<VV> Replacement radio speaker options - late model

[Dave Ziegler]

Why not just have the original speaker re-coned? There are several 
companies doing this in Hemmings.
Dave.. .
On Apr 30, 2005, at 9:25 PM, Tony Underwood wrote:

> At 11:02 hours 04/30/2005, Les wrote:
>> Hi,
>>
>> Original speaker on my '65 (AM pushbutton) is dead. Plenty of 4 ohm 
>> 6x9s available; original speaker was 10 ohm.
>
>
> You *might* still find a 10 ohm 6x9 at your local GM dealership.  
> Check with them.    It won't have the same magnet (it will be round) 
> but the impedance will be OK.
>
>
>> Can I use a 4 ohm 6x9,
>
> Yes but it's a mismatch and the output transistor will tend to draw 
> more current and deliver less output, considerably less seeing as how 
> the radio is DC/autotransformer-matched to the speaker which is why it 
> uses that odd 10 ohm speaker... to provide a good imp4edance match to 
> the single-ended class-A audio output circuit.   It's a terribly 
> inefficient design, but it does get by with using only three 
> transistors in the entire audio output circuit.   And, effectively 
> with a storage battery you have practically an unlimited source of 
> input power so the efficiency factor is moot.
>
>
>> or do I need to rig a pair of 5" or so speakers in series to get 
>> close to 10 ohms?
>
>
> Kinda complicated, that, although it will work.   Look around for a 10 
> ohm 6x9 GM replacement speaker,  or check around for an 8 ohm speaker, 
> close enough to not make much difference as far as the output match is 
> concerned.
>
>> How about a 6 ohm resistor in series with the 4 ohm speaker (I know 
>> that's resistance and not impedance)?
>
>
> Not a good idea...  it will drastically reduce audio output to the 
> speaker.    Never a good idea to put a resistor in series with a 
> speaker since all it does is limit current and thus drop power output 
> to the speaker.
>
>
>> I tried a 4 ohm speaker here and the output transistor gets kinda 
>> warm...
>
>
> Typical...  a class-A audio power amplifier will get hot, it's normal. 
>   The impedance mismatch won't have that much of an effect on the 
> output transistor temperature, but it *will* have a relatively large 
> effect on audio output power.   Transformer coupled output devices 
> rely on a good impedance match for best performance.   Have you tried 
> the vendors for a correct impedance speaker...?
>
>
> tony..
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