Need picture of backside of original midyear speaker.

[Christopher A.]

Can someone please post a picture of the backside of an original Midyear speaker please. I am interested in how the original speakers were wired.

Thanks

[Jim D.]

Re: Need picture of backside of original midyear speaker.

Here's the original out of my 65.

[Christopher A.]

Re: Need picture of backside of original midyear speaker.

Thanks so much! Just FYI to those that might be in the market for a new speaker, every reproduction speaker i have purchased has been wired incorrectly, even the 60.00 unit the I purchased from SM Electo tech that was advertised as 100 percent correct. It was only reading 1.8 ohms just like the other reproduction speaker i have, so i assume this is what ended up causing my newly rebuilt radio to burn out.

[Joe R.]

Re: Need picture of backside of original midyear speaker.

Oh Please don't start that old tale of the speaker burning out my newly rebuilt radio!!!!!!!! It simply won't happen! Your radio went out because it's 40 years old or your radio rebuilder doesn't know what he's doing. He may be snake bit also! Send it back to him and let him fix the radio.
That rumor was started by a radio rebuilder in Tennessee to scare people and drum up work for himself. He also claims to replace all the capacitors in the radio when he rebuilds one. Replacing all the capacitors would take a week working 40 hours a day. He charges enough to replace them but it don't happen. Not even once!!!!
I just needed to say that! Thanks for listening!

JR

[Christopher A.]

Re: Need picture of backside of original midyear speaker.

I'll gladly admit that I do not know a thing about electronics and I find them very confusing. The radio did not work from the moment i received it back from the rebuilder, so he is going to take it back and go over it again.

I changed the wiring on one of the extra el cheapo speakers i had on the shelf, as per the radio rebuilders instructions, and the ohm reading doubled.

[Jim S.]

Re: Need picture of backside of original midyear speaker.

Here's the original out of my 65.

Christopher,

I don't know anything about electronics either, but just for curiosity sake, I looked at my S/M speaker and it is wired differently than Jim's original . I doubt that it is wrong as I have to assume that they know what they are doing and that the wires take a different route to get to the same effect . But I agree it is different !

Jim

[Christopher A.]

Re: Need picture of backside of original midyear speaker.

I just tried a radio from another 66 out in my car and the reproduction speaker from SM blares out tunes like no other reproduction paper speaker i have heard. So, it is definitely a good quality speaker and the problem has nothing to do with my coaxial cable either, which i already knew since i installed my radio into the other 66 for testing. I am going to send my radio back to be repaired and hopefully it will be fixed correctly this time. Maybe it was just a slip up the first time. All i know is that i certainly do not want to pull this thing out again!!!!

[Jerry R.]

Re: Need picture of backside of original midyear speaker.

For posterity and those who just want to know about vette radio misconceptions:

Christopher, the value you read (1.8 ohms DC) is nominal and correct. The loading coil IS wired in parallel with the 10 ohm voice coil. Ohms law for parallel resistors applies and remember that the accuracy of your ohm meter at such low values of resistance will affect your readings.

ElectroTech makes the only electrically correct aftermarket speaker that I have seen on the market for decades and Corvette America is the only vendor that apparently sells Greg's speaker. The speakers from the other vendors that I have dealt with via personal experience or through many, many hundreds of vette radio customers have incorrect loading coils. Seriously incorrect!

You should read very close to 1.5 VDC across the green and black speaker leads with the radio connected and turned on. That assumes that the radios bias control (internal) has been adjusted into a correct load (speaker/inductor combo) in the first place. If you read .25 to .75 volts, you should immediately suspect that the inductor on your "new" speaker MAY be of the wrong value - especially if your speaker is gold anodized in color. I had rebuilt the 67 radio in my car many years ago, added a new speaker, noted that the radio barely played and sounded distorted. That inductor turned out to be the culprit. The NY supplier, who still sells that same speaker, sells units with loading coils that almost short out the output transistor. And this same speaker is sold by all but one vendor that I know of.

What does that low indicated voltage mean? In simplistic terms, as the voltage goes down, the current goes up and the heating of the output transistor goes up accordingly. The power has to go somewhere and it's not going into your speaker with a low value loading coil. It's being lost as heat and not converted into sound waves. Over time, the germanium in that big transistor on the back of your C2 radio degrades from the extra current and heating load.

Why is the inductor even on the speaker? Battery voltage goes directly to a 0.47 ohm fusible resistor in the radio and on to the output transistor which then goes to the speaker. Yes, there's very little resistance in that circuit to hold the 12 volts back and that much voltage across a 10 ohm voice coil - made of very thin wire - would tend to act as a glow plug. Put a paper cone near it and you can read between the lines. So, the loading coil dissipates much of that 12 volts DC but allows the AC sound component to pass into the voice coil and deliver sound electromagnetically. Yes, there is both DC and AC on the speaker lines.

I've beat this to death as I do every day with each new person having their radio brought back from old age decay but why fix up a car if you're going to leave the tires flat? Re-cone your original speaker or buy an electrically correct speaker and it will "blare out tunes" just as Christopher said.

And if your FM sounds great and your AM reception sucks, especially if you have a 58-63 Wonderbar that just won't stop on stations, look at that aftermarket feedline you just bought to perk up your antenna system. The odds are that it will say RG-59 on it somewhere and that's 75 ohm cable TV wire and not what was supplied with your car in the first place. The antenna trimmer Does not have enough adjustment range to compensate for that huge mismatch. Using that cable is like poking holes in the fuel line and wondering why the engine is fuel starved where AM is concerned. Contrary to what I keep reading on forums, the antenna trimmer in a correctly working system WILL have a very pronounced affect on the loudness of stations! 93 ohms impedance was the commonly accepted cable value back then, not 75.

As I get off this soapbox (Joe fired me up), spraying tuner cleaner into a volume control to get rid of the scratchy noise is just wrong. Tuner cleaner was created to remove corrosion in various forms from the METAL contacts of switched circuits in the old television tuners - both VHF and UHF. It is a corrosive substance. Volume controls have a deposited carbon track attached to a non-conductive substrate. That cleaner turns the carbon into black, sloppy mud and allows it to be wiped off the substrate over time. Rebuild a few of those volume controls that just can't be purchased anymore and you'll see what I mean. If you must clean a control, use only a very tiny amount of solution and use something made for this purpose. And I don't mean WD-40!

Sorry for the dissertation - it's just my opinion and from observations after working on old electronics for the last 56 years. I hope this will help you all to gain some judging points and prove that these old radios CAN sound and work pretty darn well. And I promise not to put this on a forum again. It's old history now...

Thanks to Christopher for bringing it up and to the NCRS member who emailed me the question. FWIW...

[Jim D.]

Re: Need picture of backside of original midyear speaker.

Thanks for the technical reply. Jerry has restored two radios for me and I matched them up with the ElectroTech speakers that he recommended. All I can say is that they perform perfectly together. Thanks again Jerry.