The BassXt stereo Bass Extender extends the low frequency response of sealed and vented box loudspeakers with a tunable 6dB peak (see below) at 20 - 50 Hz followed by a steep sub-sonic filter at very low frequency (see graph). In practice the unit is tuned to restore the -6dB frequency to flat while eliminating the extreme low frequencies which cause unnecessary cone movement and distortion. It provides VISIBLE control over cone flapping while the bass output is dramatically more extended (to typically 0.6f3), cleaner and tighter, and room modes are reduced. Increased driver power at the hump is compensated by the low cut filtering - which eliminates associated non-linear cone travel and power wastage.

A single high speed FET cascode op-amp is used in the signal path, powered from discrete low noise 80dB regulators. Peaking frequency is adjustable by front panel controls and is down 40dB at 0.1 fo. The unit can be configured to run from a 12Vac plugpack or wired to an available +/-18V to 25V supply. Up to 8dB of passband gain is also possible. The board is fully ground planed for lowest noise and a front panel LED is provided. The unit is typically positioned in the signal path between pre- and power amplifier or in a tape loop facility. Independent control of left and right channel boost frequency allows for differences in speaker placement needs.