My L/R are line arrays that cross at 90hz.  Upstream is a DEQX.  Center crosses at 90hz too, but is not controlled by DEQX.  Room is approx 18'L by 12'H by 13.5'W

Listen 70% without Center, and 30% with.

Currently run the subs in mono, and it sounds terrific.  Three bands of PEQ, found using Room EQ Wizzard, each at a node.  All under 6db.  Get +/- 3db from 120hz to 30hz, with 5db bump/rise below that centered between 20 and 30hz (think the rise is room rattling, but am not sure.)

Have read that running subs in Stereo creates greater sense of "envelopment."  Problem for me is that if each sub is placed near one of the arrays, or near symmetrical, then my unequalized response is pretty bad.

Suppose I added two subs ... would "chain" one to each stereo Submersive.  Each of those could go where it would tame it's respective Submersive.

(Suspect it'd be harder than this ... that it'd have to work well when all four were running a "mono" feed too.  Similarly, would have to get it integrated with the center channel.)

All a long way of asking two questions: (1) can two stereo subs properly configured sound better than two mono subs?, and (2) would adding two subs (and PEQ in front of them) make a big improvement to either (1) and/or (2) above?


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Hi Bruce,

This is a general response here, but please also clarify some more what you are thinking of doing and/or trying to accomplish with this.

I'm not sure exactly what you mean here:
Suppose I added two subs ... would "chain" one to each stereo Submersive.  Each of those could go where it would tame it's respective Submersive.

1)  Two subs can provide a subjectively more expansive bass presentation.  I honestly find this to correlate much more strongly with how two subwoofers may interact with a room more so than the exceedingly rare case of recorded stereo bass and reproduction of it.

It can be very interesting to sit in your listening position and again at other points in the room while running a slow frequency sweep in the room.  Depending on the acoustics of the room and the interaction of the subwoofer(s) with the room, you will often hear the output to subjectively "swim" around the room, changing with frequency.  Sometimes rattling objects or large surfaces also impact this, and sometimes there are other effects behind this. 

2) The benefit of 2 more subs would depend on many things, including placement and in-room response of the subwoofers.

I suspect there might be other ways to better get at the end goal.  Remember that for 95% of recordings, the subwoofers will behave as mono subwoofers if each is fed a Left & Right line signal.  I often like to compare the subjective imaging and space of the main speakers with and without the subwoofers muted.  Ideally the subwoofers should greatly enhance the scale, space and power of a concert drum and related sounds.  If the subwoofer seems to be calling a little too much attention to itself, do experiment with the delay settings in the DEQX or your Meridian.  If you add a small amount of delay to the subwoofer through distance setting (closer distance setting), direct delay (adding delay), or even through crossover (lower or steeper = more delay) you can shift the subjective interaction.  Obviously you then have the fun of balancing adjustments related to imaging and localization vs. total frequency response.
Mark Seaton
Seaton Sound, Inc.
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The sound I'm getting right now with two submersives in mono mode is very impressive. 

I've got one submersive at the front just off the centerline, which allows me to use it as a center channel stand (the center speaker is an almost perfect fit, so it looks great too.)  The second submersive is on a side wall near the front.  The peaks/dips of those two subs are pretty complementary, so overall I get a pretty flat response (+/- 3db from 120hz to 30hz with only three clearly node centered bands of under 5db each PEQ) across three of my four chairs.  I've also got terrific integration across the crossover frequency (90hz at 72db/octave, using the DEQX).  I played with the distance setting and side wall sub location to get that crossover range integration nice and smooth.

My primary question is "do stereo subs, properly configured, sound better than mono subs?"

I know that in my case two stereo subs alone will not sound better.  When I place both of my two existing subs near the front L/R speakers then I don't get a nice smooth response off either one individually, or off the pair together, or across the crossover region.  If I use stereo subs alone with nothing on the sidewalls instead of +/- 3db I've got big swings, lousy crossover range integration, and huge needs for aggressive PEQ.

However, I already know that if I add a side wall sub to a front sub located close to a L/R speaker, and play a bit with the phase/distance of that sidewall sub, I get back to a nice frequency response and crossover integration picture.  Put differently, if I had only two subs running in mono, with one near either L/R speaker (rather than centered) and the other on the adjacent side wall, that I get a response and crossove integration that's almost as good as what I'm getting currently.

Hence my question about doing the above "twice over" and running stereo subs.  (Basically I'd have two subs running in mono on each stereo channel.  One near the respective L/R speaker and the other on the adjacent sidewall.)  If most material under 90hz or so is essentially mono anyway then it wouldn't make any sense.  On the other hand, if there's significant material that's not essentially mono in the L/R channels then stereo subs augmented with sidewall subs might make sense.
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Do you have any accoustical treatments?

Just saw your other thread where you mentioned that you have extensive treatments.

On another thought, if you run your speakers as "large" what is range of your frequency response that falls within plus/minus 3 dbs?  Can't help but think that 90hz crossover is too high loosing some of the directional quality of your system.

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JimP -- in reverse order

The line arrays are from Selah Audio.  They've got Accuton c82 5" midranges in sealed boxes, and Fountek ribbons for the highs.  They begin to roll off around 110hz, and are down 3db at 90hz, with a nice 12db/octave roll off from there on down.

Thus, if I want to use my main L/R for low end ambiance then I've got to use their natural 12db slope, or maybe add 12db, so that I've still got plenty of mains output down to 60hz or so.  I tried this and rejected it for three reasons: (1) it didn't sound as good, likely because (2) I couldn't get as nice smooth integration between mains and subs below the crossover point, and, (3) the Accutons have more distortion down low (they are really, really, nice from 100hz on up

The room treatments are pretty extensive.  For midrange on up I've got 2" RPG BAD panels (binary diffusors with some absorbtion) on the sidewalls at the first and secondary reflection points, and, on the rear wall primary reflection points.  I tried absorbers, but those overly "damped" the room.  For the bass I've got 50ft plus of Auralex MegaLenrd broadband bass traps.  Those go floor to ceiling on the front wall side wall junction and side wall to side wall on both the front and rear wall ceiling junction.
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