I'm attempting to wire a 2ch amp bridged into a single 10. I can't get any volume to the sub, which may be a goo dthing as I've (from the way it sounds) missed something. The sub rattles even at low volume (no it's not blown, yet...) I've checked and it doesn't look like I've wired anything backwards, but I'll check again when it stops raining. Any pointers? Do I wire differently for bridged mode outside thje speaker connection?

 

Did you miss the switch on the amp for bridged mode if there is one?

Sometimes you have to run mono rca's into left & right out of your crossover. Each channel in the amp needs to receive the same signal because in bridged mode, basically one channel is "pulling" the speaker while the other channel is "pushing" the speaker... ie. double the force applied to it.

Every amp is different. Best to look in the instruction manual. If you don't have one try emailing the manufacturer, they may have a pdf format copy.

Good luck.

 

Give us some more info. amp, sub, and anything else

 

I'm using a Boss Rev-455 Amp with a Boss Sub104 10" connected via high level input to the factory HU. I also tried the high level inputs connected to the stereo in my other truck (while still powered by the F-150). At this point I wondering if my ground is adequate since I got the same results using known good input signal. I also dropped the amp out of bridged mode and tried a single channel, same result. I also tried another sub and got similar results. This afternoon, I plan to use a separate battery and use short power/ground cable directly to the battery to test. I'ma t a loss on this one and grasping at straws.

 

Well, I've solved half the problem. It looks like my Ground cable was inadequate. I have fixed this and the amp performs much better. Now I seem to have a problem with the input. Can I run the Hi-level inputs AND a pair of speakers off the rear channel of my factory HU? Wire in Parallel or Serial? With the amp hooked up, if I turn the key off/on I loose sound from the radio. If I unhook the High levels on the amp, the HU flows sound again.

 

Usually you can run rear speakers parallel to high level inputs on amplifiers but it depends a great deal on what the input impedance (resistance) is on the high level input. If it is low like a speaker (doubtful) then your total impedance load on your HU will be too low and may overheat and ruin it's built-in amplifier.

I always run a dedicated ground cable same size as the power cable, in my case 4 gauge straight from the battery. The ground OE ground straps on most vehicles between the body/frame and again frame/battery aren't that great.

Theoretically you should be able to run a wire from each rear speaker as if installing an extra speaker but hook it to your high level amp input. If you say this kills the sound from the HU then definitely don't connect it in this fashion. Sometimes factory HU's won't run dedicated + and - outputs to each speaker (keep in mind music is AC electricity and the (+) & (-) refers to the phase), rather they may use the chassis of the vehicle for (-) or combine the (-) inputs from both front and rear speakers.

Bottom line is getting good sound (ie 20hz low bass) and high fidelity from a factory HU without ground loop noise, etc is difficult at best. You're better to spend $200 and get a decent single cd deck.

You may be able to find an isolation transformer where one side connects to your rear speaker, the other side to your high level inputs. This way the amp is isolated from the rest of the OE system. Sound quality can suffer though. Talk to someone in a car audio shop.

Good luck.

 

Ok, just in case anyone else has this problem down the road, I just got in from installing a Scoche FEI-3 4 channel line out converter ($17 at Wal-mart). 5 wires in, 4 RCA out and my amp now hits like it should. Seems like I may have either been hooking the amp up wrong, or it couldn't handle the output of the HU.