One of the original speakers in my '71 needs to be replaced. The originals are 10 ohm. Can I use a 4 ohm speaker or do I have to use one with the original impedance? What would happen if I used a 4 ohm speaker?

Thanks.

 

Burns out the radio I think.

Have you looked into repairing the speaker?

Doc Rebuild has some GM replacements.

-Mark.

 

Hmmmm....modern speakers are usually 8 ohms...where did you get a 4 ohm speaker?

 

"Ohm

The measure of resistance in a circuit to the flow of an electric current. The greater the ohm value the more difficult it is for current to flow through a given circuit. Conversely, a low ohm value represents a low resistance and the easy flow of current through a circuit.

Ohms are often used in reference to loudspeakers which have a certain level of resistance associated with them. A typical speaker may have an ohm rating (rating the speaker's resistance) of 4 to 8 ohms nominal impedance (impedance being resistance to current flow). Resistance in a speaker varies, however, from low ranges often as low as 2 or 3 ohms to high ranges as high as 30 or more ohms.

As speaker impedance decreases, more current flows and the amplifier is called upon to output more power to the speaker. When shopping for speakers and amplifiers, make sure the amplifier is able to output power properly into the speakers' impedance. Many receivers are not able to operate properly with speakers having impedance loads of less than 8 ohms. While most separate amplifiers can handle lower impedance loads down to 4 ohms or less, some speakers present impedances of 1 or 2 ohms at their minimum requiring particularly robust and powerful amplifiers designed for such loads. Generally, most any separate amplifier will be able to properly power almost any speaker (with the few exceptions being in most cases highly-exotic, very expensive speaker designs) while receivers should be mated with speakers having nominal impedances (average impedances) of around 8 ohms."



This article gives a pretty good description of what is happening. In other words as the resistance (OHMs) drops, the speaker is allowing more current to flow from the amp. Underpowered amps may not be able to supply the necessary current allowed by the speaker. I often use the analogy of a water hose: Given the same amount of water pressure (Power) to a small diameter hose (say 1/2 inch diameter) the flow of water (current) will come out pretty forcefully. Given the same amount of water pressure on a 4 inch diameter hose the flow of water comes out with much less force. The larger hose has created less resistance. To get the same force with less resistance you need to increase the pressure at the source. So a speaker with less resistance (lower OHMs) needs more power to operate correctly.

 

Home/pro audio speakers are generally 8 ohms, and car audio speakers are generally 4 ohms.

If you use a 4 ohm speaker with the stock radio, you will run the risk of burning it out because it will place a much bigger load on it. A 6 ohm resistor might work, they are cheap enough, probably pick them up at Radio Shack for almost nothing.

 

The impedence rating is nominal. Home speakers are normally 8 ohms & car speakers are normally 4 ohms.
I would not be concerned about running 2 8 ohm speakers. I added 2 car stereo speakers to a 57 Chevy Wonderbar radio w/o issue in the late 60s (don't recall speaker ohms).
Radio Shack has special 4 ohm resistors that could be added to 4 ohm speakers.

I would not be concerned about running 2 4 ohm speakers on a 77 up factory stereo. I have done it.

 

you can run the 4 ohm speakers, Ues they will allow more current from the amp output, BUT Only what the volume contol allows. In other words, your radio will be a bit louder useing 4 ohm speakers in place of 10 ohm speakers with the volume control at the same spot. Unless your goung to be running full volue all the time, no problem,

 

You can always run the two 4 ohm speakers in series, in effect making one 8 ohm speaker, on the same channel.

Another option is buy factory correct speakers from Corvette catalogs like Mid-America.

 

How good are the aftermarket speakers and does the original radio have the ability to make good sound through any speaker, original, modern or reproduction? If the radio itself is capable of good sound it may be worth the effort to wire in some resistance and use a higher quality speaker.

 

The factory head unit is not and never was capable of running high quality speakers. The speakers you mention like 'around' 100 Watts RMS. Your factory radio can only give 5-10 depending on the stereo and maybe a factory amp. If you want to keep the stock radio, you need to stay with stock speakers or you will end up with bad sound. A good speaker will sound horrible on a poor stereo with an old and insufficient signal processor.

Now, upgrading to an aftermarket stereo with a digital signal processor and using amps to drive speakers will give you the best sound. You can choose your speakrs to match the output of the amps or the other way around. The head unit becomes a source for signal only, seeing as it wil usually only put out an average of 15 Watts RMS regardless of it's rating. Head units are over-rated for powering speakers.

 

I don't know one way or another on the C3 radios in '71 but on the C2's the factory speakers are 10 ohm speakers (as you mentioned yours was) with an external transformer attached. If your speaker is the same type than you MUST use a correct replacement speaker of the same impedence with the transformer or you will fry the output stages of the radio.

If the speaker you are replacing is the actual correct factory speaker than look at it again and double check to see if there is a transformer attached to it before simply replacing it with a standard aftermarket speaker.

 

My goal here is not high fidelity sound, but rather just to pass a performance verification test if I ever take the car for judging. I have a speaker box with an amp set up in the back that I run off an ipod. This is my system for when I want to listen to something while kruzin. The stock radio is rarely used. I just want to make sure that I don't do any damage to my original radio if I hook up a wrong speaker. Those things are expensive to repair.

Someone mentioned that I can repair the original speaker. How would I do this?

Thanks.

 

Stock speakers are avalailable from Mid America along with others. The cost of buying a stock replacement is easier to take than repairing an old speaker. I would suggest that route over repairing, which whenever I have experienced it, didn't turn out well.

 

The main thing is ALL the speaker's must be the same OHM because of the inbalance can burn the radio up from overload.
The radio will be OK.
The lower the OHM the more sound because of lower input is needed.
I use Infinite Speakers & their rated @4 OHM .

 

Infinity still makes 8 ohm speakers now, you could run a pair of those.

 

I completed PV with my '86 four months ago. It might be easier and better to convert the car into a non-radio option car and get all of the points. lolol. Bunky

 

I have been cionfused about this also. I wanted to retain my original am/fm stereo that was in my 70. The speakers were completely shot. I actually got the radio cleaned up and working, although the right channel is much lower than the left. When I ordered speakers from Zip, they said they were the best 4 ohm speakers for replacement, but had to drill the correct mountin holes and swap the plugs. When I replaced the old ones, they were 10 ohm. The new ones didn't have any ohm marking, so I don't know if they are 4 or 10 or ? But they work ok.

 

I believe my Delco stock radio has a warning tag on it to not use anything other than 10 ohm speakers. (Actually I believe the warning is to not use other than a 10 ohm load.) It's a 1968 radio.

 

use whatever ohm speaker you want, but its best to make them both the same or your balance will be off. Its difficult to find any that fit. I can't even remember what i did but i know they're not stock.

you won't burn anything out.

 

A major improvement can be made w/ typical aftermarket speakers, proper placement & proper mounting. 5.25 are probably the best size for the kick panels. Some 5.25 can be fitted w/o cutting. A mounting or back plate needs to be done.

A better stereo could be added later.