# Mixing stereo to mono
**URL:** https://boards.straightdope.com/t/mixing-stereo-to-mono/548032
**Category:** Factual Questions
**Created:** [July 26, 2010, 12:04pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032 "2010-07-26T12:04:29Z")
**Posts on this page:** 14
**Page:** 1
### Author:  [@Turek](https://boards.straightdope.com/u/Turek)
#### Post date: [July 26, 2010, 12:04pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/1 "2010-07-26T12:04:29Z")
When we built our house, I ran a speaker wire to the patio with the intent of putting one speaker out there so we could enjoy some tunage while enjoying our (grilled) tuna. My amplifier has a set of speaker outputs labeled “remote” so I thought I’d just twist the left and right channels together and run the combined signal to the outdoor speaker.
I’ve since determined/realized this is A Bad Thing.
What’s the correct way to do this? Optimally, I’m looking for a small box that takes a left and right channel speaker inputs and outputs a combined mono signal. I’m not looking to just run either the left or right channels to the outside speaker since this always sounds wonky. I’ve googled around, and other than determining that my original plan was wrong haven’t had much luck finding the device I’m looking for.
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [July 26, 2010, 12:37pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/2 "2010-07-26T12:37:53Z")
Just combining the speaker outputs alone isn’t really possible. The nearest you might do is a transformer, but there are issues here that are not too far short of just twisting the wires together. However with some additional circuitry before the amplifier it is both possible and quite reasonable. The question is whether your amplifier has a way of getting to the signal before the power amplifier section. This used to be made available as a tape loop - with both input and output jacks that went to a tape recorder.
The other question is whether you want to listen to the main, indoor, speakers at the same time as the outdoor speaker.
If the answers are yes to 1, and no to 2, we have a solution.
The trick is to combine the channels into mono at line level, and then send them to the power amplifier section. This could be achieved with a handful of passive components. A neat further option would be to run a bridging adaptor, which would allow both channel’s amplifiers to be used in concert to run the speaker - but that is likely an unneeded trick unless you need the extra power that would afford.
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### Author:  [@Musicat](https://boards.straightdope.com/u/Musicat)
#### Post date: [July 26, 2010, 12:48pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/3 "2010-07-26T12:48:28Z")
Why not just run another wire to a 2nd speaker outside? Then you’d have stereo as God intended.
Or use a wireless speaker hookup (for both channels) if drilling into walls isn’t your thing.
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### Author:  [@Turek](https://boards.straightdope.com/u/Turek)
#### Post date: [July 26, 2010, 1:09pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/4 "2010-07-26T13:09:31Z")
> [@Francis\_Vaughan](#):
>
> The question is whether your amplifier has a way of getting to the signal before the power amplifier section. This used to be made available as a tape loop - with both input and output jacks that went to a tape recorder.
>
> The other question is whether you want to listen to the main, indoor, speakers at the same time as the outdoor speaker.
There’s not really any way to get the signal before the amplifier. It’s an old Technics amplifier from component stereo system I still have from the 80s. Eventually, I’ll upgrade it but I’ll still be limited to the one speaker outside.
It has two sets of speaker outputs, one labeled “main” and one labeled “remote”. On the front of the unit are two push buttons, one for each set of speakers to turn that set on and off. Optimally, I’d like to be able to run both inside speakers and the single outside speaker at the same time.
> [@Musicat](#):
>
> Why not just run another wire to a 2nd speaker outside? Then you’d have stereo as God intended.
Two reasons:
1. I put the speaker wire in when the house was being built and I could crawl around the framing. At this point, it’s impossible possible to get to where I’d need a second speaker wire to go.
2. I don’t particularly WANT stereo outdoors. The listening environment is way below optimal, and having stereo separation is a waste of time and possibly detrimental, since nobody is EVER going to be sitting equidistant between the two speakers. They’d always be getting way more left channel or way more right channel depending on where they’re sitting.
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [July 26, 2010, 1:27pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/5 "2010-07-26T13:27:28Z")
> [@](#):
>
> There’s not really any way to get the signal before the amplifier. It’s an old Technics amplifier from component stereo system I still have from the 80s. Eventually, I’ll upgrade it but I’ll still be limited to the one speaker outside.
So no tape monitor button? That is all you need.
The down side would be that whilst you could listen to both inside and outside speakers, they would all be in mono.
Failing that, buy a cheap amplifier. Even off eBay. That could be hooked up for mono feed and dedicated to the outside. However it sounds as if your current main amplifier might be worse than the cheap eBay amp 🙂
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### Author:  [@Turek](https://boards.straightdope.com/u/Turek)
#### Post date: [July 26, 2010, 1:39pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/6 "2010-07-26T13:39:02Z")
> [@Turek](#):
>
> At this point, it’s impossible possible to get to where I’d need a second speaker wire to go.
And by “impossible possible,” I of course mean “impossible.” :smack:
> [@Francis\_Vaughan](#):
>
> So no tape monitor button? That is all you need.
Sorry, I misunderstood. Plus, I’m at work and not sitting in front of it.
Yes, there is a tape monitor button. There was a dual cassette unit that hooked into the system.
> [@Francis\_Vaughan](#):
>
> However it sounds as if your current main amplifier might be worse than the cheap eBay amp 🙂
Hey, man. Don’t be dissin’ my classic amp! 😃
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [July 26, 2010, 1:50pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/7 "2010-07-26T13:50:09Z")
OK, we be in business. 😃
On the back of the amp will be the connections the tape unit used. Although not labelled as such they are a break in the signal flow in just the place we need. What you can do is essentially convert the function of the tape monitor button to work as a mono button.
Depends upon how handy you are. In principle, a couple of resistors, four RCA plugs, and maybe a bit of cable, is all you need. Plus a few minutes with a soldering iron. If that is a bit daunting, there are probably boxes we can find that will do the work too.
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### Author:  [@Musicat](https://boards.straightdope.com/u/Musicat)
#### Post date: [July 26, 2010, 2:22pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/8 "2010-07-26T14:22:16Z")
> [@Francis\_Vaughan](#):
>
> In principle, a couple of resistors, four RCA plugs, and maybe a bit of cable, is all you need. Plus a few minutes with a soldering iron. If that is a bit daunting, there are probably boxes we can find that will do the work too.
Maybe easier than that. Get a “Y” cable from Radio Shack or [monoprice.com](http://monoprice.com), with two female RCA plugs on one end and one female on the other. Plug the two into the tape output and the one into the tape input using the channel you will be sending outside.
I know someone may say that we are causing problems with impedance, but I regularly connect two line level signals this way under many different circumstances and have never noticed any distortion from it. Certainly your application isn’t demanding studio-quality.
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [July 26, 2010, 2:43pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/9 "2010-07-26T14:43:54Z")
The problem with a Y connector is that you have to remove it to put the system back to stereo. The Y has shorted the left and right outputs together. Unless the outputs have a separate buffer amplifiers this means the internal signal chain will have had its L and R shorted together. The amp may have such a buffer, but a cheap component system (with the telling point that it came a dual cassette deck) suggests it may not have been designed to such a high standard. Using a pair of resistors means that even without a buffer amp the main signal chain will suffer zero to an vanishingly small amount of crosstalk between channels when the tape loop switch is “out”.
There is also a small (but unlikely) risk - some op-amps do get pretty unhappy if they drive into another’s output. This amp will be filled with capacitive coupling, but it is possible to send some amps unstable like this.
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### Author:  [@Turek](https://boards.straightdope.com/u/Turek)
#### Post date: [July 26, 2010, 3:01pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/10 "2010-07-26T15:01:57Z")
Hmm… daunting, no, but I haven’t ever messed with soldering so I’d rather find something off-the-shelf.
BTW, [this](http://en.wikipedia.org/wiki/File:SU-Z980ampTuner.jpg) is the amp I have, only mine doesn’t have the fancy digital display.
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### Author:  [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)
#### Post date: [July 26, 2010, 3:04pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/11 "2010-07-26T15:04:34Z")
Google “passive audio mixer”.
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### Author:  [@JerseyFrank](https://boards.straightdope.com/u/JerseyFrank)
#### Post date: [July 26, 2010, 3:07pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/12 "2010-07-26T15:07:31Z")
Look for a subwoofer summing box. This sort of thing is intended to take the L/R channels and combine them to allow the bass of both channels to be output via the subwoofer. It would work for your purposes too.
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### Author:  [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)
#### Post date: [July 26, 2010, 3:31pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/13 "2010-07-26T15:31:15Z")
You could try the Y cable, at worst it simply won’t work, and it might do the job.
If you aren’t feeling up to a bit of soldering (what I allude to is a passive mixer) the next step could be a cheap mixing box. Something like the Behringer MX400, which can be had for $30 US, plus a few appropriate cables would do the job. A couple of dollars and a soldering iron would be my call.
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### Author:  [@Turek](https://boards.straightdope.com/u/Turek)
#### Post date: [July 27, 2010, 12:04pm UTC](https://boards.straightdope.com/t/mixing-stereo-to-mono/548032/14 "2010-07-27T12:04:29Z")
Thanks everyone for their input. I’ll probably mess around with it some more this weekend.