[T3] FW: radio in

Jim Adney jadney at vwtype3.org
Sat Jul 12 05:03:15 PDT 2014


On 11 Jul 2014 at 21:55, Dennis Stiefel wrote:

> Actually I've tried just doing one speaker on each channel (having 2 instead
> of 3 like it is now). 

Typical speakers are 8 Ohms. If you put 2 in parallel, you've reduced 
the resistance to 4 Ohms. Three in parallel will put it at 2.666 
Ohms. So the current you're asking from the radio has gone from, for 
example, 1 A to 3 A. In the electronics world, that's a big 
difference.

If you put the 2 rear speakers in series, they now measure 16 Ohms, 
so putting that in parallel with the front speaker now asks the radio 
to drive 5.333 Ohms. So the current in the same example will now go 
from 1 A to ~1.3 A. That's not such a big deal.  

The current you actually ask the radio to provide depends on how far 
up you crank the volume, so if you keep things moderate, you can get 
away with a lot.  

Some of your posts seem to imply that this is a stereo, which is 
unusual for a Sapphire from our era. If that's the case, consider 
wiring the rear speakers as L & R, and then combine the ground 
returns from them into one conductor and pass that thru the dash 
speaker. This creates a "center channel" which might work nicely, but 
note that you can't do this unless the 2 channels have a common 
ground. Keith can probably tell you if this will work on the radio he 
fixed up for you. Be careful. If you do this wrong, you'll damage the 
radio.

-- 
*******************************
Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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