Two way speaker

[BuffaloEngineer]

Has anyone used a 2 way speaker before (one that can be used as a speaker and a microphone)? Like those used in an intercom?

I'm looking for one, but I was also wondering - can a regular speaker be used this way? I looked briefly for intercom circuits online, but it looked like they all had separate mics and speakers.

Thanks!

 

[Nigel Goodwin]

Yes, a regular speaker is all you need - even horn PA speakers can be used, and often are in factories and warehouses.

 

[hotwaterwizard]

Yes here is one such circuit. The second one I just couldn't resist putting there. LOL

 

[BuffaloEngineer]

That will never work. Coke and Pepsi? I can't even get regular Coke to work with Diet Coke.

 

[hotwaterwizard]

I have more

 

[hotwaterwizard]

You can find many more on google picture search Intercom Schematic

 

[audioguru]

An intercom or walkie-talkie that uses the speaker as a microphone sounds horrible due to the resonance of the speaker.

 

[BuffaloEngineer]

It doesn't need to sound great, just so the guy on the other end can understand what's being said. Any suggestions on how to get the most quality out of it? I'm thinking of using an op amp specifically for microphone inputs to help keep the input clean.

Also, in the app circuits, what makes the most sense to me is the DPDT switch used as a push to talk, changing it from a mic to a speaker.

 

[audioguru]

Why not use a high quality electret microphone? It costs less than $1.00.

Here is a full duplex intercom circuit that does not need a push-to-talk switch. It electronically cancels your mic's signal from coming out of your speaker which would cause acoustical feedback howling. The switch is for muting your mic.
Full-duplex Intercom - RED - Page78

 

[Hero999]

It's even possible to use a speaker as both a microphone and speaker at the same time.

If the current into the speaker is measured and the audio signal driving audio signal is subtracted from it you'll have the small current generated by it acting as a microphone. I don't know how this will work (probably not well) but it's theoretically possible.

 

[BuffaloEngineer]

I'll buy parts to do it both ways - is there anything I should look for in a speaker if I plan to use it as a microphone also? Like the cone material, or the impedance?

 

[audioguru]

I'll buy parts to do it both ways - is there anything I should look for in a speaker if I plan to use it as a microphone also? Like the cone material, or the impedance?

A speaker resonates. The extremely low output impedance of an amplifier (0.04 ohms and less) damps the resonance.

But the input impedance of a mic preamp must be high enough that it does not short the speaker when it is a microphone so its resonance makes it sound very boomy.

If the microphone preamp cuts the low frequencies then it will sound less boomy and more tinny.

 

[hotwaterwizard]

You could just use a couple of old Telephones

 

[hotwaterwizard]

Intercommunication

here is a project with the circuit board Intercommunication