Subs are breathing

My brother in law has a small Alpine amp running a pair of JL 10's in a sealed box. I haven't seen the back of the subs but am guessing that they are W0"s series. The problem is that he just added the second sub and everything sounded like crap when he brought it to me. I found his gain on max, bass boost at max(+12db), and his low pass set to 50hz. I turned the gain to zero and turned the bass boost off completly. I set his crossover to around 130-140hz range and had him turn the radio up to where he normally listen to it and brought up the gain until it started to distort and then backed it off. He loved how it sounded until he drove around for a couple of hours and the amp was getting really hot. Now he says the subs look as if they are breathing since the amp shut off and no music is coming from them. My guess is that the amp overheated and went into protection. Could it be something else like a current problem since the subs are pushing out and slowing going back in? I haven't talked to him since he called me to tell me all this. I told him to turn it all off and let the amp cool and see if that helps. Anybody??Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

When he calls me back I'll get the model numbers of the amp and subs. Also he has the amp under the seats of his 2000 Ranger. Thanks guys in advance.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

He added the second sub.  Did you by chance check the wiring?Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

I checked it when I was changing his settings. he had it right since i reversed the leads and there was almost no output from the subs even though they were moving. I haven't seen it in person since he has had this new problem.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

I just talked to him and he said when he let cool over night and started it up this morning smoke started coming out of the amp so he just turned it all off. he looked at his connections and none were touching anything that they weren't supposed to. He is checking on the model numbers and calling me back.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

Impedence load is too low is my bet.  Good call on resetting the gain!!Support the12volt.com

I've tried to figure out the amp's model #, but can't find the exact one. I remember it saying that it is a mono amp but it has 2 sets of mono outputs. I thought it may be a MRP-M200, but it may be older than that. Once I get the model #'s for the amp and subs I should be able to see if the impedence is the problem like DYohn suggested.Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"

i bet it was the MRV-M100 , its only stable to 4 ohm on each channel, so if he was driving a lower impedance, , then thats his prob.2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.

From what I remember him saying, I think his subs are W0's which are 4ohm, right? Alpine Guy, is that 4 ohm on each output or 4 ohm's overall for the amp?Pioneer DEH-P980BT, Zapco DCREF1000.4,Pioneer TS-C520PRS, Adire Extremis, MTX TA91002, TC Sounds TC-3000 15"