converting stereo into mono - help

[Rickets]

I was interested in the discussion going on about converting a stereo output into mono output.
I have a day care that has 4 rooms with one speaker in each room. One room gets the right channel on speaker "A", the other room gets the left channel on speaker "A", still yet, a third room gets the left on speaker "B", etc. As you can imagine, it sounds horrible, depending on which room your in.
I want to put in a newer CD player/amp, but they only have a stereo speaker output terminal on the back for 1 set of stereo speakers. No pre outputs like on a component system.
I know just enough about Audio electronics to know that I don't have a spare can of smoke to recharge the amp if I just connected the outputs. I also know the Z must remain at 8 ohms. I have read old posts that talk about low level dividers. Do you have any suggestions for a "speaker level" divider with 4 speaker switch system.
Regarding a HIGH level (or speaker level), will the circuit below work without the need for the can of smoke?
Or can you recommend a redesign of this for use with speaker out levels?

Sp output L ---\/\/\/\------+------Switch---------SPEAKER 1----
R1 10K | +--------------------
| |
Sp output R ---\/\/\/\------+------Switch---------SPEAKER 2----
R2 10K | +--------------------
| |
+------Switch---------SPEAKER 3----
| +---------------------
| |
+------Switch---------SPEAKER 4-----
Shealds------------------------------------------+----------------------

I can build a robot, but I can't wire a speaker output!
I am also not smarter than a 5th grader either!!!

Thanks,
Rickets

[Ed Holland]

In this situation, it would be easier to combine the line level outputs from the sources at the input to the amplifier.

It would be straightforward to make up interconnects that linked the L and R centre conductors - this won't hurt the source components. Then your speaker outputs would all be L+R signals, and you could use them indescriminately.


Hope that helps.

Ed

[Rickets]

On the new Amps, there is no way to tap into the line in levels without taking appart the unit and voiding the warrentee.
I also want to build a switch box to shut off any given speaker. At least I want to be able to shut off one speaker in a specific room.
Thanks,

[Rickets]

M
WOW, the dotted lines didn't come out too well.
Try this file attached.

[Ed Holland]

Ahh, I see, you're using a CD + AMP unit, not separates, correct?

In that case you are stuck doing something at the speaker level. However, your 10K resistors are going to block the signal almost completely, as they are >> 8ohms.

However, I'm concerned that if you did use low resistances of the order 8 ohms, (and ignored the losses that would still occur) there might still be problems with the left and right amplifiers interacting badly. That said, I wonder what those better qualified to comment would have to say on the subject.

Ed

[Rickets]

How does this circuit look.

I may have got it!

[Rickets]

Yes, you were correct. It is a CD/AMP player.

[Rickets]

I forgot one little lable all resistors will be 8 ohms. Here is the correct schemetic.
If anyone has a better idea, I Welcome the help!

And thanks for your help Ed!

[Ed Holland]

OK we're getting there. So you want to control the speakers in 4 rooms, with rooms 1&2 selected from one channel and rooms 3&4 from the other.

One way to do this would be to ignore the resistors, and put independent switches in the + line from the amp's speaker output. The shields could be connected as you show in your diagram. This presents the possible problem that if both speakers are selected, the amplifier will see a nominal 4ohm load, rather than the 8 ohms of a single speaker. Many amps can, however, drive this just fine.

The way your circuit is shown, each speaker either connects directly to the amp OR via 8 Ohms. This will not shut off the sound to that speaker, just attenuate it. The connection needs to be broken completely to shut off the speaker.

Ed

[Rickets]

I really appreciate the help Ed.
I have learned a few other things, now that I have actually re-routed the wiring, and talked to my wife, . . . again.
1: Three of the speakers will be on all the time. She only needs one of them to turn off.
2: The switch is only a SPST switch.
3: I still do not have the right and left channels playing the same sounds, because I have not summed the signals.
4: The output of the new stereo is 4-12 ohms. This could help when summing the L and R channels. I could leave the 4 ohm resistor out, and let it go to 4 ohms, but why tempt the fate of the obvious. (Murphy's law #1)

So I have re-drawn the schematic. In the little box, is where I need a summing circuit. The rest of the schematic is correct, . . . . I am pretty sure. No more changes. Because if I cannot sum the L and R, then she will live with it the way it is. One room listening to the drums and bass, and the other room listening to the horns and strings. LOL
Any help getting a summing circuit together without letting the smoke out is greatly appreciated.
At least until we are all better paid!