Add Aftermarket Subwoofer Amp to OEM MACH Test your Mach audio knowledge!

[thorney_5]

This isnt really an explorer question, but I believe the Mach audio system between explorer/expedition is the same. Besides, how could I not ask the extremely helpful and knowledgeable member base here before I go join another lesser forum??

I am installing an aftermarket amplifier/subwoofer into a 1999 ford expedition with mach audio. Through experimenting, I discovered that the head unit will not send the low (below 150 hz) signal to the rear of the truck without the factory amp plugged in. The pins on the amp connector include: power, ground, sub +/-, and high audio mute. I suspect the amp grounds or provides power to this "high audio mute" wire to tell the HU it's plugged in. I don't want to fry the head unit trying to ground this wire, I'd like to be sure. All I need is a low(hz) signal through the stock sub+/- wires to signal the new amplifier, as opposed to getting the signal off one of the rear speakers, which would only give me a filtered signal (high pass).

Does anyone have any insight on this? A very specific problem, and a very specific situation, so ive found no use in searching.

Help is much appreciated!

 

[DjDom]

If you're installing an aftermarket sub and amp, just use a crossover tapped into one of the door speaker wires. The amp should have it's own LPF (Low Pass Filter) and determine what to send to the sub.

Or, better yet, just get a new aftermarket head unit, it will sound MUCH better than the stock one. And some decent ones are pretty cheap now-a-days.
Pioneer head units can be around $60.

 

[thorney_5]

I would get a different head unit, but this is for a friend and he doesn't want one for whatever reason.

The amp has a low pass filter, but I'm worried that since the speakers are set at high pass through the head unit, the amp will have nothing to put through the subwoofer. In other words, the speakers 150hz and up range is above the highest low pass setting on the amplifier, if that makes any sense.

 

[DjDom]

That's odd. My stock headunit doesn't filter that.

The Mach system didn't come with a sub, did it?
The only reason for the speakers to have a HPF is if there is a subwoofer taking care of the lows. Otherwise, it shouldn't do that. Try cranking the bass on the headunit up. That should allow for the 40 hz range to pass through. And then use a crossover from a speaker.

 

[thorney_5]

No the stock system DID come with a sub. Sorry if I didn't make that clear in the first post. This is my entire issue. Getting the lows to the rear quarter panel where the stock sub was. When the stock amp is unplugged, the HU no longer sends the low signal to rear of the truck. My belief is that it "knows" this by some means through the 'high audio mute' wire.

 

[DjDom]

Try grounding that wire then. Nothing bad can really happen from grounding it, everything is fused..

 

[thorney_5]

Ok after a lot of tinkering, and a lot of listening to my friend complain about how long I was taking, I got it. The solution was not to ground the high audio mute wire. Turns out that is the ford equivelant of the remote turn on wire. (It was later used as just that, with a 5V relay, because Its a 5V signal) by some means that I still can't figure out, the system can determine when the power, ground, and signal(high audio mute) wires are connected. I speculate the head unit is capable of seeing the resistance or amp draw across the circuits. All I needed to do was extend the power and ground wires and piggy back them on to the new 4 gauge wire.

The high audio mute wire was hooked to the feed of a 5 volt coil relay, and the switched relay circuit was connected to accy./key on power to control the amplifiers remote turn on circuit. As soon as I performed the first test with a line output converter and the stock subwoofer wires, the new subwoofer came to life, much to the pleasure of my now grateful friend.

 

[DjDom]

Good to hear that it all worked out.
I was also curious as to why there was a 'high audio mute' wire. I've never seen a Ford head unit with that, but I thought it might have been an Expedition thing.

Anyway, a blue wire travelling from the head unit, 90% of the time is a remote turn on wire. Some are 12v, some are 5v. My ex uses a 12v turn on, so it just comes to show how a different model truck can be wired completely different..

 

[Turdle]

Just what I was looking for. I think. A wiring diagram would really help me here-

@thorney_5 are you aware of a diagram?

I edited the thread title.

 

[Amp_man47]

Hello I figured the wiring out by searching for the sub Mp on my 2000 expedition. Anyway I unhooked the amp entirely and tapped into the low level signal coming through the head unit and hooked up an Alpine MRV-500 . Unhooking the sub amp didn't cause any issues. But it's too much power for the factory sub so I put 2 W10-D4 in a sealed enclosure. Sounds great I just use the bass setting to turn the bass down when I don't need a lot of bass. Sure sounds better that one of those $45 Chinese touch screen radio I put in and to it out. Yes the head unit has a separate output for the sub low pass. Haven't hooked my scope up to check the the frequency it's putting out ut some where around 100hz-110hz. Hope this helps anyone.