In Reply to: BandPass vs. Horn bass enclosure posted by Sven on November 28, 2000 at 03:26:15:
Hi Svenbandpass boxes can be useful - in Speaker Builder back some years ago there was an article on a 6th order parallel (both chambers having a vent to the external world) - this particular box had a Carvin PS-15 fs=36.3, vas=265.3l, Re=5.7, Qe=0.469,Qms=5.77, (Qts=0.4337) Rear box 75l with fb =30Hz and front box 100.3l with fb=90hz.
Looking at this on Bob Bullock's BPBOXMOD, the 4mm xmax allows 100 watts power handling down to below 30Hz with a max excursion in the 55hz region.
This particular 'alignment' gives about 3dB of gain and the -3dB bandwith about 55Hz on the low end which now happens to be the reference sensitivty of 96.3dB or so - thats good performance for 6.2 cu.ft. of box - the 'bad' part is htat hte high end only goes to maybe 120Hz but the distortion components are attenuated by the 'front' chamber's 2nd order low pass funtion til the wavelengths get small enough to 'leak; out.
This particular box would have about the same reponse with the back chamber sealed but the venting cuts down on the cone excursion.
For comparison a 8 cu.ft. 'horn' like the short-path Belle might give similar output at 55Hz (?) but have a sensitivity of about 104dB up to maybe 350Hz or so - in this comparison the bandpass might be 'cleaner' on the low-end - you certainly have more 'real-world' experience than myself.
If a bandpass is used to fill in one-octave or so I think they can be useful in high outpu applications - in theory you might be able to get 6dB of gain but the bandwidth would be very limited.
best wishes
Freddy
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