Some more ideas for you to consider.
Apologies about the room mode calculator not working above 200hz. Actually that's probably a practical limit for modes anyway -- so I shouldn't have mentioned 'a room modes calculator' for 200-800hz it at all.. If you want to see the numbers higher anyway, you can go back to http://www.bobgolds.com/Mode/RoomModes.htm
, push the SHOW OPTIONS button, and enter a hz value after "show frequencies less than".
Originally Posted by Gooddoc
I have GIK 3.5" treatments at the 2nd reflection points and floor to ceiling GIK bass traps in all four corners. 1st reflection points are a challenge and I haven't bothered with them yet.
Cool that you already have absorbers.
Temporarily move all the 2nd reflection point absorbers to the 1st reflection point (in front of that door for example) and the floor wall locations (4 sides) and see what happens. If you don't have enough or they are rather permanently mounted, make a trip to home depot for some rigid rockwool panels. You will take these out of the bags.
If you have a front/back axial mode and you haven't seen your spouse raise an eyebrow lately, get 14 bags of fluffy fiberglass pink insulation, do not take them out of the bags, then stack them 7 wide and 8' tall across the back wall, and then give the room a listen.
Originally Posted by Gooddoc
There is some thought out there that suggests I might not even want to bother with them.
Yes, there is a school of thought that says that there's a richness of sound field gain from first reflection point (indeed bipolar speakers go out of their way at this), and another school of thought that says that first reflections should be dropped by 12 to 20dB at all frequencies. Too little reflected energy and the room is cold and dead, too much and the room echoes, has strong directional impressions, false stereo imaging, poor sound clarity, and a narrow soundstage.
Be curious. Experiment with the Simple. See if you like the sound, both by ear and by measurement. Language clarity (anything in a language you barely speak, my mother being fluent in english her entire life would suggest anything from the United Kingdom would foot the bill), imaging (Star Wars Pod Race, Mission To Mars rotation scene, etc). Presumably there's something you have been listening to that you are confident isn't sounding right -- use that too.
Alternatively, you could try diagnosis, followed by treatment. [This will go faster if you get the feedback of someone who can do this for you (or hire someone competent, probably with a degree in Acoustics, but at least does it routinely possibly with an AVS customer appreciation).]
- verify background noise
- initial speaker placement (L/R 3 feet from walls, etc)
- check speaker and cable integrity, check speaker time delay, and sound level balance
- test each speaker individually for reflections, and ensure the high frequency reflections are 12dB quieter than direct sound. Measure the ITDG (all peaks within 25-30mSec should be 12dB below the direct sound level)
- deal with room modes via subwoofer positioning and a RTA.
- set the subwoofer crossover frequency for a room reason rather than a speaker reason.
- verify a lack of vibration via a slow sweep 11hz to 400hz.
(Do you have a multi-channel digital equalizer? I don't have one, but I hear they're the cat's meow. Just a thought.)