[Wayne A. Pflughaupt]

While I'm at it, would it be a good idea to put the shelving on the left at a slight angle to improve things acoustically (I seem to recall non parallel walls being a good thing)?

The non-parallel wall thing is more for the upper frequencies than the low, to eliminate the slap back or flutter effect.

Not sure I get this shelf thing. What kind of shelves are we talking about? If they have some kind of a closed back, then they might make a difference - if they were floor-to-ceiling, virtually sealing the entire section where the curtain is. If they’re open-back, then they aren’t going to make any difference.

Your rear-location response looks like a winner. Knock down those peaks at ~25 and 55 Hz with an equalizer, and you’ll be in business. The fact that it doesn’t sound like it’s coming from the rear – absolutely wonderful. Still, even if it was, I think I’d rather have nice-sounding bass that I could localize as being behind me than wretched bass from the front.

The sub probably seems quieter at the back because the 40-50 Hz range has been substantially tamed. You’ll need to re-calibrate the sub’s level, with or without equalization.

Anyway, is the rear a better position to start from? If so, which should I try first, eq-ing or bass trapping?

Equalization will definitely be cheaper. Bass traps will serve a couple of functions. One is to reduce the span between the peaks and depressions so that less equalization is required. This is primarily above ~60-80 Hz, though.

Second, traps will dampen the bass frequencies (again, above ~60-80 Hz), so that there is less signal decay time or “overhang” (also called “ringing,” for some incomprehensible reason). For instance, if you’ve ever heard the difference in reverberation in a bare room before and after carpet and furnishings were added, that’s essentially what bass traps do for the lower frequencies. The audible result should be bass that sounds noticeably tighter. That low frequency dampening isn’t really something that equalization can do to any great extent.

So to summarize, the equalizer will smooth out the worse response irregularities, while the traps will accomplish low-frequency dampening. Both are worthwhile, but the equalization will get the most bang for the buck because bass traps aren’t cheap.

Regards,
Wayne