If Your running your subs in "parallel" then the combined wattage is nearly double of your amplifier...
So why do homeless men steal copper wire? I suppose thats another post(I'm a homeless man).
What you really need to do is check your hed unit wattage most are rms 30 x 4 or 35 x 2-, etc
A fuse doesnt have to blow to break- Electronics are designed to shut off without blowing the fuse but most times you do blow one... Is the amp only powering the subs? Serial or parallel?
The weakest amp can still run two subs but your currently pumping too much wattage for what you have and something is throwing a trigger-
Maybe you have a short? Maybe you have it wired for little effenciency-- If it works now, most things are right, and very few can be wrong- I mean electricity is pretty simple- Open end closed end works/doesn't. I prefer running 2 subs with an amp a cap and a distribution block to even out the hed unit but you really need to expand the details if you want any kind of open end discussion on professional help- As with wiring and electronics, there are miles of cable in a car and if you ask any mechanic for electrical troubleshooting on a sunday you will most likely get the middle finger...
I don't know much but what I do know is that I don't know much of what I know ;)...
Former Car Mechanic- Former United States Marine- And I still, somewhere, have that union electrician card in my wallet that says I'm on a paid triple time smoke break, son, gl ;)...
You mentioned RMS which is a general rule of "average" peak output but your peak has to fly around 12 to 15 hundred- That most likely is pounding your amp 6 feet under- See music is written in decibels and music and base can control when the sub "punches". Ive seen this problem with my own subs when I ran a **** *** legacy 1200 watt and two 12" fosgate punchers...
The amp can't take it the subs are the beast and you still have them locked up- The amp aint the beast... Don't be misguided...
Furthermore- A car battery does nothing but supply amps to start the car- Once the car is running, you don't even need a battery- And if you really wanted to, you can pull the positive wire from the battery, while started, and it will continue to run from indiana to california-
I mean you don't find batteries on dirt bikes ;) you find a magneto to generate a spark ;)...
Gas engines run as long as you feed them... Batteries are needed most for power windows, power locks, and power for your subs when your not driving... Not only will a bigger battery not fit in your very small allocated space designed by scientists, but you will just be wasting your money on something that has nothing to do with sound audio or your radio. The capisitor is designed for stored energy which it receives while the car is running, thanks to the alternator(wind turbine example) A capasitor takes the load off the amp when running Peak wattage, and nothing more- Perfect design...
Lets hope you didn't take this to some dumbass that works at best buy... It is best to do these things yourself so you can ask your own questions and discover your own answers by mans best trial and error- As there is little you can do to permantly fvk up your car per say- Unless you mix match pos neg battery terms or touch metal to both at the same time- Then again, most cars have at least 50 fuses...
Now see, steve brings up a few valid at best remarks but obvious is the only thing stated- If you run a amp that is designed to handle 1400 and your giving it 600 of course you will destroy the subs- But this was never asked- He specifically stated his subs are well above the ampherage tolerance
You don't need 00 15x mega thick size 13 steel toe wire to ground a damn sub box with a amp man...
You just dont... You ground wire is a 4 to 6 guage thick *** red beam that goes directly to the battery with a humongous fuse- There is absolutely no reason to change that
Or your battery- I really don't understand why people think battery and guage wire as the first solution to a problem about an amp giving out when you crank up the volume in a car...
you can go 1/2 as thick on your current guage wire now and still not have a problem- Thick wire is a fail safe to protect coporate liability.
I have to go on because I have done this for a living... If you have 1 sub connected to another sub which is then connected to the amp your running too much for your amp
Take one sub run it directly to one channel- and take the other sub and run it to the second channel and your problems will disappear- but you lost 1/2 your power till you get a better amp...