Help with strange amp install problem

[SRT8 10+ year member]

Hi, I have a Clarion CMD4 deck on my boat. It used to have two speakers hooked up to a Clarion 4 ch amp, two speakers powered by the deck, and the other two amp channels going to a sub. It sounded good. I then bought a Polk Audio pdx2000.2, bridged it to power the sub, and kept the 4 speakers powered by the amp. The amps are hooked up by 2 volt pre outs from the deck, the sub on the "non fadeable" one. Amp and deck settings are all correct.

Problem is, speakers sound good, but absolutely no output from the sub. With gain maxxed, you can barely feel the sub vibrating by touch. I hooked up this amp in my vehicle to test it, with the same amp settings, and it pounds!! I checked, and the amp is getting 12v power in on the boat. So what the heck is going on here, I'm at a total loss?!

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[mylows10 5,000+ posts]

Bad RCA or the setting on the deck are messed up some how

 

[keep_hope_alive Premium Member]

is the sub a dual voice coil? if you were powering the coils in stereo before, and now you've combined them at the amp, you need to ensure that polarity is not switched. that is the first thing i would check.

 

[SRT8 10+ year member]

No, svc alpine marine 10". I swapped rcas, even input signal with the front rcas vs the sub rcas to eliminate all those problems, still no output. Anything else?

 

[SRT8 10+ year member]

Someone suggested to me that when I took a V reading of 12V with the engine off, and it was putting next to no sound out, the amp is rated at 500W at 14.4V, and maybe that's why it was putting nothing out. Can anyone comment on that?

 

[mylows10 5,000+ posts]

no it should still be fine at 12 volts.has to be something going on with the deck or amp.possibly bad ground,but the amp should be grounded at the battery

 

[SRT8 10+ year member]

It's grounded right to the battery now. The amp worked in my vehicle when i installed it to test, and the other amp worked off the same set of pre outs, so its a real mystery!

 

[NT_Hardcore 10+ year member]

what is the ohm configuration of the sub on the boat and the sub in you car?

 

[SRT8 10+ year member]

Both are SVC 4 ohm. In car it's a Kicker Comp 10, in the boat it's an Alpine SWR-M100 4 ohm. I tried the Kicker sub off the boat amp with the same result, just barely vibrating.

 

[SRT8 10+ year member]

It works!! I re did the sub amp ground, turned the gain all the way down on the speaker amp, turned up the deck, set the sub gain, re-set the speaker amp gain. Now she pounds pretty good.

I think it was the amp ground that was the biggest problem.