The Clair Brothers CS21 is a sub-low frequency
loudspeaker designed to provide maximum
sub bass reinforcement and low frequency
augmentation in fixed installations. Its compact
size makes it an ideal companion to two-way and
three-way full range installation loudspeakers
such as CAT214, R2, R3 and R4. It is one of
the most compact, 21” installation subwoofers
available today.
CS21’s unique features are a compact 30” cube
design and symmetrical 4-port configuration to
extend the low frequency response of the 21”
woofer.

The high performance 21” woofer provides 100
dB SPL for a 1 watt input measured at 1 meter,
with usable in-room frequency response down
to 32Hz. Its compact size enables the box to be
placed in permanent applications without being
obtrusive.
As with all Clair Brothers products, the CS21 is
constructed of the finest Baltic birch plywood
with a rugged epoxy finish to withstand the most
demanding conditions.
The speaker grille is constructed of a durable 14
gauge steel which is powder coated and backed
with a high grade reticulated foam.