how to install 2 car stereos?

Question

I want to install 2 car stereos in my car for lots of reasons so i can run my 8 track and my cd/mp3 player and not have to unplug and swap them around because it gets anoying after a while 8 track has got some good music nd i also like my rap

and because if i can be able to swap the 8 track with a cassete player some times lol i have alot of music and no i cant put them on the computer to burn on cd and i dnt want to pay 300 bucks for it to be done by a pro i just want it a diy job

Answer 1

I have actually done this before.

You will need 1 relay to switch power sources.
Connect the power and ground to both sources. Take the remote wire from the CD player (blue or blue/white) and connect it to pin 85 of the relay. Connect pin 86 of the relay to ground. Cut the switched power wire on the 8 track and connect the wire from the 8 track to pin 87A, connect the power side of the wire you just cut to pin 87.
What this will do is simply turn the power to the 8 track off when the CD player is turned on. When the CD player is turned off, power will return to the 8 track. No switches-no buttons, the relay does the work.

Now for the speaker wires..
First of all.. most 8 track players have a common ground speaker output, If this is the case, you will need this converter:
http://peripheralelectronics.com/prodDetail.asp?strProductID=588&strSearch=floating%20ground

Now both radios will have a floating ground output (each speaker has its own pos and neg, and do not use common ground or chassis ground)

To switch the outputs between sources, you will need this switcher.
http://peripheralelectronics.com/prodDetail.asp?strProductID=677&strSearch=speaker%20switcher
This is a 2 channel switcher, you will need 2 of these if you want to switch all 4 speaker wires.

It is alot of wiring, but this is the proper way to do it. Once installed, to listen to the cd player, turn it on. To listed to the 8 track, turn the CD player off. It's that simple.

Answer 2

Yes, you can do it, but the output to the speakers (as mentioned above) are the "tricky" part.

For the power, it is pretty straight-forward. I would run two sets of power to the fuse box, using different circuits and I would use different ground points.

For the output to the speakers, you really need to find and install a switch box that will allow you to choose which stereo is feeding the amplifier or speakers. If you have four speakers, then you will have 8 wires. You will need a switch box that has two inputs (A & B) each with 8 wires in and an output that has 8 outputs. I don't know of a radio switch that has 24 connections. You could try using an older printer switch that supports "Centronics" connectors. Those printers used that many inputs. It would also be possible to make a box with four switches and toggle each one individually. That would be more work, but the parts are more readily available and the net result would be smaller and easier to install in a car.
Be sure to use high-quality audio switches than can handle the wattages of your stereos. A cheap-o Radio Shack toggle probably won't work. You'll probably lose quite a bit of frequency response and wonder why your audio sounds "flat" if you use cheap switches.

(side note: given that it is an 8-track player, it probably has an internal amplifier and does not have "line out". That means you cannot use an external amp that needs "line in" levels of sound. Don't share an external amp and an internal amp. If one radio has an internal amp, then you need to hook up it's wires to the switch box directly. If the other has an external amp, then you need to route the wires after the external amp to the switch box.)

When you use this switch box, I recommend you shut off both stereos before switching. If you don't a momentary short could occur and that would ruin the radio's amp (possibly both of them).

When you are done, post pictures. :)

Answer 3

Car Stereos

Answer 4

Stereos

Answer 5

well, back in my days when I used to work at radioshack, they used to sell a speaker selector switch that you could run the outputs from a stereo to 2 sets of speakers & then you could choose to listen to either set or both sets.

We also used this in the same type of installation you are talking about where you had 2 sources, but one set of speakers. Naturally, you could run your each side in series, that way you wouldn't overheat either unit. Granted, it may not sound as loud due to the impedeance difference.

I looked on radioshack.com but didn't see the switch listed - maybe they don't sell it anymore. I did find it on eBay though - it's in the lower right hand corner of the pic in the auction:
http://cgi.ebay.com/2-Speaker-Selectors-Switches-Plus-Mystery-Box_W0QQitemZ320118650695QQihZ011QQcategoryZ64596QQrdZ1QQcmdZViewItem


If you decide to use this switch, to be on the safe side make sure both source units are off.

Answer 6

You can install 2 stereos buy you'll need a switch to select the unit want to use. This is very important to avoid short circuits and connections problem. You can use the same power wires to connect both stereos but for the speakers you'll need a switch and/or some diodes.

Answer 7

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Answer 8

You need to isolate the speakers so that they're only connected to one radio at a time. Don't bother trying diodes; audio signals are AC. The easiest way to isolate the speakers is to use relays; ideally, 4PDT relays. Connect the speakers to the common terminals; wire the NC terminals to the original deck, and wire the after-market deck's outputs to the NO terminals. If you use the after-market deck's remote output to activate the relay(s), then when you switch the deck on the speakers will automatically connect to the new deck. Turn it off and they'll switch back to the old deck.

You'll need a 4PDT relay for each pair of speakers (or four SPDT relays for each speaker pair).

Here's a diagram (scroll to the bottom of the page): http://www.underthedash.com/relayindex.html

Answer 9

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Answer 10

It will take more than a switch....and don't use diodes, you'll only have half a wave-form using them.

See KaeZoo's answer.

To Dammm,

What happens when you rectify AC with a diode?

Answer: You get a half wave pulsed DC signal. Do you know what that sounds like?