This is a simple type of loudspeaker
enclosure where the box is completely sealed and airtight. This name was cooked up by the company Acoustic Research, who undoubtedly thought that 'acoustic suspension' sounded more clever (and had more branding potential) than 'box'.
So what is the point?
The idea is to totally absorb the back wave - the sound radiated from the back of the driver. The enclosure itself is (ideally) built strongly, and well damped, so that the sound does get absorbed, and not transmitted via resonating enclosure panels. Thus all you hear is the front wave of the speaker driver.
Why doesn't everyone use them?
The main reason is bass extension. Where a driver is suitable for both bass reflex and sealed enclosures, the ported one will give a little more, usually by about half an octave. The ported speaker will also be able to play a little louder, in most applications.
On the bright side, the acoustic suspension enclosure
- is easy to design and build
- is very forgiving of driver variation (in manufacturing, or due to use and ageing)
- suits most drivers,
- uses relatively small enclosures
- gives some of the most tuneful bass possible,
- can give very clean sound, with good transient response, partly because the backwave is not used (the backwave is never in phase with the frontwave), and partly because the time for resonances to decay to nothing is minimal.
- the rolloff is quite shallow.
- the real thing matches the mathematical model / design predictions better than most other enclosure types do.