5.1 Surround Sound in a Black Box theater?

So, my performance space was recently issued a grant to help purchase the necessary equipment to host film events and things of that nature. We've nailed down quite a few areas (mechanical screen 300+" diagonal, projector, LED lights to replace Fresnels so as not to have that hot a light near the screen) and all that is left is how best to approach the surround sound aspect. Since we're a non-profit, budget is always a major issue, even though we did a grant to handle a good chunk of the costs.

The space is 28' deep and 46' wide, though it is possible to reconfigure to 28' wide and 46' deep. We currently have 2 QSC K-12s that we use as our main speakers. Would getting 3 more of those (as well as a sub) be a good idea? We mostly do solo performance, dance and weird things most spaces won't touch, so I'm thinking that a separate speaker system would be worth looking for the film events. I'm guessing they don't need to be nearly as big as the K-12s. I'm also guessing that we would need a specific playback device built for 5.1 and a separate mixer/receiver to handle it as well.

Any help is appreciated. Thanks a lot in advanced!!

Several years ago I did a 5.1 system using three SRM450s and two SRM350s, and a Machie SRS1500 sub under the risers. Windows PC running SCS and a Delta 1010, fed into a sound console, using auxes and/or groups to feed the individual speakers.

It sounded pretty awesome when playing AC3 files. It also sounded pretty good when playing anything else. I also used the speaker arrangement to move sound effects around the theater.

When I ran standard musicals, both vocals and band played through all five speakers ... L and R played their stereo channels, C played a mono mix, and the rears also were stereo but attenuated 10-20db. I always used all three front speakers for main sound of all sources (I don't like the "fad" of putting vocals through C and band through LR -- it's disorienting.)

My only regret for this setup was purchasing those SRM350s ... very weak compared to the 450s. So unless the K10s have comparable sound quality to the K12s (I haven't heard the K10s before) I suggest you pay the extra money and put K12s all around. It will also give you more flexibility if you need to pull the rear speakers to use as on-stage FX speakers, etc.

In your setup I would recommend you try leaving your theater in landscape format (wider than deep) to accentuate the channel separation when playing stereo and surround material.

The center channel is the most important channel in cinema, so I would use another K12 for the center. The surround channels are much less important so a K10 would probably be OK if the budget is tight.

If you don't have the budget for a surround processor and Blu-Rays will be your source material, you could buy a Blu-Ray player with a 7.1 analog out like the Denon DN-500BD and run each channel through a balancing adapter like the RDL FP-UBC6 and then straight to the K12s. If you still need mics run the center channel through your normal mixer.

If budget is tight and you want lesser speakers for the rear surround positions, I suggest you forget the K10s as they are still very expensive, and pick up a pair of Harbinger speakers ... dirt cheap and they still sound pretty good, certainly more than good enough for surround work. A friend of mine who does a lot of sound and has a lot of equipment bought a pair of Harbingers to use as stage monitors, and I am borrowing one of them for a small wedding reception. I was surprised at the clearness of sound coming out of them. And they have a two channel mic/line mixer built in.

Ahh, surround in live venues can wonderful, for many things beyond video playback.

When doing musical theatre sound reinforcement in the 90's, my default FOH drive racks included a Miles Tri-Sonic MTI-3A Imager.
We used these units in venues ranging from 400 - 700 seats as an affordable way to generate Left-Center-Right-Surround (LCRS) from a stereo band feed, which was converted into LCRS, plus a mono vocals feed that fed center only, and a direct feed to surround, for reverb and effects.
I've also heard great surround / distributed sound in smaller venues as well.

There are likely low-buck ways to generate the same signals using current consoles, to use the normal stereo pan mixing approach to achieve LCRS. (Discrete Quad is another approach, but I found that less workable for typical stereo-based shows.)

This thread is about surround sound, but as a side note, Well done LCR is terrific, providing an even and smooth sound stage for stereo music for the entire audience, not just those sitting down the center line, with firmly planted center vocals. This works really well for musical theatre. After having used LCR setups, either standard L-R only or mono clusters only each fall far short, for the sound localization for those audience members not sitting at the center of each aisle. (Those Dolby guys who added multi-channel and surround to the 'talkies' way back when had it right.)

We used surround speakers to enhance the sound of the band and vocalists in the room, and also for sound effects.
The stereo band mix fed difference signals (L - R) into surrounds (e.g. only stuff purely in left, or purely in right, nothing panned center), and vocal reverbs and ambient and special sound effects could also be routed only to the surrounds.

The actual source of the ambient sounds makes a big difference, and feeding reverb into the room from the back/sides just into the surrounds allowed us to 'load' the room with more, great reverb, without feedback and without losing the vocal presence and intelligibility. This was a very minimal version of some of active acoustic enhancement systems.

Likewise, sound effects work very well (not unlike the movies) for both ambient and specific effects, as humans can easily localize the sources, and it really does envelop the listener. The effects can only be pushed so far, though, or they break the '4th wall' and pull people out of the show. (e.g. quiet thunder and rain all around draws you into the show, but big thunder and rain all around makes you think there is a storm outside and worry that you didn't close the car windows.) While it might seem that more directional effects from a single source would not work through a multi-speaker surround array, even those effects worked well as being generally behind or to the side of the audience, even if different audience members heard the sound as coming from rear left, rear right, or rear center, depending on where they sat.

We typically ran a center cluster that covered the venue, along with left and right sides that covered most seats.
(We typically also ran front fill, under-balcony fill, balcony fill, etc., for intelligibility in tough rooms, but that's secondary.)
Surround speakers were smaller, and worked better if they had a wider dispersion, with 4 or more speakers at a lower volume, rather than two larger surrounds. 6 - 8 sounded really sweet. They did not need to be high power, and we sometimes connected them in series/parallel to reduce the amount of amp channels.

The MTI-3A from Mike Miles was a great unit that seemed to combine concepts from the original stereo-based LCRS Dolby Optical Movie 4.0/4.1 Theater Surround sound, along with concepts from Bob Carver's Sonic Holography.

Here are links to the archive of the Miles information, including the AES pre-print that includes the math:

http://www.milestech.com/
http://www.milestech.com/mti3.htm
http://www.milestech.com/tricompa.htm
http://www.milestech.com/aesimpre.htm

Early 4.0 stereo-optical surround sound added Left and Right to get Center (Mono), and subtracted Right from Left to get Surround. If I recall, the Optical Surround processing of stereo-optical movie theatre tracks that conveniently ended up on many movies on VHS format also included Dolby-B noise reduction, some delay to the surround channels, and band limited (e.g. included only 100Hz to 7KHz) the surround channels. The decoder was implemented in home receivers. This was prior to the implementation of pro-logic 'steering', and prior to stereo surround (5.1, 7.1) channels. (The whole interesting story about how we got the .1 LFE channels also starts back at optical movie soundtracks...)

(Side note - One early 'low buck' way to generate surround was to just hang a high impedance speaker across the stereo amplifier's L+ and R+ outputs, which only reproduced the L - R sounds. (When you bridge an amp, you wire it the same way, but then invert the input on one channel, so they add. This skips the invert, so they subtract.))

My take on Carver's sonic holography was that it was a way to make speaker-based listening sound more like headphones, to get rid of the extra sound from the right speaker heard in the left ear (and vice versa), by adding some 'negative right' to the left speaker with appropriate triangulation delay, and vice versa. When I heard it, it sounded great for home hi-fi, but had a super small sweet spot (as in bolt the listening chair down to the floor.)

So, as I understood it, the Miles unit took a stereo input, and created the following:

Left Out - Left In with some negative Right In
Right Out - Right In with some negative Left In
Surround Out - Left In Minus Right In
Center Out - Left In Plus Right In

There was a matrix control that adjusted how much of the opposite side was included, and also how much L+R went to center.
If you turned the knob all the way down, you got plain Left into Left, plain Right into Right, and nothing from L and R into Center.
(The Milestech AES pre-print has the equations and math as to why it all sums acoustically.)

This setup made stereo band mixes sound great, because you could get even coverage across LCR, and the panning was just right. Even if you had something hard panned to one side, the 'negative' amount added in to the other side meant those on the other side of the house still heard the instrument. This solved the classic PA stereo issue of the audience on the sides not hearing a full band mix, because they were missing the sounds panned to the opposite side.

Then, the Miles unit had a direct input for Center (where I fed vocals from an per-channel assignable mono bus (not a console sum of L+R) or aux-fed mono feed, if there wasn't a true assignable mono bus.)

Finally, there was a direct input for surrounds, which I fed from an aux bus that included input-channel returns for reverbs, etc.

I generally found the setup to sound really good without a lot of fuss for each instrument.

It would seem to me that one could re-create these signals easily in modern consoles. For surround, bring the L and R channels back into unused inputs, invert the right channel polarity (or use a pin 2-3 polarity swap XLR barrel), and only assign those two channels yo a pre-fade aux bus, and out to the surround amps/speakers. Similarly, you could create the 'negative' L & R feed into the opposite side with inverted channels, but would need to introduce the inverted opposite channel downstream of the L&R busses (e.g. into a matrix or similar) so you aren't introducing electronic feedback.

This approach tends to require extra work for both installation of surround speakers, and by providing overlapping (rather than zoned) LCR arrays. The two approaches can be used independently, and worked really well for us.

A final note on LCR speaker sizes. I think arrays/speakers of the same size/family are preferred, but this can be done with a smaller center, with mostly vocals, along with a larger set of L-R sides. Likewise, can be done with a a larger center, where it handles more of the L+R load. The Miles 'Matrix' control also could be used to adjust that. In any case, the center does have an important role, and needs a decent speaker/array.

-larry-

By film events, do you mean actual D-cinema, legacy 35/16mm film, or DVD/Bluray/Direct from someone's personal computer? How audio decoding is handled is going to vary greatly based on the actual playback device. The first two options pretty much require a Dolby or equivalant decoder/decrypter/processor, and the third option is wide open. If doing surround with consumer media as the source, you may need to add delay processing to the surrounds to time align them.