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Dual Opposed Subwoofer Theory?

Chromatischism said:
Okay, that's what I thought. I posted two companies that make better dual opposed subs.
Click to expand...
define "better"? For me, smaller is better, so the SVS Micro 3000 is a better choice than the Rhytmik G22 Direct Servo subwoofer, even if the specs for the G22 might be better. I would not compare a small/mini sub (like kef kc62 or svs micro 3000) against a "big" sub.

next time i read what was written before :p
 
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Ilkless said:
the 2 drivers can easily be spaced within 1/4 wavelength of each other due to the large wavelengths in their passband
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Wouldn't that make it a single sub with two drivers, without the benefits of a multi-sub system?
 
Alexium said:
Wouldn't that make it a single sub with two drivers, without the benefits of a multi-sub system?
Click to expand...

Yes, but the benefits of a multi-sub system occur when spacing is further apart than in any meaningful dual-opposed configuration. Multi subs spread out how the room is energised, dual opposed claim to cancel out enclosure vibrations.
 
Ilkless said:
Yes, but the benefits of a multi-sub system occur when spacing is further apart than in any meaningful dual-opposed configuration. Multi subs spread out how the room is energised, dual opposed claim to cancel out enclosure vibrations.
Click to expand...
It's not just a claim, it actually does.
 
Ilkless said:
Yes, but the benefits of a multi-sub system occur when spacing is further apart than in any meaningful dual-opposed configuration. Multi subs spread out how the room is energised, dual opposed claim to cancel out enclosure vibrations.
Click to expand...
I see! Thank you, I missed he point then, and never heard about this concept before.
 
Ilkless said:
Yes, but the benefits of a multi-sub system occur when spacing is further apart than in any meaningful dual-opposed configuration. Multi subs spread out how the room is energised, dual opposed claim to cancel out enclosure vibrations.
Click to expand...

That's what I had custom built for myself. These are the CAD drawings (all measurements in mm):

rythmik3.jpg

rythmik4.jpg


And this is the result. It was my desire to have the subwoofer box match the design of the TV cabinet as much as possible, but in the end it was not possible to get a veneer match. So I had to settle for something close in colour but without the grain:

dsc01114.jpg


I have two subwoofer boxes, each box has two drivers. It is quite overwhelming and the bass response, as measured with REW, is not as lumpy compared to if I only had one. Sorry I don't have a graph with me to post.
 
I just finished a pair of dual opposed subs myself but they aren't nearly as pretty as @Keith_W's.

The fact that the don't vibrate at all let you reclaim space by using them as furniture - doubling as a table or shelf.
 
Thank you @maverickronin. There were quite a few reasons why I thought it was advantageous to go with this design. First is the vibration cancellation. Second is double output at where in-room measurements showed that placing the subs there would result in the smoothest in-room response. Third is that each driver has half the excursion needed to produce the same volume, which bring the 4th and 5th benefits: more time spent in the linear magnetic portion of the motor, and less cone breakup. Then there are the benefits of a high Q design, and the Rythmik drivers I used are servo controlled. The whole thing is integrated into the main speakers with DSP. The result is remarkably linear bass and to be frank, a little too much output unless I turn the volume all the way down.
 
I had one question that came to my mind.

Usually Dual-Opposed Subwoofers (DOS) are designed like this:
(view from the side)
1670078768411.png


Theoretically speaking, would this design also work fine?

1670078808235.png


I am asking as I am aiming for a slim design and the latter driver arrangement would allow that
I think it would work just fine but any comments would be welcome
Thank you
 
ppataki said:
I had one question that came to my mind.

Usually Dual-Opposed Subwoofers (DOS) are designed like this:
(view from the side)
View attachment 247496

Theoretically speaking, would this design also work fine?

View attachment 247497

I am asking as I am aiming for a slim design and the latter driver arrangement would allow that
I think it would work just fine but any comments would be welcome
Thank you
Click to expand...

The second one wouldn't really be dual opposed any longer since the axis between the woofers is no longer symmetrical. When the drivers are moving, the imbalance of the forces will make the cabinet vibrate. Acoustically, that's not usually much of a problem, (and it can easily be considered a plus as that vibration will couple to your floor and chair) but you loose the ability to use it as an end table you can set your drink on.

If you're trying to fit as many drivers as possible in a tall and slim volume then it should be fine, depending on your crossover frequency.

It really depends on your needs and goals.
 
Ilkless said:
Well, yes but not so much if both are spread apart wide enough as to mimic a multisub configuration.
Click to expand...

That sounds like a weird design and an extremely large (or long?) subwoofer :)
 
ppataki said:
What do you mean by imbalance please?
Click to expand...
For every action there is an equal and opposite reaction. With a driver perfectly opposed, there is perfect canceling. I'm not saying it will wobble like a washing machine, but being off-axis from the other driver there will be a less than perfect effect. Use HDF and ensure that thing is heavy and stable.
 
Chromatischism said:
For every action there is an equal and opposite reaction. With a driver perfectly opposed, there is perfect canceling. I'm not saying it will wobble like a washing machine, but being off-axis from the other driver there will be a less than perfect effect. Use HDF and ensure that thing is heavy and stable.
Click to expand...
maverickronin said:
he second one wouldn't really be dual opposed any longer since the axis between the woofers is no longer symmetrical. When the drivers are moving, the imbalance of the forces will make the cabinet vibrate. Acoustically, that's not usually much of a problem, (and it can easily be considered a plus as that vibration will couple to your floor and chair) but you loose the ability to use it as an end table you can set your drink on.

If you're trying to fit as many drivers as possible in a tall and slim volume then it should be fine, depending on your crossover frequency.

It really depends on your needs and goals.
Click to expand...
Thanks @maverickronin and @Chromatischism, much appreciated!
I will think about it twice, maybe I will just stick to using 1 driver but with a bigger size - will simulate different scenarios and decide accordingly
 
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