I said I would try follow-up with the setbacks and breakthroughs. I do not know how to post the graphs in this format so I will just try to accurately describe the highlights and observations.
I spent 2 days measuring under the most controlled circumstances I could manage. Focusing on speaker position, this is what I found.
Started at my established listening position. Speaker centerlines - 50" from back wall, 83.5" apart, 36.5 from angled (45deg) sidewalls, and 115" from listening postion. Speakers were tilted back 4 degrees (guess, one washer in the bottom of the stand mount, will measure exactly later).
I will descibe the sequential set up for 7 different test runs with the Real Traps Test CD, because the measured results changed very little.
#0.. Baseline
#1.. Changed tilt to upright.
#2.. moved speakers straight back 6".
#3.. moved speakers forward 12".
#4.. moved speakers toward each other 6" each.
#5.. moved speakers back 6".
When I sat down and graphed the numbers...
Steady rise from 53db @ 32hz. to 63bd @ 38hz
6db drop @ 42hz. rising steadily to 76db @ 55hz.
9db dip @64hz rising to 77db @ 70hz.
Drops to 67db @ 86hz.
Rises to a steady 69bd @ 90hz. to 118hz.
Starts to dip steadily @ 118hz. to 53db @ 138hz.
Broad null for 10hz.
Rises steadily to 67db @ 172hz.
Things get real eratic at this point with wide 2,3,4hz wide swings down to < 50db and back up. Does seem to be another deep (<50db) broad null at 230hz. to 270hz.
In general terms, and to my untrained eyes, I have a big boost from 45hz to 82hz with a little dip thrown in the middle of that, another small dip @ 85hz, and 2 serious nulls @ 135hz to 175hz and 230hz. to 300hz.
Experimenting a little more
#6.. Opened laundry room door, checking for suckout.
Virtually no change. (big surprise).
#7.. Pulled single speaker out into middle of room (13' from back wall, facing into open area) and measured @ 2' with mono source. (closed LR door)
Same pattern of boosts and nulls, just a little less dynamic. Who would have thought? The tones really started to audibly oscillate @ 105hz through 135hz. Reinforcement/filtering, who knows?
Really surprised me how little the pattern changed through all 8 tests. I took the time to listen to familiar music in-between each test run and the position changes were easily perceptable.
At this point, I have some acoustic reference material coming for study so, although I can recognize the pattern, I don't know what it really means.
Other interesting (to me) observations. Putting the 1.6's closer together than I remember trying before starts to push the sound stage to the front of the speakers instead of behind and starting to produce the clarity in the vocal registers that I was seeking at the start of this. Despite the nice clarity, it is too bright to listen to anything but female vocals and acoustic instruments in that position and the soundstage is too narrow.
Next step... read a little theory and build some really big DIY bass traps to test.
Please forgive the typos, mispellings, and my grammar.
Regards,
Jim S.