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[Karim Ben]

Hello!

I work at a small independent movie theater. Non-profit, voluntary run, etc. We screen movies, and are upgrading from stereo to a 5.1 configuration with a cinema sound processor. In addition to this, we already have a concert system (mainly experimental music) with several speakers already in place, especially on the sides of the seats.

We cannot have 2 complete systems in parallel, and are looking at sharing amps and speakers between cinema and concerts application.

Our first "idea" was so use Y cables on the amps, with one input coming from the cinema processor, and the other from the concerts console - but that would mean signal can come from both at the same time, and I guess could cause problems with impedance, ground loops, etc.

Ideally, we'd need a unit which could let us switch between the two systems, so 4 pairs of inputs into 4 separate outputs (front left, front right, side left, side right). Center / subs for cinema and concert subs will be handled separately, as well as a bunch of other concert amps/speakers. Another two pair of inputs would be good for expandability to a 7.1 cinema system with rear left and rear right, but there are no concrete plans at the moment.

It would be ideal to have it rackmounted on the amps rack.

The only device I could find is the Radial SW4: http://www.radialeng.com/product/sw4 - way too expensive for us.

Then I found out about this piece of gear: http://www.networksound.com/index.php/products/pbays/xlrswitch - unfortunately they never produced them and only have a prototype without enclosure available (as on the picture). I don't know how easy it would be to build a back cover.

Sescom does a small unit with 1 pair into 1 output, I guess we could use 4 of them but I don't know if it could be mounted on a rack somehow... http://www.sescom.com/product.asp?item=SES-XLR-AB

A plus but not necessary functionality would be to have the possibility to select A or B or A+B, in case we need to send audio together over a movie but I've not seen it at all on devices.

Anyone know of another device or of a custom company that could easily build one?

Budget is in the ~200-300$ mark.

Thanks!

[Eric Snodgrass]

Is your audio going through an audio console?  A console with enough outputs can be configured easily to route the audio to any or all of the speakers in your system.

[Karim Ben]

Sorry, I should have added some more details. (also I originally wrote "mixtable" instead of console in my first post, apologies for the bad english...)

The goal of the cinema part of the setup is to be set and forget. People doing the screenings are not trained to handle the audio console. And no one wants to have untrained people fiddle with the console . They need to be able to simply turn the system on, and handle the movie from the cinema server or bluray player, etc.
Also, our console does not have enough inputs and outputs to be able to have the cinema system permanently hooked up, without having to unplug everything everytime there is a non-cinema event. We don't have the budget for something bigger.

[Don T. Williams]

Two Behringer DS2800's would give your 4 inputs up to 8 way distribution.  I know that is more outputs than you need but the street price is around $200.00, so this might be a solution.  I have a Radial SW4 for my concert system and love it!  Transformers and ground lift switches solve lots of problems.

Double pole or (even 3 pole) ON/ON switches might be a solution.  Most of the custom cable mfgs. can build a panel or box with 4 inputs and 2 X 4 outs.   

Full disclosure: I am a dealer for Behringer, Radial and many, many other brands, but only sell locally.  I do not sell mail order or on line.

[Mike Caldwell]

A DSP unit with the needed presets programed would not only give a simple way to make the switch over but would also offer any needed system processing.

That said a unit that would have the input and output numbers you need would probably be over your budget.

Whirlwind makes this switcher unit that sounds like it would work for you.
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/miclineinst-switchers/ab-8-8-channel-mic-line-switcher

They also make these passive combiners.
http://whirlwindusa.com/catalog/black-boxes-effects-and-dis/combiners/imp-line-level-combiner

Building a selector switch system would not be too hard to do.
A couple of four pole double throw switches, project box and some xlr connectors would do it.

You are correct in NOT wanting to do a hardwired Y combiner connection.

[Erik Jerde]

Hello!

I work at a small independent movie theater. Non-profit, voluntary run, etc. We screen movies, and are upgrading from stereo to a 5.1 configuration with a cinema sound processor. In addition to this, we already have a concert system (mainly experimental music) with several speakers already in place, especially on the sides of the seats.

We cannot have 2 complete systems in parallel, and are looking at sharing amps and speakers between cinema and concerts application.

Our first "idea" was so use Y cables on the amps, with one input coming from the cinema processor, and the other from the concerts console - but that would mean signal can come from both at the same time, and I guess could cause problems with impedance, ground loops, etc.

Ideally, we'd need a unit which could let us switch between the two systems, so 4 pairs of inputs into 4 separate outputs (front left, front right, side left, side right). Center / subs for cinema and concert subs will be handled separately, as well as a bunch of other concert amps/speakers. Another two pair of inputs would be good for expandability to a 7.1 cinema system with rear left and rear right, but there are no concrete plans at the moment.

It would be ideal to have it rackmounted on the amps rack.

The only device I could find is the Radial SW4: http://www.radialeng.com/product/sw4 - way too expensive for us.

Then I found out about this piece of gear: http://www.networksound.com/index.php/products/pbays/xlrswitch - unfortunately they never produced them and only have a prototype without enclosure available (as on the picture). I don't know how easy it would be to build a back cover.

Sescom does a small unit with 1 pair into 1 output, I guess we could use 4 of them but I don't know if it could be mounted on a rack somehow... http://www.sescom.com/product.asp?item=SES-XLR-AB

A plus but not necessary functionality would be to have the possibility to select A or B or A+B, in case we need to send audio together over a movie but I've not seen it at all on devices.

Anyone know of another device or of a custom company that could easily build one?

Budget is in the ~200-300$ mark.

Thanks!

A balanced audio matrix might fit the bill for you.  I've got a client with a Kramer VS-88A which is 8x8 stereo balanced audio matrix.  That would easily fit the specs you laid out with expansion possibilities.  If memory serves you can set it up to recall pre-set routing as well which would simplify recall, although still not completely idiot proof.

https://www.kramerav.com/us/product/vs-88a

PM me if you want me to ask my client if they want to sell it.  I think it's sitting on a shelf right now.

[Karim Ben]

Thanks for the replies so far!

I had discarded units such as the Kramer and first Whirlwind because of either the price tag or the additional connectivity conversion that was needed. But an used Whirlwind AB-8 could be a solution.

Regarding the Behringer DS2800, it only has 2 inputs, so we'd need at least four of them... (unless I'm missing something).

The Whirlwind line combiner could work even if not switchable. Searching for line combiner instead of a switcher I found the IMG Stageline LC31 https://www.img-stageline.com/products/audio-tools/line-combiner-line-splitter/lc-31/ which could work well as a cheap solution. How do those combiners behave if one of the input signals is muted / off?
(I have no idea if IMG is considered a high-, middle- or low-end manufacturer)
At least as a first temporary / emergency solution, in order to have the cinema system hooked up as quickly as possible, those combiners could do the trick if they behave well.

From the looks of it, I guess electronically for a cheap solution it's EITHER an A/B switch OR a line combiner, I guess an A/B + C as combining both all in the same box is just too expensive.

If you know of a small company that does custom work though, I could still inquire to see if it's doable.

Thanks!

[Keith Broughton]

I once patched 2 consoles to 1 processor using Y cables with the first console connected directly to the Y cables and the second connected through iso transformers to the Y cables.
May not be the "perfect" solution but it worked well with no ground issues or level problems.
This might work well for you.

[Don T. Williams]

Thanks for the replies so far!


Regarding the Behringer DS2800, it only has 2 inputs, so we'd need at least four of them... (unless I'm missing something).

Oops!  You are correct!  Somehow in try to think through a solution I got your needs backward.  You need 2 X 4 in to 4 out, which is what I use my Radial for.  BE's console or House console for opener to racks and stacks.  Sorry, and I know the Radial is out of your budget.

[Karim Ben]

I once patched 2 consoles to 1 processor using Y cables with the first console connected directly to the Y cables and the second connected through iso transformers to the Y cables.
May not be the "perfect" solution but it worked well with no ground issues or level problems.
This might work well for you.

So if I understand correctly, this is what the Whirlwind Line Combiner and IMG StageLine LC31 do, right?

The LC-31 has been designed to mix together two line signals to one signal. It has two independent signal ways (A and B) so that e. g. the stereo outputs of two mixers may be connected to the stereo input of an amplifier.
For galvanic isolation of the two signal sources, each input signal is routed via a transformer. In addition, the signal ground of this decoupled input can be  separated by means of a switch from the ground of the output and the ground of the other input. Thus, a ground loop which may cause an interfering hum noise can be interrupted. It occurs e. g. when the two signal sources have contact in the rack both via the signal ground and via the earthed conductor of the power supply or a conductive connection of the housings.

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