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Alright, here's the scoop.

My buddy and I installed a class D amp today along with a 12'' sub. Power to the amp is fine. (REM is installed correctly, ground is grounded and the connection to the battery is fine) and the amplifier light is green (indicating that the amp is working correctly)

Heres the problem...im using a 3000 watt amp to power the sub, and the subwoofer sounds like it's getting 50. I checked the settings on the amplifier and the gain is maxed. The fuses on the amplifier and by the battery are fine. I'm using 14 gauge speaker wire to connect the sub to the amp.

The sub is correctly connected to the sub (I didn't mix up +/-) otherwise it sound severely distorted. The sub sounds fine, it's just getting hardly any power. I double checked all the connections, even from the sub to the inside of the box. Everything is fine.


Thanks for your time!

 
Rep Power: 195

First of all, even if you mix up the positive and negative on the sub it will still play. It will just be out of phase with the speakers. It will pull in instead of pushing out so will cancel the bass of the other drivers.

14 gauge is way to small if it is an actual 3000 watt amp. (what single sub are you running that you need 3000 watts????

Do you know someone else that has a system that you could switch your sub into? That would be the easiest way to check the sub.

Kenny did a post on how to set an amp using a digital multimeter. That would be a good way to check the output of the amp.

 
Rep Power: 212

You're right on the mixing up the (+/-), my bad. I saw Kenny's post and ordered a digital multimeter last night. Should be in next week. I don't know what kind of single sub would need that kind of power, it's not my system. We did the installation behind the engineering building on campus (public safety gave us some pretty weird looks). Yeah, an engineering lab that doesn't have a digital multimeter, I know We don't know anyone who has a system we could swap the sub into. My car is back home because parent's won't let me bring it freshman year ()

I had a feeling 14 was way too small, but the problem is the wire isn't even getting hot. That's why I am confused.

 
Rep Power: 195

It may not get hot but when you really start pushing that kind of power through the wiring it will cause the amp to shut down. With a sub, you are pushing massive amounts of short bursts of current through the wiring. To show this, disconnect your sub amp and crank the system as loud as you can without distorting the speakers and see if your headlights dim. The disconnect the speaker amp and do the same with the sub amp at the same volume and see if the lights dim. It takes a great amount of power to move a driver that large that far.
I use pro audio speaker cable from my DJ days to my sub. These ran my 18" Yamaha subs with no problem.
I have an older Denon receiver in my home theater setup and when I was running 16 gauge speaker wire and if I was really pushing the system over half way the amp would shut down. Since I switched to 8 gauge wire I haven't had that issue.

 
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are you using a LOC?

 
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Other things to check. Are you using the stock deck or aftermarket head unit? If aftermarket, is the sub level turned up? Is the subwoofer enabled? What is the crossover point set at? Are you sure you used the sub pre outs? On some units with only 2 sets of pre outs, the rear can be switched for sub. Was the switch set correctly?

 
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Tigger is pretty spot on with his questions and answers, yeah mixing -/+ will still play, but may severely damage your subs...

I'm definately wondering what kind of single sub you are using bringing 3000 watts to it.
If your friend, or whoever is running sony xplod subs, tell him to toss those nasty things out.

14 gauge is way too small for sub speaker wires, I'd use at least 8 gauge

And once you get your DMM, properly set your amp, dont max gain/bass boost, it will blow the speaker sending 3000watts to it

 
Rep Power: 212

Sorry for the delayed response - he's got an aftermarket head unit (Boss BV9990), and it only has 1 sub pre-out, which confused the heck out of me, so I connected the RCA's (from the amp) to the two RCA pre-outs (same way I did it in my civic). Sub level is maxed on the head unit (trust me thats the first thing I checked haha). Not sure what you mean if the subwoofer is enabled.

I didn't mess with the max gain/bass boost, thanks to Kenny's post, still waiting on that multimeter to arrive.

8 gauge wire is en-route. Oh and, what's a LOC?

Additional question (sorry if this sounds a little newbie, only 18 here and this is my second time doing this haha) are capacitors a worthy investment?

 
Rep Power: 195

On some headunits you can disable the sub output.

Did you connect the amp only to the brown RCA? You would use a Y adapter unless the amp allows for a single input (would have switches on it for this) Do not hook the amp to any other color RCA if you are only using it for the sub.

Capacitors can be useful if you have a very power hungry amp. They store additional energy allowing your amp to hit momentary peak power points without over-taxing the alternator. They are not a replacement for an under powered alternator or weak battery.

 
Rep Power: 292

So, theres only 1 preout on the back?

or is there a front/rear? may you have possibly plugged 1 rca into front, and 1 rca to rear?

Capacitors are a good investment. Should you spend upwards of $50 for one? No

 
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This may help

 
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Yeah, there's only one sub pre-out. Its' brown with a brown tip (as noted in the diagram). I didn't connect anything to it because there was only one, so I just connected it to the RCA pre-outs in the back of the head unit.

 
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I think I know your problem, you have a mono sub out, and your amp is stereo input

You shud have a mono switch on your amp, im assuming

 
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If you connect to the preouts that are not the sub out, you are possibly sending a full signal to the sub. Now I say possible as the high pass filter may be set cutting off the lower frequencies. I would also assume that a regular preout does not pass frequencies below 50Hz as to not damage regular speakers (but I could be wrong on that)
Anyway, you do not want to connect your sub amp to those outputs. Get a Y adapter and only use the brown RCA. You should notice a huge difference in the sound. And your sub control on the headunit will actually work.
Right now the only sub control you have is the bass level and that will increase the bass going to the rest of the speakers possibly damaging them if you turn it up all of the way to get the sub louder.

 
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Alright I'll have to give the Y-connector a shot. Never considered that, actually. No mono switch on the amp. Just a master/slave switch and a phase switch.