When I got my 74 only one speaker inside the car did still work. I was not sure if the radio was the problem, or if the speakers were shot. I tested the speakers while they were still inside the car, and they were indeed defective.
I have to repair my radio anyway (see here) as it does not work properly. My friend Steve who is so kind to repair the radio for me already found out that the radio had a defect which caused the speakers to burn through.
So it was clear that I would need new speakers for my car.

In the past I already had to install replacement speakers in most of my cars. I´m always replacing them with replacement speakers from Turnswitch. They do have some really good reproduction speakers which fit perfectly with only minor modifications necessary. I have dealt with them a couple of times and they are always extremely helpful and friendly and their speakers are great. That is why I can truly recommend them and will use them again if I ever need some speakers in the future.

If you have a stereo/tape radio you need their round 3 1/2" speakers with the block cover to be able to reuse the factory mounting clips for the front speakers in the dash.
The mounting ears have to be cut off and the speaker is then held in with the wire clips used on many GM applications.

The cover blocks are the shape of the original magnet structure and go over the magnets for the wire clip. They are made of wood and you have to glue them onto the speaker in the same orientation as the original magnet. Also make sure that polarity is correct - for some reason it's exactly opposite to the original speakers and you have to connect the positive cable (green or blue) to the speaker lead with the red dot. On the original speakers the wires on the front speakers were soldered on - I re-did it with connectors on the new speakers as they are easier to install and to remove with them.
The new front speakers do not have a dust screen on them, so I carefully removed the screen from the original speakers and glued it to the replacements speakers. So they are protected now and it looks factory correct as you could see the missing screen through the speaker grilles on the dash.
To remove the left speaker and install the new one you have to remove the AC hose to get access to the speaker. The speaker cables are relatively short so be careful not to damage them when you pull the speaker out.

For the rear speakers you need their 6x9 speakers which come with a dust screen already installed.
Here you need to do some more modifications as the original speakers have an additional bracket with a bolt, which holds the insulated cardboard cover in the trunk in place. Without this bracket you cant install this cover.

I carefully drilled out the rivet which holds the original bracket in place and also drilled a hole into the metal frame of the new speaker. I then used a small bolt and nut instead of a rivet to install it onto the new speaker. This works really well, but you have to be extremely careful when you drill this hole as you can easily damage the membrane of the speaker underneath if you drill too deep … (I made this mistake when I drilled out the rivet on the old speaker and immediately had a hole in the old membrane…)

The terminals of the rear speakers were connected with a special connector which you can´t reuse with the new speakers unfortunately, so I had to cut the wire and install a supplied connector instead. On the rear speakers you also have to ground the negative terminal to the car. A short ground cable to do this properly is also supplied with the speakers.
Then you can screw the speakers back into the car and connect them.

Here is some more useful info about replacement speakers from the turnkey website:

"Many replacement speakers now sold by the discount stores, auto parts stores and mail order restoration parts houses are labeled as  "4 to 8 ohm compatible"  and are in fact 4 ohm speakers. These speakers can damage the older transistor radios. 4 ohm speakers will measure around 3.2 ohms with a DC ohmmeter. An 8 - 10 ohm speaker will measure around 7.4 ohms with a DC ohmmeter. The DC resistance is the critical number for the Delco radios as the output transistor is in series with the speaker. A properly operating Delco radio should have 1.5 volts DC across the speaker voice coil. A 4 ohm speaker will draw twice the current of an 8 ohm and cause the amplifier transistor (the half dollar size device mounted to the black finned heat sink on the back of a Delco radio) to run very hot. The speaker cone should be displaced in an upward (away from the magnet) direction about 1/8" when a Delco radio is turned on. If the cone moves down toward the magnet, the speaker leads need to be reversed".

I´m looking forward to installing the hopefully eventually repaired radio into the car and to test the sound of the new speakers. They should normally sound a little better than the original ones.

The original right front speaker unclipped from the car.

The original right front speaker unclipped from the car. Here you can see the original dust screen which you will have to reuse with the front speakers.

The replacement and the original speaker, as you can see the magnet looks different and you have to cut off the mounting ears.

The replacement speaker with the cover block installed. You have to order it separately for your Cadillac.

The replacement speaker with the old dust screen installed.
The new speaker back in the car with the supplied connectors.

The original left speaker removed - you have to remove the AC hose to get to it.

The replacement 6x9 speaker and the factory installed original speaker. Note the bracket - you have to move it to the new speaker and install it there.

The replacement 6x9 speaker and the factory installed original speaker. Note the bracket - you have to move it to the new speaker and install it there.
I drilled out the rivet to be able to remove the bracket. Be extremely careful when you drill it out!
Instead of the original rivet I used a short bolt to install the bracket to the new speaker.

Tags:1974, 1974 Cadillac Coupe DeVille, 1974 Cadillac Repair Tip, 10 Ohm, Speakers, Radio