120 Ohm Speaker

[Manu]

Anyone know how much a 120 Ohm Speaker costs?

 

[Sebi]

I've never seen a loudspeaker with higher impedance as 50ohm.
The 100V line amplifier output impedance is 120ohm, but need a matching transformer for each loudspeaker.

 

[Manu]

Do you think adding audio transformers with 8 ohm speakers is a good solution?

The following circuit: **broken link removed**

I only have 16 ohm speakers.

 

[Sebi]

In this case no need transformer. Try out with 16ohm speakers. The cause of hi-ohms speaker requirement: in microphone mode produced more signal.

 

[Gene]

The problem with a 2-way, hands free intercom is that the speaker also must act as a microphone without feeding back on itself. Normally the best is between 8 ohms and 120 ohms. Commercial intercoms operate in the 45 ohm range. This seems to allow the speaker to act (somewhat) as a microphone and speaker without too much distortion. If you did a search for "speakers 45 ohm" you will find some suppliers like:

https://www.surplussales.com/Microphones-Audio/MicroAudio-7.html

This is one possibility.

 

[Manu]

In this case no need transformer. Try out with 16ohm speakers. The cause of hi-ohms speaker requirement: in microphone mode produced more signal.

I tried it with 16ohm, wasn't that bad. Well, I am just gonna look around. and stick with 16ohm for the moment.

Thanks for replying guys. It helped alot.

 

[Madmartin]

Maybe you give a try to two telephones speakers.
(the old-style type with a mechanical dial)
I think I remember them to have resistances as high as 500 ohms

 

[Sebi]

The phone is good idea, but as i remember the old telephone with dial contain 75ohm speaker with steel-membrane. The Taiwan-junk wall phone contain often 50ohm speaker, and (here in Europe) the door-phone systems working with 50ohm (plastic-membrane) speakers.