Car Stereos: amp install, farad cap, kicker l7

Question
i have dual kicker L7, they are 3000 watt subs, so i got two kicker 1500.1 amps to power them, i need help bridging them because there is only one terminal on the side of the sub box. i connected the amps: positive to negative and then positive form one amp to positive on the box and then negative on the other amp to negative on the box. what happens is one stays powered up and the other one turns on and turns back off, and keeps repeating that. when i tried to power the amps separately they stayed powered, so i know that they both work properly. i also have a 5 farad cap on the power line. i also have a kicker 850.4 amp that i would like to install to power the 4 car speakers once i am done with this problem.

Answer
Hi Joey,

You should never try to "bridge" two amplifiers together unless they're specifically designed for that function.  The ZX1500.1 amplifier isn't made to be used this way.  If you want to use two amplifiers to power the subs, you'll need to add another terminal so that each amplifier can be connected to one terminal.  However, I'm not sure you have the right amp/sub combination for that type of setup.

The subwoofer package might be rated for 3000 watts peak, but that's not a number you should be paying any attention to.  12" L7's have an RMS rating of 750 watts each, so the RMS power handling of the sub box is 1500 watts.  When you're matching sub power with amplifier power, you should always look at RMS ratings and ignore peak ratings.

The next thing you need to know is the impedance of the subwoofer system.  If the box and subs were sold as a package (most likely, if there's only one terminal set) then the owner's manual should tell you the final impedance of the system.  If you don't have the owner's manual, but you know the model number of the subwoofer system, the last number should be the impedance.  For example, the 08DS12L72 is a 2-ohm system.  If you don't have the owner's manual and don't know the model number, then you'll need an ohmmeter to determine the impedance.  Measure the resistance between the two terminals.  A 2-ohm package will probably show a resistance around 1.5 ohms; a 4-ohm package will probably show a resistance around 3.5 ohms.

If you have a 2-ohm subwoofer package, then a single ZX1500.1 would be perfect to power it, because the amplifier is rated for 1500 watts at 2 ohms.  That matches the RMS power handling of both subwoofers together.  

If the sub box is 4-ohm, things become a little trickier.  You could still power the box with a single ZX1500.1, but you'd only get 750 watts.  The fact is, that might be enough for your needs.  The difference in sound between 750 watts and 1500 watts isn't as much as you might think.  I suspect, however, that you're hoping to get as much output from the subs as possible.  In that case, you have three options:

1) Add another terminal to the subwoofer box, and power each subwoofer with an amplifier rated for 750 watts at 2 ohms, such as a ZX750.1.  You'll have to re-wire the sub voice coils in parallel, so that each sub becomes a 2-ohm load.  

2) Find an amplifier rated at or near 1500 watts at 4 ohms.  In Kicker's lineup, the ZX2500.1 comes closest, with a rating of 1250 watts at 4 ohms.  

3)  Re-wire the subs so that the final impedance comes to 1 ohm instead of 4 ohms.  Find an amplifier rated for around 1500 watts at 1 ohm.  Kicker doesn't currently make any amplifiers for a 1-ohm load (except the Warhorse, which is far too much power for your application, as well as hideously expensive).

Hope this helps!

Brian