problem with subs or amp

[fearless_gamer]

Hello everyone, i seem to have a problem with my stereo lately, it will hit hard but then sometimes it will get softer for a min or two, then hit hard again, it will repeat this constantly, but sometimes it doesnt do it..i thought maybe a loose wire but i took it all out of my car and checked everything and reinstalled it and it stopped for a few days but now is back. I was wondering if anyone would be able to point me in the right direction. Any help would be greatly appreciated, thanks in advance.

[ppia600]

What subs, what amp.... what headunit?? How are the subs wired to the amp? Etc...

[fearless_gamer]

sry, i always forget that part...Sony xplode hu (forgot what model, but older) 2 koiiler 12" 1000watt 4Ohm DVC wired for 4Ohms on gspot 1004t amp bridged.. only using one channel, it is a 4 channel amp, 4Ohm min. bridged, 2Ohm min. stereo.

[ppia600]

So are the coils of the woofers connected in series on the woofer and then paralled at the amp? I would definately bridge the two rear channels of the amp to 4 ohms to max the amp out at least. Do you have a multimeter to check a few things?

-Turn off the amp and read the ohm load at the amp where the woofers are connected
-Make sure the amps power ground wire is solid and clean directly to the cars body.. not to a seat bolt.
-Disconnect the rca's at the amp and read from the ground side of the rca cable (the outside part) to the frame of the car, it should not be over about two ohms.

[fearless_gamer]

i do believe its wired series at the coils (+ to - then + to amp - to amp), then parellel at the amp.. i dont have a multimeter on hand right now but i could get one tomorrow, has good ground to body, cleaned off all the paint til bare metal then bolted it on.

[ppia600]

You could have amplifier output transistor problems, a bad solder connection on the amp board or even a shorted coil on one of the woofers. A couple more things to add to the last checks:

-Make sure the fuse under the hood isn't intermittently opening up. Sometimes they can get so hot one end will melt away from the connector inside the fuse and disconnect power temporarily. The fuse will still look good in the middle but be disconnected on the end under the metal shell where you can't see.
-Make sure the connections to the woofers inside the box aren't loose or touching eachother in any way

This is something you can do that won't hurt anything, is cheap, and will protect the amp and the cd player's rca circuit: Buy a ground loop isolator and install it behind the cd player between the rca's going to the amp. 1- it will prevent any ground loop issues and also keep the amp from drawing power through the rca cables and frying the deck's internal rca grounds. 2-If you install this ground loop isolator and there is suddenly no sound from the amp: You either have a bad rca ground inside the radio, fried rca cable grounds, or cracked ground connection inside the amp where the ground wire connection is soldered.

Let us know what you get

[fearless_gamer]

Ok thanks alot for the help, i will try out the list you gave me tomorow, and i will let you kno my findings. gotta go for now.

[Perry Babin]

If you're only using one channel for bass, move the woofers to a different channel.

If you had it bridged and had two input signals, it would lead me to think that one signal line was dropping out. If you're only using one channel, this doesn't apply.

On some amplifiers, if the shield ground is broken, the output will drop and/or become distorted. This is generally due to an intermittent connection in the RCA cable's shield ground. It can also happen if the shield ground in the head unit is faulty (broken solder connections).

[fearless_gamer]

well i finally got to check the amp with the multimeter and with the amp off and at the speaker output terminals read 0 ohms and the rca cables read about 0.5 ohms, i switched the subs to the other channel and it sorta fixed it but now i have feedback from the cd player through the subs... i rechecked all the positive and negetive connections and they are all good..

[BDiddy1054]

I have a sub in a custom box that is shutting my amp off due to it being to the magnet being to close to the bottom of the box and not allowing the air to spread through the box, instead it is just shooting right back up towards the speaker, and it cant handle it, therefor shutting of my amp. this is according to the car audio place i take it too. They told me i could try polyfill to fool the speaker but i am trying to sell the speaker and get one of the new shallow subs, any suggestions?