# low ohm on JL amp



## Ninety-Nine SE-L (May 5, 2002)

I have a JL 300/4 amp and 4 Boston Accoustics speakers all around (fronts are 2 piece components, rear are 2-way). Lately, I've been getting excessive distortion in all 4 speakers. I thought at first I blew the rears, but then the sound started spreading to the fronts, even at normal volumes. I took a look at my JL amp and I saw the red temp light and the low ohm indicator were both on, and yes, the amp was hot as hell, I couldn't put my hand on it.

I measured the resistance of each speaker (4Ω speakers), here are the results: FR-3.9Ω, FL-4.5Ω, RR-5.0Ω, RL-4.2Ω

It may be possible that 5Ω speaker is causing a problem, but I thought it would read much lower or much higher if it were blown.

Anyway, after the amp cooled, I turned it on alone and got just the green light, as soon as I turned on the radio, I got the yellow (low Ω) light. When the amp is cool, I don't hear any distortion, when it gets hot, the distortion starts.


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## sr20dem0n (Mar 19, 2003)

All of those resistances are high, you shuld be getting around 3.5 with each speaker and they definitely shouldn't vary so much. Either way, a high resistance won't cause a problem, it's when the coil burns up and shorts out and you get a very low resistance that you get problems. It's possible the amp is going bad or you're getting a short somewhere (wire might be pinched or cut), that's about all I can think of. Use your ohmmeter to test the resistance between each of the 8 wires and ground, if you get anything less than infinity you probably have a short somewhere. Also test the resistance of your tweeters individually, one of them could be shorted out and throwing the amp into protection. Testing the resistance of the woofer/tweeter/xover system from before the crossover won't show the tweeter at all, it could be a dead short and you wouldn't know it unless you tested the resistance of the tweeter by itself.


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## wickedsr20 (Aug 8, 2002)

I have the same amp and usually if the low ohm indicator is tripping, it's usually due to a possibly grounded out or shorted speaker if the amp is tested good. Are your front mids or tweeters getting water on them? Any speaker wires that could be touching ground? Possibly try putting the amp in another vehicle to make sure the amp itself is good. Just my best guesses.


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## SentraStyleEMW (Aug 15, 2002)

Ninety-Nine SE-L said:


> I have a JL 300/4 amp and 4 Boston Accoustics speakers all around (fronts are 2 piece components, rear are 2-way). Lately, I've been getting excessive distortion in all 4 speakers. I thought at first I blew the rears, but then the sound started spreading to the fronts, even at normal volumes. I took a look at my JL amp and I saw the red temp light and the low ohm indicator were both on, and yes, the amp was hot as hell, I couldn't put my hand on it.
> 
> I measured the resistance of each speaker (4Ω speakers), here are the results: FR-3.9Ω, FL-4.5Ω, RR-5.0Ω, RL-4.2Ω
> 
> ...


I can get you a good deal on a new one


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## Ninety-Nine SE-L (May 5, 2002)

SentraStyleEMW said:


> I can get you a good deal on a new one


haha, I know you can. Lemme make sure it's the amp before I do anything tho. I don't see why the amp would act up like this tho, I can't see how it would suddenly start unless I blew a speaker and the resistance on that speaker suddenly dropped to almost nothing.


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## wickedsr20 (Aug 8, 2002)

Ninety-Nine SE-L said:


> I don't see why the amp would act up like this tho, I can't see how it would suddenly start unless I blew a speaker and the resistance on that speaker suddenly dropped to almost nothing.


That's why I was asking about a possible wet speaker because a wet speaker will cause crazy resistance changes when wet, then when they dry, it plays like normal. Also a speaker wire or terminal that is touching ground will exhibit the same characteristics at louder volumes, but not lower ones.

I'm betting on moisture on the front speakers.


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## Ninety-Nine SE-L (May 5, 2002)

it could be moisture, but it's been hot out and no rain today, any moisture would've evaporated out.


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## captain_shrapnel (Sep 10, 2004)

I think it is one of 2 things: Either the amp is defective, or you have a shorted wire somewhere. I would put my money on choice 2, track your wiring and look to see if the wiring is touching together anywhere or grounding out on the car chassis. An ohmeter on a speaker will only give a general ideal of whats going on, because rated impedance is not the same as dc resistance. If you saw an open circuit, or a short circuit it would tell you your speaker is fragged, but thats about it. Also, don't use an ohmeter for too long on a voice coil. Theoretically, the tiny dc current its sending through you voice coil can magnetize it slightly and cause distortion.


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## Ninety-Nine SE-L (May 5, 2002)

Ok, I disconnected all of the speaker wires from the amp and tested their resistance to the ground. With all 8 wires disconnected, I put my ohm meter up to the chassis and up to each wire individually. All of them read infinity so I see no evidence that any of the speaker wires are shorting to the car's chassis.

After putting all the wires back, I turned the amp/radio back on and checked the switches/levels on the back of the amp. All filters are disabled, input voltage is set to low for both front and rear (I have 4V, I think). Rear gain is at minimum, Front gain is just above that. 

No matter what, the yellow light is still on, after a while the red light goes on indicating it's too hot (and it's DEFINATELY HOT). I can hear a little distortion in the low/medium volume ranges, but anything above medium (say 12+) you can hear the distortion BAD.


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## Ninety-Nine SE-L (May 5, 2002)

BTW, the amp is like brand new, maybe 2 years old and no damages whatsoever (externally)


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## captain_shrapnel (Sep 10, 2004)

Hmmmm, doesn't look good. Sounds like something in the amp is fried, I would take it to a dealer and have it bench tested. Sorry man, hope I'm wrong.


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## Ninety-Nine SE-L (May 5, 2002)

it's no big deal if the amp actually is fried, Kenny can help me out


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## SentraStyleEMW (Aug 15, 2002)

Ninety-Nine SE-L said:


> it's no big deal if the amp actually is fried, Kenny can help me out


I know I can...the question is...do I feel like it.  .










Just kidding...bring it in (preferably on a Tuesday)...I'll take care of it for you.


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## Ninety-Nine SE-L (May 5, 2002)

sweet. BTW, where can I get some carpet that matches my trunk? If I'm gonna take out the amp, I guess I'll do something about the piece of MDF sitting in the middle of my trunk 

thanks, bro.


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## SentraStyleEMW (Aug 15, 2002)

Ninety-Nine SE-L said:


> sweet. BTW, where can I get some carpet that matches my trunk? If I'm gonna take out the amp, I guess I'll do something about the piece of MDF sitting in the middle of my trunk
> 
> thanks, bro.


I'll see if I have something that matches back in the install bay when you bring it in.


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