Acoustic suspension

The bass vent boosts low-frequency output, but with the tradeoff of introducing phase delay and accuracy problems in reproducing transient signals.

Most Acoustic Research designs used a PVA sealer on the foam surrounds to enable a longer component life and enhance performance.

They also have lower group delay at low frequencies compared to bass reflex designs, resulting in better transient response.

As noted by Small,[6] an analysis performed by Thiele[7] suggested that the differences among correctly adjusted systems of both types are likely to be inaudible.

In the 2000s, most subwoofers, bass amplifier cabinets and sound reinforcement system speaker cabinets use bass reflex ports, rather than a sealed-box design, in order to obtain more extended low-frequency response and to get higher sound pressure level (SPL).

Given a driver that is suitable for either type of enclosure, the ideal bass reflex cabinet will be larger, have a lower −3 dB point, but both systems will have equal voltage sensitivity in the passband.

While boxed hi-fi speakers are often described as being acoustic suspension or ported (bass reflex), depending on the absence or presence of a port tube or vent, it is also true that, in typical box speakers with more than two drivers, the midrange drivers between the woofer and tweeter are usually designed as acoustic suspension, with a separate, sealed air-space, even if the woofer itself is not.

[citation needed] However, one notable exception to this was the Sonus Faber Stradivari Homage, which used a ported enclosure for the midrange.