Somebody here must know how to do this...

[skavan]

Here's the goal:

I have one large room.
On one axis I have a projection screen.
On another axis I have a plasma.
My various sources (audio part of it) travel through a pioneer 59txi en route to the speakers.

I have sufficient speakers for a 6.1 system on the plasma and 5.1 on the projection. The projection system uses all the same speakers as the plasma system (with an additional centre channel).

I need some way of switching the speakers based on whether I'm using projector or plasma.

So, said another way...imagine I have speakers A,B,C,D,E,F,G (forget about subs for now). When I'm watching the plasma:
LEFT = A
RIGHT = B
CTRE = C
SL = D
SR = E
SB = F

Now, when I'm watching the projector:
LEFT = D
RIGHT = A
CTRE = G
SL =F
SR = E

In an ideal world, I'd love a third option - when I'm listening to stereo:
LEFT = D
RIGHT = E

Now, if I wandered behind my amp and replugged all the speakers every time I switched modes, this would be easy --- but who wants to do that!
In an ideal world, I press a button on the remote and all the speakers switch to their correct functions.

Someone out there must be:
a) Bright enough to understand the above
b) creative enough to know how I cd achieve this

- oh, and it probably goes without saying - I want to keep the sound quality high...so an array of crappy speaker swicthers may not cut it - if they drop sound quality.

(P.S. I do have an AMX control system - with relays and such - if that helps..)

[dnsey]

This would be very easy to achieve using a DPDT relay for each speaker, actuated (via diodes) from a 'mode switch' (rotary or pushbutton bank as you prefer). If you wanted to be really clever, you could derive the control signal from the video source power-up signal.
As far as quality's concerned, it would be dictated by your choice of relay.

[jan.didden]

First thing that comes to my mind is that probably you'd want to switch the audio inputs to the power amp as that is much simpler, less power etc than switching the speakers.

As to the switching, what you really need is to rotate the total stuff one click clockwise and back, isn't it? From east-west to north-south. So you need a 7-in, 2 x 7 out switcher, user in reverse: you put all channels in each of the 7 'output' jacks, but offset one click. Then the 'input' row actually goes to the power amp. By selecting one or the other setting you rotate one click or back.

Now the hard stuff: I have no idea this is a standard product, but the Behringer MX882 might fit the bill at just over a 100 bucks. Check their website for the manual.

Jan Didden

[skavan]

Thanks for the two directional suggestions.

Let me take them in reverse order.

a) Use Line Level...
This is a good idea, but would mean I'd have to swicth out my receiver (VSX-59txi) to a pre + power amp scenario and then route the pre-outs iinto a matrix switcher like an extron crosspoint. In addition, I wonder how much signal degradation would transpire? I wonder (thinking out loud) whether its possible to grab the 7.1 signal from my receiver do my maytrix stuff and then shove it back in...(kind of like an insert on a pro mixing desk) - anyone know the answer to this?

b) Relay based solution.
This is interesting, though I can't quite wrap my head around how it would actually work? Signal comes into an array of relays. I don't think one can connect the speakers to the output side of the relays as one would end up cross wiring all the speakers....so I think the relays would have to feed additional groups of relays...in fact, to handle 7.1 (forget the .1), one would need 7 + 49 + 7 relays ( I think). Is this what you had in mind?
Ugh - my brain hurts thinking about it. Please advise...

and thanks everyone for your input - this is great.

s.

[1audio]

You could make a simple matrix with relays or buy one and control it from the AMX. The most expensive part is programming the AMX. I would use a line level switcher, connect the best amps to the best speakers and route the signals that way. Much better than speaker switchers.

There are connercial matrix switchers available for the pro market and for the industrial market. I had a stack of HP switchers that I dumpes a few moths ago when the project they were intended for fizzled. They are too expensive but the interface and programming would be.

This is an option and the AMX should be able to control it:
http://www.extron.com/product/produc...00&subtype=108
Or
http://www.extron.com/technology/archive.asp?id=joel85

Shop on eBay or wherever for similar products.
-Demian

[1audio]

1) Line level- Better if you can do it- no power through the relays. This is what kills relays. But you must check your receiver for pre out and line in. Possible on upper level receivers.

2) Speaker level relays, you need a relay for each speaker at each combination or 7 X3 or 21 2 form A contact relays rated for 5A minimum.

3) Switch- 14 pole three position. Again possible. I don't have the patience to wire it. You could use the switch out of an old printer selector switch. (26 pole switch in many of them).

Check your receiver. It may be time to make or buy seperate amps for all of the speakers and use the receiver as a processor.

Or possibly re-arrange your room?

Have fun- -Demian

[purplepeople]

Another way would be a line-level gold plated patch bay using RCA cables.

With good connectors and cable, it will be "relatively" inexpensive and very high quality. It also provides an easy way to lock out the system from unintended ears, just by plugging into "dead" ends.

You'd still have to be (un)plugging cables, but at least it will be on the front of your rack.

:)ensen.

[dnsey]

Maybe I'm missing something, but it seems to me that it can be done with six relays (speaker or line as you prefer). I've shown SPDT, but you could of course use DPDT if you want to switch the earthy side as well.
The bottom diagram is an add-on to enable the 'ideal' stereo option. In this case, the main relay bank should be in the 'plasma' position, so that the auxiliary relay can select 'home theatre' or 'stereo'.
Relay coils can be controlled by a simple switch, a switch / diode matrix (more elegant), or an automated system.

[1audio]

This can be done simpler. But hazards exist-
1) You can't always use common grounds on speaker applications. The amp may have bridged outputs. There may be other complications if the return lines from the speakers get crossed.
2) If three different layouts are desired three speaker relay arrays are needed. Leaving unused speakers connected may not work if the channels are used differently. Some reduction in relay count may be possible.
-Demian

[skavan]

dnsey --- this is fantasic...

I'm thinking I should go with speaker level as I don't then have to rejig my receiver set-up.

your diagram seems to work for all my use cases...and I'm not quite sure why I was so convinced that I needed a much more comprehensive array of relays -- maybe I was drinking something that I shouldn't have been!

Now, my questions get more granular...

a) It seems that I need DPDT Relays (speakers are AC so I need both sides) that are two-pole and capable of handling speaker level signals - without degradation....any ideas on where I might find such a beast ... and what it's called.

b) I have an AMX control system that is capable (via Remote) of triggering 8 independant 12V, 200mA outputs as either a toggle or pulse - perhaps I can use this as the relay actuator? Alternately, it also has 8 relays that I could use.

c) When you say a 'switch diode matrix' what do you mean?

Thanks so much folks -- for the guidance on this...amazing!