NEW ITEM! Getting a room's bass right is probably one of THE most difficult things to conquer in room setup. Passive bass traps work, but they're big and rarely pretty. The Swiss-engineered PSI Audio AVAA C214 works like a 'virtual black hole' for room-mode bass (15–160 Hz): a sensor reads the pressure in the room and two drivers actively absorb the excess, for absorption PSI rates at up to 45 times its physical size. It's a slim aluminum column (about 8.3" x 25"), needs no calibration, and never connects to your system. Place it in a corner, plug it in, switch it on. Black or white, sold individually; most rooms benefit from a pair.
NEW! The Black Box Carbon replaces Synergistic Research's original Black Box. It's a fully passive low-frequency resonator array that targets bass nodes and room modes without the bulk of conventional bass traps, now in a stiffer carbon fiber and aluminum chassis with bronze inserts for stacking two units. 9.5" x 9.5" x 6" (8" on its Stiletto feet), about 8 lbs.
Had I not heard it myself at the 2013 Rocky Mountain Audio Fest (Denver, CO)- I wouldn't have believed it: A demo with a Bose Wave Radio and the FEQ + HFT setup changed that. Synergistic claims this has an effect on resonances and frequencies above the audible band, and goes on to explain some of the principles of operation. Must be heard to be believed.
The HFTs work on their own as a standalone solution. (The FEQ field generator they were originally paired with is no longer offered here.)