Hooking up amp with speaker level imputs

Here's the deal, I helped a friend install an MTX 4202 amp and MTX Thunderform in his SS last night. He has the factory Monsoon HU, so we just tapped into the speakers in the rear to pick up the high level imputs to connect to the speaker level imputs on his amp. I know, it's better to use a LOC like a PAC OEM, but this should have worked, shouldn't it? The amp has power, but the sub just barely moves, like it isn't getting any juice.

The only things I can think of are
1. Its a 2 channel amp that we bridged, so maybe we weren't supposed to tap into both the left and right rear speakers to connect to the speaker level imputs, or maybe those are supposed to be "bridged" also like the output to the sub.

2. The signal carried in the speaker wires doesn't work with the speaker level imputs on the amp and we need a LOC

3. The amp isn't working. It's a refurbished unit he bought from souddomain.


Current setup. Hope this makes sense.


L Speaker R Speaker
[ ] [ ]
+ - + -
| | | |
| | | |
| |____________-_____ _____-____________| |
|______________+___ | | ____+______________|
| | | |
|Speaker Level Imput|
| Jack on Amp |
| |
| |
| |
+ - - +
| |
| |
| |
[sub]
/___\

Well, the image I made didn't work too well because it left-justified everything. Hope you get the idea at least.

The wires you tapped into are probably being hi-passed. Try tapping the wires BEFORE the POS Monsoon amp or right behind the HU.

I never thought about that possibility. I'll have to try that tonight and see what happens.

If the amp has speaker level inputs, don't worry about an LOC. In most cases the speaker level inputs will work just fine as long as you have okay to good equipment that you are running.

I helped a friend put a sub and amp into his SS the other night and we tapped off of the the rear speakers to get a signal and it works and sounds just fine.

Make sure you have the crossover set correctly on the amp also.

The inputs wouldn't really make a difference here for when the amp is bridged it's mostly a difference on the output stage of the amp that is different. On some amps they have a bridged switch but that just means that you can use just one of the RCA inputs for an input and it feeds both channels of the amp with that one input. So, like I said, the inputs shouldn't make a difference here.

Like you said, it may be a bad amp, maybe see if you can hook it up in a different car maybe and see if it works to test it out.

HTH!

Ted

Turns out the amp was fine, and it appears that the wires we tapped into were high passed. Tapped in before the monsoon amp and it works great now. Thanks for the advice.