Stereo Subs Live??

[SLProductions]

I am installing a system in a rectangle room with two dual 18 subs under the stage, with the possibility of running them in stereo. I've never heard of anyone except modern high-end home theaters using stereo subs. Any thoughts on this?

Here's the layout: Room - 65' x 45' with the stage at one end of the room on the 45' wall. The stage is about 30' wide and against the right wall(so not centered in the room). The audience will be centered in front of the stage with the left side (15' x 65') as dead space for other uses. The mains are a stereo line source config, and the subs are centered in the stage, approx 2' apart, facing the audience. They are approx 15' from the right and back walls. The room will be used for live bands, dance music, movies and theater productions. I am the resident engineer so I get the final say on the setup. I can always experiment, but thought I would include you guys for ideas on phase relation/cancellation, audience sound experience etc.

[kooz]

I hope your system includes a digital processor/crossover. If not, get one, and learn to use a program like SMAART or FuzzMeasure to tune your rig.

You're going to run into acoustical problems maintaining the stereo image in the room if your stage (and therefore, PA) are off center to the long axis, causing some strange modes. The software will let you monitor and document, while the crossover/processor will help you adjust/compensate for those modes.

How high is the ceiling? How high above the floor is the stage? Is the PA stacked or flown?

[SLProductions]

Originally Posted by kooz

I hope your system includes a digital processor/crossover...

...How high is the ceiling? How high above the floor is the stage? Is the PA stacked or flown?

Yes, the crossover is the Behringer DCX 2496 along with 31 band graphics. I'm running a 3-way system, highs, mids, subs(on a separate fader). The ceiling is 25', and the line source towers are custom two ways, 14' tall on the floor in front of the stage.

The stage is 3' high and fully insulated with a wave shaped front curve. The stage back wall consists of 18' micro-suade theater curtains with 2" insulation board behind, 1 1/2" to 3" off the wall sawtooth pattern. The boards cover the 540 sq ft behind the curtain.

[SLProductions]

Installing this weekend, any thoughts?

[dbbubba]

I have installed sound systems in almost every kind of room imaginable from upscale home theaters to large scale line arrays in arenas.

There really is NO stereo effect to be had in stereo subs.
In home theater it seems to be an add on and mostly bragging rights for the owner.

Mostly, there is no stereo sub information in a Dolby Digital or any other film release format, so there really can't be anything "stereo" going on.

In live p.a. situations the subs are positioned on either side of the stage (usually) in order to cover the room evenly.
I have also used arrays under the center of a stage with great results.
I never ran them in stereo however.
In fact, I wanted them to couple as much as possible!

If you think about it, there is very little to zero stereo LOW END information (L/R) recorded into anything,

In the live rigs I use we very often put the subs on an AUX which makes them be a mono send to all of the subs in the system.
The Nexo Geo S Series system I use quite often does have the subs wired to stereo, but again.... the source material will not be sending any information that is really stereo.

Unless you have source material like a special effect that requires low end to move I wouldn't worry about it.

The sub speakers themselves would have to be fairly wide spread to to hear much stereo effect anyways.

I'd put them close together and go for coupling before I'd spread them out and attempt to find a way to get "stereo" from a source that didn't have stereo.
Coupling them would give you MORE low end and in "film" soundtrack reproduction the sub is considered a LFE (low freq. effects) which means that more is better.

[SLProductions]

Thanks Danny,

So you've had Nexo's in stereo without a problem?

Mono is my gut anyway, especially since I've always used it for subs with good results. But here I've got this extra bus and snake return all alone and unused, and I'm thinking, what the heck, it's already there, why not, right?

This just makes me wonder, why do people NOT do it (if they have the capabilities)? What's taboo about it? tutt Are there really phase correlation issues? I guess it's not really a big deal, but, if we're audio innovators, always pushing our boundaries to get to that next step in sound reproduction, this is our responsibility to find out. Besides, we can't have the Lucas putting us under the table, can we? haha

The only material I can think of that may have stereo LFE would be synthesized electronic, this would affect a lot of dance clubs where people go to experience bass at its highest potential. I guess it's something I can test just to see. It really sounds like something John Meyer needs to have a go at in his testing labs and give us all an answer.

[dbbubba]

Yeah, the Nexo rig is stereo.
The proprietary crossover and entire system is designed to work as a unit.

A lot of times live rigs have stereo subs just for the sake of simplicity.
The again, a lot of people put their subs on an AUX.
I am hot and cold on that idea.

No matter what anyone tells you, Ol' Uncle Danny will tell you that a stereo rig sounds better than a mono rig.
Even if you have next to nothing panned very hard small things like reverb and slight panning make the system sound much bigger.
This really seems to be true outdoors.

The coolest thing with subs is doing the cardioid array thing.

The Nexo line array (they call it a tangent array) subs are manufactured as cardiod units.
There are drivers ported to fire out the front and out the back.
The crossover handles all of the delay parameters for the cardioid set-up.

You can also do it with conventional subs if you have a delay line that will delay at 4 msecs.
It is a bit to describe here, but it does work.
It DOES focus the low end energy forward which makes the wattage you have be used in the most efficient way.

You can't do the cardioid sub set up with the subs under a stage however.
They need to be free standing with AT LEAST four feet of space around them.

[SLProductions]

My reasons for putting subs on a bus:

1. Assignability - You can assign the kick, and unassign the harmonica.

2. Control - Fade up to let the end of a song ring out (discretely of course), or fade down when it's just overkill, instead of running across all the LF knobs on the board.

3. Because you can.


My reasons for NOT putting subs on a bus:

1. Installs where there isn't a bright house engineer always on hand.


I'm a big proponent to Uncle Danny's live stereo mixing, I would only not do it if the system/room couldn't wangle it. We deserve stereo, the band isn't mono, unless it's comprised with one guy with a mouth harp. Why should we, with two ears, have to hear multiple musicians and stereo efx coming through as mono meshed sound?

The cardioid array is a great idea, it's things like this that have brought us where we are today! With technology (and a good bit of $$), people are actually doing live surround sound today. The person that built these 14' planar loaded towers is actually working on a new 5000w sub driver patent for pro audio. It's really getting up there with Servodrive without the servo troubles. It's cool to see stuff like this and line arrays coming down the pipeline. And to think, it's all for us engineers!