Hooking Up a Mono Speaker to a Stereo Amp

Connecting amplifier outputs together is a bad idea.

You have not provided many details. If the amp is fed by "line level" signals (via external cords) then I suspect a "line level" mixer might be something to think about.

Have you checked all components for a stereo/mono switch?

Could you recommend a "line level" mixer?

What I am trying to do is take an output from an apple I pad (or cell phone) and amply it then supply a signal to a whole house system that had mono speakers installed in each room (with a volume control in each room). I have a conponent type amplifier now to use.

Thanks for the resonses

A lot depends on the amplifier you are using. Some amps have what is called Bridge Mode that allows you to hook the stereo outputs to one load (speaker). Most amps do not allow that, but there is a better way to do this...

You don't need a mixer for line level signals if you plan to run both left and right to the same input of one channel of an amp.

Simply buy an RCA Y cord at Radio Shack and connect the left/right outputs of the iPad or iPhone into the Y cable, then the other end of the Y cable to one input of the amp.

The second channel of the power amp should be unconnected at both the input and output terminals. To be safe you could buy an 8Ω power resistor and connect that at the unused channel output of the power amp. That is called a dummy load and is also available at Radio Shack.

The simplest and safest way to accomplish that is to buy a "Bluetooth" audio adapter... It will link your IPad/IPhone audio output wirelessly to your audio amplifier via the built in line output... They are readily available from Bestbuy, Amazon, etc. with price range approx. $35.00 and above!

As far as I am aware (not a Blue Tooth expert), you can only have one set of speakers and the range is limited to 30 yards or so.....thats what I read online too....

Also WLAN is often limited in distance without a repeater, but can also power the right speakers, more than one pair I believe.....

See here:-

The 10 Best Wireless Speakers

Where you can read:-

Bluetooth is the longer-established wireless streaming system that doesn't have quite as many features as AirPlay, but supports many more devices. Bluetooth works by pairing, so a device can only stream to a single speaker set at a time. They tend to be less expensive than AirPlay speakers, and many can run on rechargeable batteries, making them easier to carry around the house or set up outside. That said, you can still find some large, powerful Bluetooth speakers that don't travel easily but sound excellent if you know where to look.

Best of luck to all concerned.

Andy- In the OP post #5, what he need is an interface between an IPad/IPhone and his audio system that feeds signal throughout the different rooms in the house.... The Bluetooth capable interface that I suggested can stay in one place together or near his audio system and his Apple gadget.....in which case the limited distance of the Bluetooth range will never be a problem!

My understanding was, the OP's house has a sound system that is already installed feeding signal to all the rooms, and all he needs is a way of patching a new audio input coming from an Apple device!

Didn't he explain it well!!! DUUUHHHH!!

Thanks for the heads up.....

Correct

You can simply just use one channel of the amp most people do not know that 1-2 watts is quite correct for most and if you are playing at 10 watts people will think your a old rock and roller. The tricky part is power is logarithmic (like virtually everything) and if you want to play very loud you can use a 100 or 200 watts up. Being in this business I am guessing you are talking about some common mono speakers installed throughout your house. Check to see that there are not transformers on the speakers which will tell you that you have 70 volt speakers and require than a 70 volt amp. Use a Mackie,shure or similar mixer is the correct way to get mono- using a Y cable as is suggested by some, will cause canceling due to phase shifting between the two channels, and the sound will be not better than half of stereo. Use a Shure mono mixer like the SCM268 employ two mono inputs 1 and 2 for instance turn both up to half way and use the mono output to drive your amp. Or build a Y cable with a 4148 diode in each leg.

It is incredibly unlikely that a domestic collection of loudspeakers would be made up of the 70V line speakers (or in Europe 100V line speakers) which are normally used for public address systems, so you can forget about looking for transformers.

Certainly a mixer is the best way to get a mono signal from a stereo output, but a passive mixer, aka Y cable, will work just as well if the amplification is available elsewhere. A passive mixer will not cause phase shifting if it contains only resistive components. Putting diodes in a Y cable is an interesting way of getting guaranteed distortion.

You obviously have never done this. as stated it does not sound better than half of stereo in fact the dynamic range (of stereo content) becomes less. And in reply to the diode, I regress this will only help the source from becoming mono. I strike the diode comment but it will not cause any distortion. And to suggest that you know he does not have 70 volt speakers is uniformed.

Unless you are listening to music, just hook one side in each room. Balance the load on the amp. Otherwise a mixer is needed. No big deal.

You can't, you will blow the power amp, unless the music source is mono and the volume of left and right channel is exactly the same or very closely matched.

I noticed that you used the word "speaker" in the plural form, meaning more than one! Perhaps you could hook one mono speaker to one channel and the other speaker to the other channel?

Are they of the same type? They come in different impedances such as 4 Ohm, 8 Ohm, 16 Ohm, and possibly a few other choices. If they are not the same, they will sound and perform differently. And if they are not the same impedance as that which your amplifier expects, then the power output will be less than what the stereo is capable of providing.

The reason you should not tie the stereo outputs together is that they share a common dual power supply. Stereo signals swing high and low at different rates and times creating the illusion of being "in the room". By connecting the outputs together, one channel might be peaking in the V+ at the same instant the other channel is peaking at the V- and the two connected output transistors will try to drive out that mystical aura of "magic smoke" that makes it all work. Then you can go out and buy a properly matched set of speakers for a new stereo.

What was originally driving the speakers?

Is there a wiring hub or distribution box?

Does your amplifier have a "stereo/mono" option select?

What is the impedance of your room speakers?

You can't connect the amp outputs together, and you can't drive multiple speakers with a single amplifier circuit without impedance matching.

Maybe you could use one of these.

You can divide the speakers in half and wire each half in parallel using the amplifier as 2 amplifiers...

This is one half...

That shows a series circuit not a parallel circuit.

Also, if he has 8 ohm speakers, that would be a 32 ohm load on each amplifier channel, which may not work.

Now how did that happen....yes you are quite right, the diagram is incorrect and does show speakers wired in series, which might overload the channel, usually 16 ohms max...If you know the ohms of your speakers, then you can use a combination of series parallel wiring scheme, but if not, I would assume they are 8 ohms, and limit series wiring to 2 speakers, otherwise go parallel....thnks to WJMFIRE for catching that....

http://cie-wc.edu/Series_Parallel_9_14.pdf

I remember this from college: Tube amps do not like high impedance, but they can be shorted. Solid state amps do not like low impedance, but can be run open circuit.

So, if you run 32 ohms, I don't think it will hurt the amp. If you run 2 ohms, you could fry it.

Shorting the secondary winding of a tube amplifier output transformer is a terrible idea.

Not "overload", "under-load", with possibly very high voltage transients plus clipping, due to running with very little load.....

We have very little solid infos supplied by the OP up to now, certainly not enough to give good infos on connecting.

If it was me, I would check if the amp has a Mono/Stereo switch first, then if yes, I would connect half of the speakers to one channel and the other half to the other and switch to Mono.

How they would need to be connected to the two Mono channels is a small problem, but assuming say that the amp is say 8 Ohm impedance, then two 4 Ohm speakers can be connected in series, or 4 x 32 Ohm in parallel.....there are many possibilities......

I personally would run both channels and fit single speaker boxes, but with two sepate speakers in each box, not really Hi Fi, but still better than Mono......

Or better still, buy a wireless speaker system and simply add stereo pairs where required all over the house, ebay has some that work and are very reasonably priced. This also allows units to remain portable and to be used everywhere within range (put the transmitter up high!), even in the garden on a good day!!!

That way, no cables or impedance matching.......WONDERFUL!!!

I dont believe that series wiring would overload the amp, just reduce the SPL by x4. If you wired in series/parallel with 4 speakers you can achieve the 8 ohm requirement.

A high quality stereo amplifier is made up of two independent mono amplifiers on a single chassis(think Macintosh, Carver, Mark Levinson, etc). These two amplifiers can be paralleled to drive as a monaural source. Cheap home type stereo amplifiers cannot be paralleled.

I recall something about push-pull amps and how they're not suppose to be hooked up to another source, but I could be wrong. Geez, that was back in EE 312 in 1986! I didn't really like that class too much, but I remember something about Class A and Class B amps (push-pull).

It is always a bad idea to parallel two amplifiers. They differ slightly in amplification factor (due to components tolerances) and damping factor.

Your classic examples with end transformer start to feed each other.

Also distortion level will increase.

The OP can split his (lines) keep 2 wires and connect one part to the left output and another part to the right output.

Important is also that he transforms the stereo source signal into a mono one or he will hear "half the music". (L and R inputs in parallel or better with some resistors to the mono creation)

Connecting the speakers according the impedance load capacity is important too.

And if you want to do it perfect, check also the phase of the speakers:

When a drummer hits the base drum (= pressure wave), your speaker cone should also come towards you. (if not reverse + and minus or red and black input to the speaker)

...some expensive ones also not. In fact, in my personal opinion/experience, the higher the cost/value of the amp, the more likely it is that the two channels cannot be simply connected to each other....

In fact, generally speaking (pun intended), the cheaper the amp, the lower the power output = the higher the likelihood that the outputs can be connected together (paralleled), but one can NEVER be 100% certain unless it is stated in the manual.....

Using a stereo/mono switch on Mono to make both L & R speakers the same output electronically, can be a useful trick if available.

Or, with some amps, one can connect the R & L input signals TO the amp, together to achieve the same effect, assuming that at that point, both signals are "relative to ground", which can also be easily checked out first using a meter or Scope and a bit of common sense.........

True, for high-end amplifiers, this is called "Bridging".

Bridging, for what I learned is NOT parallel.

With bridging, one amp (when in bridging mode), gets a reversed input signal (180 degrees phase shifted) and the amps' outputs come in bridge, kind of series, NOT parallel. The load impedance also has to be doubled.

Say if each amp is designed for 4 ohms, the bridged load should be 8 ohms.

Most of the time, the negatives (output connectors) are jumped together and the speaker is connected between the 2 positive outputs. ( one of each amp)

We need to start with basics here.

I stand corrected in my correction. Series connected.

Years ago, when I was in college, I helped friends with their home and car stereo systems. A good friend of mine watched me wire up a new stereo, amp and speakers in his 1980 Buick Regal. He watched me twist the wires and cover with electrical tape.

He thought it was pretty simple, so he tried to wire his home stereo system up. He took all the wires, removed a little too much insulation, then twisted all the wires together. His stereo was a cheapie all in one system (receiver, cassette and turntable) and I was surprised he didn't fry the unit. When I told him that he had to wire each one separately, he didn't "get it". So, now when I help my friends with electrical stuff, it doesn't surprise me when they don't understand what I'm doing, consequently, they're scared of electricity!

Get a mono amp, sum the channels together with a pre-amp that has a mono feature, and then drive the speakers around the house. Mono amps are cheap - so you could use several 10watt amplifiers to drive small groups of speakers. Ceiling speakers are usually low power and frequency response not so hot, so all it provides is some ambiance music.

10 Watt is a bad idea either.

These amps are clipping fast, distort the music and burn the speaker coils easy.

The myth that the power rate of speakers need to be higher than the amp rating is a dangerous approach.

The trick is just to get a oversized amps and limit the output. At least they will be provided with a clean signal (or the one you provide, without getting synthesized)

Just connecting L an R together, provides a mono signal.

When doing this without a resistor, you lose quality (attenuation of part of the frequency spectrum)

For plenty of speakers, consider a system with so called 75 or 100 Volts output.

High impedance, the speakers also can be adjusted in volume with tapped transformers for this purpose.

Contrary to the assertion in #1, it may not be best practice, but it is possible to parallel stereo amplifier outputs into a single speaker. When going down this road I would put a small resistor, of the order of 0.1 to 0.5 ohms, in series with each positive speaker lead before joining them at the speaker.

However, as others have indicated, the best practice is to mix the two stereo signals before feeding them to the amplifier, using a cheap powered mixer and a splitter cable on the output to feed both amplifier channels. Each amplifier output can then feed the same mono signal to separate chains of room speakers. Equally with a bit of soldering one can put 1k - 10k resistors in series with the outputs of the iPhone/iPad and then join the leads to make a purely resistive mixer.

Do not connect both channels of the amp to a single speaker.

You connect half of the speakers to one channel (L) and the other half of the speakers to the other channel (R). You have to match the total impedance of the speakers to the amp.

You then set the output of the amp to 'Mono' (L=R). If you haven't got a 'mono' switch then you will only hear the L or R output depending on which room you are in.

But somewhere in the passage between rooms there will be a stereo effect .

Good to see somebody gave the correct answer.

Keep up the good work cobber...

See the attached site (copy and paste) to hook up an 8 ohm speaker network to match an 8 ohm amplifier output.

Also stated by others, if your system is 70/100V line output, then place as many parallel speakers with transformers of either 70V or 100V line that are under, or match the total power output of the amplifier.

EG if the amplifier has 10 Watts output then use a maximum of 10 x 1 Watt speakers or 5 x 2 Watt speakers, or 3 x 3 Watt speakers.

https://www.google.com.au/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjY_fbr7ZvKAhWiI6YKHXhPD4cQjRwIBw&url=http%3A%2F%2Fwww.hometoys.com%2Fcontent.php%3Fpost_type%3D1874&psig=AFQjCNEmw_nREWTW5spQ7Nk_5jEJpynAgA&ust=1452398945506902

Just don't. Assuming you amp doesn't have a 'mono' button, set the /original/ device output to Mono so each channel is getting the same signal. In iPod: Settings -> General -> Accessibility -> Mono Audio. If your device won't do mono output get a stereo-mono converter lead with the right output/input plugs on.

Did it this way (lead) when I was a student placing speakers around the house for parties. You can also control relative volume with the balance toggle.

Depending on the age of the system and its complexity, it might be a "70 volt" system. to verify take down one of the ceiling speakers and see if there is a matching transformer mounted to it. If yes, you will either have to use the existing amplifier, rewire the entire house, or buy a new amp that does what you want. Using the existing amp means you will have to configure your desired sound system and feed it into one of the existing (hopefully they exist) aux inputs on the distribution amplifier. The configuration settings, I will leave to others. At any rate, if you are any type of audiophile, I think you will be less than happy with the result. (Try two separate rooms with long wires to see if it is acceptable). An alternative would be wireless speakers, some carry the info over the power lines, others use Bluetooth or equivalent.

All of the responses so far have some truth in them. I do not play with electronics, I have worked in electronics for 50 years, including running the service shop of a stereo store. As I understand your situation, you have an ordinary stereo amplifier and you have a sound system in the house with speakers in each room. You want to connect your device to the amp and get sound in each room. Since the sound system is mono, that tells me that it was not intended for hi-fi. Also if there are more than 3 speakers then the system has to 70 volt line system. You will need to find the 70 volt transformer and connect one speaker output of the amp to it. If the amp does not have a mono switch on it you will have to make one. For get the diode trick, it will cause super distortion. Use 2 10K resistors, solder the ends together where they will be connected to the amp; the other ends will be connected to each of the outputs of your source device. Use an old stereo cable that is shielded to avoid hum. Yes you can use common ground here. Ground the shields and keep the signal carrier wires insulated. Since you did not give a make or model number, I do not know the power output of your amp. It takes only around 5 watts to do what you said you wanted if the volume is at normal speech levels.

Hooking Up a Mono Speaker to a Stereo Amp with a twist.

Frank, I too have worked in electronics for over 50 years. And I have a question. Consider a whole house stereo, 70 volt system with transformers as volume controls to the speakers. What do you do about one or two rooms that need mono there? I have looked for a day or two for the answer on the web and cannot find one. The question is asked a-lot of times, but no real answer. Best one I found was using the "monogizer 200" by the now out of business company Audioplex. I'd like to get one to reverse eng. but so far no luck. Do you know of a way to do this I have never heard of?

Thanks

Two line transformers and 2 speakers in a single enclosure and call it mono?

Thank you for your reply.

It brought a smile, sorry to offend you.

I'm just helping a home builder for free, as a friend.

I've searched the web for two days and have been unable to locate a technical answer.

Thought an eng'ing site would have an answer and be willing to share.

Thanks for your time anyhow

No offence taken. I'm just intrigued by the statement that some of the rooms need mono. It would be the first time that I have seen mono to be a specific advantage. As I see it though, any other solution would be much more expensive. You could, for example, tap the 70V signals, put them through a mixer, and put the mixed signal through another amplifier to a single speaker. The question then is "Why go to all that trouble?"

Actually it's a research/build/replace project for a builder friend of mine. He builds high end homes and the cust's want it. I didn't really ask who wants it, but a days web research seems to show the "monogizer 200" (stereo to mono, at output) seems to be a rare find and referenced in a-lot of audio blogs. I am designing a printed circuit board for the other item he can no longer get.

Basically now I'm curious. No one who knows how it works is talking, and I'm curious just how they did it. Maybe sometime in the future I'll get a hold of one and reverse engineer it. OR maybe I'll finish the printed circuit board project hub and go on to something else. Have a good one.

Feed the amp with a mono signal. Your iPad will have a stereo signal. Take two resistors of 1KOhms and short both their ends at the output at one side and feed the audio through the two ends. These resistors will prevent shorting of the L and R channels and will mix them to mono. Now take a Y cable and connect the pair to the amps L and R input and the single end to the resistors.

Now divide your speakers into two groups and connect each group to one output channel. It is better to find out ohms of each speaker and the make a series parallel combination so that the end result is what the amp is designed for...mostly four or eight ohms.

Never connect a Y cable for making two outputs to one. Other way is allowed.

Gajanan Phadte

I would combine channels of your source to make it mono and connect half your speakers to each channel out. I assume (and take all related risks) that since there are volume controls there is some type of matching network for the speakers. I have also seen stereo to mono speaker level transformers at one time but on the surface they didn't seem like a good idea.

I did that one time, and for my surprise, discovered that the left and right voice tracks were of opposed polarity, so I ended up with an instant karaoke; I just put a switch to one of the channels ( to defeat that effect), and the girl I built that for was delighted ! She was a terrible singer, but a fabulous spectacle to see her rack bouncing with her motions and little jumps.

Cancellation of vocals is possible only in case of karaoke or bridge mode selection. Only other possibility is a mistake or a fault.

Gajanan Phadte

You have said nothing to suggest you have one of those high voltage, 70 volt line amps with tapped transformers.

You have an ordinary household stereo amp and some 8 ohm speakers that may be anywhere 4 to 16 ohms ish

You don't want some connected to L and some to R because it will sound crap sat in a room listening to 1 side.

[If you have loads of odd speakers:

The speakers with the lower impedance will run louder so put them further from the amp as the long wire will bring an 8 up to 10, 12 and more

Put low ohms in series to bring their total up, parallel to bring them down. The plate on the back of the amp will probably say that the amp wants to see around 8 ohms on each of the channels L&R

Put the louder speakers in the larger rooms

If you are too far away from output ohms the range your amp likes, you won't be able to crank it right up without damaging the amp or heating speakers/wires up

If the amp has not got it's ideal ohms + wattage loads connected, you definitely cannot run it unattended, it will be a fire hazard, (why would an amp be run unattended?]

Anyway you have 2 nice balanced pairs of wires coming from the rooms with 8 ohms and equal wattage power handling.....

The L and R need to be added to be L+R and L+R

Best way: switch the amp to mono and connect the speakers to L and R outputs

Second best: on the input side connect the grounds together (outer rings) ,cut the centre wires and add a 5 to 20k resistor in series with the centres and join them together after the resistors, then run them into the left and right inputs

3 rd best do this on the output with 2x 4 ohm high wattage resistors ..... connect the speaker -ves to amp output -ves. ...... Amp output positive L to one resistor, R to the other. Join the two free resistor ends together, join both speaker +ves to the joined resistors

With last option expect some of the sound quality to be lost, and about half the amp power go to heating up the resistors. If the original sound source eg some audiobook CD's, is mono then the resistors wont heat up, but if you have some proper music playing where the original L and R sides are totally different most of the time, they will get hot, so chose resistors rated much higher than the amp can deliver.

options 2 and 3 are just high (10k) and low (8ohm) impedance versions of a 2 resistor voltage adder

this is a 3 resistor adder:

https://www.google.es/url?sa=i&source=images&cd=&cad=rja&uact=8&ved=2ahUKEwjEspOhnP7cAhVJ6RoKHdYXBm0Qjhx6BAgBEAM&url=https%3A%2F%2Fwww.allaboutcircuits.com%2Ftextbook%2Fsemiconductors%2Fchpt-8%2Faverager-summer-circuits%2F&psig=AOvVaw0lRQL9PsqBjreWxzXlhnmQ&ust=1534943488577085

Certainly, if the survival of the <...amp...> is not in the equation. Why make scrap electronic junk just for the sake of it, though (rhetorical question - NNTR)?