Many measurements already, which graphs to post?

[Sonic Icons]

Hi,

I just set up REW and took some measurements of the surround sound system in my living room. Thanks for the excellent help files and forum tips, especially about setting up the SoundBlaster Live! USB card to work with REW. The system includes 5.0 speakers at present (no subwoofer yet). I am interested in adding acoustic treatments, i.e. "bass traps" or "acoustic panels" on the walls; maybe adding subwoofer and acoustic treatments at about the same time. I was able to measure every speaker, through the multichannel analog inputs of my Marantz SR5500 AVR, at six room positions (left, center, right "on couch" positions, also left, center, right "in front of couch"). So that's 6*5=30 measurements in all, and many graphs can be generated from each measurement, such as FR, spectral decay, waterfall. I would like suggestions on which graphs to post first.

I realize that a good drawing of the room and system layout will also be helpful; am working on that.

[Wayne A. Pflughaupt]

Welcome to the Shack!

People usually post subwoofer graphs on this Forum for some feedback on their response, and how to proceed with equalizing. We don’t get too many graphs of main channels, but if you want to post some, I’d say start with FR charts for the front left, right and center as measured from the primary listening position.

Regards,
Wayne

[Sonic Icons]

OK, here are the front left, center, and right speakers measured at the listening position. The couch was moved back 30 inches to allow placing the tripod-mounted SPL meter where the couch usually sits. The vertical scale is 25 dB to 85 dB rather than 45 dB to 105 dB because the lowered vertical scale fits my results better. I didn't change the pre-impulse response window from "Hann" to "Tukey 0.25" (missed those "REW tips" when acquiring the speaker responses) but did change the "Pref-ref Window width" to 125 ms. Front left, right = Phase Technology V12, center = Phase Technology V8.

left
si_left1.jpg
center
si_centre1.jpg
right
si_right1.jpg

[Sonic Icons]

Wow, the attachments worked

[brucek]

Those are very good responses for main speakers. Even the center has good low end response.

I guess you can see a consistant peak around 40Hz that could be eliminated with equalization in a sub. Even though the mains extend quite low, it's not possible to do a lot of correction with treatments at the very low frequencies. This is where it's nice to add a sub with the mains set to small and then use an equalizer to correct the sub.

brucek

[Sonic Icons]

Thanks for the comments. I can see now that one advantage of using a sub with other speakers set to small, & some reasonable crossover frequency like 70 to 80 Hz (in my system), is easier electronic equalization in a range where practical acoustic treatments don't work well. (Well maybe filling a good fraction of the room volume with acoustic absorbing fiberglass would get rid of that peak at 40 Hz, but most people wouldn't consider that practical.) I've also noticed that many mid-priced subs have a built-in one-band equalizer to help with rooms like mine.