This problem sounds very familiar
i think the same thing was happening to someone's sub, my friend installed. Since i didn't do the install myself, i couldn't really tell you how everything was run. but if i remember correctly the sub blew after like 15 min of troubleshooting, and i dont' think we ever resolved the problem. but i'll try and remember if we did figure it out (but it was probably a good 4 or 5 years ago)
if you believe the first sub blew from similar problems, then it is probably a problem with the amp (clipping as GSteg stated).
but since you said it only started with the new sub, i'm thinking it might be a defective sub? (which doesn't make much sense in my mind, but you never know)
i would just try single out the problem. try using a different sub, to see if the problem remains, try using a different amp, and see if that is the problem. and even try maybe using a portable cd player or something, and get the RCA signal from a different source.
i think the same thing was happening to someone's sub, my friend installed. Since i didn't do the install myself, i couldn't really tell you how everything was run. but if i remember correctly the sub blew after like 15 min of troubleshooting, and i dont' think we ever resolved the problem. but i'll try and remember if we did figure it out (but it was probably a good 4 or 5 years ago)
if you believe the first sub blew from similar problems, then it is probably a problem with the amp (clipping as GSteg stated).
but since you said it only started with the new sub, i'm thinking it might be a defective sub? (which doesn't make much sense in my mind, but you never know)
i would just try single out the problem. try using a different sub, to see if the problem remains, try using a different amp, and see if that is the problem. and even try maybe using a portable cd player or something, and get the RCA signal from a different source.
