connecting 2 radios to one set of speakers

ytd

ytd

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Inspired by the recent thread on updating boat radios to include bluetooth capability, I purchased a replacement radio which has bluetooth and nice big buttons but doesn't have a CD player. I never liked the location of the exiting radio so I was thinking of putting the new one in a better spot. That would leave the task of making a plug to fit the hole where the old radio was. If I leave the old one there can I just connect the new radio's speaker wires to the speakers without disconnecting the old radio or will it effectively short circuit the new radio's output. Only one would be turned on at any time but leaving the old one there would give me the option of playing CDs.
 
if only one is on at a time i can't see why not, four speakers can be connected in series or parallel to one head set and the ohms is what is important, what you are are doing is in quite the opposite, I look forward to the discussion :) I must admit I've never thought of that before.
 
Bad Idea.
You could of course put a changeover switch to select which radio connects to the speakers.
But you'd need to switch both sides of both channels so a 4 pole 2way switch.
 
I think it would knacker the output transistors. The speakers of any one radio are powered by transistors which are designed to deliver power to speakers. If power from another radio was fed IN to the output, I would expect it to burn out the transistors which are not meant to have electricity coming in, where it would normally just be going out. Sorry if that sounds like someone explaining the rules of cricket to a foreigner!
Personally I wouldn't consider it, find another solution, cheers Jerry
 
lw395 said:
Bad Idea.
You could of course put a changeover switch to select which radio connects to the speakers.
But you'd need to switch both sides of both channels so a 4 pole 2way switch.
Click to expand...

This would mean that it would be possible to switch on a radio without it being connected to a set of speakers. It may damage the radio.
 
If you're not thinking of a changeover switch ( or, better still a relay that picks automatically to "capture" the speakers when one radio is powered on, and allows the normally closed contacts to route to the other radio when not picked), then you should have a look at the output circuits of the radios in question. Lots nowadays have big coupling capacitors in line with the speakers, so no DC can pass through, and should not suffer damage by connecting directly. However, you may find that some distortion or power loss is introduced.
Go for the relay, simple, foolproof.
 
Don't do it. If you accidentally turn on both sets then one will effectively short the other to ground if a positive peak on one signal happens to coincide with a negative peak on the other. This won't do either set any good! You could maybe use a two way switch in +12V supply line so that it isn't possible to power both at once.
 
Billjratt has got it.
A SPDT switch and a relay. Switch the power to the radios through the SPDT switch and use the power to one of the radios to energise the relay. When the switch is in one position the relay is not energised and the "off" contacts connect the speakers to that radio. When the switch is in the other position the relay is energised and the "on" contacts switch the speakers to the other radio.

One switch and the radios can only be turned on when they are connected to the speakers.
 
It can only happen on a forum....... the over complication is amazing......

There is a cheaper, simpler and far more suitable solution..........




Another set of speakers!!!!!
 
I resisted putting a radio/cd player in the boat as I did not want to cut holes in the wood. She's a classic and has been restored to original condition.

A simple solution was found in the form of the Creative D100 bluetooth speaker. The sound is excellent, the speaker totally portable so you have sound where you want it and you can stream music, radio etc from any bluetooth device. Set-up was very easy.

Available from Amazon with plenty of user reviews to read before. BTW, I have no connection with either Amazon or Creative.

Edit: This may not help the o.p having re-read the post but it might make life easier for other :-)
 
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Alpha22 said:
It can only happen on a forum....... the over complication is amazing......

There is a cheaper, simpler and far more suitable solution..........




Another set of speakers!!!!!
Click to expand...

A couple of speakers is going to cost more than any of the switch/relays suggestions which have been made. If those speakers then need cutouts so that they can be mounted properly then it won't be simpler either.
 
Hello again. My relay is picked by the fact that one of the radios is switched on.(If you don't want to go inside, choose the wire that sends up the electric aerial) it doesn't need any manual switch and will cater for the speakers automatically - the speakers can only connect to one radio so no damage is possible.
Normally Closed ------------\*
spacespacespacespacespacespace \---------------Common________________ This is my attempt to depict a set of changeover contacts
Normally Open --------------*

(Because this effin 'puter doesn't do spaces or left zero inserts)
The speaker wires are connected to the COM terminals (4 of them, or, if it's common ground, 2 of them) The NC terminals go to the radio that DOESN'T pick the relay and the NO terms go to the radio which you have wired the relay coil to. Simples
 
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A relay is a sound idea.
If you are concerned that no load may damage the radio, a resistor of say 27ohms across each radio output will probably be plenty of load. It would need to be fairly watty though, so not cheap.

Note that most car audio has 'bridge' outputs, so spkr- is not ground, it is the mirror of spkr+, so you really do need to switch all 4 wires.

Driving audio power up the output of an amplifier while it is not powered might do all sorts of things, depending on what protection circuitry is present.
Ranging from no effect, through turning on the other unit, to damage.
 
Billjratt said:
Hello again. My relay is picked by the fact that one of the radios is switched on.(If you don't want to go inside, choose the wire that sends up the electric aerial) it doesn't need any manual switch and will cater for the speakers automatically - the speakers can only connect to one radio so no damage is possible.
Normally Closed ------------\*
spacespacespacespacespacespace \---------------Common________________ This is my attempt to depict a set of changeover contacts
Normally Open --------------*

(Because this effin 'puter doesn't do spaces or left zero inserts)
The speaker wires are connected to the COM terminals (4 of them, or, if it's common ground, 2 of them) The NC terminals go to the radio that DOESN'T pick the relay and the NO terms go to the radio which you have wired the relay coil to. Simples
Click to expand...

That could work but it would need another set of contacts to switch the power to the other radio.

Unless that is done the "picking" radio could be working but if the other radio were mistakenly switched on then it would be outputting to fresh air.
 
But that wouldn't damage anything,(original post) and if it gets to the stage where an operator cannot figure out which box the noise is attached to, perhaps other interlocks may be required?
Like, don't leave the harbour 'til you're sober...
 
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