new 1/11/2004
The Gen III JBL and MACH system is the same power-wise, except in the
96 SHO which had an additional and separate 20Wrms subwoofer amp/speaker
assembly in the center rear package tray. The 96-99 RCU (rear control
unit in trunk) puts out 4 channels of 20W each (4x20W), and a 5th
channel line level (i.e. low power) output to the JBL subwoofer
amplifier (which I think this 5th output was removed in 98 RCU, if not
earlier).
Each sail speaker is parallelled with a door speaker. The left front
(LF) output on the RCU electrically drives both the LF sail and LF
speaker. However, each door speaker has a passive (i.e. non-powered),
low frequency crosser circuit over to filter out hi-frequency audio
which should only be acoustically produced by the sail speakers. I'm
not sure if the sail speaker has a hi frequency crossover, but I would
assume that it would. Anyways, you only get 20W for the LF side that has
2 speakers (ditto for the right front).
The Gen II SHO's had the separate subwoofer amplifier that use to do
85W. Ford went down on performance and cost for 96 Gen III, and then
eventually killed the sub altogether.
The JBL systems for SHO and T-birds in the late 80's and early 90's
all had 85Wrms sub amps, giving 165W total RMS power (add in the 4x20W
satellites).
If you want top-notch Ford OEM/stock system, check out the current
Ford Mustang MACH 460 and MACH 1000 options. 460/1000 are peak power
designators, not RMS