Operating rather like a subwoofer in reverse, this crafty device controls low frequencies but takes up far less space than conventional bass traps.
 
Swiss monitor loudspeaker manufacturers PSI have done exactly that with their new AVAA C20 active bass trap. The product’s odd acronym stands for ‘Active Velocity Acoustic Absorber’, and it is designed to serve as an active replacement for a conventional broadband bass-trap panel. The manufacturers claim it behaves acoustically much like “a hole in the wall” of somewhere between five and 20 times its own size — meaning somewhere between one and four square metres, depending on the acoustic properties of the environment — which is pretty impressive for a box which is only 509mm high and 424mm wide, and which weighs 13kg! The AVAA is roughly a tenth of the size of a conventional broadband bass trap of comparable performance, which is extraordinary.The only rear-panel control is a sensitivity potentiometer, which under most circumstances should be turned fully clockwise.
 
Since the tri-corner area of a room is where the greatest number of room modes coalesce, the AVAA has been designed with a trapezoidal profile to fit neatly into that space. The two rearward side panels are set at 90 degrees to each other to sit snugly against the adjacent walls, while the inside corner is chamfered off to leave a 50mm deep ‘chimney’ for convective cooling of the amplifier chassis (and to access the power switch). The company have released no specifications for the drive unit, power amplifier or the signal processing, other than to say that it is an all-analogue system.
 
An active bass absorber which acts to create a virtual ‘hole in the wall’ such that direct bass sound waves no longer reflect back into the room from the vicinity of each AVAA unit. This evens out the bass response dramatically and reduces LF resonances and LF reverb duration.