PA D5000.5 Intermittent Distortion and Popping protection.

Hi,
I have mm6501's in front and mm651's in the rear, running 2 mm840 subs. I initially had the subs wired for 4ohm and then decided to rewire to 1ohm. The issue I've been having is the amp seems to pop protection at lower volumes than I found to be the max these subs can handle. It's intermittent, one day they can reach louder volumes fine. I also been noticing that sometimes the whole system will sound muddy and I'll notice distortion at even lower volume. I'm not sure if I'm looking at a faulty amp or not. I've been also thinking that I need check and see how much voltage the amp is getting when this is happening.
My wiring is pretty good, the ground and power are both 4 gauge and the ground measured low resistance.
Any other things that are worth checking out?

What's your gain set to? Sounds like you're overdriving your amp. The noise sounds like a bad ground.

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Originally Posted by MacLeod

What's your gain set to? Sounds like you're overdriving your amp. The noise sounds like a bad ground.

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I set the gain on the subs by turning up the gain until I heard distortion and then backed off a 1/4 turn, the gain is probably around 3/4 or less. That was with the deck turned up to around 3/4 volume, then I set the door speakers. Thing is if I was overworking the amp I would expect it to be hot, seems like it happens more when I first start driving. I can turn it up to where I set the max volume sometimes, other times it will pop before that. The ground should be pretty good I tested resistance before I laid the carpet back, it was fraction of a ohm.
It also almost sounds like the volume is fluctuating, like it gets lower. This has been happening with the lower volumes.

Yeah you're gain is WAY too high. Really shouldn't be higher than halfway. Back it down to a little below half and see what that does.

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Originally Posted by MacLeod

Yeah you're gain is WAY too high. Really shouldn't be higher than halfway. Back it down to a little below half and see what that does.

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Yep that fixed it, seemed like the subs were pretty mellow with it that high. After backing the door speakers off more to match the subs sound alot better and have alot more volume.
Thanks for your help.

Cool. Glad that did the trick.

Well protection hit a couple times on my drive last night. I go for a drive it starts acting up, it wont go near the same volumes without protection tripping. Maybe I'm asking to much from the amp or voltage could be dropping low and causing it to trip maybe? I'm gonna check if the battery is holding much of a charge, I checked power at the amp and it was steady 13.9 while playing.

Try hooking up only 1 sub so youre running 2 ohms and see if this fixes the problem. If it does and your power and ground wires are proper then you might have a bad amp and should contract Polk CS. These amps are rated at 1 ohms on the sub channel but it may still be too much load for this one.

Quote:

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Originally Posted by MacLeod

Try hooking up only 1 sub so youre running 2 ohms and see if this fixes the problem. If it does and your power and ground wires are proper then you might have a bad amp and should contract Polk CS. These amps are rated at 1 ohms on the sub channel but it may still be too much load for this one.

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Well I never had a issue with protection when I was running the pair at 4 ohm, though they were kinda lethargic . I guess before I call it the amp I should pull the subs and double check that I don't have any stray strands grounding. Not sure what else I can check, maybe the resistance on the voice coils (see if one of them vary).
I also just realized a mistake I made, the wiring going to the subs is way to small...That could be the issue. I thought with such a short run I didn't need much but I keep hearing 12 or even 10 gauge for 500 rms.

No. That size wire is fine. Unless you're running it 300', 16 gauge or better is fine.

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Originally Posted by MacLeod

No. That size wire is fine. Unless you're running it 300', 16 gauge or better is fine.

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I'm running 16 gauge, I bought some thicker gauge since i pulling the subs anyhow (removing that many screws is a chore). I wanted to pull the wiring that was in the box it looked like it had gotten wet and looked like it corroded on the outside strands (i cut it back pretty far and still it looked sorta dusty on the outside strands). I've been recreating when it trips and it sounds like one of the subs is going first (popping or shorting type sound). Hopefully the sub that I suspect shows a weird resistance reading on one of the voice coils. Not sure why it's intermittent, one day they shake the mirrors next day they don't even get close without hitting protection ( usually though when i turn them up cold it seems to happen).