Horning Eufrodites - help needed with boomy bass

While I realize that you've indicated the boominess is present even at low volume levels, have you considered the possibility that at least part of the problem might be microphonics involving your source component(s), or possibly even both of the two amplifiers you've used.

I see in a post you made a couple of months ago that you are using, or at least were using at that time, an ARC CD7 as your source, which is replete with tubes. Is it by any chance placed between or close to the speakers?

Just a thought. Regards,
-- Al

Edit: Just after submitting this post, I saw the photos of the room to which you just provided a link. I think I may have had a point. Re your earlier mention of the problem being most pronounced on the left side of the room, I note that the left channel amplifier appears to be significantly closer to the corresponding speaker than the right channel amplifier.

The front left side is the culprit..I thought this was in the back of the room. The wall is deflecting and reinforcing the bass and the cabinet below and the space below that is acting as a storage drum. Wow your room looks great..but consider taking that nich/nook/ storage out and leave the radiator it won't interfere any way. Tom

Tom is right,
I have done much more extensive structural changes in my room in order to tame room bass modes. It is a difficult decision, but by looking at it, shouldn't be that difficult to implement technically- and, you will thank yourself later.
Without some serious re-building you will be "doomed", as far, as the bass goes

Sorry the boards-in-the-port didn't help.

Equalization or a solid state amp are probably your least room-intrusive possibilities at this point. And nothing wrong with room treatment.

Unfortunately I don't have any more inexpensive suggestions.

It is possible that a couple of small, cheap subwoofers, placed one behind each of your speakers and operating out-of-phase, would introduce enough cancellation to smooth things out.

Duke

Must be sleepy time in Paris..