Polk Audio amp issues?

Hayabusa

Am I the only one with this issue? I have 2 of the Polk Audio c300.2 amps, one running a pair of 6.5's and the other running a single MTX 7500 10" (bridged) Sony HU with 4v preouts. I have the gains on the amps set to ~half. Listening to moderate-high volumes after about 30 minutes (drive home is about an hour) one of the amps will shut off. Usually its the one powering the sub, then a few minutes later, the other one shuts off. Both amps are in the trunk mounted to the floor. There is nothing on top of them, or surrounding them. This happens everyday. I laid down the rear seat so I can see the amps, and when they shut off the red thermal light comes on. Even with the seat down for more airflow. Whats going on with both of these amps? Do I need to buy aux fans for them? Is this a common problem with the Polk amps? Or do I just have two defective units?

audiobliss

I would say it's not a common problem as I haven't heard of it before. When the amps shut-off, are they warm to the touch?

The C300.2 will do 450 watts bridged into a 4 ohm load. The MTX 7510 (I assume that's the sub you have) will handle 400rms and presents a 4 ohm load. As far as I can tell, that's matched up pretty well. That set-up in and of itself shouldn't be giving you any problems.

How is everything wired? Distro block? Guage? Grounded where/how? Guage?

If it's not getting hot, I'd say you have a wiring problem. Maybe too small wires are getting hot or maybe they're shorting out somewhere.

If the amp is getting hot...I'm not sure. If nothing's around it and you even have your back seat flipped down sometimes, ventilation shouldn't be a problem. I might would try setting a fan in there temporarily just to see what happens.

Toxis

are you grounding both amps to the same spot?

MacLeod

I tend to think its a wiring issue rather than a problem with the amps.

The protection light will come on not only if it gets too hot but if its being ran at too low an impedance or is not getting enough voltage or if it shorts or the ground goes sour.

Since happening with both amps, I doubt youre wired the speakers wrong. You could have the gain set too high tho. You really shouldnt be at the noon position. The gains on the amp powering my front speakers is virtually at zero. Fiddle around with the gains and see how that helps.

My next guess would be the ground. Make sure they are secured properly at the point of ground and at the amp. For extra measure, scrape off the paint at the ground point so its touching bare metal.

Another thing, make sure youre using the same guage wire for power AND ground. Using 8 AWG power and 14 AWG ground can screw things up.

Hayabusa

Both amps get to the point of instant burn if I touch them. If I set the gains any lower than half, I end up having to turn the radio up max to get it to the loudness I like to listen to which puts in a lot of distortion. But if I have the gains at half, then I can set the radio to half and its a lot louder and cleaner. As far as wiring goes... I have two distro blocks. One for positive, one for negative. Positive is coming right from the battery (no caps) at 0 gauge. Then from there I have 8 gauge going to the two amps. Negative is 0 gauge to a point in the trunk (paint scraped off) though to be honest I dont think that actual connection is very good... But would that make the amps so hot to the touch that you can burn your hand? From that d.bock, same thing, two 8 gauges to the amps. both are being powered from the same source and grounded from the same source. And again, usually the sub amp geos to thermal first, then the the other one. Usually within 5-10 minutes of each other. And from what I remember there are three lights on the amps. the blue light with shows if its on/normal, the red one next to it (middle) which is thermal, and the on on the right which I also think is red, which is for low imp. That one DOES come on occasionally only on the sub amp when playing certain M. Manson songs with tight hard quick bass. But when playing rap type bass, long low deep bass, its fine.

audiobliss

Very interesting. I've never done an installation, so I'll refrain from commenting on your wiring except to say that using two distribution blocks and running the ground like that certainly seems to be unnecessary.

If the amps are getting that hot, I would definitely say stop using them until you figure out what the problem is!!!! How long does it usuallly take for them to get hot and shut-off? Have they done this since installation or has it just recently started happening?

One of your problems is...M. Manson...you shouldn't be listening to him anyways, man....:p
j/k

Someone should be able to set you straight. Looks like I'll learn on this one, too.

nadams

Sounds like on the sub amp, your impedance is dropping on heavy bass hits (which is normal), but it sounds like it's dropping too low for the amp, and making it work harder. Not sure why your other amp is shutting off, though... it should have enough power for 6.5's

Hayabusa

The reason I am using two d.blocks is so that I dont have to have 2 grounding wires running to the same spot, or to two different spots. I listen to all kinds of music from rap to hardcore metal to classical etc.

Both amps are getting hot enough to flip the thermal switch to turn them off.. its usually happening after ~30-45 minutes of continual play. Most of the times its at higher volumes, but lately its just happening at normal volumes. Maybe I will try to build an amp box that has some 12v fans to move air across them and see how that works.

audiobliss

While that may improve things, it doesn't sound like ventilation is the problem; sounds like something else is at fault. Thus, I still wouldnt' play 'em too much until you get it figured out. I'd hate to ruin some Polk MOMO amps! :eek:

Toxis

Hayabusa wrote:

The reason I am using two d.blocks is so that I dont have to have 2 grounding wires running to the same spot, or to two different spots.

but you DO have them going to one spot... the distro. Now it's better to have dual grounds. It could be that your ground location is to weak for the current draw you keep putting on it and you're straining the amps.

exalted512

you got me...do you have a DMM?
-Cody

MacLeod

One thing jumps out at me here. If you turn the gains down, you get distortion when you turn the head unit up??? Lowering your gains will almost guarantee youll never hear distortion unless you push your speakers too far. And if you cant get the volume loud enough with 175 watts per channel at half gain then youve got more problems than overheating amps.

Im still leaning to a wiring issue and most likely a ground problem but as mentioned above, it sounds like youve got deeper issues. Sounds like the entire installation has issues.

bknauss

If you're giving the C300.2 a distorted signal and have it in bridged mode, it doesn't like that. As for the components, I haven't heard of that problem before. I've got MMC570s in my doors being driven by a C300 and haven't had any problems in the year+ I've had it.