# Setting up 2 subwoofers facing different directions?



## n00b (Nov 19, 2012)

Hi

I currently have 1 sub facing the back in the front left corner, however bass feels a bit low in the room. Due to room limitations it isn't really possible to move the sub elsewhere apart from the back left corner where the bass response felt even lower. However I am thinking of adding a second sub and putting it in the back corner facing the right side which is where the bass feels low. My question is would this improve or make the sound worse? I could also have the back sub facing the front but then the 2 subs would be facing each other directly in line.

Thanks


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## tattoo_Dan (Jan 17, 2009)

n00b said:


> Hi
> 
> I currently have 1 sub facing the back in the front left corner, however bass feels a bit low in the room. Due to room limitations it isn't really possible to move the sub elsewhere apart from the back left corner where the bass response felt even lower. However I am thinking of adding a second sub and putting it in the back corner facing the right side which is where the bass feels low. My question is would this improve or make the sound worse? I could also have the back sub facing the front but then the 2 subs would be facing each other directly in line.
> 
> Thanks



well,first off,adding a second sub(preferably same model) is ALWAYS a huge benefit,

secondly,I know you said moving the sub you have is not an option,but I would at least try it even if temporarily in other spots in the room,do the bass crawl, http://www.audioholics.com/tweaks/speaker-setup-guidelines/crawling-for-bass-subwoofer-placement and if that works in a different place(which it most surely will),dig deep and over ride the WAF & move it !

also sometimes moving the main sitting position even a foot or two can make a big difference,and moving the sub a foot or two can also change things.


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## Zeitgeist (Apr 4, 2009)

My best advice is to try it and see how it sounds.

You don't normally want 2 subs directly facing eachother, unless there is a few feet between them.


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## hjones4841 (Jan 21, 2009)

If you have room for two side by side, co-location can add at least 6db more output. However, having them separated can result in smoother freq response. Corners are best for low bass output, but that placement excites more room resonances, or "modes," so overall smoothness can be worse.


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## n00b (Nov 19, 2012)

Side by side isn't really an option due to narrow front space. That would have been one of my first attempts if it was. The problems isn't the wife, its the room logistics. There are doors and windows on the right side of the room! I suppose I could put them on top of each other, however that would double the bass on one side of the room but its the other side of the room where I feel the weak bass is. My speakers are slimline and the crossover is 120hz so I can kind of tell where the sub is coming from in the room at the higher range of frequencies. I don't really want to fork out for another sub yet if it might sound worse that before due to poor placement. Do you think having the second sub in the back corner facing sideways would improve the smoothness across the room or potentially make it more imbalanced? There is about 10 ft between where the front and back subs would go. Would that be ok for the subs to be facing each other?


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## tattoo_Dan (Jan 17, 2009)

n00b said:


> Side by side isn't really an option due to narrow front space. That would have been one of my first attempts if it was. The problems isn't the wife, its the room logistics. There are doors and windows on the right side of the room! I suppose I could put them on top of each other, however that would double the bass on one side of the room but its the other side of the room where I feel the weak bass is. My speakers are slimline and *the crossover is 120hz* so I can kind of tell where the sub is coming from in the room at the higher range of frequencies. I don't really want to fork out for another sub yet if it might sound worse that before due to poor placement. Do you think having the second sub in the back corner facing sideways would improve the smoothness across the room or potentially make it more imbalanced? There is about 10 ft between where the front and back subs would go. Would that be ok for the subs to be facing each other?



you have the sub set at 120 ? if so,try it much lower and see how it sounds,like start at 80


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## n00b (Nov 19, 2012)

Can't realistically lower the sub since my speakers are slimline that only go down to 120hz. I'll try it though and see how it sounds.


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## gdstupak (Jul 13, 2010)

In my experience, the direction that the driver faces isn't a big concern (unless they are very close). The concern with using multiple subs is getting them to work in phase with each other. When drivers are out of phase (one is pushing while the other is pulling), that will decrease output. 
Most subs have phase adjustment knobs that might or might not help the situation. You may have a situation where at 80hz, they are out of phase (not working with each other), so you can tweak the phase adjustment knob to get them in phase. 
But now you go to measure 60hz, and that may be out of phase, so you tweak the phase adjstment knob until they are in phase at 60hz. But then 80hz just got readjusted out of phase.

I had that problem when running two different subs (different drivers, different amps, different enclosures). But now I run two of the same woofer drivers with one amp, they stay in phase at all frequencies all the time.

Not trying to scare you out of using 2 subs, but letting you know why it is important to use the same equipment (if possible) and to have them set up correctly.

As far as crossing over above 80hz. Do it if you need to, keep that sub in the front of the room. If you get a second sub and place it in the rear, then set that one up so it won't play over 80hz.


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## n00b (Nov 19, 2012)

gdstupak said:


> In my experience, the direction that the driver faces isn't a big concern (unless they are very close). The concern with using multiple subs is getting them to work in phase with each other. When drivers are out of phase (one is pushing while the other is pulling), that will decrease output.
> Most subs have phase adjustment knobs that might or might not help the situation. You may have a situation where at 80hz, they are out of phase (not working with each other), so you can tweak the phase adjustment knob to get them in phase.
> But now you go to measure 60hz, and that may be out of phase, so you tweak the phase adjstment knob until they are in phase at 60hz. But then 80hz just got readjusted out of phase.
> 
> ...


That's some pretty good information. Thanks. I will purchase the exact same sub if I decide to get one. Have heard of the problems when buying two different ones. Regarding the phase adjustment, at the front of the room it will be 0 and at the back of the room facing the front it will be 180. But what about if it is at the back of the room facing sideways? Should the be 90 or a bit more since its not at the midpoint of the wall? Due to room constraints the only way to get two subs on different sides at the front would be to place the front speakers on top of the subs, however I thought that would be a bad idea. Would it?


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## gdstupak (Jul 13, 2010)

As far as I know, the only way you can determine how to adjust the phase of each sub is to actually adjust them as you test them.
They can be tested using the REW program available on this forum...
...Or the old-school way, which is how I do it. Play test tones which go up and down the frequency range (for subs this would be 20hz-120hz). If the two subs are in phase with each other, then increasing the volume of one of the subs will increase the overall volume. If the subs are out of phase, then increasing the volume of one of the subs will decrease the overall volume (or the overall volume may remain constant instead of increasing).

EDIT...... I think technically there is a way to determine how to set phase based on speaker location, but it takes actual distance measurements and other criteria. It's not as easy as just saying that one sub is in front of the room and one is at the rear of the room.


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## AudiocRaver (Jun 6, 2012)

gdstupak said:


> As far as crossing over above 80hz. Do it if you need to, keep that sub in the front of the room. If you get a second sub and place it in the rear, then set that one up so it won't play over 80hz.


Reinforcing Glenn's great advice, running that rear sub above 80 Hz, you would really start to hear those higher frequencies from that direction. Keeping it below 80 Hz will avoid that and will hopefully give you a good kick-in-the-pants deep-frequency boost for the room. Sounds like Glenn has been there before, I would definitely follow his lead.


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## bambino (Feb 21, 2010)

Zeitgeist said:


> My best advice is to try it and see how it sounds.
> 
> You don't normally want 2 subs directly facing eachother, unless there is a few feet between them.


+1 Two subs facing eachother = cancellation.


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## n00b (Nov 19, 2012)

Yes I will definitely try listen to gdstupak's advice as he is definitely far more knowledgeable than me at this stuff. The other option I have due to narrow space is to put the front speakers on top of the subs. I haven't considered this before as I thought fronts and subs wouldn't sound good in the same place but I don't have too many other different options to consider. Would setting them up like that work?


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## bambino (Feb 21, 2010)

That would work just be sure to isolate them so the mains don't rattle off the subs. If you could put the subs beside the mains would be best. IMO.:T


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## gdstupak (Jul 13, 2010)

bambino said:


> +1 Two subs facing eachother = cancellation.


Only if they are out of phase with each other. And if they are out of phase, distance nor direction matters, they will cancel each other out, even more than 10' apart from each other.
Many sub systems have multiple subs facing each other only 1 foot apart, including mine.

When 2 drivers are in phase, they will physically push out and pull in at the same time, so even if the drivers are facing each other only 6" apart, they will not cancel each other out.
When 2 drivers are out of phase, one will push out as the other pulls in, which gives a neutral effect.


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## bambino (Feb 21, 2010)

gdstupak said:


> Only if they are out of phase with each other. And if they are out of phase, distance nor direction matters, they will cancel each other out, even more than 10' apart from each other.
> Many sub systems have multiple subs facing each other only 1 foot apart, including mine.
> 
> When 2 drivers are in phase, they will physically push out and pull in at the same time, so even if the drivers are facing each other only 6" apart, they will not cancel each other out.
> When 2 drivers are out of phase, one will push out as the other pulls in, which gives a neutral effect.


Yeap, i know but if not.........:whistling:


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## AudiocRaver (Jun 6, 2012)

Going to have to agree with Glenn on this one, in-phase/out-of-phase is what matters. A sub is basically omnidirectional, so the direction it is facing is of minor importance, except when close to a wall, where frequency response can be affected. If two subs are out of phase, the direction they face won't fix anything, either. At least that's what makes sense to me. Tell me if I'm missing something.

Agreed that two subs very close together and facing each other could cause distortion or have some strange effect in that they would be fighting each other's motion. It might even affect the impedance of the drivers somewhat.


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## n00b (Nov 19, 2012)

AudiocRaver said:


> Going to have to agree with Glenn on this one, in-phase/out-of-phase is what matters. A sub is basically omnidirectional, so the direction it is facing is of minor importance, except when close to a wall, where frequency response can be affected. If two subs are out of phase, the direction they face won't fix anything, either. At least that's what makes sense to me. Tell me if I'm missing something.
> 
> Agreed that two subs very close together and facing each other could cause distortion or have some strange effect in that they would be fighting each other's motion. It might even affect the impedance of the drivers somewhat.


Well they wouldn't be that close to each other. Maybe around 8-10 ft distance between the front firing ports of each one. Is that enough distance for any weird issues not to occur if they are in phase?


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## gdstupak (Jul 13, 2010)

If they were closer than 1 foot, then I would say not to have the drivers facing each other. But of course if you did need to put them right next to each other (less than 1 foot), I don't see why you would want to put the drivers facing each other anyway.
As long as you have several inches of clearance for the driver (several inches of clearance from a wall, or from the floor, or from another sub), it normally doesn't make a difference which way you face it.

As far as placing subs next to or under the main speakers... There is nothing wrong with that. The only reason it is usually best to have a separate sub, is so you can move it to the best sounding location. The best sounding location may be the same location as your main speakers, or it may be at the rear of the room. Or if you have to place it with the main speaker because of WAF, then do that.


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## AudiocRaver (Jun 6, 2012)

n00b said:


> Well they wouldn't be that close to each other. Maybe around 8-10 ft distance between the front firing ports of each one. Is that enough distance for any weird issues not to occur if they are in phase?


Yes. And I second Glenn's last post, too.


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## bluemax_1 (Feb 14, 2011)

Just to add to the info here:

When using two subs, the phase knob is not the best way to get them to play properly together. The phase knob only adjusts phase around a particular frequency, meaning if you get the subs in-phase at one frequency, they'll be out of phase at a different frequency.

The best way to integrate them (especially if placement options are limited) is with individual delay adjustments, i.e. the receiver needs to have separate subwoofer pre-outs that allow for individual distance settings. Adjusting the delay via distance settings affects the delay through the whole frequency range reproduced by the sub, so once they're sync'ed, they'll stay sync'ed even at different frequencies (unlike using the phase adjustment knob).

That coupled with a measurement tool like REW will allow you to optimize their phase integration.


Max


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