Man, that was some hard info to find. Im thinking that maybe you have 2 front door speakers, 2 rear speakers, 1 subwoofer, and possibly 2 door tweeters. This is all I could find though from Explorerforum.com:
The factory-installed sound systems in Ford Explorers are typically offered in three different levels: Base, Premium, and Audiophile The basic elements of the three different levels are:
1) Base systems use a 4X6 Watt Midline radio (AM/FM, AM/FM/Cassette, or AM/FM/CD) with 4 speakers
2) Premium Systems use a 4X20 Watt Premium Radio (AM/FM/Cassette, AM/FM/CD, or AM/FM/Cass/CD) with 4 speakers the amplifier was external from 1990 through 1997; integrated into the radio from 1998 through 2001
the speakers are upgraded over the "Base" level speakers (1990-1997) in 1998, the "Base" speakers were upgraded to Premium level
3) Audiophile Systems these systems are branded; Ford/JBL from 1990-1997, Ford/Mach from 1998
through 2001 use a 4X15 Watt Premium radio (AM/FM/Cassette, or AM/FM/Cassette/CD)
the amplifier was external from 1990 through 1997; integrated into the radio from 1998 through 2001
the speakers are upgraded over the "Premium" level speakers the Audiophile Systems include a Subwoofer in a sealed enclosure with a dedicated subwoofer amplifier
the speaker size for all applications is 5.5"X7.5" in four locations (front doors, rear doors on 4dr; front doors, rear qtr trim on 95+ 2dr models)
the Base system speakers are "full-range" in 1998, the Base speakers were upgraded to Premium level to improve performance
Premium System speakers are "Full-Range" with whizzer cones added for increased fidelity on high-frequencies
Audiophile System speakers are usually 2 speakers (a 4.0" mid-range, and a 1.0" tweeter) in a sealed enclosure (in some model years, the enclosures
are used in all four locations, in others, they are used only in the front, with Premium Full-Range speakers in the rear)
The subwoofer enclosure is located in the right rear quarter trim on all models, from 1990 through 2001. If your truck has a storage compartment in the right rear quarter trim, then you DO NOT have a Subwoofer, and
you DO NOT have a Ford/JBL or Ford/Mach Audio System
For 1990 through 1994, Explorers had DIN size head units in them.
For 1990 through 1992, the DIN radios had a 64mmX192mm bezel size, and the trim panel was installed OVER the radio
For 1993 and 1994, the "Next Generation" DIN radios with 59mmX188mm bezels were used, and the radios were installed INTO the trim panel
For 1995, the radio head unit size was increased to 1.5 DIN (the chassis was 50mm high at the rear, 90mm at the front)
For 1998, the opening in the instrument panel was modified to accept a radio chassis that was 90mm high from front to back
The electrical connectors were the same from 1990 through 1994. Base systems had two flat-bladed vertical connectors - one for Power, and one for Speakers. Premium and Audiophile systems
used the same Power connector, but had shielded cable connections to the amplifier. There was another 6-pin shielded connector for interface to a remote CD changer.
Electrical architecture changed in 1995 to a "distributed system" for the Audiophile Systems. The head unit in these systems does not contain a tuner or amplifier; they were both integrated into a "Rear Control Unit", which was slightly larger than a typical Ford radio
amplifier, and bolted to the Subwoofer enclosure in the right rear quarter. This architecture applied ONLY to the Ford/JBL Audiophile system, and only for the 1995 through 1997 model years.
Electrical architecture changed again in 1998, and finally commonized connectors and pinouts between "Base" and "Premium" systems so that head unit upgrades could be accomplished without having to modify vehicle wiring. The power amplifiers for Premium and Audiophile head units were integrated into the radio chassis, and the Subwoofer amplifier is the only remote amp used.
Base systems are rated at 24 Watts RMS (actually, Continuous Average Power)@ 10%THD Premium Systems are rated at 80 Watts RMS @ 10% THD
Audiophile Systems are rated at 145 Watts RMS @ 2% THD (4X15W from the head unit or remote Parametric Amp; 1X85W from the SW Amp) Audiophile Systems have an Advertised Peak Power rating of 290 Watts
For 1990 through 1997, the Subwoofer had a 6.5" driver in a 9 Liter sealed enclosure. In 1998, the Subwoofer was upgraded to an 8.0" driver and a 15
liter sealed enclosure.
The Ford part numbering system for radios uses a five digit base part number, with a four letter alpha-numeric prefix, which identifies the original model year and carline application, and a two letter alpha suffix that identifies the component change level. The prefix F57F, for example, is broken down by: F = decade (1990's); 5 = Model Year (1995); 7 = Carline Application (Ranger/Explorer); F = Electronics Division Release part.
Following are the base part numbers for the different families of radios used in Explorers over the years.
-19B131- Midline AM/FM
-19B132- Midline AM/FM/Cassette
-19B165- Premium AM/FM/Cassette (1990-97)
-18C815- Premium AM/FM/CD (1990-94)
-18C815- Midline AM/FM/CD (1998-2001)
-18C852- Audiophile AM/FM/Cassette (1995-97)
-18C868- Premium AM/FM/Cass/CD (1998-2001)
-18C815- Premium AM/FM/6CD (2002)
Typically it is possible to exchange head units of the same family, e.g., a DIN size Midline Cassette is a straight plug-in in place of a DIN size Midline AM/FM. A DIN size Premium CDR is a plug-in for a DIN size Premium Cassette. Upgrading to the next "level" of
system, i.e., from "Midline" to "Premium", or from "Premium" to "Audiophile" is more complicated, and usually requires adding additional amplifiers and wiring. This can get rather expensive and time-consuming, as most of the factory wiring is integrated instead of done in over-lays.
From 1998 on, it IS possible to upgrade from a Midline Cassette or a Midline CD to a Premium Dual Media radio or the Premium 6CD radio without having to change or add wiring. The Dual Media radios and the 6CD radios are available in both "Premium" and "Audiophile" levels. The Premium models can be used for upgrading, the Audiophile models should only be used with the factory
subwoofered system (their output is equalized for a subwoofered system, and will not sound right in a system without one).
Door Panel Removal:
For both front and back door panels , make sure you unscrew the two screws under the handle and one near side view mirror. Next you'll need to pop off the black trim piece surrounding the pull handle, you should see a place to stick a flat head screw driver and just pop it off. Now the tricky part, some people will say you need a special tool to do this but I never have needed it. There are about 8-9 little plastic trim clip that hold the plastic panel to the door. You'll need a flat head screw driver, slide it between the plastic and metal, I usually start at the bottom. Feel around till you find the first black clip and carefully pry the panel back. Do this for each clip. On the Driver side some models have a control module you need to remove this using its clip. Remove the light from the light housing (if so equipped). Remove Power window trim and/or buttons. Then Door panel is ready to be removed slide door panel up then away. To put the door back on, simply reverse this process. Once you do it once, its really simple.
Head Unit removal:
Open up the dash. Pull out the ash tray, push down on the clip above the tray to fully take it out. Let it hang. Use the ratchet set to remove the two small screws on the side of the ash tray holder assembly. Pull that out. Now, gently, but firmly, start pulling the face assembly away. It might be easier if you put the steering wheel in a lowered position, as well as the shifter, if it's automatic. Make your way around the whole dash, watch for wire connections, such as maybe an alarm LED, and if you have 4x4, the 4x4 button cluster (disconnect this with the help of the screwdrivier). Hardest part will be getting this whole dash face over the steering wheel column. Use the "keys" (you can buy the head unit keys at your local Wal-mart) to get out the old radio. Replace trim in reverse order.