A design for the enclosure of a loudspeaker. With acoustic suspension speakers the enclosure is sealed so that it is air tight, which causes the air within to become a very active part of the woofer's suspension. This raises the resonant frequency of the driver and lowers its compliance. Acoustic suspension speakers tend to be less efficient than bass reflex designs, and begin fading away their bass at a higher frequency. But the rate at which the bass output reduces tends to be less than an equivalent bass reflex speaker, so they frequently produce greater bass extension. Also called infinite baffle.