How to create a mono speaker

djenkinson

Standard Member
I was wondering if anyone knew an easy way to turn a stereo output into a mono one? I have a normal amp in my living room, but for reasons to complex to go into (!) only one speaker.

I would much rather have a blended L and R mix through that speaker rather than just one side... but how? I am guessing that splicing the cables together is not the way to go? Basic internet searches haven't highlighted anything.

Any thoughts much appreciated

Daniel
 

BlueWizard

Distinguished Member
If your amp is an older amp, it might have a stereo/mono switch. Switch to mono and only use one amp channel.

It is not advised that you use two amp channels on one speaker directly, because that opens the possibility that one channel will short the other. But you could connect them if you isolated them with some resistance.

If you put a 2 ohms power resistor in series with each speaker line BEFORE they join together at the speakers, that would provide the isolation, but 2 ohms is a lower resistance path than the 8 ohms speaker, so current is going to want to flow into the other amp channel more easily than it would flow into the speaker. But the path from one amp channel to the other is going to see 4 ohms, and that prevents a dead short.

If you raise the resistance to, say, 6 ohms or 8 ohms, then the speaker path looks more appealing to the current, but you lose half your signal on the resistor, which mean half the output from the speaker.

The resistors would have to be large 10w or greater power resistors.

This will function, but it is far from ideal. And I don't really recommend it.

The ideal solution would be if your amp had a Stereo/Mono switch. That would solve all the problems.

Again, what you are trying to do is rare, and potentially damaging to the amp. If you could give us a better explanation of the circumstances perhaps we can come up with a better solution.

Steve/bluewizard
 

djenkinson

Standard Member
Thanks for the reply. It sounds complicated... which I feared having googled it.

My situation is quite simple and I am trying to make the best of a rather less than ideal situation.

I have a Sony Amp (quite a nice one, but fairly old) which runs 2 stereo ceiling speakers in the kitchen.

In the living room I used to have 2 normal speakers, but due to lack of space they have now gone. I therefore have one ceiling speaker (the builder put this in for me because he had some "spare cable"! He only put one cable in however so even one of those 'stereo' speakers from one speaker wouldn't work I assume).

My options therefore are:

1. For this speaker to just play one channel - yuck
2. Or explore some kind of compromise to try and get it to play mono

Sounds tricky. Any thoughts appreciated.

Daniel
 

gingerbiscuit69

Standard Member
Theres no direct way to splice two unbalanced sources together into one output source. Doing do would mean the shared mono information would amplify together making say the kick drum twice as loud, but any stereo imaging between the L/R would cause destructive interferance, where a possitive of one frequency, may have a negative at the same time on the other channel, canceling each other out, then suddenly being identical, leading to the impression of the music 'pumping' as frequencys amplitude jumps up and down (amplitude being what affects the output level ie: volume).

I know through a balanced three core (+,-,E) say on XLR leads you can link (L->R) 1->1, 2->3, 3->2 and get a sum mono signal.

On a budget (ie: you should just fix it properly), the only thing i can think of is to run your stereo source into one of these on mono TRS jacks : Behringer ULTRA-DI DI20 2 Channel DI/Splitter Box | DV247 converting your left and right unbalanced sources, into balanced sources, which internally sum mono's the signal. You can then simply make an XLR->RCA lead to take you to the amplifier input. Catch is you would need to power it with 9v battery.

Hope that helps, Pat
 
Last edited:

BlueWizard

Distinguished Member
...

In the living room I used to have 2 normal speakers, but due to lack of space they have now gone. I therefore have one ceiling speaker (the builder put this in for me because he had some "spare cable"! He only put one cable in however so even one of those 'stereo' speakers from one speaker wouldn't work I assume).

....

Daniel

I'm confused, you have one speaker with cable in your living room, or you simply have the cable?

I can see that he might have given you the cable for free, but it seems odd that he gave you the speaker for free.

Also, is the cable in the ceiling attached, or is it free in the wall/ceiling. Because if it is free, not nailed down, you can use it to pull a double wire set through.

Or, you can attach a long 'fish tape' or heavy string to the wire, pull it back into the kitchen, then attach two pair of wire to the 'tape' or string, and use the string to pull them both through to the living room.

Once you have two pair of wires, then it is a matter of adding the second speaker.

Steve/bluewizard
 

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