Subs cutting out
 

I just upgraded my my sub to a 500watt rockford and it is cutting out with my 450 Watt alpine amp. The sub is wired for 2ohms and the amp is stable at 2ohms.
When the truck is off i can put the head unit to about 20 before the the sub will cut out.
If the truck is started then i can put it to about 25 until the sub will cut out.

I Have no idea what this problem is caused by and would like your guy's opinions.

Also the Jewel on the amp is dimming when the sub hits and i am not sure if that is normal.

upgrade your power and ground wire

you have a shitty electrical. cant support the current draw, that's why the amp is cutting out. keeping doing this and the amp will break.

you need a better battery and better wiring for power/ground.

dont be stupid and waste money on a cap.

Ok well i went and braved the -25 weather outside after school today and ran a ground cable directly from my battery to the negative on the amp and it still cuts out the same. Now i figure that it would not be the power wire because when the truck is started I can turn it up much louder before it cuts out. (good chance that i am wrong) So that would leave it to too small of a battery when the truck is off and a not powerful enough alternator when the truck is on? (this is on a 2004 f250 so it should be a decent alternator)

Also when trying a bigger power wire could i just run two 4 gauge wires together rather then a 2gauge wire and accomplish the same goal?

Turn the gain down on your amp. To me it sounds like you are overdriving the input stage of the amp. The gain is not a volume control. If you have a 4 gauge power and ground it will be more than adequate. What is the head unit? Stock + lineout convertor or high level inputs on amp?

I have a http://www.kenwood.ca/Car_Entertainment/CD_Receivers/KDC-X794 with 4v preouts. My amp is a http://www.crutchfield.com/S-8AI1xE58ZMc/p_500MRPM450/Alpine-MRP-M450.html?tab=review that puts out 400 at 2ohms RMS. To get good volume out of the subs i have to turn up my gain to near max. Does that indicate that i need a bigger amp?

turn the gain down lol. if you want more bass get a bigger amp or more subs/better box. you gonna fry your amp like this in no time.

Ok i understand that i should turn down the amp but I would still like to find out what the issue is causing the amp to cut out at different volumes when the truck is on compared to when it is off.

Off, the battery is resting at 12 volts or less. With the truck running, the voltage comes up to 14.4 under normal conditions. More input voltage = more power output. It was not even close to -25 today dude.... brave the conditions.... turn the gain down. Put the sub into a proper box for the ideal results.

Made a box with its recommended dimensions and i will just have to turn the gain down until i get a new amp. And yes it was -25 outside this morning. I live up north in the country, not in Calgary like you do.