Amplifier(?) help

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Streetz
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I'm actually unsure if it's the amp, headunit or subwoofers...

I recently just installed a new subwoofer setup (2 RF P3D412, a Profile AP2000 amplifier and a custom vent box). For about a week everything worked fine, than the subwoofers have a constant humming sound coming out of them. When the music is up loud and deep bass hits the subwoofers make a horrible distortion sound. I don't really know how to describe it other then it's not right and is freaking me out. When that happens all the lights inside and outside dim. I've tried different RCA cables and moving the ground to a new place (had to move it anyways). The amp is pushing about 75-80% (350-400w x 2) even though the subwoofers are able to handle full load.

The humming is constant and will get louder or softer if I change the output of the amplifier. It's not real loud, just enough to be annoying if I have music muted or paused. Also I noticed yesterday it only happens when playing a CD, didn't hum when switched to radio. When I unplug the RCA cables the humming stops. When I disable the subwoofer output via headunit, the humming still continues which leads me to believe it's not the HU. Last thing is when I turn on the car a popping noise comes from the subwoofers for a brief second.

I have an old Pioneer headunit that needs to be replaced soon because it's been acting up for a while now, but with the joly season coming up, money is short and would like to wait until next year if at all possible.

I'm not sure where to start with the problem, or what could be causing it. I checked the subwoofer wiring, everything's hooked correctly. I thought maybe I need a cap or do "the big 4" which I haven't done yet, or the headunit. I'm thinking power is the issue and a cap is needed. I'm praying it's not the new amp or subs though. Any help is greatly appreciated, so thanks in advance for any help! //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 
sounds like you have several problems, making it hard to diagnose. If all the lights are dimming with the bass then your electrical system is not keeping up, may be as simple as a poor ground or too small of a power cable going to the amps, or a loose power wire connection. If you disconnect the RCA's at the amp and the humming goes away but disconnect them at headunit and the humming is still there then it's coming from the RCA cables, or more accurately, where the RCA's are run - you obviously have them close to a noisy spot somewhere. The popping noise is probably from the same source as the hum.

As for the odd sound in the subs, you have to do some substitutions. Try using a different sub box, then a different amp, etc .. until you figure out which one is the offender.

 
Thanks for your reply...

The ground is very good, moved to a new spot at the bottom of my trunk. Used sandpaper and got all the paint off, good connection there. Both ground and positive wires are 4 gauge, biggest the amp can take, so maybe a cap is needed.

When I tried a second set of RCAs, they weren't ran through the car. Since it was for testing purposes, I had plugged them in the CD player out the door and straight to the trunk and amplifier so it can't be the way the current ones are run.

This box is brand new and made per the subwoofers' specs. I thought maybe it was the box I had them in before (from my old system) so went out and got a new one made, same thing so that rules out the box. Guess I'll try and get my amp tested this week.

For substituting the subs, I assumed since they BOTH did it and at the exact same time it wasn't them. I can take one from my previous setup and see if it does it as well to be sure it's not the subs. If it's not, then I guess everything just points to my amplifier //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

EDIT ADDED: I forgot to mention that the distortion sounds happen every 2 or 3 times from the deep bass notes. Example, playing a song, same beat throughout it. Deep bass for 1 second every 4 seconds. The distortion will happen every other time, or 3 times. This is why I thought maybe it was the box, bad circulation. But I'll still get my amp tested and a cap purchased.

 
hmm I had a similar problem with my subs sort of humming or pulsing. Turns out I had 2 sets of RCA's jumped together, and where they were connected the metal connector was touching the metal of the car...creating what I believe was a ground loop. Try to isolate things. Take one thing out at a time and when the problem stops, you've found your bad component.

 
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Streetz

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