View Full Version : Amp Problems

03-30-2007, 01:58 PM
I have a Clarion 500 watt 4 channel amp and 4 MB Quart 6.5 speakers that came with my boat and wanted to add a sub. I bought an Infinity Reference DVC 12" sub ( 300 watts RMS/1200 watts peak), wired everything up, and my amp keeps turning off at higher volumes. I say higher volumes, because I expected it to be much louder than it gets before it kicks the amp into protect mode. The way that I have everyting wired is the 4 MB Quarts are wired on channels 1 and 2 in parallel. This should be a 2 ohm load per channel, if my research has been correct thus far. The sub is a DVC sub with each voice coil being 4 ohms. I have it wired on channels 3 and 4 in stereo, (one channnel per voice coil). I have tried running the VCs in a series with the amp bridged, and also in parallel with the amp bridged (I know 1 ohm load on this amp is probably not good, but I will try anything to get this to work without having to buy another amp for my sub). Hopefully I have given enough detail about what I have done, now I need to know how to make it work. And am I just expecting too much out of a 500 watt 4 channel amp? Any suggestions or additional questions to clarify would be much appreciated.

03-30-2007, 03:42 PM

03-30-2007, 07:18 PM
what size power wire you runnin?

03-30-2007, 08:30 PM
chevy- "I know 1 ohm load on this amp is probably not good"- there aren't many amps that will work with that load and bridging it into that load is effectively showing the amp 1/2 ohm.

I agree- what is the power wire gauge? The ground wire needs to be the same, the battery and ground connections need to be spotless and don't try grounding to the motor.

Describe the installation in detail and post some photos. Wire gauge, how the ends are terminated, the age and condition of the battery, no-load battery voltage on the terminals and at the amp.

Use a digital multi-meter to read the resistance on each pair of speaker wires, then check form one wire to the tower. If you have any continuity to the tower, there's your problem.

03-30-2007, 09:44 PM
Both the power and ground wires are 8ga and have gold ring terminals crimped on to them. I don't have any speakers on the tower, these are all in the boat, not that it matters. I am running my ground to the battery as I figured that this would be the best ground available in the boat, and also talked to a few audio installers and that is what they said would work best. The battery is an Optima Yellow top, and is a few years old. I have checked it with a load tester, and everything passes OK. I did forget to mention that the MB Quarts have external crossovers as well. I think that I'm going to go through and look at every wire and make shue that one is not hooked up wrong, anything grounding that shouldn't be, etc. I have the sub currently hooked up 1vc per channel, so 4ohm load there that the amp is seeing. I am wondering if since the mbs are component speakers with a crossover if that is throwing the impedence off at the amp or not as well. Although I can disconnect the sub and turn the speakers up until they blow without the amp cutting off. Thanks for the suggestions, please keep them comming. If you think that this is too much for this amp to handle, any suggestions on a cheap but good sub amp along with what to look for would be nice as well.

03-30-2007, 10:10 PM
I forgot to mention the best way of running a dual VC woofer and one 4 ch amp with the sub crossed over passively. It's dual VC but they aren't exactly the same, no matter how much the company and the customers want it to be and this means that the woofer should be wired series or parallel, depending on the amp. I don't know of a speaker manufacturer that recommends wiring their dual VC woofers in stereo.

Bridged, a 2 ohm load looks like 1 ohm to the amp and while it sounds reasonable to wire one coil to each channel, the differences can cause one channel to drive its coil harder and the other channel can shut down because of it. Amps don't like to see voltage at the output and are protected from it. If you want to see what the amp may be seeing, connect a volt meter to a speaker and set it to either AC millivolts or the lowest scale, then press the cone in (evenly around the center) or you can tap it. You should see a voltage reading and when you consider more cone excursion, the voltage will increase, too.

If you aren't using a crossover on the woofer, that will cause problems, too. A passive crossover on the woofer, wired in series will be the safest load for your amp and if you wire it in "tri-mode", it should sound good without having to buy another amp. You would need to use a passive high-pass on the satellites and wire them to their own channels, then use a passive low-pass on the woofer, wired to the amp the same way as if you were bridging the channels.

How far from the battery is the amp and what are the fuse ratings on the amp when you add them together? If it's more than about 40A and the amp is more than about 10' from the battery, the power cables may be a bit on the small size. Another thing, I would recommend soldering the ring terminals in addition to crimping. If they're only crimped, they can still corrode. Is this the only battery you have on the boat? Your amp's positive is connected to the battery positive too, right?

03-30-2007, 10:14 PM
If I read this correctly, you have two pairs of satellites, right? If you tend to not fade between them and equal power to the satellites is the way you like the sound, you could bridge one pair of channels and wire the woofer to that, VCs in series. You'll still have good output from the woofer but the amp will be a lot happier. If you use the active crossovers, you can have more usable power too, since the drivers won't be operating out of their preferred frequency range. Two ohms on a channel running in normal mode should be OK but the amp will draw more current than if it runs in stereo on all channels.

The most common causes of amps shutting down are:
1) Excessive heat,
2) Impedance below the protection circuit's threshold, caused by shorted wires, voice coils and wiring too many speakers in parallel or the amp being bridged,
3) Voltage drops, caused by charging system inadequacy/failure/bad connections/improper wire sizing.

03-31-2007, 06:45 PM
Jim, thanks for all of the suggestions. I haven't really had much of a chance to mess with anything today, but I hope to tonight. My wife and I were at one of the ski shops around here, which just happens to be by a Best Buy. We stopped in there and they had a 2/1 channel Alpine amp on clearance, so I just bit the bullett and bought it. Any suggestions on wiring two amps now. I'm guessing that I can just use a jumper to wire my receiver signal wire from the 4 ch amp to the sub amp that I have(receiver signal wire being the one white wire from the head unit, to the amp to tell it to turn on). I'm going to put each of the 4 speakers back on their own channel, and just bridge out the 2 channels on the sub amp for my sub.

04-09-2007, 11:44 AM
Returned the small Alpine amp that I bought and got a larger one. Bought an Alpine monoblock amp (MRP-M450), this thing is awesome. Once my sub had enough power to it, I was able to figure out that it was blown. The new amp was cutting out as well, but at even lower volumes, but I could hear the distortion and scraping from the sub. It was at that time that everyting made sence. When a voice coil is blown, it is shorted out and causes the amp to go into protection mode. Bought a new sub, the same infinity that I previously bought and this thing slams hard. Not sure if I would have had all the problems of overheating amps and everything else, but I'm glad that it is figured out. P.S. I already took my beatings for buying the current Alpine amp, so I'm keeping it, and am not even going to see if it would have worked the previous way.