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Dual Opposed Subwoofer & Room Acoustics

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#1
Ok, so I need a subwoofer for my main system. What sold me was the addition of one to my office system, which, shockingly, had a bigger effect on the midrange than on the actual low end energy for the purposes of music. I want to see what my main speakers can do when freed up from sub duty.

I posted in a previous thread about which subs to get, and you all helpfully steered me in the direction of a few good manufacturers. I'm now looking at practical implementation.

My question here: I see the Rythmik G22 ( https://www.rythmikaudio.com/G22.html ) ... I really don't have space for two subs, but it looks like this might be a good way to compromise on dual subs, from an acoustic perspective. Would a dual opposed driver help make sub placement easier with only one unit? Does anyone know if the opposed configuration serves to smooth out in-room response from any one location? I would think it might, but I can't find any evidence for/against this, or measurements.
 
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#2
The sub configuration – sealed, ported, bandpass, opposed drivers etc. – has no bearing on ease of sub placement. Neither will one configuration be better at smoothing out response compared to another. Any smoothing that might be realized by dual subs requires two units in two separate locations.

Regards,
Wayne A. Pflughaupt
 
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Thread Starter #3
The sub configuration – sealed, ported, bandpass, opposed drivers etc. – has no bearing on ease of sub placement. Neither will one configuration be better at smoothing out response compared to another. Any smoothing that might be realized by dual subs requires two units in two separate locations.

Regards,
Wayne A. Pflughaupt
Interesting, so is this simply because the driver is effectively non-directional at these frequencies? I guess the intuitive thought here is that a driver facing in each direction, actively driven, would be filling the room with the sound from two directions.
 

win

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#4
A subwoofer already radiates its energy omnidirectionally. You can mount a subwoofer with the driver facing up, down, backwards, forwards, and it's not going to change the in room modal response. That's what you're fighting. And you can't win the battle with only one subwoofer, unfortunately. The issue becomes larger when you want a flat frequency response across a larger area.
 

Willem

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#5
Indeed. A smoother response needs two (or more) locations rather than two drivers, which is not to say that two opposing drivers are not a good idea for different reasons. So your best bet would be two smaller subs, helped by some kind of dsp room eq. How large/small is the room?
 
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Thread Starter #6
Indeed. A smoother response needs two (or more) locations rather than two drivers, which is not to say that two opposing drivers are not a good idea for different reasons. So your best bet would be two smaller subs, helped by some kind of dsp room eq. How large/small is the room?
Room is 7.6m x 6.4m / 25ft x 21ft. Ceilings are 3.3m / 11ft.

So... I guess cubic area is 160m^3 / 5775ft^3.

The actual listening position is only 3m from the speakers, though, and the "listening area" is about 3m x 3m, it's just part of a larger room.
 

FrantzM

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#7
Repeating what some have posted. At least 2 subs... In different locations. Integration is nor simple nor for the impatient...
 
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Thread Starter #8
In terms of the finalists, I'm considering the following:
Again, this is driven more by aesthetics and by space than anything else. I -can- do the dual sub if I go with a small enough dual sub, but it seems like the output on the singles above are all way better than the sb-100.

So, given this list, dual subs over any single sub?
 

FrantzM

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#9
For the same price, go dual. This may however require:
Some DSP unit... I suggest the miniDSP 2 x 4 HD ($200)
A good measuring microphone miniDSp UMik-1
The wonderful and free REW (Room EQ Wizard) , Donate please, this is an incredibly powerful software

Then it will take time (lot) and learning and experimenting but the results... Ahh!!!! The results!!!
 
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Thread Starter #10
For the same price, go dual. This may however require:
Some DSP unit... I suggest the miniDSP 2 x 4 HD ($200)
A good measuring microphone miniDSp UMik-1
The wonderful and free REW (Room EQ Wizard) , Donate please, this is an incredibly powerful software

Then it will take time (lot) and learning and experimenting but the results... Ahh!!!! The results!!!
Cool, I have all of the above lying around (and yeah, I donate, it's awesome software).

Ok, duals it is, I'll report back. Thanks all!
 
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#11
In terms of the finalists, I'm considering the following:
Again, this is driven more by aesthetics and by space than anything else. I -can- do the dual sub if I go with a small enough dual sub, but it seems like the output on the singles above are all way better than the sb-100.

So, given this list, dual subs over any single sub?
Two, but instead of two SB-1000, get two SB-2000(non-pro). I think they're still in stock here: https://www.amazon.com/dp/B00IE5MOUM
 

yourmando

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#12
Ok, so I need a subwoofer for my main system. What sold me was the addition of one to my office system, which, shockingly, had a bigger effect on the midrange than on the actual low end energy for the purposes of music. I want to see what my main speakers can do when freed up from sub duty.

I posted in a previous thread about which subs to get, and you all helpfully steered me in the direction of a few good manufacturers. I'm now looking at practical implementation.

My question here: I see the Rythmik G22 ( https://www.rythmikaudio.com/G22.html ) ... I really don't have space for two subs, but it looks like this might be a good way to compromise on dual subs, from an acoustic perspective. Would a dual opposed driver help make sub placement easier with only one unit? Does anyone know if the opposed configuration serves to smooth out in-room response from any one location? I would think it might, but I can't find any evidence for/against this, or measurements.
I have 3 Rythmik G22s. The reasons I got them, and that are unique to dual opposed subs are:

1. Dual opposed drivers cancel cabinet movement/resonance because the driver forces moving in equal and opposite directions cancel. This was important to be because I have old wooden floors that are like a trampoline, and I would otherwise have to have heavy padding or other isolation system to prevent the floor resonating too much.

Also, when I was looking for good sub locations, one of the best locations I found was right under the rear surrounds. Because the sub cabinets are pretty much inert, I was able to mount the speakers in short mic stands sitting directly on top of the subwoofers.

2. Dual opposed subs are one of the best ways to get the most output out of the smallest possible volume. For me, this worked best with my room size, and also opened up more location options. With dual opposed, I get the same output as two 12” sealed subs, in a form factor that’s almost as small as one 12” sealed sub. One G22 is gives 1.5db less output at 20hz that the sealed 18” F18, but in a much smaller footprint. 2 of my 3 sub locations would only be possible in this smaller size.

As others have said, a dual opposed subwoofer will just act like a single subwoofer with more output, so you’ll want to get a sub at a size that will allow you to place 2 or more subs in the room.

An exception would be if you only need to optimize for 1mlistening position, and don’t care about smoothing the Bass response across multiple seats in the room. In the 1 seat case, you can usually do fine with a single well placed and EQd sub.
 
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Thread Starter #13
I have 3 Rythmik G22s. The reasons I got them, and that are unique to dual opposed subs are:

1. Dual opposed drivers cancel cabinet movement/resonance because the driver forces moving in equal and opposite directions cancel. This was important to be because I have old wooden floors that are like a trampoline, and I would otherwise have to have heavy padding or other isolation system to prevent the floor resonating too much.

Also, when I was looking for good sub locations, one of the best locations I found was right under the rear surrounds. Because the sub cabinets are pretty much inert, I was able to mount the speakers in short mic stands sitting directly on top of the subwoofers.

2. Dual opposed subs are one of the best ways to get the most output out of the smallest possible volume. For me, this worked best with my room size, and also opened up more location options. With dual opposed, I get the same output as two 12” sealed subs, in a form factor that’s almost as small as one 12” sealed sub. One G22 is gives 1.5db less output at 20hz that the sealed 18” F18, but in a much smaller footprint. 2 of my 3 sub locations would only be possible in this smaller size.

As others have said, a dual opposed subwoofer will just act like a single subwoofer with more output, so you’ll want to get a sub at a size that will allow you to place 2 or more subs in the room.

An exception would be if you only need to optimize for 1mlistening position, and don’t care about smoothing the Bass response across multiple seats in the room. In the 1 seat case, you can usually do fine with a single well placed and EQd sub.
Good to know. I have concrete floors, so not an issue there, but I can see that being a super handy feature of the opposing design. And indeed, re: space, I can't believe how small the G22 is for the output.
 

yourmando

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#14
Good to know. I have concrete floors, so not an issue there, but I can see that being a super handy feature of the opposing design. And indeed, re: space, I can't believe how small the G22 is for the output.
Yup. Also, here is a dumb chart I made when I was shopping, showing the price of dual sealed subs vs their equivalent number of F12 (single 12") subs.

The dual sealed are much more cost effective vs the amount of output you get. (The vented subs are even more cost effective for the output, but they are much, much larger.)

 
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Thread Starter #16
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#17
Again, this is driven more by aesthetics and by space than anything else. I -can- do the dual sub if I go with a small enough dual sub, but it seems like the output on the singles above are all way better than the sb-100.

So, given this list, dual subs over any single sub?
Keep in mind that the “smoother response” people are talking about requires the subs to be in two separate locations. Two subs at the same location in the room is functionally no different than a single sub, although it will get more headroom.

In your situation with the listening area being a relatively small area of a much larger room, I highly doubt you’ll get any of the “improved response” benefit from separated dual subs. I’ve had rooms like that before, and the bass sounded just fine in any seats well away from room boundaries.

Regards,
Wayne A. Pflughaupt
 
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Thread Starter #18
Keep in mind that the “smoother response” people are talking about requires the subs to be in two separate locations. Two subs at the same location in the room is functionally no different than a single sub, although it will get more headroom.

In your situation with the listening area being a relatively small area of a much larger room, I highly doubt you’ll get any of the “improved response” benefit from separated dual subs. I’ve had rooms like that before, and the bass sounded just fine in any seats well away from room boundarews.

Regards,
Wayne A. Pflughaupt
Got it, so unless I'm going to put one sub, like, across the room from the other, I don't get much benefit from having both up front spaced about as far apart as my speakers (2.5m)?

If that's the case, I might just go back to the G22 and call it it day, maybe get a second some time if I find another place to put it, since I definitely don't need the headroom, I'm no bass head. Really just trying to offload my main speakers (Meridian DSP 5200.2)
 

yourmando

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#20
Got it, so unless I'm going to put one sub, like, across the room from the other, I don't get much benefit from having both up front spaced about as far apart as my speakers (2.5m)?

If that's the case, I might just go back to the G22 and call it it day, maybe get a second some time if I find another place to put it, since I definitely don't need the headroom, I'm no bass head. Really just trying to offload my main speakers (Meridian DSP 5200.2)
Unfortunately I don’t think it’s that simple.

Are you optimizing for multiple seating locations our just your one seat? If just one seat, I’m reasonably confident you can get one sub with good placement and eq to work.

If you want even bass over 2 or more seats, it’s tougher.

The results you get depend entirely on your room at subwoofer frequencies. You might be lucky have both good and even bass from just one sub. Totally depends in the room, and it’s somewhat of a crap shoot as most real world rooms are hard to model—they are not rectangular boxes.

My room is open on 3 sides in the mid wall to other rooms, and the back wall is a giant bay window, which lets bass right through. I can place a sub anywhere in my room and get giant suck outs in mostly the same frequency ranges. And moving across seats—really inconsistent bass with wide variation in frequency response. Othears get a big bass boost that’s easy to knock down, with more consistent bass response across seats w/ no fancy multi-sub optimization.

In my room, I can only get good results with multiple sub optimization, and even then I still have one consistency problem that I need to work out at around 60hz, where there is a dip on some seats.
 
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