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4 minutes ago, David Layton said:

My 73 has 4 speakers.  The radio I have now is the early '80s Japanese Frankfurt which is set up for 4 speakers and has a fader.  Unfortunately, I recently learned that the DIN plug is an auxiliary OUT for an amp and not an IN plug suitable for a Bluetooth. 


As my build is very orthodox, with the Recaros set to be upholstered as a nod to the stock seats, I am thinking of looking around for a vintage Frankfurt or Bavaria stereo with the aux in DIN.  These Frankfurts only had 2 speaker connections, so would it be possible to tie left front and rear together and the same with the right?  The one minor drawback is no fader control.




I looked at the old-look new radios and they just don't look right IMHO.




Another thing to keep in mind is the ohm load on the internal amplifier channels. The mono head units expect an 8 ohm load but the stereo head units expect a 4 ohm load per channel. Most car speakers are 4 ohms, so wiring a pair to each channel on a 70s Frankfurt Stereo is going to pull the load down to 2 or push it up to 8 depending on how you wire it. 8 would be better than 2 in terms of damaging the deck but it won't sound good. 

So, if you want the stock deck to run 4 speakers you'll need 4 2 ohm or 4 8 ohm speakers, wired appropriately for a 4 ohm load.



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Got the Frankfurt back from the shop. Looks like there was a short inside. Most of parts that were replaced were typical resistors and such, with the exception of the AM/FM toggle switch that broke and is NLA. So it all works, but it’s just set on FM. Pic is a test fit with the Kooglewerks bracket. 








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