How far can room treatments solve boomy bass?

I don't understand the concept that acoustic treatment for a "too small" room is not the answer. It's exactly (part of) the answer. The modal distribution in a small room is lumpy well up into the upper bass region. The larger the room, the lower the frequency where that lumpy response starts to even out.

If your speakers are so large that the drivers don't "integrate" within the listening space, then yeah, that's a problem, too, but a small room is the worst offender when it comes to acoustic response in the low frequencies. Fix those and things will definitely get better.

You can get much closer to unity absorption (which isn't a limit) with 4" - 6" of fiberglass. You don't want to overdamp the other frequencies, though.

The reason spacing off the wall helps is because pressure doubles on a rigid wall while velocity goes to zero. As you move away from the wall, there is a tradeoff between pressure and velocity. No damping occurs with no velocity -- therefore, spacing off the wall (or more thickness) is needed. At lower frequencies, this leads to ~ 6" panels to get effective absorption. Bass traps in the corner become a viable (if unsightly) alternative.

You can't fix acoustic problems with EQ. You're using the wrong tool. Fix the acoustics, and THEN see where you stand.

For those problems that are caused by uneven modal distrubtion . . . why not fix them where they live, which is in the acoustics? Trying to EQ out the lumpiness is just fighting the symptom, not the cause.

Don't you agree that proper acoustic treatment reduces the amount of EQ required to bring the response into "flat" (or "desired") response?

Also, can you elaborate on the specific quarter-wave effect you are seeing in rooms? Are you talking woofer-to-floor distance, woofer-to-front-wall, etc.?

Any cable that corrects room response issues is seriously broken. Why do people fall for this crap?

If one implements the wrong solution for an acoustic problem, then yeah, it's not going to work very well. But if I have a spike at (say) 43 Hz, and I install a tuned acoustic filter (Helmholz, etc.) designed for maximum absorption at 43 Hz, and things don't get better, then I either need

a) better placement
b) more filter

This isn't voodoo.