Okay, so I recently bought a 98 Mustang GT 'vert with Mach460 but it already had an aftermarket deck installed. Sound was only coming out of the 4 tweeters. Ugh. So after tons of research on here and online, I saw that you need a new Metra harness with pre-outs to feed the amps and also the amp turn on wire needed to be connected to wake up the rear amps. Well, I ordered the harness and it didn't work, I even ordered a 12V to 5V reducer but neither worked. So, either my amps were smoked or ???
Here's what I ended up doing instead. I replaced the stock rear 6-1/2" woofer with a pair of JVC coaxials. I ran some 18/4 wire to the rear that I spliced into the rear speaker leads of the aftermarket deck. That got me rear sound in full range. So onto the front. I found out that the leads (gray plug) that feed the front tweeters send a full range signal from the aftermarket deck so after removing the front woofer and unplugging the tweeter lead, I used the tweeter lead and the cheap gray adapters by Metra to install new 5x7/6x8 MB Quart coaxials in the doors.
So now I have full range sound in front and rear with much improved highs and lows. I was able to sell the stock woofers on eBay for more than it cost me to buy 2 sets of coaxials and the speaker adapter harnesses from Amazon. What a win-win!
Here's what I ended up doing instead. I replaced the stock rear 6-1/2" woofer with a pair of JVC coaxials. I ran some 18/4 wire to the rear that I spliced into the rear speaker leads of the aftermarket deck. That got me rear sound in full range. So onto the front. I found out that the leads (gray plug) that feed the front tweeters send a full range signal from the aftermarket deck so after removing the front woofer and unplugging the tweeter lead, I used the tweeter lead and the cheap gray adapters by Metra to install new 5x7/6x8 MB Quart coaxials in the doors.
So now I have full range sound in front and rear with much improved highs and lows. I was able to sell the stock woofers on eBay for more than it cost me to buy 2 sets of coaxials and the speaker adapter harnesses from Amazon. What a win-win!