2 Radios plugged into 1 Speaker?

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lee01

lee01

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So I will install a new radio in my glove box, but I would like to hook up my original solid state AM radio on dash speaker in my 71 Duster.
So hooking up two radio to one speaker is it doable?

Wanted to know if I can do this or not....the stock radio look cool...would be sweet to still have it hooked....but don't want to fry anything.
 
I read a few place that if i put a toogle switch between the two it would work...any one can chime in?
 
yes, it will work. get a single pole double throw (spdt) type switch. that way you can turn both off or power one or the other.
 
So far every answer is right. Yes you can, No, with switches and relays. The technicial answer would be no, not without knowing a lot of other things about the electronic circuits in both radios. If it just something you have to do then the simplest way is to use a double pole double throw toggle switch or relay. Things to consider are, Neither unit should be powered on without the speaker attached, depending on the device it could damage it, so care should be exercised when powering up either radio to make sure the switch is in the correct position. To those that say just hook them both up to the speaker at the same time, I say don't. It might work and it might not depending on the output power configuration of each radio. Even if it does work it will not work at the optimum performance, there will be a impedance mismatch that could result in reduced audio and or distortion. The best way to hook it up would be through a triple pole double throw relay where the two speaker leads go through two of the poles and power to the two radios is routed through the third pole. This would insure that only the radio with the speaker hooked up to it could be turned on. Just my 2 cents.
 
BobbyY said:
So far every answer is right. Yes you can, No, with switches and relays. The technicial answer would be no, not without knowing a lot of other things about the electronic circuits in both radios. If it just something you have to do then the simplest way is to use a double pole double throw toggle switch or relay. Things to consider are, Neither unit should be powered on without the speaker attached, depending on the device it could damage it, so care should be exercised when powering up either radio to make sure the switch is in the correct position. To those that say just hook them both up to the speaker at the same time, I say don't. It might work and it might not depending on the output power configuration of each radio. Even if it does work it will not work at the optimum performance, there will be a impedance mismatch that could result in reduced audio and or distortion. The best way to hook it up would be through a triple pole double throw relay where the two speaker leads go through two of the poles and power to the two radios is routed through the third pole. This would insure that only the radio with the speaker hooked up to it could be turned on. Just my 2 cents.
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BobbyY has it right here. If you hook up both radio's to the same speaker, only one radio can be on at the same time - otherwise you risk the possibility of burning out one of the outputs on either radio - whichever radio has the strongest components. Could be the one with the oldest parts or the cheapest parts, you will never really know until you wire it up. Basically you don't want to do it. Most modern amplifiers will have resistance built into them so that they can be turned on without a load (ie speaker) but it's not recommended with the volume turned up - even just a little. Relays would be the best bet that way it's automatic rather than a switch. A switch would be simple to do, but if you switch from one radio to the other leaving one on without a load, you could fry the output amps. Just my 2 cents worth.
 
Why not just wire two diodes into the speaker wires coming off both radios so that the power from the amplifier on one radio doesnt backfeed into the amp on the other and fry it?
 
Diodes won't work here. In fact they may make a "fuzzbox" out of your radio(s). An audio amp in the classical sense is a linear device. A diode is not. It is the furthest thing FROM a linear device, and is in fact the very definition of distortion.
 
I seem to remember speakers with dual voice coils. Not sure if they are available anymore, I will check and post back if I find some.
 
I googled "dual voice coil speakers", there are many available. One application is to use one speaker, for stereo radio. When choosing one, pay attention to speaker impedance, for your application.
 
Well I used to repair OEM radios for Ford GM & Chrysler as well as for Audiovox. The answer is yes it will work but it may through the impedance of the speaker off. Typically you want an impedance of 8 or 4 ohms.When you connect anything in parallel be it another speaker or the second leads from another radio your are going to lower the impedance. For example if you have two 8 ohm speakers in parallel you will have 4 ohms of impedance. So the answer is it will probably work but the impedance will be off and your radios won't perform as well. Try putting a single pull double throw switch on one of the speaker leads going to the speaker with each radio connected to one of the other two terminals.

Good Luck
 
superchargeddrt said:
. The answer is yes it will work but
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In my opinion you are on very dangerous ground here. Depending on "what radios" he has, the audio output may be "single ended" or required to be above ground "balanced." Additionally, any failure in either output stage could take out components in the other radio
 
I agree with 67Dart. Just because you can or because it might work why not just do it right. Also absolutely no to the diode thing. In it's simplest form the diode rectifies AC to DC, every look at a power suply, AC out of the transformer through the diode and you end up with DC. Audio is AC so no go there. As to the AB switch, ther are a number of different types out there and you would have to try and pin out what wires went where even then I'm unsure how many of them switch. Keep it simple and clean with either the switch or relay.

Bobby Y
 
You CAN buy 3 pole relays and switches. This may be the easiest solution. (A 3PDT switch has 9 terminals and is essentially 3 x "two way" switches in one housing)

One pole to switch power between the two

The two other poles to switch both speaker terminals.

3PDTToggle.jpg


3PDT relay would have 11 terminals -- 9 for the contacts and 2 more for the coil.

5X840_AS01
 
67Dart273 said:
In my opinion you are on very dangerous ground here. Depending on "what radios" he has, the audio output may be "single ended" or required to be above ground "balanced." Additionally, any failure in either output stage could take out components in the other radio
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I see where you're going here and you're right but if he went with a double pull double throw he could switch both positive and negative between each radio. The only other danger he could run into is if the dash speaker had a permanently grounded negative lead.
 
Many years ago, I added a cassette deck to my 67 Dart. I used two 6x9s in the package tray. If I wanted to listen to crappy am radio, I turned the stock radio on, still hooked up to the front speaker. If I wanted to rock, I turned on the cassette deck. Much easier, and much better sound quality!
 
BobbyY said:
Even if it does work it will not work at the optimum performance, there will be a impedance mismatch that could result in reduced audio and or distortion.
Click to expand...

.....reduced audio.........distortion......single dash speaker.....all go hand in hand don't they?
 
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