I did manage to come up with a possible 6th order bandpass design, that works out to just over 5 cu.ft. per driver and is -3dB at 40 Hz.
Start with a box that's separated into two chambers, the larger one being 3.5 cu.ft. (net) and the smaller being 1.5 cu.ft. (net) The driver is going to sit on the panel separating these two chambers. To tune, leave off the cover for the smaller chamber and vent the larger chamber into the smaller one, aiming for a measured Fb of 50.5 Hz (shelf vents or round vents). Then, close the smaller chamber and vent to the outside - aim for a measured Fb of around 79 Hz. Use with a 100 Hz 12dB/oct low-pass filter. You can decrease the upper resonance frequency (if you're using shelf vents, just add extra panels inside the vents to lower Fb. This should give you an alignment that does 40 Hz to just under 100 Hz at -3dB. Of course you'll need to use the rest of your system to cover everything above 100 Hz. If it sounds like crap, just cut off the front chamber - the driver should do pretty well in a 3.5 cu.ft. box tuned to 50.5 Hz, but don't expect any low bass.
Of course, as with all 6th order bandpass designs, getting it to actually sound like what the design programs suggest require that the T/S parameters be correct, the box built to exact requirements, and several burnt offerings be given at the next full moon for good luck :-).
|
|
