Ceiling speaker amplifier to mono circuit.

[roganty]

I got my self an e-audio Bluetooth amplifier (link)

I would like to combine the stereo output into a single mono speaker.

I have found this http://techtalk.parts-express.com/forum/tech-talk-forum/60443-stereo-to-mono-summing-circuit but I'm a little confused as to what what size resistors to use.

Some searching suggests using resistors that match the resistance of the speaker, but I'm not sure if I would need to use 8ohm resistors, or 4ohm resistors.

It seams like the more I search, the more confused I'm getting.
Thanks for any help you can provide.

Anthony

 

[Lucid]

The thing you're looking at won't work for speaker level. There's too much power in the signal (current and voltage too high). It'll blow it to bits.

Even if you reduce the input signal down to a safe level then it still won't work because the output won't be strong enough to drive a speaker.

It's. .. the ...wrong... thing.

No amount of tinkering is going to change the Laws of Physics.


What you need is a summing transformer. KEF makes one for £39. You might be able to find something similar and a shade cheaper from less well know brands. The KEF one is here: https://www.ceiling-speakers.co.uk/KEF-Audio-Stereo-to-Mono-Transformer-accessories-127.asp

This will work with high current high voltage signals and maintain a decent output level to drive a speaker.

You might also want to have a look at single point stereo speakers. This looks like one speaker, but it has two speaker inputs. It has a mono woofer and stereo tweeters. No need for any conversion. Just hook up the amp.in stereo and the speaker does the rest.

 

[roganty]

The thing you're looking at won't work for speaker level. There's too much power in the signal (current and voltage too high). It'll blow it to bits.

Even if you reduce the input signal down to a safe level then it still won't work because the output won't be strong enough to drive a speaker.

It's. .. the ...wrong... thing.

No amount of tinkering is going to change the Laws of Physics.

Thanks for shattering my world!

I had hopped something like this might have been man enough for the job

What you need is a summing transformer. KEF makes one for £39. You might be able to find something similar and a shade cheaper from less well know brands. The KEF one is here: https://www.ceiling-speakers.co.uk/KEF-Audio-Stereo-to-Mono-Transformer-accessories-127.asp

This will work with high current high voltage signals and maintain a decent output level to drive a speaker.

You might also want to have a look at single point stereo speakers. This looks like one speaker, but it has two speaker inputs. It has a mono woofer and stereo tweeters. No need for any conversion. Just hook up the amp.in stereo and the speaker does the rest.

I had hoped not to spend too much on this, so I might just end up hooking a single speaker up to one channel and make do.

 

[Lucid]

Thanks for shattering my world!

That pesky thing "the truth" eh. It's a bitch, ain't it?

Of course, I could have lied and said "sure, go for it", but that wouldn't have ended well.... or not for you, at least.

There would have been a fraction of a second when you'd have reached the dizzy heights of elation thinking you'd cracked it. But before you could have even uttered the starting sound of yes you'd have witnessed the flash and heard a pop that is the precursor to the little puff of magic smoke escaping. Then silence, followed by that falling feeling in the pit of your stomach as you struggled to come to terms with the fact you killed the little box you were never supposed to use in the first place, and in the process you killed the amp too.

I had hopped something like this might have been man enough for the job

Yes? And I'd hoped to be a millionaire by now, but that hasn't happened either.

Anyway, let's continue to play. How exactly do you propose to use that resistor, or those resistors?

I had hoped not to spend too much on this, so I might just end up hooking a single speaker up to one channel and make do.

No, I get it. You're trying to do this on the cheap and you've jumped in with the amp purchase before fully researching the ins and outs of this. Now you're trying to rescue the situation and hoping to make a silk purse from a sows ear.

You can of course run one speaker from a single channel. The issue you'll come across is that you'll have less (or none) of the other channel instruments and vocals in a stereo mix.

 

[winston1]

[QUOTE="Lucid, post: 4206936, member: 208119"

There would have been a fraction of a second when you'd have reached the dizzy heights of elation thinking you'd cracked it. But before you could have even uttered the starting sound of yes you'd have witnessed the flash and heard a pop that is the precursor to the little puff of magic smoke escaping. Then silence, followed by that falling feeling in the pit of your stomach as you struggled to come to terms with the fact you killed the little box you were never supposed to use in the first place, and in the process you killed the amp too.
[/QUOTE]

None of that would of happened. It just would not have worked that's all. 1K resistors are far too high for any destructive current to flow from speaker circuits.

 

[kentishman]

Depending upon what device you are using to send to the bluetooth amp, you may be able to set the device to Mono. For example, on an iPhone, go to
Settings;
General;
Accessibilty;
Hearing;
Then turn on Mono Audio.

You can then connect a single speaker to either output of the bluetooth amp.

 

[roganty]

None of that would of happened. It just would not have worked that's all. 1K resistors are far too high for any destructive current to flow from speaker circuits.

Thanks for that little bit of hope winston1, I'm now sat amongst my shattered world with a tube of super glue!
It's like a trillion piece double sided puzzle

Depending upon what device you are using to send to the bluetooth amp, you may be able to set the device to Mono. For example, on an iPhone, go to
Settings;
General;
Accessibilty;
Hearing;
Then turn on Mono Audio.

You can then connect a single speaker to either output of the bluetooth amp.

Yeah, not quite so simple on Android. Even the first search result didn't match up with whats on my phone.

 

[roganty]

Yes? And I'd hoped to be a millionaire by now, but that hasn't happened either.

Yes, and I'm still waiting for my numbers to come up on the lottery.

No, I get it. You're trying to do this on the cheap and you've jumped in with the amp purchase before fully researching the ins and outs of this. Now you're trying to rescue the situation and hoping to make a silk purse from a sows ear.

You can of course run one speaker from a single channel. The issue you'll come across is that you'll have less (or none) of the other channel instruments and vocals in a stereo mix.

Not quite, I was only researching cheap amps
My only rash decision was the speakers.

Not wanting to spend too much, and not needing the best audio quality or volume, I was just going to use the one channel anyway.

But some interesting searches brought some hope.
Connecting single speaker to stereo amp.. (avforums.com)
And this one was always mentioned Why Not Wye?


Obviously I should of asked in a more audio/electrical oriented forum than a diy forum...

 

[kentishman]

But some interesting searches brought some hope.
Connecting single speaker to stereo amp.. (avforums.com)
And this one was always mentioned Why Not Wye?


Obviously I should of asked in a more audio/electrical oriented forum than a diy forum...

Those search results still refer to summing the physical analogue inputs of an amplifier. On a bluetooth-linked amp, that summing needs to be done before the bluetooth link, and if the bluetooth transmitter is inbuilt to whichever device is being used to play from, then it has to be done in software (like using the accessibility option). Using an external bluetooth transmitter device, then a couple of resistors could be used to sum to Mono, again on the inputs.

The laws of physics will be the same no matter which forum you, or any of us, post in.

 

[roganty]

Those search results still refer to summing the physical analogue inputs of an amplifier. On a bluetooth-linked amp, that summing needs to be done before the bluetooth link, and if the bluetooth transmitter is inbuilt to whichever device is being used to play from, then it has to be done in software (like using the accessibility option). Using an external bluetooth transmitter device, then a couple of resistors could be used to sum to Mono, again on the inputs.

Thanks, it seams like I'm searching to one thing and I'm getting results for something else.

A bit more searching, and I'll just carry on with my original plan and hook the speaker to one output and mono the source in software.


Edit: It seams this would be the circuit to convert stereo output to mono.

 

[Lucid]

Thanks, it seams like I'm searching to one thing and I'm getting results for something else.

A bit more searching, and I'll just carry on with my original plan and hook the speaker to one output and mono the source in software.


Edit: It seams this would be the circuit to convert stereo output to mono.

No.

Once again, as I think we've all tried to tell you, all the circuits you've found refer to converting say the stereo output from a CD player to mono BEFORE it gets to the amp. These are low voltage and almost-zero-current signals.

NONE of what you've found deals with converting the higher-voltage higher-current signals that come from the speaker outputs.

Therefore, nothing you have found using a simple resistor network is going to solve your problem. It really is that simple. Either get the transformer (£40) or buy a cheap single point stereo speaker (again, about £40) and stop wasting your time and everyone else's in a fruitless search for hen's teeth.

@kentishman is correct. It doesn't matter where you ask the question, the answer for someone on a shoestring budget will always be the same.

 

[kentishman]

It seams this would be the circuit to convert stereo output to mono.

Indeed it does... but it does it at LINE levels, not SPEAKER levels; i.e. on the INPUT to an amplifier not on the OUTPUTS. There would be no (or very little) audio from a speaker if that circuit was inserted between the speaker outputs of an amplifier and a speaker.

 

[roganty]

No.

Once again, as I think we've all tried to tell you, all the circuits you've found refer to converting say the stereo output from a CD player to mono BEFORE it gets to the amp. These are low voltage and almost-zero-current signals.

Indeed it does... but it does it at LINE levels, not SPEAKER levels; i.e. on the INPUT to an amplifier not on the OUTPUTS. There would be no (or very little) audio from a speaker if that circuit was inserted between the speaker outputs of an amplifier and a speaker.

Edit: It seams this would be the circuit to convert stereo output to mono.

Maybe I should have said might instead of would.

Therefore, nothing you have found using a simple resistor network is going to solve your problem. It really is that simple. Either get the transformer (£40) or buy a cheap single point stereo speaker (again, about £40) and stop wasting your time and everyone else's in a fruitless search for hen's teeth.

I'd already said I wouldn't bother.

Also, the item that you linked to was basically a transformer (with other bits)
If you check the latest musing I believe that is two transformers, one for left and one for right.



It's all academic now

I'll just carry on with my original plan and hook the speaker to one output and mono the source in software.

 

[Lucid]

Maybe I should have said might instead of would.

You can say whatever you wish; it still won't make a line level summing box work for speaker level signals.

I'd already said I wouldn't bother.

Yes. You do seem extraordinarily determined to cut your nose off to spite your face.

Also, the item that you linked to was basically a transformer (with other bits)

If you check the latest musing I believe that is two transformers, one for left and one for right.

It's one transformer with three windings. The Web page describes the wiring. There are inputs for the left and right speaker wires from the amp, and a single output to connect to the mono speaker.

 

[SFK]

Apologies if I am missing an obvious reason why you can not do this.

But why not buy a single ceiling speaker that contains two speakers so you can use both channels?
https://www.amazon.co.uk/Audio-Sinl..._rd_t=40701&psc=1&refRID=DDE9HKERW7MQ5KEVKRJY
Sfk