I checked my receipt for the two harness numbers:
1) Made by Metra
#70-5512 ("Ford Premium Integrator") $26
2) Made by Al (who?) - has two numbers:
Model "FWH1" and serial number "701771" ("Low level adapter") - what the heck is that? $15
I think maybe the low level adapter are the ones I've seen advertised on autotoys.com and/or Crutchfield - they have a box hanging off the wires, which might just be a simple resistor voltage divider. But why would there be two harnesses...ARG! I'll search around the net and see if I can find more info on these harnesses.
I think the low level adapter resides between the head unit and factory amp. It does not make sense as you said since the factory amp's inputs are speaker level inputs (which is why I asked about that in my first msg).
Perhaps the aftermarket head units have more powerful amplifiers than the factory head unit, so the "speaker level" inputs of the factory amp will not handle aftermarket head unit outputs?
The Sony head unit has a small plastic surround, and I was told "keys" are needed to get it out, so I'm not sure if I can get the head unit out to see what he really did...
The Polk dx7's are great for mid and upper range, and sound great with my 12" sealed sub! They do have weak bass (I can not hear any different between the 80hz, 120hz, and no high pass filtering settings of the Sony head unit, so it seems they are weak below 100hz). They are rated for 45hz, but that might be at more than 3dB down as they do not specify.
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1999 Contour Sport
V6 5 Speed
