Magnet size is not a factor, the only factor is the "impedance" of the
speaker voice coil, and that is very uncritical also, unless you are driving
it with a super high power BOOM box of the type used in the high school
kid's Honda Civics with the chrome wheels and the 6 inch diameter exhaust
tip. Any speaker with an impedance of 4 to 16 ohms will work just fine
with your radio - the impedance is on the box it came in, and is probably
either 4 or 8 ohms. The only thing that will bother the radio is a dead
short on the speaker wires, or running it with no speaker at all. The
output circuit is a single ended power transistor - it isn't particularly
fussy or delicate as long as the power polarity isn't reversed, and the
output is not shorted to ground.
Magnet size on a speaker is the new "horsepower" race amongst the speaker
vendors - they all claim to have a bigger magnet than the next guy. The
size of the magnet is not the important factor, but the uniformity of field
strength over the voice coil motion range is, and larger magnets tend to do
a better job there. However, the older speakers used pure metal magnet,
while the new ones are ceramic - which have to be bigger to produce the same
flux in the gap. More flux makes for a better energy conversion from current
in the voice coil to sound level (read "louder music at the same volume
setting").
The marketing guys turned this larger magnet situation into a whiz-bang new
hype. Ignore it.
All you care about on a speaker is the cone resonance, the maximum power
handling capacity (only if you are driving it with a monster amp), the
frequency range, and the harmonic distortion. None of these are important
for a car radio from the 60's, believe me!
My 67 convertible also tends to favor the front speaker with the balance
control set in the middle, especially with the top down. However, I have
had people tell me the rear speaker is too loud when the top is up and there
are people in the back seat, so I have to re-adjust the balance control. I
think the front windshield/dashboard creates a projection device that helps
the radio volume for the front seat passengers. I guess that is why they
have a balance control - I get the same complaints in my Limousine (the 47
Packard).
Dick Benjamin (I never played one on TV, but I used to be an injunear)
----- Original Message -----
From: <DONALDDICKINSOND@xxxxxx>
To: <mailing-list@xxxxxxxxxxxxxxxx>
Sent: Saturday, April 03, 2004 6:34 AM
Subject: IML: 67 Imperial Rear speaker
> Very interesting discussion of front speaker replacement/repair for 67
> imperial. Let me ask the experts on the rear seat speaker for my 67
convertible.
> The rear. as opposed to the front, was a standard size which I picked up
at
> Radio shack, my questions:
>
> 1) How am I sure the speaker is connected correctly (polarity)?
>
> 2) I did not get a "small magnet" but the radio seems to drive it OK
(except
> front to back balance favors the front speaker) what is risk of driving
the
> larger mag?
>
>
> Don Dickinson
> Prospect, KY
>
> 1955 Imperial Newport, Canyon Tan and Desert Sand
> 1967 Imperial Custom Convertible, Ivory and Burgundy
>
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