Hi all,
I have built several sub designs and enjoyed them and recently did an open baffle subwoofer with 4 drivers in it and I liked it a lot and I also did a dual opposed sealed sub recently and I really love how dead the box is. It got me thinking more about how to mass up some open baffle subs but to take advantage of some other concepts mixed in such as doing open baffles that are opposed to cancel the structure vibrations.
I have 8x 12" drivers just sitting, waiting for a project, so I was thinking of a segue into an experiment (for me at least) to explore this with them. I don't see much of this when I search but I'm sure it's been done many times and maybe it's just not great for the effort and cost, I don't know. I do know that I liked my 4 driver open baffle sub a lot. And I like my dual opposed sealed. So I'm thinking I'll throw together a basic platform to test these 8 drivers to see how it behaves and sounds (full active DSP to shape the output).
I'm thinking of two baffles, front and back, 4 drivers per baffle, opposed arrangement and all in phase so that structure vibrations are canceled. My goal is to build these taller like towers, 4 drivers tall basically. The opposed arrangement would be to keep the scaffold tower dead and from shaking so so that the drivers don't walk around flapping in the air.
What I'm curious about though is how the drivers will interact with the room. Off axis will still be lower right? So floor proximity shouldn't get pummeled the way a sealed sub does? I ask because of the idea of exciting or coupling heavily to a wooden subfloor vs concrete. If the drivers are 90 degrees off axis from the floor since they will face into the room, will the floor receive as much energy under the scaffold tower as a traditional cabinet sub?
Very best,
I have built several sub designs and enjoyed them and recently did an open baffle subwoofer with 4 drivers in it and I liked it a lot and I also did a dual opposed sealed sub recently and I really love how dead the box is. It got me thinking more about how to mass up some open baffle subs but to take advantage of some other concepts mixed in such as doing open baffles that are opposed to cancel the structure vibrations.
I have 8x 12" drivers just sitting, waiting for a project, so I was thinking of a segue into an experiment (for me at least) to explore this with them. I don't see much of this when I search but I'm sure it's been done many times and maybe it's just not great for the effort and cost, I don't know. I do know that I liked my 4 driver open baffle sub a lot. And I like my dual opposed sealed. So I'm thinking I'll throw together a basic platform to test these 8 drivers to see how it behaves and sounds (full active DSP to shape the output).
I'm thinking of two baffles, front and back, 4 drivers per baffle, opposed arrangement and all in phase so that structure vibrations are canceled. My goal is to build these taller like towers, 4 drivers tall basically. The opposed arrangement would be to keep the scaffold tower dead and from shaking so so that the drivers don't walk around flapping in the air.
What I'm curious about though is how the drivers will interact with the room. Off axis will still be lower right? So floor proximity shouldn't get pummeled the way a sealed sub does? I ask because of the idea of exciting or coupling heavily to a wooden subfloor vs concrete. If the drivers are 90 degrees off axis from the floor since they will face into the room, will the floor receive as much energy under the scaffold tower as a traditional cabinet sub?
Very best,
A picture of what structure you are thinking of would be helpful.
Sounds like you want a doubled up version of the W baffle used on the Orion 4: https://www.linkwitzlab.com/orion-rev4.htm
The XSD speakers use the same principle: https://www.diyaudio.com/community/threads/the-xsd-speaker.385717/
The XSD speakers use the same principle: https://www.diyaudio.com/community/threads/the-xsd-speaker.385717/
Hrm,
Maybe I explained poorly. I will try to paint a new mental picture.
Imagine a front baffle, 16" wide by 60" tall. It has 4 x 12" sub drivers on it facing towards you.
Behind this baffle, about 15" behind it (depth) there is an identical baffle with 4 more 12" sub drivers, but facing away from you.
Magnet to magnet, aligned (opposed).
A sub tower that is open baffle with 8 total drivers, 4 in opposition (newton's third law to kill vibrations to the scaffold/baffle/structure).
Then shape output via DSP entirely.
Very best,
Maybe I explained poorly. I will try to paint a new mental picture.
Imagine a front baffle, 16" wide by 60" tall. It has 4 x 12" sub drivers on it facing towards you.
Behind this baffle, about 15" behind it (depth) there is an identical baffle with 4 more 12" sub drivers, but facing away from you.
Magnet to magnet, aligned (opposed).
A sub tower that is open baffle with 8 total drivers, 4 in opposition (newton's third law to kill vibrations to the scaffold/baffle/structure).
Then shape output via DSP entirely.
Very best,
Concept still applies. Loading an even numbern of woofers push-push in the slot makes for active reaction force cancelation
My concept from 200
https://www.t-linespeakers.org/FALL/dipole.html
And XRK’s is another example (i prefer push-push with good woofers): v
dave
I don't see any vibration killing going on in your "new mental picture" of two separate open baffles, each with four drivers facing towards and away from you, all drivers wired in the same polarity.
If the panels are connected with braces, if that's what you mean by "scaffold", perhaps.
Hi,
Yes, two baffles coupled via braces. 4 drivers per baffle. Magnet to magnet, aligned in opposition but same polarity. Quad-opposed basically. Should cancel forces between them imposed onto the scaffold/baffles I think?
Very best,
If the woofers in the rear baffle are moving in the opposite direction from those in the front baffle, and both baffles are open, you would get a quadrupole radiation pattern in the horizontal plane. That would increase low frequency cancellation, throwing away power. You'd need to have all the woofers moving in the same direction at the same time to preserve dipole radiation, but then you wouldn't get cancellation of vibrations.
See:
Last edited:
Interesting thanks, this is why I was asking as I figured it was more complicated. In a sealed box, opposed but same polarity, he forces in the box are canceled. So in two open baffles this doesn't happen? I guess I'm hung up on the force of motion vs the wavefront being not the same thing and that if they're opposed he forces cancel but a wavefront still emanates from the radiators. Or does this still happen, forces cancel, but you lose low end SPL due to the wrapping around of the frequencies and canceling each other as you mentioned?
Thank you, that video perfectly explains what I needed to know.
This will not work! Hah. Saved me some plywood.
So, building on that, since I cannot do opposition to reduce structure vibrations between the drivers, if I have the drivers facing the same direction and same polarity but on two baffles, one behind the other, this is still a dipole and will not have low frequency cancelation?
Very best,
Last edited:
Thanks; so I'm better off just having them all in the same plane, same polarity then.
Very best,
Hi Dave,
So coming back to this then, I'm trying to see how the drivers are oriented so that active force cancelation is preserved, so push-push and facing opposite directions. But they could be magnet to magnet or the other way around too (I think?). I guess I'm wondering then how the pattern radiates from the sides of the drivers without low frequency cancelation? Or is it because of the shape of the baffle, the drivers are essentially on the same plane as he wavelength wraps around?
Very best,
Probably.
You can still have two baffles, if you want, one behind the other. It will still work much the same as if they were all on one baffle. Just so long as all the cones are moving towards you together and away from you together.
Celestion did it with the 6000 subwoofer back in the 80s:
https://www.stereophile.com/floorloudspeakers/892/index.html
Thanks, interesting.
Overall I would like to minimize floor space and not need big boxes, and yet still be able to cram as many cheap 12" sub drivers into an open baffle setup as I can and then shape it with DSP. If I can put two baffles togeher, one in front of the other, drivers facing same direction, all moving in same polarity/phase, and still get good net summation of SPL, that's good too for me. It would make for a more stable tower if I have two baffles coupled compared to one big tall baffle tower.
I guess I keep getting confused with the earlier comments about quad-poles and then the examples with alternating woofer directions in pairs on some examples above and how that's differen?
Very best,
It is tricky to get your head round, where you have two totally separate baffles. Just think about how the cones are moving. If all the cones move towards you at the same time, and away at the same time, you get dipole radiation (but no vibration cancellation). If the cones on the rear baffle are moving away from you while the cones on the front baffle are moving towards you, you get quadrupole radiation (but the vibrations will cancel).
Of course, if you create a W baffle, rather than having two separate baffles, it's different. Then you can get both force cancellation and dipole radiation. But you have to consider cavity resonances. That's how the Orion 4 and the SLOB and XSD do it.
Of course, if you create a W baffle, rather than having two separate baffles, it's different. Then you can get both force cancellation and dipole radiation. But you have to consider cavity resonances. That's how the Orion 4 and the SLOB and XSD do it.
Thanks, I think I have this part. Good point about direction of the movement.
Now, to build on this, what's different in Dave's examples above where the drivers are magnet to magnet and magnet to cone and sideways relative to the face of the speaker, and he comments of it being push push and also still canceling vibrations?
Very best,
Ok thanks; I will start searching for "w frame" to learn more.
Any particular great info/source links on w frames relative to bass?
Very best,