What are the different types of boxes and how do they affect the sound a sub produces?
Derek
Posted on
Infinite Baffle, or Sealed Box designs isolate the front bass wave from the back. They do not have to be sealed - the front door of your house would do just fine as long as the front wave can't get to the back wave. They have the advantage of small size, low distortion below the tuning frequency and simplicity of design. The disadvantage is they do not go down as low as other designs.
Acoustic Suspension of Ported designs create a second tuning frequency with the port. This will ususally extend the response further than Sealed boxes. They have the disadvantage of bass dropping off twice as fast below tuning and very high distortion below tuning (Think turntable rumble). They are also more complicated to design.
The Bandpass box is actually a dirivative a an invention by Amor Bose call The Acoustimass. The Acoustimass uses sound from both sides of the woofer, so it's very efficient. Distortion is low because only the damped ports are heard, not the raw driver and they ususally don't even require a crossover. Response can be exactly controlled because there are now three tuning frequencies to work with (two ports and the driver). The port tuning is ussuallt calculated to create two slight "sholder" peaks. This makes it possible to create a truly FLAT response. The disadvantage: They are very hard to create without heavy calculations and to avoid law suits (punn intended) manufacturers design out one of the ports so it doesn't look like the Bose design.
There are a few other designs that wont work in cars; Transmision Lines create very long absorbing tubes in small cabinets and Accoustic Horns try to match the driver impedence with the impedence of the air in the room by using a folded horn and the corner of the room as part of the speaker. This was used by Klipsch and SpeakerLab.
Hope this helps.
Anonymous
Posted on
small correction on dereks explaination......acoustic suspension is a sealed enclosure