Car Stereos: amp problem?, farad capacitor, ohm subs

Question
I have a Visonik v418xt 1000 watt amp, I've been running two 500 watt peak subs on it for 2 years, its been great.

I just replaced the subs with two JL Audio W3v3's. The amp still works, and the subs POUND, but in heavy bass loads (especially a lot of steady bassdrum beats), the amp's protection light comes on, and it stops running for a second, then starts again. I can't even get through a chorus of a song without it quitting periodically! Both subs are 4 ohms, and their wires join into one terminal in the box; They are connected to channel 3's positive terminal bridged with channel 4's negative. This setup used to work for me, why is it not working with these subs?

Do I just need a bigger amp? Will a 1 farad capacitor do the trick?

Answer
Hi Tyson,

Your amplifier requires a minimum impedance of 4 ohms when you're using it in "bridged" mode.  When you combine two 4-ohm subs in parallel, you end up with a 2-ohm load at the amplifier.  This results in the amplifier shutting down from over-current.  I'm guessing that your first set of subs were a different impedance, so they didn't cause a problem.

A capacitor definitely won't help you.  You don't necessarily need a bigger amplifier, but a mono amplifier that's stable with a 2-ohm load should fix the problem.  Alternately, you could install a second terminal block on the sub box, and connect the subs in 2-channel mode instead of bridged.  This would stop the amp from shutting down, but you'd only be sending 125 watts to each sub--acceptable, but well below their rated maximum power.

Hope this helps!

Brian