Amp/subwoofer problems

[Lurch]

Car audio buffs:

I have a 10" sub installed in my XJ powered by an old, early 90's Denon amp that I picked up for free on the forum. Amp is a 2 channel bridged at 2 ohm giving ~150 watts to the sub. The setup has worked fine for a couple years, but recently started giving me problems.

Bass will sound normal out of the sub for a minute or two, then either cut out completely or sound really distorted coming out of the sub. I've checked all ground, power, RCA and speaker wire connections and everything looks good. Amp is not overheating because this happens before it even gets hot.

Only recent change I made to the setup was the fusing and connection at the battery, the amp is getting power.

What should I be looking for - Is the amp or sub toast? A power problem? Bad connection somewhere?

I never realized how much I like having the bass in my music until its gone. :guitar:

 

[GrimmJeeper]

did your sub get wet when you dunked the rear end in moab, or did any water get into its enclosure? corrosion from moisture on the copper voice coil will cause exactly what you're describing.

 

[Lurch]

Very likely. I took the sub out of the box and inspected it, no evidence of moisture in the box and no visible corrosion on the coil. Doesn't mean it isn't there, hard to see it very well.

 

[GrimmJeeper]

you would be able to feel it by pushing the cone in straight slowly by hand, it will feel like there is sand in there.

if the water got high enough to wet the amp itself or the carpet around it you could have popped a couple of its internal capacitors which might also be causing your problem.

 

[Lurch]

Sub seems fine, at least none of the symptoms you're describing. Water definitely did not make it up to the amp, its under the pass seat. I'm beginning to think the amp is the culprit though. It doesn't make sense that the sub would sound fine for a song or two then go bad. The amps 20+ years old, maybe the capacitors or something else just went bad. It gets pretty damn hot under there.

 

[GrimmJeeper]

if you want you can try plugging your speaker into my amp, its only 300w RMS. that will tell you if its the speaker. then we can try my sub on your amp.

 

[Lurch]

Bumping this thread because I am still having problems after inspecting all of the power and grounds. The issue is the sub is distorting or not firing at all at higher volumes. It's a dual voice coil 4 ohm sub wired in parallel to the amp at 2 ohms. The sub is 200 watts RMS and the two channel 4 ohm amp is 150 watts RMS bridged at 2 ohms mono.

Check the video out. The impedance is steady at 2 ohms with key off so I know that it's wired correctly. When I turn the radio on, but still low, the Ohms jump up into the 20's. When I turn the radio up more to a normal listening level they jump all over the place, even into the negatives and the sub starts distorting.

Any thoughts?? This was never a problem until about a year ago.

http://youtu.be/0rjSnbe3Tb0

 

[smokinu]

Your 4ohm sub didnt like running at 2ohms anymore. It happens ive had a few cheaper subs do what you are discribing after some abuse.

I have 2 12's pushing 2000 watts.

 

[sidewaysstarion]

Bumping this thread because I am still having problems after inspecting all of the power and grounds. The issue is the sub is distorting or not firing at all at higher volumes. It's a dual voice coil 4 ohm sub wired in parallel to the amp at 2 ohms. The sub is 200 watts RMS and the two channel 4 ohm amp is 150 watts RMS bridged at 2 ohms mono.

Check the video out. The impedance is steady at 2 ohms with key off so I know that it's wired correctly. When I turn the radio on, but still low, the Ohms jump up into the 20's. When I turn the radio up more to a normal listening level they jump all over the place, even into the negatives and the sub starts distorting.

Any thoughts?? This was never a problem until about a year ago.

http://youtu.be/0rjSnbe3Tb0

When you are going to check any part for continuity, you must remove the power. Ohm meters supply their own power from an internal battery. Leaving power on while testing resistance will damage the meter.

http://www.wikihow.com/Use-a-Multimeter

The reason why your ohm reading are all over the map is because you are trying to measure the resistance of a circuit that is powered and its freaking the meter out.