Double Bandpass Enclosure Design - Critique!

i don't get anything when i click on your links.

i can see them now.

each side of your enclosure kind of looks like one of these:

http://www.the12volt.com/caraudio/boxes6.asp

i have no idea what your box will do, but i will take a stab in the dark. one thing to keep in mind is that with two ports into one enclosure, there isn't as much of a 'smoothing' effect as an 'averaging' effect, so my best guess would be that you won't get smoothing across a wide frequency range as it will just all average out to some sort of single frequency tuning.

"Hm. So how do regular bandpass designs specialize in two different frequencies then? Shouldn't they be "averaged" as well?"

...by walling-off the enclosure behind the driver from the enclosure in front of the driver.

the bose bass module is one of the more complex designs going and combines all the chambers. as implemented, most folks consider it a dud. i suspect that the design choice was chosen to stack resonances on top of resonances in order to get the most spl out of the lowest cost driver possible in the smallest cabinet possible, and it made amar a billionaire, so i suppose it was a success? panem et circenses...

Ahoy Captain Clams!

if you can provide links to driver specifications, and a few details about the box dimensions I will be happy to simulate the system so you can see what it would do.

Regards,
Eric

"But that wall is ported in most bandpass designs I've looked at."

take another look at them. not so.

most bandpass are the 4th order, sealed rear cab, ported front cab.

very rare are 6th order, where the rear cab is vented.

combining all the resonances as in the bose bass modules is very rare and like i said, most folks have found them to be not worth building.

Hello Captain,

I was just looking at the diagrams closer, and realize you have the rear chamber vented to a front chamber. I didn't catch that initially... Such a design is a bit over my head for simulation, however, I can try to come up with a bandpass box design for these drivers if you are interested. Some drivers can produce pretty decent results in 6th order boxes. Your cabinet "shape" could be used to accomplish this, but there would be a vent coming from the rear chamber into the open, and a vent from both front chambers to the open.

I would say that the drivers you have there are, IMO, not worth wasting a very complicated build on. They just don't have the sort of displacement capabilities that would make the trouble worth it...

What useful passband are you after?

Regards,
Eric

That driver is far to small to be useful as a sub IMO unless you're looking for a very small box. By no means will the following design be amazing, and it might be bigger then you want, but it will do OK for cheap. Check the attachments.

Goldwood GW-12PC-4
Dayton SA70

Just an FYI, you can basically achieve the same results with a standard ported cab outside of the built in bandpass filter of the high frequencies.

Cool! That certainly looks unique. Just be aware that the SPL chart I posted would be the limit of output, and xmax is slightly exceeded with 70 watts.

Having had a night to sleep on the idea, I realised why there is a reason no common simulation software would let you even bother with this...

If you have 2 drivers, sharing a rear chamber, but each with different front chambers, then you are creating a situation like having 2 drivers with different characteristics sharing a common chamber. It's usually a bad idea.

I would not consider that goldwood 12" or the dayton 10" options considered to be much of an improvement over the current pyramid drivers. I don't think I would waste money on either for a functioning 18-70hz sub.

If a bandpass box is not producing useful box gain over a traditional vented or sealed box, then it's being implemented poorly. Properly designed bandpass is a way to achieve greater box gain within a desired bandwidth than possible with simpler box alignments. 6th has a better chance of producing useful gain and wider bandwidth than 4th order. That said, with the ability these days to freely simulate various horn loaded, tapped horn, line and tapped line options, often the bandpass box options are passed up. There are cases where within box size restrictions, a bandpass can still offer the greatest box gain with an acceptable response even over more sophisticated box designs... It's all about finding the level of box sophistication that fits the driver and box size limits set.

How much amplification will you have for this?

Regards,
Eric

The 18-70hz requirement is really what cut the bandpass advantage, at least for those Goldwoods.

(vs ported full 6db increase)

What I attached in post #19 would be ideal for the Goldwoods low end. There seems to be a 20hz range that maximizes output, so you could move that up to 40-60 (and gain even more output) or higher.

Other woofers may have a wider range, I just looked for something around $60 that would maximize SPL for cheap. This is all with only that $50 70 watt amp.

Not sure which one you liked. First one's 30-50hz second 40-60hz. Here's the newest winisd

https://www.facebook.com/WinISD

you have to have facebook...

The goldwoods do not have enough of an advantage over the current pyramid drivers to warrant an exchange of money IMO.

Consider, a DCS450.

Regards,
Eric

Just hit next. Winisd cant predict an alignment for bandpass.


Hopefully OP can model all this himself now, but check the VAS on the drivers in question.

No secret, just have to find the proper volume and tune for each chamber.

for a good starting point, try tuning the front and the rear chamber to about the same frequency.

That would be a very bad starting point.

For a good starting point, try setting the front chamber to about 1/4 the volume of the rear chamber, and tuning them about 2 octaves apart; with the larger {rear} chamber tuned lower.