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stereo subwoofers

post #1 of 12
Thread Starter 

why or why not?

post #2 of 12

The prevailing wisdom has been that sub-bass is non-directional, therefore requiring only one point of origin.


I recall the sub I owned had dual voice coils (one for each of the stereo channels) on the same speaker, not to reproduce a stereo signal but to produce all the bass regardless of channel.


This was years ago, but I expect that this has not changed.

post #3 of 12
post #4 of 12

Are we talking about two subwoofers with one channel or two channels?


Two channels:

With a properly designed subwoofer (no port noise, lots of distortion ..) and a crossover freq. of 80 Hz you shouldn't be able to locate the sub with your ears. Also, there's usually not much difference between left and right channels at and below 80 Hz.


One channel:

For two subs one in the front, one in the back, both centered seems to be the best setup.

Edited by xnor - 10/8/12 at 2:00pm
post #5 of 12

When your dealing with a large space i.e. living/great room/dining/kitchen combo like me (and I don't care what anyone says) subs can become painfully directional. In my set up I have one HSU MBM-12 mk2 Mid-Bass Module covering 100-50hz and one HSU VTF-15H covering 16-50hz and I feel I need one more of each to balance the room. 


Also if you run a traditional setup i.e. two or more of the same subs or subs covering the same range, Audyssey can do front and back sub effects which is pretty cool. 


post #6 of 12

O yeah so two channels to cover two separate ranges like me...

post #7 of 12
Originally Posted by NinjaBoot View Post

O yeah so two channels to cover two separate ranges like me...

That's not what I meant with channels. I was talking about channels as in left/right (= stereo).


Your two subs are still mono (one channel). What I don't get is why would a sub that covers <50 Hz change the directivity of a single sub that covers 50 Hz - 100 Hz? Also, why choose different subs?

post #8 of 12
Its the room size the reveals the sub location. When I had the the HT equipment in a 15x14 room the sub was never leaning in any direction (and one was enough). In my great room even after a tedious sub crawl you can audible place the sub in either the left or right side of the room (which is IMO undesirable).

As for the second part of your question if I understand correctly. I have one sub which is designed to cover the mid-bass range for punch and and midrange diffusion.

And as for stereo sub channel... I would happily run a stereo only setup with two towers and two subs in left and right. Not two 15's but two B&W towers and subs would be sweet.
post #9 of 12

A lot of audio engineers and studio designers say more subs are better. Not for SPL purposes, but to even out room modes and cause less acoustic problems in the room.

post #10 of 12

Placement within the room makes a huge difference. As close to center/front as possible. It's not so bad if the bass comes from mainly the front. That's where your soundstage is.

post #11 of 12
I remember Harman making a bit deal out of multiple subwoofers with the HK990 (despite that, the thing has bugs in it's subwoofer routines - go figure rolleyes.gif). The idea being lower distortion and so on. From a somewhat different POV, multiple drivers reproducing the same signal (ignoring time alignment or comb filtering as problems) should mean less excursion and lower distortion. The multi-subs for more re-enforcement and "smoother" response is something I've seen published from THX. The resultant configurations in a given room for these two solutions will look very different.

Regarding "stereo" subwoofers - it depends on what you mean by stereo. Some older surround processors will actually compute the LF output in stereo (I own such a device), and hooking up two subwoofers to them is preferable to a single unit (although in my scenario, the two subs are stacked one on top of the other in the same place - I've tried them spread out, and it didn't do much for me, but it sure took up more floorspace!). This is different than modern devices that can handle multiple concurrent subwoofer outputs, but either separately level or (if they're really sophisticated) EQ them (like the Levinson 502, it only works on "one" LFE channel, it can just ("just" - it's one of the most sophisticated cinema processors ever made! tongue_smile.gif) EQ four output subwoofers to take that one channel (the summed LF and the LFE)). I think the true "stereo" devices are relatively rare these days (in my processor, it actually takes all of the "left" channels and drops them on one subwoofer, and all of the "right" channels and drops them on the other subwoofer, and LFE is sent to both; the way the manual would have you set the thing up it's more like having two true full-range speakers as your L/R than having a subwoofer).

Personally I like the "stereo sub" setup on the processor that does it that way, but I would not hook up a similar arrangement on a processor that only has a single sub out (e.g. with splitters). If I was re-doing everything I would probably look for a more modern controller that could at least collectively EQ the subwoofers (the Velodyne controller can do this with two or three (I forget) subs, they aren't "independent" but the device measures the overall system with however-many subs it can hook up to, and then goes from there), as opposed to simply trying to have a ton of woofers throughout the room. I should also mention that I'm not a big subwoofer fan in general - I only have subs on the "stereo" system. Everything else I'm fine with letting it go over a cliff at 40hz or thereabouts. redface.gif (I've just accepted that I don't like a lot of sub-bass).

Oh yeah, I agree with bigshot on placement - if you haven't done the bass crawl at least, you should do that before considering adding multiple subs. In my current setup, I just stacked them in the best place I found for one, because I didn't like giving up so much space to both cabinets. It isn't perfect, but it works well enough for me (or as they say, "close enough for gov't work!").
Edited by obobskivich - 10/14/12 at 10:19pm
post #12 of 12

After many years reading and reading on this topic,  I could say many things that have been said before. My background when it comes to bass also extends to sound design and I've done much experimenting with bass psychoacoustics in (mostly) headphones and speakers.


From my experience working with STEREO (I'm working on moving to surround or some other appropriate medium), delta information in the bass, characterized by level or phase differences between channels, has a significant effect for AT LEAST headphone listening. The topic here is stereo subwoofers, though (L and R). It would take me a long time to organize my thoughts and explain the science behind my observations, so I'll say that I personally experience a difference with stereo bass (in a room, haven't tried outdoors).


Acoustic summing (different frequencies in each channel) definitely sounds different to me than electrical summing. Live stereo recordings using microphones have stereo information that rolls off (becomes less stereo) based on how they are spaced, i.e. phase differences between channels become less dramatic and progressively more mono as frequency of the recorded sound drops. Highly-produced. mixed recordings have much different phase characteristics (as it's independent from a live event). A doubled L/R guitar track that contains strong phase differences in the <80hz range is diff sounding to me than if they were summed. Much of the music I listen to contains delta bass information.


For example, listen to the synth track INDIGO CHILDREN (JLE mix) from Puscifer. The effect is super-obvious on headphones. Try comparing that with speakers if you have a capable system.

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