The extensively internally-braced cabinet features features double-tuned, high-pressure loading, through a rounded 236mm diameter low-tuned bass-reflex vent and a wide, high-tuned quarter wave tunnel. This provides optimised breathing at high SPLs, yet keeping the total system weight to a minimum.
Slider feet on cabinet bottom and side enable stacking of multiple BQ211’s into vertical LF arrays: The additional front-positioned NL4 connector caters for easy “reverse connection” in cardioid arrays.

The BQ211 is powered and controlled by the ALC amplified loudspeaker controller; Through the SDP™ (Speaker Drive Processor) circuit, the ALC offers BQ211-specific drive processing with response optimisation, dedicated power and excursion protection, hybrid filtering and cardoid processing.

Through the SIS™ (Signal Integrity Sensing) circuit, the cable-length and connector resistance between the BQ211 and ALC is completely compensated (damping factor 10.000), further increasing response accuracy.
The quarter wave pipe principle in combination with a low tuning frequency, forms a true wideband subwoofer with high SPL performance down to the lowest frequencies.

Typical applications for the BQ211 include groundstacked sub-bass extension of main sound systems, used in multiples depending on the application and sound pressure level / dispersion pattern control requirements.