?

I am using HDMI with ASIO. Finally got it to work after buying a UMIK-1.

Yes, I did perform the measurements in the exact location as was performed with DIRAC. I did 9 measurement points covering a cube measuring 13"Hx28"Wx16"D. Is that okay?

My current goal is to optimize my 2 subwoofer locations for smoothest response. But I started with these measurement to try to educate myself about REW. Figuring you have to learn how to crawl before you can walk, so to speak.

 

[Matthew J Poes]

Matthew, thanks so much for the info.

When taking REW measurements, bass management and the cross-over (80Hz in this case) are bypassed? So, if I select the mains for measurement in REW, only the mains will be swept?

I am using HDMI with ASIO. Finally got it to work after buying a UMIK-1.

Yes, I did perform the measurements in the exact location as was performed with DIRAC. I did 9 measurement points covering a cube measuring 13"Hx28"Wx16"D. Is that okay?

My current goal is to optimize my 2 subwoofer locations for smoothest response. But I started with these measurement to try to educate myself about REW. Figuring you have to learn how to crawl before you can walk, so to speak.

So the bass management isn’t bypassed by ASIO or REW. If you select the left speaker then both the subwoofer and left main speaker should work (assuming you have the speaker set to small with a crossover point set). However If you directly select the subwoofer channel your processor sees that as an LFE channel signal and only sends it to the sub. If you want to see the subs response without the mains, that should work.

If you want to optimize the sub placement I would actually suggest turning the crossover point as high as possible and turning DIRAC correction off. then measure the subwoofers. Also don’t assume that a position that has the smoothest response for each individual sub would yield the smoothest response for both together. That isn’t necessarily true. While I would measure them individually, also make sure to measure them together as well. Also before moving them, try flipping the phase on one or the other sub. You never know what will be smoothest until you try.

Finally, be sure to keep an eye on the time alignment. While precise time alignment of the subs is not as important as being in phase, I’ve seen some measurements recently that suggested that the time alignment was just too far off.

To look at time alignment you can look at the excess group delay and minimum phase delay as well as the spectrogram set for wavelet. I happen to find the wavelet the best option myself. It’s very intuitive.