# Dual Subs Mono vs Stereo



## pioferro (Nov 26, 2011)

Hi!

Wanted to share my experience using dual subs in my audio system. I'm a constant tweaker, always trying to extract the last ounce of performance from my gear, so I'm always messing around with placement, crossover points, phase, acoustic panels, etc. I do not, however, run any kind of EQ.

Anyways, I was very pleased with my subs running in "stereo", using the left channel signal for the left sub, the right for the right. I had the subs placed between and slightly behind the mains, integrated very smoothly. However, a few weeks ago I came across a section in a book that suggested running dual subs, but doing so with a mono / L+R summed signal. 

Here are excerpts from two audio pro's and their very different views on the matter:

In his book "Get Better Sound", Jim Smith believes acoustically recorded music suffers with one sub or non stereo sub's. From the book - "direct and reflected long wavelength, low frequency cues will arrive at each stereo microphones at slightly different times. Therefore, stereo subwoofers play these differing time-arrival spacial ques in each channel. Subwoofers provide the cues for a sense of space that can transform a system from simply sounding good to sounding uncannily real" - page 35 of Get Better Sound


_______________________________Counterpoint_____________________________________________________

Floyd E. Toole writes in reference to his experiments - "with music and film soundtracks differences in "spaciousness" were in the small to non-existent category, but the differences in "bass" were sometimes obvious, as the interaction of the two woofers and room modes changed as they moves in and out of phase" - "even with contrived stereo signals, spatial differences were difficult to tie down." 

Pages 238 / 239 of "Sound Reproduction - The Acoustics and Psychacoustics of Loudspeakers and Rooms" by Floyd E. Toole

Both authors agree, 2 subs are better than 1. Toole really likes 4 in a home theater set up.

If you have stereo subs, you owe it to yourself to try summing the signal and trying different locations for your subs. I ended up placing my subs closer to the corners of the front wall, behind the mains. A spot I've always liked aesthetically, but didn't quite work with the stereo set up. Now, both locations sound great, but I'm getting a bit more room gain closer to the corners, so I was able to lower the level of the subs for better dynamics. 

I'm not knocking the stereo set up, I was very happy with it for months. If you tend to listen and prefer acoustically recorded music, Jim Smith's set up might be your best bet. 
But the summed method is working really well for me. It might be the fact that I listen to very little acoustically recorded music. My music tastes are broad - from Jimi Hendrix, to Modest Mouse, to Drake, to Spanish artists like Camila, to Ricardo Arjona. But they are studio albums.

Wanted to share this experience in case your an obsessive tweaker like I am. You might be rewarded with another layer of musical enjoyment without changing one piece of equipment.

Cheers!!


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## pddufrene (Mar 14, 2013)

Very interesting, thanks for the read. When I get my other sub, I may have to give this method a try just for fun.


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## vann_d (Apr 7, 2009)

I've always run mine in mono for a couple reasons:

running subs in stereo requires more equipment and setup in general because most AVR's do not handle more than one subwoofer channel. Even if they are .2 they are generally mono. I'd need external crossovers for my L and R channels.
I'd have to get more gear to sum in the LFE channel for movies or have a separate, dedicated LFE subwoofer due to the limitations listed in (1.)


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## rrskda (Apr 22, 2014)

Good read, thanks!

Wouldn't Floyd's counterpoint apply to two subs in mono as well? Or maybe I'm not clear on how the physics works. But it seems to me that unless the two subs are placed in perfectly mirror locations of one another, there would inevitably be some phasing.


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## BeeMan458 (Nov 25, 2012)

rrskda said:


> Wouldn't Floyd's counterpoint apply to two subs in mono as well? Or maybe I'm not clear on how the physics works. But it seems to me that unless the two subs are placed in perfectly mirror locations of one another, there would inevitably be some phasing.


And there is, hence the need for the phase control so one can adjust the phase so they're equal. Distance setting changes is another way to adjust for the phenomenon you describe.


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## tonyvdb (Sep 5, 2007)

Another thing to keep in mind is that the frequencies below 80Hz are such long wavelengths that a stereo image would just about impossible to hear as those frequencies are non directional. Chanel separation is non existent down that low.


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## pioferro (Nov 26, 2011)

rrskda said:


> Good read, thanks!
> 
> Wouldn't Floyd's counterpoint apply to two subs in mono as well? Or maybe I'm not clear on how the physics works. But it seems to me that unless the two subs are placed in perfectly mirror locations of one another, there would inevitably be some phasing.


FYI - Floyd didn't answer Smith directly, I wrote "counterpoint" to contrast the difference of opinion.

Here's an interesting article on stereo vs mono bass by Tom Nousaine.

http://www.nousaine.com/pdfs/Stereo Bass.pdf


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