Ed,

First, listening to sine wave signals is meaningless. In any small room, the peaks and dips produced by room modes are widely spaced and easy to hear. If you crank up a 50 Hz tone there will be several places in the room where it is loud and other places where it disappears completely. When listening to music however, the overtone structure subjectively smoothes out these variations to some degree.

What we are trying to avoid is the infamous "bass suckout" where several room modes pile up across a bandwidth of an octave or so. This is most apt to happen near the geometric center of the room.

In your case, I doubt that the room is actually soaking up low frequencies even though it sounds bass-shy compared to your previous facility. Mastering engineers tend to work at moderate sound levels and a certain amount of bass boost is needed to make the low frequencies audible. The trick is to get acceptable bass balance without screwing up stereo imaging in the mid range.

There is no bass trapping in the front of your room, so I would expect to get maximum bass coupling with the speakers near the front corners. If it is one-note bass, then the speakers can be shifted experimentally to tune out the offending frequency.

Moving your listening location forward or back can also make an audible difference in low frequency balance. Again, you can't be too near or too far from the speakers without messing up the stereo image.

Pick up three or four 4x8 sheets of inexpensive fiberboard (pegboard without the holes) at Home Depot. Try covering the front of the acoustic screen. If it makes the bass response worse, forget it. If it brings up the bass but adds too much high frequency bounce, cover the back instead. You might also try covering the soffit opening and even covering most of the angled rear trap faces.

If you can get the room to the point where it sounds well-balanced but bass-shy, then three or four dB of EQ, or the addition of a subwoofer, should achieve the response you are looking for.

Regards,

Geo. A.