Theoretically, the band-pass enclosure would provide both high-pass and low-pass filter properties itself, unlike other types of enclosure which only has high-pass property.
I wonder why band-pass subwoofers usually come with active low-pass crossovers. Does band-pass subwoofer without active low-pass crossovers exist in the commercial markets? I’ve never seen one, yet. But anyone has seen any models—the band-pass subwoofers that utilize mechanical crossover or its theoretically physical property, without utilizing external active crossover?
If there literally exists, how about sound quality? Let’s assume we have a conventional sealed subwoofer with active crossover set around 90Hz cut-off frequency equipped and a PASSIVE band-pass subwoofer designed to have cut-off frequency at the same 90Hz (if this configuration possible), which one should give better sound, given the drivers are the same model that suit to both sealed and band-pass cabinets?
I wonder why band-pass subwoofers usually come with active low-pass crossovers. Does band-pass subwoofer without active low-pass crossovers exist in the commercial markets? I’ve never seen one, yet. But anyone has seen any models—the band-pass subwoofers that utilize mechanical crossover or its theoretically physical property, without utilizing external active crossover?
If there literally exists, how about sound quality? Let’s assume we have a conventional sealed subwoofer with active crossover set around 90Hz cut-off frequency equipped and a PASSIVE band-pass subwoofer designed to have cut-off frequency at the same 90Hz (if this configuration possible), which one should give better sound, given the drivers are the same model that suit to both sealed and band-pass cabinets?
In theory it should be the same. Bandpass enclosures have a couple of potential benefits as a subwoofer, one is that distortion is low-passed and the other is a choice of increased sensitivity if you can find the right driver for your needed band.
To limit cone excursion and to save amp power for the useful bandwidth.
The "acoustic bandpass" feature of most bandpass designs can suffer from out-of-band harmonic resonances, which could make it sound pretty bad if they're not filtered out or dealt with by other means such as lining or stuffing the enclosure, but of which can result in lower passband sensitivity. Having said that, with careful design choices and some luck, it is possible to design and built a bandpass enclosure with so little out-of-band resonances that it can be used without filtering (see the "Enigma" project on my site for an example of one).
As for sound quality, if the overall response curve is identical, then I doubt you'd hear the difference between it and a sealed subwoofer with a HP filter, until you start turning it up, at which point the bandpass design will start to sound better (assuming that the vents are large enough to reduce power compression), as it will have lower THD, all else being equal.
As for sound quality, if the overall response curve is identical, then I doubt you'd hear the difference between it and a sealed subwoofer with a HP filter, until you start turning it up, at which point the bandpass design will start to sound better (assuming that the vents are large enough to reduce power compression), as it will have lower THD, all else being equal.
@ presscot
Below is my bandpass response with a 8" Silver Flute W20RC38-08 measured at the mouth of the port.
If one is not too fussy with sound quality, the bandpass can be used on it's own.
Bear in mind the peaks from 1kHz~5kHz will affect the mids.
Just playing the bandpass alone, you can hear the mids even though it's not loud.
For users that are sound quality conscious, using an external electronic crossover will prevent the mids from bleeding out of the bandpass.
The Blue plot below is with my electronic crossover set at 250Hz (24dB/oct).
It killed off all the unwanted frequencies from 1kHz onwards.
The trade-off is you'll need an extra amplifier and an electronic crossover.
Regards
Mike
AmpsLab-Spk
Below is my bandpass response with a 8" Silver Flute W20RC38-08 measured at the mouth of the port.
If one is not too fussy with sound quality, the bandpass can be used on it's own.
Bear in mind the peaks from 1kHz~5kHz will affect the mids.
Just playing the bandpass alone, you can hear the mids even though it's not loud.
For users that are sound quality conscious, using an external electronic crossover will prevent the mids from bleeding out of the bandpass.
The Blue plot below is with my electronic crossover set at 250Hz (24dB/oct).
It killed off all the unwanted frequencies from 1kHz onwards.
The trade-off is you'll need an extra amplifier and an electronic crossover.
Regards
Mike
AmpsLab-Spk
Check your Fb on that BP build. I'm betting that they're lower than expected. I used to have a similar bandpass response with my Enigma build. Turned out that Fb was lower than expected, because the vent length calculation rules lose accuracy when the vents start to exceed about 10% of the chamber's volume. I had to cut them back about 30% or so to achieve target Fb and a flatter passband response.
I use bandpass subwoofers in my system for a response from ~30hz to 100hz. The low-pass mechanical filter starts around 90Hz and I use an electrical active crossover from 250Hz to block higher frequencies. So it is a mix of "natural" and "electric" filtering. The same with the high-pass from my midbass horns, I use the mechanical filter that the cut-off from the horn presents but limit electrically below that. What I try to achieve is a "natural" crossover between sub and midbass. Works for me, but ymmv.
Thanks for your advice.
The response is deliberate.
I like my bass to have a bit of boost at 50Hz~40Hz.
Below is my box sim for a Triple Chamber Bandpass using two Dayton DA135-8.
For this BP, I went for a wider bandwidth instead of a flat response.
In the final build, the response is exactly what the sim predicted.
This is what my Triple-Chamber BP looks like on the inside. It's a very compact tower. It can be used as a speaker stand to support a 2-way or a flower pot.
Regards
Mike
AmpsLab-Spk
Nice little bandpass sub, Michael. I use a Dayton dual VC driver, but a single 8". They seem to work best in a bandpass enclosure. I built 8 of them and stacked them, four per side as a line source so the bass is pretty homogeneous everywhere in the room (sort of SBA effect, i.o.w.) The properties of the room (13' x 8' x 39') made this the best option for proper bass.
The SD215A-88 is excellent value for money.
I tested her out in a direct radiator and a bandpass.
For some reason, the voice coil in my unit hits the back plate.
And this is not playing loud.
When I tried it in a bandpass, it happened again.
I'm not suggesting your subs are not good.
I'm just sharing my experiences here.
Maybe my units are faulty.
None of my woofers and I have quite a few, exhibited this.
The voice coil hitting the back plate normally happens when too much power is pumped into the woofer.
I can actually hear the "clack" when it hits the back plate.
I tested her out in a direct radiator and a bandpass.
For some reason, the voice coil in my unit hits the back plate.
And this is not playing loud.
When I tried it in a bandpass, it happened again.
I'm not suggesting your subs are not good.
I'm just sharing my experiences here.
Maybe my units are faulty.
None of my woofers and I have quite a few, exhibited this.
The voice coil hitting the back plate normally happens when too much power is pumped into the woofer.
I can actually hear the "clack" when it hits the back plate.
Good that you mention it, I did not experienced this (yet) because I do not play very loud and the load is spread over 8 units that are also acoustically coupled so it raises the efficiency and lowers distortion. We'll see.
Last edited:
Better avoid this, then. While other woofers may not hit backplates when too much power is pumped into it, something else may happen. I am not too concerned.
That's great. Thought I should just mentioned what happened with my Dayton.
I'm actually quite fond with this woofer.
Maybe the spider in my units are the problem.
Sometimes, Dayton products can have faults.
I once bought a Dayton D250P-8 compression driver.
When I tested it out, it just didn't sound right.
I opened it up and to my horror, there were iron fillings in the voice coil gap. Quite a fair bit.
Took some effort to remove them completely because they were sicking to the walls because of the magnet.
I'm actually quite fond with this woofer.
Maybe the spider in my units are the problem.
Sometimes, Dayton products can have faults.
I once bought a Dayton D250P-8 compression driver.
When I tested it out, it just didn't sound right.
I opened it up and to my horror, there were iron fillings in the voice coil gap. Quite a fair bit.
Took some effort to remove them completely because they were sicking to the walls because of the magnet.
That's different to the previous response you posted, which was this ...
The above response is what I'd expect to see if the bandpass alignment was tuned too low.
Looking drawings and photos of the SD215A-88 driver, rated for 6mm Xmax, it appears it's voice coil would have to completely leave the gap to contact the "bumped up" back plate.
I'd suspect a stray piece of adhesive, possibly from gluing on the back plate is what the voice coil is "clacking" on.
I had a driver with that problem "cure" itself after testing it at high power.
Have you measured your SD215A-88's mechanical excursion limit by hand, and if so, what is it?
Art
It didn't occur to me that it could be adhesive.
I tried pushing the cone manually but didn't feel anything.
I moved on to testing other woofers after that.
Didn't have time.
Mike
I tried pushing the cone manually but didn't feel anything.
I moved on to testing other woofers after that.
Didn't have time.
Mike
Yes, it is different. I tuned it that way.
I found the box sim for this BP.
It came out exactly as predicted.
If I had wanted a flat response, the box would be about 37 liters.
I preferred a compact 25L.
Moreover, with a flat response, the bandwidth is narrower.
That was not what I was going for.
BP are very sensitive to T/S.
If they are not accurate, the sim will be off.
Mike
I have not had any trouble with the SD215A-88, and this is the first time I've heard of anyone having issues with it.