C2 Radio/Speaker Question-Issue

[John L.]

Couple of years back had my '66 radio refurbished by ElectroDesign and purchased new speaker from S+M Electro Tech. Both installed and operating in car but few things do not seem right and would like your feedback:
1) When playing radio, I have to adjust the treble/bass switch to full treble side to obtain best music clarity. If I move the switch to the mid range for example, music clarity is not good.
2) Also, I need to keep the radio volume knob to more than about 25% of volume capacity to keep speaker sound from being distorted/overwhelmed, speaker can not seem to handle increased volume above this point.
3) Lately, after playing radio for 15 minutes or so, there is a static sound from the speaker and this sound continues even when I turn the volume knob down to no sound. However, the intensity of the sound does not change as I drive the car, thus do not believe it is capacitor related.

Thanks for the feed back

[Jim D.]

Re: C2 Radio/Speaker Question-Issue

Call Jerry at ElectroDesign. He'll have all the answers.

[Jerry R.]

Re: C2 Radio/Speaker Question-Issue

That was over 5 years ago John - time races by...

The recessed nichrome wire bias control in the bottom panel of the radio may be starting to corrode again. They all do it and that is very often one of the problems that kills a radio. You can check for that by placing a DC voltmeter across the green and black speaker wires with everything hooked up. You should read close to 1.5 volts. Any other reading indicates a radio amp or speaker situation.

I routinely boost the audio level and treble in C2's now but back then I didn't. That is very easy to do and C2's did not have good performance up in that range. Additionally, as we age our ears lose sensitivity to high frequencies rapidly. That could be a contributing part of it. My grad work was in audiology when I was young and I still messed my hearing up. hah But I miss the highs dearly now.

But items 1 and 2 that you mentioned could also be caused by the speaker itself. It's not that Greg's speaker was of poor quality (far from it) but rather that if dust/dirt/corrosion (probably not the issue) gets between the magnet or frame and moving voice coil, the coil form can rub on the sides. It will therefore not be moving freely and high frequencies can be affected a bit more than lower frequencies. And it can be dramatic.

One other thing that happens is that, during shipping, the speakers (and everything else) takes a beating by the gentleness of the carriers. I see it all the time now on sets coming and going. The speaker magnet is centered in the voice coil form with tight tolerances. If it is bumped firmly it will move off center and drag and potholes can then exacerbate the problem over time. The sound will definitely become distorted and if bad enough, it will almost totally be muffled.

And yes, it could be the radio. But other than the common bias control problem, your set has caps that should last many more decades than the original Delco devices could.

As far as item 3 goes, check this. Unplug the audio auxiliary input cord, clean the metal tip/ring/sleeve and plug it back in very "firmly". If it is not plugged in firmly, the shield sleeve will not be grounded and the two channel input wires will be exposed to any external noise like blower motors, distributor/spark plugs, generator/alternators, turn signal flashers, brake switch contacts and a load of other "amplitude" signal sources. And the radio just loves to pick up that stuff and amplify it in the audio amp.

OK, I've rambled enough but those are things to consider. There are other potential problems but the forums hard drive only has so much space and I typed too much already.

By the way, your radio had the scratchy volume control problem and apparently it has not returned. That's not contributing noise unless you actually turn it.

For what it's worth... _Jerry_