4th order bandpass to 35Hz ... sonic advantage?

[mayhem13]

For Hifi helper woofer to compliment either a fullrange or coax…..is there really such low HD as claimed?

 

[BP1Fanatic]

When a driver moves, it distorts.
Per a given voltage, a driver moves less in bandpass enclosure than a sealed or vented enclosure.

 

[mayhem13]

Is it just that?….or is it the distortion components are also less audible or contained by the enclosure the driver is firing into? Of course this assumes the enclosure is completely inert

 

[stv]

The acoustic bandpass will suppress (attenuate) harmonic parts above passband.
I heard PA bandpass enclosures are more likely to get damaged because you don't hear the distorsion of an overloaded driver so much.

 

[Brian Steele]

THD plot for my Enigma 10" BP driven at the driver's RMS wattage rating. Yes, THD is reduced by the acoustic bandpass. However, the acoustic bandpass is less effective at the lower of the subwoofer's passband because the HD that's generated at these lower frequencies is still within the acoustic passband.

 

[GM]

Yeah, can't fool Mother Nature as we're always 'robbing Peter to pay Paul'.

 

[Brian Steele]

Modern DSP options do allow for some interesting scenarios though. Like possibly a dual 4th order BP, with one section designed for 50~100 Hz and another designed for 25~50 Hz, and the combination aligned using DSP, resulting 25 Hz to 100 Hz at pretty low THD, output primarily dependent on the thermal limits of the drivers. Hmm... .

 

[Milsdrewbulch]

For thermal improvements port the magnet side. Not the cone side. Reverse the wiring.

Also FYI by definition a 4th order bandpass has only 2nd order slopes. 2+2=4.

 

[mayhem13]

But isn’t that a catch 22?….id expect and increase in motor and suspension noise?

 

[Freedom666]

in some designs for pro use thermal stability can outweigh sonic aspects.

 

[BP1Fanatic]

I always try to design BP4's with magnet in vented chamber. I have yet to blow a driver in a BP4 enclosure. I've blown multiple drivers in sealed enclosures.

 

[mayhem13]

Agreed. I should have clarified for home consumption.

 

[BP1Fanatic]

The wooden table, on its side and in my avatar, is a 2 x 12" BP4 for home theater, built in 1998.

 

[mayhem13]

Modern DSP options do allow for some interesting scenarios though. Like possibly a dual 4th order BP, with one section designed for 50~100 Hz and another designed for 25~50 Hz, and the combination aligned using DSP, resulting 25 Hz to 100 Hz at pretty low THD, output primarily dependent on the thermal limits of the drivers. Hmm... .

Yes….you would need a 2x4 DSP unit for 2 channel……that’s easily doable and cheap enough these days for those serious about bass. ICE amp boards are getting less expensive and more capable every day it seems. A quite serious and capable dual BP4 stereo arrangement could be DIYed for less than a grand these days.

I think size the great limiting factor these days for many folks….with the cost of the average square foot of living space skyrocketing, every inch counts. My wife actually liked my idea for an attic mounted Infinite Baffle system……too hot up there now to work though…..maybe in the fall.