#AudioWednesday BANDPASS SPEAKER CABINET - a specialized cabinet design which uses a combination of sealed and vented box volumes to produce a shaped speaker response. Bandpass boxes are a critically tuned design and internal pressures can be very high. Small air leaks can seriously reduce performance, and panel flex can be much more of a problem than usual - particularly with enclosures using built-in acoustical gain. Since all speaker output comes from the vent, air speed within the vent can be very high. This can produce some turbulence and noise (particularly with high gain enclosures), which can be reduced or eliminated by rounding the ends of the vent with a quarter-round router bit or a round file. The inside end of the vent must be at least one diameter away from any inside cabinet walls, or flow restriction will occur. Advantages of Bandpass Enclosures 1 - Acoustical gain can be built in. This means that one speaker can be as loud as four or more (using the same power input) at a limited part of the frequency spectrum. Acoustical gain and low frequency extension are inversely related; a high gain box will not go as low as a low gain box. Experiment with gain and cut-off values to find the best compromise. 2 - Specific low frequency cut-offs can be designed, including lower cut-offs than would normally be possible with simple sealed or vented boxes. 3 - A reduction in cone excursion can be included in a design, which can reduce distortion and improve power handling. Disadvantages of Bandpass Enclosures 1 - Box construction is considerably more complex. 2 - Enclosures which add acoustical gain can be boomy. The higher the gain, the less crisp and detailed the bass is likely to be. 3 - Boxes designed for extended low frequency performance will have less SPL output than either vented or sealed enclosures. 4 - Generally requires 50 to 100% more total enclosure volume than vented or sealed types. 5 - Usually has less power handling than a simple sealed box. Designing bandpass enclosures for increased power handing can result in very poor deep bass response.
Posted on: Wed, 22 Oct 2014 05:46:40 +0000