Running 2 radios into 1 external speaker - will it cause problems?

[Turbo T]

I'm wondering if this is ok to do...? Or will there be back feed problems from one radio into the other? Would it damage the speaker output of the other radio? Could I perhaps put diodes inline on the + side?

BTW this is going into a small vehicle that doesn't have any extra room but for one external speaker.

 

[Shockwave]

This will depend on the radios in use. Some radios use a floating speaker output that is not common to chassis ground. Motorola does this on some radios. If you tie this speaker in parallel with a rig that has a common ground speaker, the audio chip may pop. Diodes are not useful to isolate AF like they can with DC but an isolation transformer may help.

 

[bcrewcaptain]

easiest solution, put a switch on the speaker leads. I did the same thing years back in a mobile setup.
3 position switch on one of the speaker leads, you're done.

 

[KD4UPL]

External speakers can be very small. I can't imagine you can't find an extra 4 square inches in a vehicle somewhere. Connecting two radio's outputs to one speaker is asking for trouble. A diode won't work for isolation, this isn't DC.
A DPDT switch is your best bet. If you could possibly find a dual voicecoil speaker that would work too. I don't know of any smaller than about 8" however.

 

[Captain Kilowatt]

You can do it using three 70 volt line transformers meant for PA distribution systems.Each radio gets connected to the 8 ohm tap on a transformer and a speaker gets connected to a third transformer at the 8 ohm tap as well. All three transformer's 70 volt taps get connected together, It works and provides some isolation however it is a bit clunky with the transformers having to be put somewhere.

 

[W5LZ]

There are also various audio chips that can combine two or more audio inputs and output that combination into a standard speaker. It's been a long time since I knew anything about it so can't say what those chips are. It isn't an uncommon thingy so should be a fairly 'standard' type circuit.
- 'Doc

 

[Lil'Yeshua]

I'm not sure if they make one small enough but If you can find a speaker small enough,a dual voice coil speaker would solve that problem. I drove a Suzuki Sprint(3 cyl) for a while. I made speaker enclosures for the doors and a custom rear shelf with custom tuned speaker enclosures fastened to it. A good midrange tweeter might fill the bill.
Here's a pic of my custom(I installed)A-pillar tweeters. I also have a center channel speaker but that's driven by a mono stereo output.


Note:You could replace the stock speaker with a coaxial speaker and separate the tweeter(midrange if traixial) from the woofer and use that. The world's full of possibilities.

 

[Turbo T]

External speakers can be very small. I can't imagine you can't find an extra 4 square inches in a vehicle somewhere.

Have you ever tried putting extra external speakers in a small vehicle? I am not working with a 1970 Cadillac now. The dual voice coils sounds good though. I think I'll look into that. Thanks.

BTW I did find some tiny Diesel brand speakers at a truck stop but wasn't thinking they'd be worth it.

 

[Lil'Yeshua]

Shop around. You will find better deals. car speakers at Crutchfield.com
dual voice coil speakers at Crutchfield.com

 

[Captain Kilowatt]

Have you ever tried putting extra external speakers in a small vehicle? I am not working with a 1970 Cadillac now. The dual voice coils sounds good though. I think I'll look into that. Thanks.

BTW I did find some tiny Diesel brand speakers at a truck stop but wasn't thinking they'd be worth it.

I went with an external speaker under the seat and it worked fairly well. Lots of room under the seat and out of the way too.

 

[Lil'Yeshua]

I run a little Uniden external speaker stuffed in an unused headrest. Mine aren't solid.

 

[Moleculo]

easiest solution, put a switch on the speaker leads. I did the same thing years back in a mobile setup.
3 position switch on one of the speaker leads, you're done.

Welcome back Bcrew...haven't heard from you in a while

 

[Lil'Yeshua]

With speaker switching,you may need a L-pad so you won't damage your radios output amplifiers.
L-PADS