Doom878

I have an Alpine head unit, RF amp, and an RF 12" sub in a ported box since 2001. As many years as I can remember, anytime I played music for more than like 70 minutes depending on how bass heavy it is, the amp would get too hot and turn off the sub to cool down. I kind of lived with it figuring it was the limited quality of my amp. However yesterday driving home in the heat, instead of temporary killing it, the bass now comes out distorted and sound totally awful as if it were rattling. It never stops doing this and even this morning after cooling down overnight it still happens. This applies to all inputs (Aux, CD, FM). Is this that the amp finally went bad? Sub blew?

fliplyricist1

sounds like your amp has been clipping and sending a clipped signal to your sub (which basically kills a sub over time)

My best guess is that your one of both of your sub coils is damaged...and your amp simply either doesnt have the juice or thermal ability to keep up. Either that or you had your amp gain turned up too high all this time when is not a good thing. Kill two birds with one stone and replace both. This time get an amp that has good active thermal cooling on-board...and make sure you install it in a place with plenty of ventillation on all sides...maybe even install an external pc fan if your area is very hot/humid. And make sure you set your gains correctly...the higher the gain is not always better...you have to match your levels properly to attain the correct, clean power distribution.

Doom878

Thanks for the reply. My friend had set the gain so I will check that out after work. Just to clarify the noise I hear, it's not so much rattling. It sounds like your hitting a bongo drum as it is very annoying. For now I set my HP rating (not sure what that means) from Off to 180hz and the bass is severely decreased. Does that change anything or is it still likely the sub coils? Also, my friend has another sub that I could test. Can I turn down the gain on my amp (if it was up) and use his (assuming it sounds normal). I don't want to mess up his sub but he's not using it for a few months.

fliplyricist1

it's really hard to tell if I'm not there. but typically if the sub 'just doesn't sound right' usually that means there's a problem with the coils or something separated. HP rating...is that on your amplifier or your headunit? The only thing I can think of for HP is your highpass filter...but that wouldn't make much sense for your subwoofer. If it is indeed a crossover, then you now have your subwoofer tuned to play up to 180hz, which should theoretically make it louder since it's playing more tunes.

If hp is for the phase, then switching the phase could definitely have caused a huge decrease in output, as it would put the sub out of its optimal phase.

if you really want to test if the sub is damaged, play a continuous sine wave signal at about 45hz ...it'll make it obvious if it is blown.

you can download 45hz sine tones by doing a search accordingly on google

good luck

Doom878

I have an Alpine CDA 7863 and that's where I adjusted the HP. It's always been like that where if I were to turn it on that it would significantly lower the bass.

fliplyricist1

sounds like you have your subwoofer rca cables mixed up with your front or rear crossovers on your headunit

hp should be your highpass crossover...your subs crossover should be controlled by a seperate subwoofer crossover or the lp (lowpass) crossover...the hp shouldn't affect your sub (only your front stage speakers) if your installation is correct

no biggie...but play a 45hz sine wave if you really want to find out.