Passive radiators in a bandpass?? possible?

[greysplash]

I was wondering if it would be possible to build a bandpass cabinet with radiators in place of ports?
ALSO, if you were building a higher order bandpass, could you use ports for internal "linkages" and radiator(s) for the external ones. I think this would could make for a more interesting looking system if it is indeed possible.

I would think from a logistical standpoint having radiators in, say a 4th order, would reduce port noise and provide a tighter bass response, but how would one go about calculating the radiators (and mass) needed??

[vasyachkin]

could you drive a car with seven wheels ?

yes !

[greysplash]

lol... Are my assumptions on the advantages right and are there any other advantages/disadvantages?? Also, how would I got about calculating all this stuff?? thanks!

[danklugherz]

lol... Are my assumptions on the advantages right and are there any other advantages/disadvantages?? Also, how would I got about calculating all this stuff?? thanks!

Well Vas? I think the mans waiting for your expert advice. Don't leave him hanging.

[zach_t]

Good thoughts. To the system, ports vs. PR shouldn't matter, they are actually the same, a oscillating mass that is. Someone has to have tried it, so I am guessing there is a reason why I don’t recall seeing a commercial version.

I would start with a simple bandpass enclosure first, determine the proper port tuning for volume. TO determine the PR, I would model the driver and volume of chamber as a single ported box and determine the PR and added mass to get to the same tuning.

I really like this idea. Since most of the output of a bandpass enclosure is the port, it would nice if a cone was providing that acoustic energy.

[Jeff B.]

lol... Are my assumptions on the advantages right and are there any other advantages/disadvantages?? Also, how would I got about calculating all this stuff?? thanks!

Yes, if you prefer you can use a passive radiator instead of a port. It might be tricky though. Not because of the math, but because in a bandpass alignment the port tuning is actually quite a bit higher in frequency compared to a typical vented alignment. This means you need a fairly lightweight passive radiator and that may be harder to find, and stll have adequate excursion. In the end, you may be better off with the standard port, but if you still want to know how to do it read on:

As for the math - can you use Unibox? If so, then you just need to use a little creativity. Design using the bandpass system at the bottom to get the response you want. Then make note of the Fb and Vb for the vented section of the bandpass. Next enter your passive radiator parameters into passive radiator section just above that in Unibox and use the same Vb as it called for, for the vented volume in the bandpass alignment. Now determine the amount of added mass necessary to tune the Fb of the passive radiator to same frequency as the Fb required for the bandpass alignment. Now, you've got the passive radiator you need to do what you are describing.

Jeff B.

[natediggidy]

Way back when I was foolin around with car audio, I had a box that started out as a bandpass sub using a Polk DB-series 10" sub. After I got a bigger-louder sub/box, I experimented around with the first box and ended up with the original sub inside like a traditional bandpass but with a P/R in place of the original port (front chamber) and a port added to the rear chamber. It turned out really smooth and clean sounding. Talk about dumb luck .

I only mention this to say some really wacky things can actually work. I'd never be able to duplicate that box, tho'. I have absolutely no recollection what the tuning was on that thing .

[Mayhem13]

Jeffs method looks like a sound one to model such a project but given the cost of PRs, the large size and limited Freq range of Bpass, why not just go with a regular PR alignment? UNLESS the goal is really low stuff, say crossed below 40hz and tuned for lets say 18hz or so-now things get interesting. A 4th Order Bandbass may be just the thing for such a narrow Freq band.

[robseyes]

The "BMF-1" from Av123.com is essentially a bandpass design with 1 active 15inch driver & 3 18 inch passives, but its vaporware until its finally released (been talked about for months).

[HareBrained]

Way back when I was foolin around with car audio, I had a box that started out as a bandpass sub using a Polk DB-series 10" sub. After I got a bigger-louder sub/box, I experimented around with the first box and ended up with the original sub inside like a traditional bandpass but with a P/R in place of the original port (front chamber) and a port added to the rear chamber. It turned out really smooth and clean sounding. Talk about dumb luck .

I only mention this to say some really wacky things can actually work. I'd never be able to duplicate that box, tho'. I have absolutely no recollection what the tuning was on that thing .

6th order BP. Nice. Now replace the second port with a second PR.

[depthsounder]

I think a passive radiator would be great for a bandpass with small chambers. For example, the MCM 55-2421 requires extremely an extremely small box volume due to its unusually low qts and vas. Trying to use standard vents to tune a bandpass with this woofer requires impracticably long ports. PRs might be the way to solve this problem and keep a small box volume.

-David

[Dirk]

If forced to tune by ear, I'd initially mount the PR in the box backwards, thereby giving you easy access. Listen for a bit, toss on a bit more mass, listen for a bit, remove some mass...

[jkrutke]

I've done a passive radiator bandpass twice, the first time being 15 years ago. Here's a 4 chamber system with with two 6" woofers and 8" lightweight PR's



It works well, but Jeff is right about finding a PR with low enough mass to start with. My 3rd design which I never built for various reasons had a hand made PR diaphragm. I've got a drawing and some written notes somewhere. If anyone is interested, I'll dig it up.

[HareBrained]

Along the same lines of depthsounder, I think a PR bandpass would be good for high-excursion subs that require large port areas to avoid port noise. And thus require long ports. Cone excursion is better with the PR/BP vs. a port.

I played around with Jeff B.'s method using Unibox and found it easiest to put the vented Vb into the PR model and then plug the PR Fb back into the BP model. The TB W6 Neo or two W5 Neo's with a SD215PR with 0-25g modeled pretty well. Two W6 and a SD270PR works for more radiating area.

Seas PR's (sold by those in Madison) have very little MMg.

[isaeagle4031]

This is essentially what my Logitech Z4 system is. A 6th order BP that uses an 8" "pressure driver". Not bad, but it is a little boomy.

I have been working on a 6th order series-tuned that uses PRs for the internal ports, but flared ports for the final.

[vasyachkin]

Well Vas? I think the mans waiting for your expert advice. Don't leave him hanging.

i just don't think its worth it.

you have to go back to the reasons why PRs are used when they're used and why they're not used when they're not.

if you understand those you will understand that in a bandpass box using them is silly, although possible.

[Pete Schumacher ®]

I was wondering if it would be possible to build a bandpass cabinet with radiators in place of ports?
ALSO, if you were building a higher order bandpass, could you use ports for internal "linkages" and radiator(s) for the external ones. I think this would could make for a more interesting looking system if it is indeed possible.

I would think from a logistical standpoint having radiators in, say a 4th order, would reduce port noise and provide a tighter bass response, but how would one go about calculating the radiators (and mass) needed??

I ran the RSS390HF through WinISD and determined a "small" 4th order alignment using the Dayton 15" DVC PR. Using 2 cubic feet for the rear chamber and 1.8 cubic feet for the front, you get lower and upper F3 of 26Hz and 80Hz.

There is one great benefit to doing this. Any distortion products produced by the driver that would normally have been picked up by the port resonance will no longer be heard. The PR does a much better job at masking internal "noises" that might be produced by the driver.

[vasyachkin]

There is one great benefit to doing this. Any distortion products produced by the driver that would normally have been picked up by the port resonance will no longer be heard. The PR does a much better job at masking internal "noises" that might be produced by the driver.

i haven't thought of this ...

so you're saying bandpass box can be used to effectively lower distortion of the speaker system without lowering the distortion of the driver itself by filtering out harmonics ?

because i was trying to figure out ANY advantage of bandpass loading versus lowpass filtering aside from a small bump in output ... and the one you mention could almost make it worth it ... probably still not worth it though

[greysplash]

How about a dual (or triple)-chamber-reflex system with PR's instead of ports??

What an interesting speaker that would be... One full range driver but the appearance of 3 (or 4) cones. I like to tinker and am seriously considering the possibility of doing this. However I think that I'll run into volume problems... a large driver with little volume needed.

Has anyone tried this and/or do you guys think it would produce results worth building?? Im thinking of possibly modding Wolf's 3CR-Ti's that were showcased a couple months back. Im having a hard time finding tried and true designs for chamber-reflex systems.

[darkkhild]

"Along the same lines of depthsounder, I think a PR bandpass would be good for high-excursion subs that require large port areas to avoid port noise. And thus require long ports. Cone excursion is better with the PR/BP vs. a port.

I played around with Jeff B.'s method using Unibox and found it easiest to put the vented Vb into the PR model and then plug the PR Fb back into the BP model. The TB W6 Neo or two W5 Neo's with a SD215PR with 0-25g modeled pretty well. Two W6 and a SD270PR works for more radiating area.

Seas PR's (sold by those in Madison) have very little MMg."

Harebrained,

What were the size of the enclosures your were modeling for this design?
Thanks!!