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I guess the waterfall indicates that I have some serious issues around 60hz
When you see a waterfall with a correct decay of signal over time (as you have at 60Hz) in the first 300msec, and then a narrow signal jutting out of nowhere, it is usually an indication of noise, and not a room problem. You would likely see this noise if you examined the spectrum without any stimulus from a sweep. 60Hz is especially curious since it is associated with hum.

Take a non-sweep spectrum reading of your system and see what you get.

Read this post to give you idea of how to do that.

brucek
 

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here is spectrum with no signal running (black graph) (was that was I was supposed to do?)
Yep, but I see no noise out of the ordinary, so I can't really account for the ringing you had at 60Hz in your waterfall, other than it may have been something turned on at the time that caused it (refrigerator, etc).

Try another waterfall and it may be gone. be sure to do your testing at 75dBSPL at the listening position, so you can then see the level of noise ringing (if there is any). Anything below about 55dB you can ignore.

Your response seems fine though. It doesn't extend too low (around 35Hz), but it seems fine.

brucek
 

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now the ringing effect suddenly appears to be gone, and then it appeared again a little while later.
Yeah, could be something turning on and off.

The one with the heaviest dips is unfortunately the center position... Could that be due to cancellation between my two main speakers or something?
Those are fairly sharp dips. Narrow sharp dips are hard to detect by the human ear.

Hopefully, you're not using a soundfield in your receiver to get the center channel measured. The receiver must be set to stereo only. Any soundfield will operate its steering with phase and so the results are to be ignored since REW is a mono signal.
To get the Center to play, you must disconnect a main speaker and plug in the center in its place. You can have the other main playing if you want to check for interaction.

brucek
 

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the three different seating positions(left, center, right
Ahh, OK, my bad. I thought you were referring to cancellation from mains to center channel.

Anyway, it's too bad you can't identify how they define bandwidth and Q. Then you could associate it with a particular equalizer that uses the same math in REW.
What you're doing though seems to be working.

brucek
 
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