Dual opposed better for long room?

[Mort]

I have a long room, 15x40 with living areas at either end. There are in-ceiling speakers at either end run off individual Wiim amps. They do not reproduce low frequencies adequately and I want to add a sub.

For various reasons I can get only one subwoofer in the room, roughly in between the two 'spaces' along one long wall.

Because it's in between the listening areas, would a dual opposed like Rythmik G22 (basically two F12s firing in opposite directions) be advantageous in some way?

The G22 is a big expensive unit. I could, alternatively get a smaller, cheaper front firing F15. ( I'm not wed to Rythmik but mostly own them. Have SVS also. )

Thoughts?

 

[SteveC]

Not a direct answer to your question, but a suggestion. If you haven't already I recommend you download the free REW software and use the room simulator to try different combinations of subs and locations. In my case, in my small 12' by 15' room, I got the best predicted response by placing my SVS subs side-by-side between the primary KEF R3 mains. Measurements and my ears confirmed that this suggestion was much better than the previous placements close to the walls. It might save you some money, too! https://www.roomeqwizard.com/

 

[digitalfrost]

Because it's in between the listening areas, would a dual opposed like Rythmik G22 (basically two F12s firing in opposite directions) be advantageous in some way?

No. The speed of sound is ~ 343m/s. That means 40hz has a wavelength of 343 / 40 ~ 8.6m. In other words, the enclosure of the subwoofer is invisible for the soundwave, as is it very small against the sound. The subwoofer has a monopole radiation pattern, i.e. it will radiate the same into all directions (it radiates into 4pi space which is a sphere). It does not matter which direction the chassis faces.

Once you move up to shorther wavelengths (higher frequencies) eventually the wavelength will be small against the speaker baffle. Where that happens the radiation of the speaker will change into 2pi space, since the waves can "see" the baffle. Because of this, frequencies that are smaller than the baffle width will be louder, as we radiate the same amount of energy into half the space. This is called the baffle-step and has to be compensated for in the crossover. https://sound-au.com/bafflestep.htm

For subwoofers it does not matter.

That said I like dual opposed subs quite a lot because the enclosure is inert. Regardless of weight and how loud you play it will not move about the floor.

 

[Mort]

Does the dual vs driver subwoofer potentially help with room modes more in a longer room with listening areas at either end?

 

[Blumlein 88]

Does the dual vs driver subwoofer potentially help with room modes more in a longer room with listening areas at either end?

No, that is what digitalfrost was getting at. If it were a speaker at higher frequencies the speaker output would be directional and it might matter. With a sub, even with a woofer on only one side it will radiate omni-directionally at the frequencies a sub covers. A dual woofer sub would radiate the same. The advantage in such a dual woofer is more output capability and that driving forces from each are opposed. So they can cancel out with less sound/resonances from the cabinet.

 

[Oddball]

As noted, dual subs might give you some SPL advantage that for sure you will need in this large room, but otherwise are just subs like the rest of them. Some of them could also be used as coffee tables as the cancel out the enclosure movement, but that is not really that relevant for most.

If only 1 sub in such a large room, I would be more concerned about placing it (relatively) near-field to the MLP as each meter of distance will cost you valuable 3-4dB of output at the MLP. At the end of the day, you will need to see what is the best trade off between realistic or desirable placement options, SPL and frequency response.

Realistically, this is a scenario for 2 larger subs or preferably 4 subs to achieve close to reference output, uniformity in FQ response and cancelation of the room modes in most of the listening area. Also, with 1 sub, you might be faced with some room modes so that while it sounds relatively OK at MLP, people dining in the back might hear awful positive room modes in low frequencies.

 

[Mort]

Thanks all. Even though I have read this before, I struggle to apply it. Thanks for your patience.

Regarding subwoofer driver size: Although it's a large room, it's rare to play very loudly or need a lot of amplification.

The LR ceiling speakers are quite close with 10 foot ceilings in each listening area, maybe 5-7 feet seated. The sub will be at least 15 feet and sometimes further from listening areas.

Will I likely benefit from a driver larger than 12"? What would be any perceived difference?

 

[digitalfrost]

Realistically, this is a scenario for 2 larger subs or preferably 4 subs to achieve close to reference output, uniformity in FQ response and cancelation of the room modes in most of the listening area. Also, with 1 sub, you might be faced with some room modes so that while it sounds relatively OK at MLP, people dining in the back might hear awful positive room modes in low frequencies.

If he was willing to sacrifice some wall space this would also be perfect for a single- or a double bass array.

 

[Oddball]

Thanks all. Even though I have read this before, I struggle to apply it. Thanks for your patience.

Regarding subwoofer driver size: Although it's a large room, it's rare to play very loudly or need a lot of amplification.

The LR ceiling speakers are quite close with 10 foot ceilings in each listening area, maybe 5-7 feet seated. The sub will be at least 15 feet and sometimes further from listening areas.

Will I likely benefit from a driver larger than 12"? What would be any perceived difference?

Honestly, 15 feet will be challenging for most subs. Also, sub optimisation you run (nor sure what EQ system though) will be limited to a single area. Trying to combine two remote MLPs for optimisation will likely ruin optimisation for both positions. Optimisation for entire listening space if needed is done with the use of more subs in double bass array configuration. Single bass array as noted might also have some benefits in certain rooms, but also requires at least 2 subs.

 

[Blumlein 88]

You could look into the REW simulation and perhaps you can use two subs vertically separated. You can do that in the REW simulation and that may or may not be acceptable in your room.

 

[Mort]

Y'all are very helpful. I guess this is the dilemma. In theory one big sub could do it but I think it's going to be hard to integrate.

I was hoping dual opposed might help but it seems I need to figure out a way to do subs closer to these listening positions.

I should really get some measurements. I have my microphone, I just need to spend some time with it

 

[Flaesh]

living areas at either end.

Your room is longer than mine! The most living area is the middle half of the room. I prefer front bass and am wary of subwoofers behind the listener.
I have no hope that this will help .

 

[Flaesh]

I need to figure out a way to do subs closer to these listening positions.

I missed this yesterday! This changes things.
I assume you saw the link in my signature?).

I should really get some measurements.

Yeah. For both listening positions. The SSS configuration can be quite useful in such a room, especially if the bass in the listening positions is poor. But switching between the two systems is not a trivial task.
Or maybe the reality is not so bad and you can get by with a plain room correction for each audio system.