How to wire an aftermarket amp to subwoofer
 

I recently purchased a 2005 Mustang GT which came with a shaker 1000 system. The original radio and 4 amps in the trunk were replaced with aftermarket units. The amplifier going to the subwoofer in the trunk is not connected to the subwoofer. It is connected to the radio and has power. The amp is an Alpine MRP-M450 Mono subwoofer amplifier. There are only 2 wires coming from the amp (speaker output) to connect to the subwoofer. I was wondering how to connect it to the subwoofer since the subwoofer has two wire harness connections. Any assistance would be greatly appreciated.

Each speaker in the OE subwoofer has two voice coils. The Shaker1000 has
four amps for those, one for each coil. That amp only has one output, and
will not work correctly with all four voice coils. It's also a 4ohm amplifier, each
coil in each speaker is 4.6 ohms.

That amp is 400 watts x 1 at 2 ohm.

You will have to wire in series parallel to get all four coils working:
https://cimg8.ibsrv.net/gimg/mustang...35dcbfba4e.png

Each speaker represents a COIL. There are TWO speakers in the box, but each one has TWO COILS. This will bring the ohm load to
9.2 ohms. This will reduce the amps power output, which is fine, as each coil is only capable of 80 watts (78.5) at 4.6 ohm. It will
work.

If you wired all four coils in parallel, you're down to 1.15 ohm, the amp may shut down.

You can also only wire TWO coils, one from each speaker, in parallel for a 2.30 ohm load,
and this would be your best bet. The amp is 400 watts, which is too powerful for only two
speakers, so be careful if you go this route.

You will need a pin-out of the speaker inputs on the OE box... Don't have that on hand...

I would go back to the factory 4-amp rack, as low as $100 on eBay, if all the connectors
are still there.

Thanks for the information especially the diagram. I know little or nothing about car stereos, but I’m a DYI’er and like to figure things out. Could I assume from what you said that the factory 4-amp rack only powers the subwoofer and not the car speakers? I should mention that the car also has a second amp an Alpine MRP-F250 which I’m guessing connects to each of the 4 speakers. I’m not sure if that makes a difference with the subwoofer setup.

Instead of messing around with the wiring harness I was wondering if there is access to the subwoofer’s four voice coils? If so would I be able to follow your diagram and wire in series parallel all four coils and just leave the harness alone?

Thanks

The AMPS are for the subwoofers. OE: there are two up front for the door subs. There are
four in back for the trunk subs. OE: The 6x8 door and deck speakers are powered by the radio.

Have no idea what the Alpine amp is for, unless the 6x8s were replaced with better ones, and
those are amped. I will be amping my rear infinities. I replaced all my 6x8" speakers, and they
can take amps now, but I only need to do the deck speakers.

You could take the subwoofers out of the sub-box, and make your own input terminals,
install them in, through the housing.

I don’t know if the factory 4-amp rack or the subwoofer in the trunk work as they are not connected. In the next few weeks I plan on installing a new radio and then I can see if the factory connections for the 4-amp rack are still there and test to see if they work. If not I’ll see if I can connect the aftermarket amp to the sub.

Thanks for the info.