Ceiling speaker amplifier to mono circuit.

[roganty]

No.

Thank you, and good day to you sir.

 

[Lucid]

Hello @Lucid

This little 'idea' is still playing through my head [don't ask, it'll be replaced soon!]


I understand that this will not work with speaker level signals.

But what if the resistors were replaced with appropriately sized resistors? (like these wirewound resistors*)

Or is it still a defiantly not?


*These resistors match the output of the amp I have (15w @ 4ohms)

The problem isn't so much in making the amp signal compatible with the summing circuit. It's what it does to the power of the signal after it has been summed.

Putting really big resistors in front of a line level summing circuit as a way to bring speaker level down to line level does work. It's used on some subs so that they can be connected in parallel to the main speakers, but safely so that say 30V and 4 amps of speaker level signal can be converted down to drive a subwoofer line input that expects maybe 1-2 Volts and virtually no current. But here's the big difference: The sub has its own internal amplifier. The signal that results from the reduction and summing to mono doesn't have anywhere near the power to drive a speaker properly.

In making the signal safe to pass through the summing circuit, it's no longer suitable to drive a speaker. It needs to be amplified again.

It's not possible to keep the power and make the signal safe to pass through line level gear with a modified version of the circuit you've shown. The two objectives are incompatible with each other. If you retain the power level - even in a slightly reduced form - you'll still wreck the circuit. But if you protect the circuit by reducing the signal power, you haven't enough oomph left to drive a speaker directly. Do you see?

 

[roganty]

The problem isn't so much in making the amp signal compatible with the summing circuit. It's what it does to the power of the signal after it has been summed.

[...really interesting explanation cut to make quote shorter...]

It's not possible to keep the power and make the signal safe to pass through line level gear with a modified version of the circuit you've shown. The two objectives are incompatible with each other. If you retain the power level - even in a slightly reduced form - you'll still wreck the circuit. But if you protect the circuit by reducing the signal power, you haven't enough oomph left to drive a speaker directly. Do you see?

@Lucid, Thank you for taking the time (again) for explaining everything.

In making the signal safe to pass through the summing circuit, it's no longer suitable to drive a speaker. It needs to be amplified again.

Which is why the product you recommended in post #2 was transformer based.
So the only DIY option is a 1:1 transformer with 2 winding's on the primary coil.

That is something I am not looking at getting into. So, case closed.


I can now hopefully push this idea out of my head and move on.

Thank you
Anthony

 

[Lucid]

@Lucid, Thank you for taking the time (again) for explaining everything.

You're very welcome

Which is why the product you recommended in post #2 was transformer based.

There is the other solution, which is a different speaker to the one you're currently using. I also referred to this in post #2.

The single point stereo speaker has a summing circuit of sorts built into it. It takes the left and right speaker cables, sums the signal for the bass frequencies, but keeps them apart for the upper-end frequencies where they feed two tweeters.

I use these speakers regularly for bathroom and en suite installs. Despite having a 6-6.5" mid-bass driver, I've yet to find a place where one wouldn't fit. My single point stereo speakers start from around £150, but I have seen unbranded versions selling on Ebay for as little as £40. I think this is a far more sensible solution than a £40 transformer coupled to a £10-£20 4" speaker.

 

[roganty]

There is the other solution, which is a different speaker to the one you're currently using. I also referred to this in post #2.
[...]
I use these speakers regularly for bathroom and en suite installs. Despite having a 6-6.5" mid-bass driver, I've yet to find a place where one wouldn't fit. My single point stereo speakers start from around £150, but I have seen unbranded versions selling on Ebay for as little as £40. I think this is a far more sensible solution than a £40 transformer coupled to a £10-£20 4" speaker.

^ Ok, lets not get into this again.

So I'll just leave it there and say thank you again.

Thank you for your help
Anthony