# 2 Subs in stereo mode + 5.1



## Dragon777 (Apr 20, 2008)

Hello,

I am running a SVS PB13-Ultra in my 5.1 setup at the moment which is placed on the left besides the left main speaker, but when listening to stereo music I can feel and hear the placement of the sub even if it plays only below 80Hz. If e.g. a string bass is played from the right, it simply doesn´t feel right to have the impact coming from the left and it draws the sound of the bass to the left in the stereo imaging.

Therefore, I would like to add a second PB13-Ultra and run a true stereo subwoofer setup for music. But my Audiolab 8000AP is only able to handle mono subwoofer (one output). Is there a surround processor out there that is able to handle two subwoofers in dedicated stereo mode and still use both of them in parallel-mono mode for the .1 LFE signals of 5.1 tracks?

Or do you recommend Y-splitting the main speaker RCA outputs and run one through into the power amp and one into the sub while setting the processor to "no subwoofer"? That would mean the main speakers play fullrange and I would have to adjust the woofers to the main speakers via equalizer.

It is important that I am still able to correct the bass signals via REQ and Behringer DSP1124P in this new setup.

Any suggestions?

Thanks alot!
D


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## Owen Bartley (Oct 18, 2006)

Dragon, as far as I know, most receivers handle the subwoofer channel in mono, even if there are multiple outputs. There may be some dedicated 2-ch gear that does L/R separation, but I don't know any specific models. 

I'll take a different approach than you asked about, but only because it was the first thing that came to mind. What are your main speakers? Are they large enough to play below 80Hz? I think the 8000AP allows you to specify crossover settings for each speaker, so if you have large(-ish) mains, I'd start by changing that setting. Experiment a little bit moving the crossover lower and testing that same troublesome string bass. With some luck, that might solve your problem, but I would think it should at least improve the situation some. If not, maybe adding a second sub on the right split from the same mono channel would even out the very low frequency notes that the main L/R speakers can still provide good imaging.

I'll just add as an afterthought that moving the sub might help too, but I'm sure you have it optimized, and a PB13 isn't exactly easy to move around and slot into your decor.


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## Jungle Jack (Jul 28, 2009)

Hello,
I believe the Denon AVR-4311 and Onkyo TX-NR3009/5009 handle dual Subwoofers separately. Audyssey XT32/SubEQ HT calibrates each Subwoofer separately and I think it is indeed in stereo.
Cheers,
JJ


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## tonyvdb (Sep 5, 2007)

Anything below 80Hz should not be able to be localized to where the subs are placed. It sounds like you may have a crossover set too high. Corner placement us usually the best location to put a sub but not always. Your best test is to place the PB13u as close to your main seating position as you can and then play some bass heavy music or several test tones and crawl around the outside of the room. where the sub sounds the best thats the location you want to place the sub. (yes I know the PB13 is very heavy as I have one as well LOL)


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## Dragon777 (Apr 20, 2008)

Hi guys,

thanks for the suggestions. The problem is not the crossover, which is set to 80Hz. First of all, even with 80Hz crossover, there are still higher frequencies coming from the sub making it trackable. But the main problem is what you feel instead of what you hear. You can feel the impact coming from the left and no crossover could change that. I think playing the two subs in stereo mode would be far better. It would also allow for a higher crossover frequency if the subs are placed directly beside the main speakers. Dual mono subs may even out the problem as well, but if I go for two PB13-ultra beasts, I would really like to keep away from any compromises.

My main speakers are Mordaunt-Short Performance 6, btw, which are capable of playing below 80Hz, but which are more on the slender side in terms of bass and could use some help from the woofers up to about 120Hz.

If not able to do the setup with my Audiolab 8000AP, I would need a processor only, not a receiver with integrated amps. And all those Japanese AV-tanks are stuffed with way too much features for my taste. I dont want to pay for loads of bells and whistles which I don´t need anyway, but want good sound instead.

Moving the SVS around is no option. First of all, the WAF-factor does not allow a different placement, and second - well, this thing is huge and almost not moveable with the spikes attached.

Best
D


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## tonyvdb (Sep 5, 2007)

Dragon777 said:


> The problem is not the crossover, which is set to 80Hz. First of all, even with 80Hz crossover, there are still higher frequencies coming from the sub making it trackable.


Have you tried a crossover of 60Hz? Thats what I have mine set to....


> But the main problem is what you feel instead of what you hear. You can feel the impact coming from the left and no crossover could change that.


Hmmmm, you should not be able to localize anything below 80Hz as those frequencies are non directional by nature because of the size of the wave. particularly below 40Hz


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## Drudge (Sep 1, 2008)

I have a single sub set-up as well and I get the same situation as Dragon777.On some material you can sense the direction of the pressure wave coming from the sub.When I had a ported(passive radiator) sub it was even more noticeable,but with the sealed sub I own now it is less so.It may have something to due with the group delay.

I've read many times that with a single sub if the positioning,the crossover splice,distortion levels aren't just right,then this will always be an issue.More than one sub is always the better solution.


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## Dragon777 (Apr 20, 2008)

Hello,

setting the crossover to 60Hz does not solve the problem as the pressure is still to be felt from one side only. And als my main speakers bass output is a bit thin, I would prefer a higher crossover, anyway.

Is there any argument against Y-Splitting the RCA main speaker outputs and connect them to a main speaker and a sub each? When setting the processor to "no sub", the LFE signal of 5.1 tracks will be sent to the main speakers and the sub this way. I wonder if this may be too demanding for the main speakers.

In this setup, I would have to EQ the subwoofers to blend with the mains that are also playing down to about 40Hz. In order to avoid a non-linear, overblown bass, I would have to tame the subs in the higher bass regions. Am I losing bass impact on LFE effects this way because the subs cannot play to their full potential up to 120Hz of the LFE channel?

Best
D


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## tesseract (Aug 9, 2010)

A properly placed sub will pressurize the whole room, it will not be localized (given the listening position is proper, too). If lowering the XO doesn't work, then moving the sub is the only option.

Perhaps the sight of the sub to the left gives the impression that the sound comes from that side?


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## mrspis (Oct 7, 2011)

2 subs in stereo is overkill...


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## tesseract (Aug 9, 2010)

mrspis said:


> 2 subs in stereo is overkill...


Two or more subs knock down response peaks and fill in nulls. In my experience, one sub isn't enough.

http://blog.acousticfrontiers.com/storage/low-frequency_optimization_using_multiple_subwoofers.pdf

http://www.harman.com/EN-US/OurCompany/Technologyleadership/Documents/White Papers/multsubs.pdf


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