I have a stock 68 Xr7 factory radio and speaker. I wish to replace the speaker and update the radio at a later date. Is the radio 4 or 8 ohms? If I use this speaker, will it work with an updated radio?
Old radios, including that one, are 8 ohms. 4 ohm speakers short the unit out. Use an 8 ohm speaker and you won’t have any problems.
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Hey Royce, hope you are doing great. Follow up to your post. I bench tested my radio before I put it in the car back in 08 and it worked and has never worked in the car. I am not sure if I checked the ohm rating on the speakers when I did the restoration. When you say short out the unit, I want to clarify permanent damage or wont work until correct speakers are used? 
Also just for being specifc, I installed a 69 AM/FM and put speakers on the package tray and behind the kick panels. Cannot specify on the speakers now but can look through my recipts when I get home if the info is needed.
It depends on the radio. Many just sound terrible with 4 ohm speakers. If they are on their last legs it might be the end.
Thanks Royce, I have the console out for another project. I will likely pull the radio out and bench test it with a speaker again. Then chase the speaker stuff after that :). Hope all is well.
The amplifiers they used back then were not capable of delivering much current. So a 4 ohm speaker doubled the current requirement. This caused the output transistors to over heat pretty rapidly, burn up and fail permanently. At low volume the 4 ohm speakers won’t cause any real harm but the first time you try to turn it up may be the last time. Because a 4 ohm speaker has greater voltage sensitivity (meaning they play a little louder at a given volume setting) people do get by using them in some cases. The best thing to do is to use a small amplifier with high level inputs to drive the speakers. The input of the amplifier will have very high impedance and present a very easy to drive load to the radio. Modern amplifier designs are optimized for lower impedance speakers so you won’t have to worry about that.
That’s a great solution! The other thing as Royce mentioned was the radio sounds terrible driving 4 ohm speakers at higher volume. This is because the amps are distorting their output as they try to drive half their rated load impedance. The added output amp solves that problem too.
Quick side note - just got back from Boston and was noticing these odd umbrella things hanging over the church pulpits. Turns out these were the very earliest audio amplifiers!
Does anyone sell an 8 ohm speaker that fits in the door of a ‘69? Looks like the ones I bought from WCCC are 4 ohm, at least if the currently offered ones are same as a decade ago. I saw some on CJPony advertised to fit, but also 4 ohm.
You will probably have to buy speakers from eBay.