As the question states, I’m looking into upgrading an old AM only radio to output to more than the original configuration it was designed for (I believe two small door speakers and one in-dash speaker).
If I wanted to add some rear deck speakers, could I do it by splicing into the wires currently present, or would I have to do something else? There seems to be a finite number of wires coming out of the unit, and I really don’t want to try to open up an old car radio if I don’t have to.
You can do it, but the audio quality will suffer. Most importantly, however many watts you’re currently putting out will have to be split by two elements. Also, you may want to experiment with hooking them up in series, instead of in parallel. I forget the specifics, but I think you retain more power, but make the signal muddier. It’s been awhile, and I’ve only experimented with this on subwoofers. Another thing to consider is that the ohms are going to change. That’s pretty important when you’re dealing with an amp, I’m not sure of the significance when you’re only using the power from the receiver.
Also, if you’re upgrading to speakers, you might want to consider adding a modern receiver. They’re quite inexpensive for a basic model, and will have at least four outputs for you. If you’re handy enough to run wires to the rear deck and install speakers back there, you should have no problem installing a new receiver (especially considering that you’ve already gotten access to it).
I gotta ask, for what reason do you need to add more speakers to an AM radio?
I mean even if the speakers were a total free bonus deal its not like youre going to improve anything.
that and with a strictly AM radio I am betting that you have a very very low wattage output. Santo is right about series instead of parallel being something you might need to do.
Parallel is hooking speakers up to the right channel, and 2 to the left by simply connecting the grounds from both speakers to the stereos ground then doing the same with the “hot” wires. this effectively doubles your resistance (iirc)
series is hooking one hot wire to the stereos hot, then taking the ground from that and connecting to the hot of speaker number 2 then from that back to the stereos ground.
(note you can do this without any crazy wire configuration throughout your car, just run the wires like normal but hook them up as above instead…I hope that made sense)
(this halves your resistance again with the iirc)
Well, here’s the story. I am restoring a 1968 Mercury, which came with an aftermarket receiver in it (an 8-track… how cool is that!), but I want to put the car back as close to stock as possible. According to the Marti report, the car originally came with an AM radio only. The speakers are garbage, so after stripping out the interior, I happened to come across an original AM radio (not this car’s original, but from the same year, make and model of my car). I thought that I’d like to put this AM radio back in, and upgrade the speakers. I know I’m not going to be cranking out the traffic report or some talk radio show, but I did want to perhaps get some surround sound, and put speakers in the back. The stock stereo was hooked up to a single in-dash speaker and two small door speakers, all of which are shot.
So Critical1 that’s the why. And you are right, Santo, in that I have access to everything right now, and could easily run wires to a rear set of speakers, so this is the right time to do it.
However, Critical1, you make a good point. Perhaps a better solution would be to hide a new, state of the art receiver and just have the AM radio in there for cosmetic purposes. After all, I can see myself wanting to listen to some music and have it sound good when I drive it. Since AM radio has very few stations that even play music, a work-around may be in order.
SFP
I’d be worried about impedance. A standard radio can usually handle 4 and 8 ohm speakers. If your existing speakers are 4 ohms and you put in another pair of 4 ohms in parallel, that gives you 2 ohms and the output stage is going to be in trouble and might fry at even moderate volume. If you have 8 ohms and put 8 ohms in series, then you’re just going to get really bad sound.
If your old radio can only handle 4 ohms (for example) then you’ve got a real problem. If the radio doesn’t put out many watts, then adding more speakers isn’t going to work no matter what.
I would go so far as to replace the center speaker on the dash and hook the AM up to that alone. with a modern speaker you should be able to get usable sound out of just one and isnt AM mono anyway?
and as pointed out, you may have a 4 ohm system there, I forgot about those in old cars. that would complicate the hell out of a 4 speaker system.
you could get an amp to drive the speakers, and then just hook up an ipod/mp3 player of your choice to a single 1/8" stereo jack that you have some place handy (glove box/center console…whatever) you dont even need an actual receiver unless you want to hear fm. well even then you could just get an mp3 player with a built in receiver. and the advantage of that is the entire system would be buried in the car except for the player that you can take in the house.
I doubt surgery on such a unit will have any effect whatsoever, unless you are qualified willing and able to perform a “historic-radio-resection” in which case your probably making enough money to buy a better radio. Maybe even a satellite radio.
In use you’ll probably find it’s louder if you wire them in parallel (red to red, black to black on all speaker) but such an arrangement allows significant quantities of current through the output transistors and power supply. Especially if you connect more than two speakers per output wire which often causes the output transistor or power supply to overheat and shutdown or just overheat and quit. Sometimes it even causes the ever elusive “motor boating”. A condition characterized by the sound popping in and out like a motor boat engine. At the very least you’ll experience nasty sounding audio clipping at anything above barely usable volume levels.
If you wire them in series (radio + >red>black>red>black>red>black - radio black in a big loop) it will limit current and save the radio at the expense of lower output and increased phase sensitivity (nasal sounding voices, the “wah wah” effect that God intended only for Jimmy Hendrix) when you move your head around in the vehicle. Take your pick.
:0
This is probably your best bet. When it gets warm, I’m going to help my buddy build a center console that will fit above the driveline hump of his '6? Buick to hold a modern receiver. We’re going to gut the speakers, too, but I like the idea given of leaving the center speaker to be powered by the original AM radio.
Keep us updated with what you end up doing, I’ll probably be asking for my own advice in April.
You can safely wire them in series and test how it sounds. If the two speakers are identical it might sound OK, but otherwise it might sound bad. The problem is that a speaker doesn’t have a constant impedance, but rather one that varies with frequency. With two different speakers they may have different variation, interfering with the relative amount of sound that comes from the two speakers as a function of frequency.
If the speaker impedances are high enough, you can wire them in parallel. This is much less sensitive to variation in the impedance of the two speakers versus frequency. If the impedances are too small, you can add a small resistor in series with the two parallel-wired speakers. I have a four speaker selector box with a “protection” button that does this. If the radio expects 4 ohm speakers, and that’s what you have, you’d want a 2 ohm resistor. It would have to be rated for the wattage your radio outputs.
Option 4*: Since it’s an old AM radio, does it maybe have only one speaker output? If you have four identical speakers, you could wire two of them in parallel, wire the other two in parallel, then wire the two pairs together in series. This will give you the same impedance as one speaker alone, apart from differences between the speaker impedances.
*Option 3 being hiding a new stereo hidden somewhere as mentioned above. Probably the best option. You could wire the center speaker to the AM radio, and it’d even be functional.