# Does LEFT + RIGHT = mono?



## joed (Mar 13, 2005)

NO. They are two separate circuits. You can't just connect them.
Look on your receiver and see if it has a mono switch. otherwise just use one side.


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## diyorpay (Sep 21, 2010)

Keep researching.
I think I remember that doing what you suggest may give you the difference between the 2 stereo feeds.
A poor mans center channel.
Check car system designs too.
Either way, it won't be mono.


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## GrayHair (Apr 9, 2015)

Combining two frequencies results in the _Sum _AND the _Difference_ of the frequencies.


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## AllanJ (Nov 24, 2007)

I say that "left" plus "right" does equal "mono."

It could differ if the source material was recorded using more than two channels and the producer mixed the various tracks to get "left" and "right" and "mono" where my starting sentence ends up being false. At one point in ancient history, record producers issued both mono and stereo versions of the same album.

You may or may not "short together" the two stereo channels of your amp to create a single signal that would have the content that would pass for "mono." There may or may not be electronic interaction at the point you made the short where the result produces distortion. I own one amp that has this "problem." The "stereo-mono" switch on many receivers does short together the two channels.

Simplified descriptions of various stereo processes assume that left plus right equals mono. For example FM stereo radio modulates L+R asthe main channel and L-R as a subchannel. The stereo receiver adds the main channel and the subchannel to get "left" and subtracts the subchannel from the main channel to get "right".A mono FM receiver demodulates only the main channel which becomes the (sole) output.

Oops, I forgot to answer the OP's original question. +1 No, you may not short together the speaker terminals and/or connect both sets of speaker terminals to the same speaker voice coil to get mono. Now, there exist a few speakers with two separate voice coils where, incidentally, if you connected the left amp output to one voice coil and the right output to the other then you get mono.

I do not like the idea of using just one side. I have some (vinyl LP) records where just the vocals were on the left channel and just the instrumental accompaniment was on the right channel. Does not sound too good in a store or restaurant with widely spaced speakers each playing just one of the channels.


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## quatsch (Feb 4, 2021)

A 10K, 1/4W resistor from the high side of each speaker, feeding into another amplifier high impedance input high side will give mono sound out of the third amp. Shunt the amp input with a 1K.

10K \
*_*|------amp input
10K / 1K
gnd


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## Ronnie833 (Jan 9, 2021)

quatsch said:


> A 10K, 1/4W resistor from the high side of each speaker, feeding into another amplifier high impedance input high side will give mono sound out of the third amp. Shunt the amp input with a 1K.
> 
> 10K \
> *_*|------amp input
> ...


It would be much easier for me to get my 4th speaker fixed.


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