JL 300/4 Speaker Distortion

Didn't you get a manual with that amp?  If not, download it https://mobile.jlaudio.com/pdfs/7111.pdf.  "Each input section contains a pair of RCA-type input jacks, an input voltage switch, and an input sensitiviy rotary control".  That rotary control (screw) is the gain.

Did you have this installed?  If so, did you ask any of these questions of them?  The front speaker wiring is not bridged, but it appears that both speakers are connected to the right channel.  Indeed, this is a parallel connection and puts a 2 ohm impedance (I'm assuming those are 4 ohm speakers) on one channel.  But it should not be too low of a per-channel load on the amp.  The wires should be the same way the rear ones appear to be wired.

The wiring is shown in the manual as well as procedures for adjustments.  Two things I'd recommend an immediate upgrade on:  the front set of speakers and the RCAs.

Read the manual completely and let the forum know if there is something that you don't understand.

I'd love to know why the installer wired both front speakers to one channel.   The only logical explanations that come to mind are a bad amp (the other channel is dead) or bad drugs.

As for the gain, flip the "input voltage" switch to "low" and use a screwdriver to turn the "input. sens." dial.  That's your gain control.

Changing the RCA would be last priority.  The highest priority is to put in a pair of components in the front that will not only be at least the RMS power capability as the amp produces, but that will provide a quality sound to go with the quality amplifier.  You may as well have a Profile amp in there at this point.  At least trade up to a higher quality coaxial, but I wouldn't even suggest that baby step.  Get a pair of components that are rated 75 watts RMS or higher, preferably higher.

And, you will need to keep your deck controls at flat or below, nothing in the + ranges.  Do a  search of this forum for "gain" under topics and you will find loads of good info.  But until you get capable speakers into this car, the amp will most likely be sending your Pioneers to an early grave.  And the sound will suck in the meantime.  Setting the gain by ear, using test tones, means that you will be giving those speakers full power using a sine wave, which will be well over their thermal power handling capacity.  At this point, until the replacement speakers are installed, I would say just keep the controls to minimum (no +s) and only adjust the gain screw up from the 0 point enough that the sound is clean when the deck is playing at full tilt, or at about 3/4 of the way.

When you get the new speakers, which should include higher power-handling for the rear as well, you will then have the opportunity to use this system the way it should be used, with complete use of all the controls.  Stay off of any bass boosts, though.  You don't have anything to supply bass (subwoofer) so don't try to make bass happen where it doesn't exist.

sh0wty wrote:

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I did have it installed. When I picked it up, it sounded decent, all the settings on the radio were set to negatives (Bass, Treble, Highs, Mids, Lows). I set them a bit higher and the distortion was too much to bear. I asked what has to be done to correct this distortion, I was told to get new speakers that can handle more RMS.

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Please tell me that you will NEVER go back to that shop again.

Also, getting new speakers is ONE answer to correct the distortion, not the only one.   By lowering the input sensitivity (gain) you can effectively send 50w RMS to your speakers and they should sound fine.   You'll just be using 2/3 of your amp's capability instead of 100% of it.  If you want to use 100% of it, then you need to get  a decent set of comps like Steve suggested.

Personally, I think it's ridiculous that you have to even deal with all of this.  If you bought your stuff off eBay and then installed it yourself (or had a buddy install it), then yeah, this is all part of the learning curve.   However, if you buy your stuff from a shop and pay to have it installed professionally, then you shouldn't have to put up with this kind of aggravation.

stevdart wrote:

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When you get the new speakers, which should include higher power-handling for the rear as well, you will then have the opportunity to use this system the way it should be used, with complete use of all the controls.  Stay off of any bass boosts, though.  You don't have anything to supply bass (subwoofer) so don't try to make bass happen where it doesn't exist.

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Also, make sure your crossovers (filter frequencies) are set on both the front and the rear speakers.  You mentioned that the filter is set to "HP" which is good.  Start with the "95Hz" setting with the 24db slope and then slowly work your way down from 95Hz until you start to hear distortion.  You probably shouldn't go below 80Hz with a 24db slope on those speakers.  You'll have little, it any, low bass, but you won't have distortion either.

Believe me, if one of your amp's channels is blown, you'll know.

I have to tell you though, after re-reading your posts and taking a closer look at your pictures, I'm concerned with what gauge power wire was run from your battery to your amp, how it was run, and what type of fuse was used (near the battery).  This just looks like a complete and total hack job.

sh0wty wrote:

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1. The engine noise is unbearable now when the amp was installed. And now seems a bit higher after I rewired the channels.

2. Im having my doubts whether there is something wrong with that channel that wasnt wired. It sounds great, but when the volume is toned down you can hear like a 'murmur' (If that makes any sense) but when turned up it sounds good. Anyone know if this is a sign of the channel gone bad?

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This is ridiculous.   Before I go on a tirade and start throwing out more advice, I have a couple of questions for you:

1)  Did you buy the amp new?

2)  Did you buy the amp from an authorized dealer?

3)  Was the amp installed by the dealer you bought it from?

4)  If the amp was not installed by the dealer you bought it from, was it installed by an individual, a retail chain, or an independent shop?

1 - USED

2- Bought it from the guy who works at the shop.  It was his own personal equipment.

3- Yes they installed it at the shop.

First of all u shouldn't have left the workshop until the sound was right. 50W RMS is plenty of power for your ears. I don't think the distortions have anything to do with the amp being too powerful for the speakers. The problems could be :

- Bad wiring of the speakers (wich can be seen on the pictures)

- Bad settings of the crossovers > Theoretically u should set the crossover point at double the Fs of the speaker. U can set it lower but with a steep slope but don't go beyond the Fs.

- Bad/No acoustical treatment of the front door > people often blame it on speakers that can't handle the power !

sh0wty wrote:

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Thanks for all the input fella's, im gonna pay him a visit. Thing is though all the speakers are sounding great, just that strange noise i hear when the volume is low coming from the channel that wasnt wired. Sounds like a low murmur but when cranked up it sounds ok. I dont want to go saying that the amp has a bad channel when I really do not know if it does..

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You sound like me back in the day when I was the consumate nice guy, always making excuses for people who screwed me over.

TCSS is right.  C'mon on, man.   He knew EXACTLY what he was doing.  Do you want to know where your engine noise most likely comes from?  It most likely comes from running a crappy set of RCAs on the same side of the car as the power wire running from the battery to the amp.  With a good set of RCAs, this probably wouldn't be an issue, but from what I can see in your pictures, you've got a crappy set of RCAs.

Everything this guy did from top to bottom is probably crap.   I'd be shocked if you have the right guage of power wire, the right fuse near your battery, and a good ground near the applifier.

Personally, I don't think you want him (or anyone else from his shop) touching your car.   Here's what I would do:

1.)  Fine a GOOD, REPUTABLE shop.

2.)  Have them bench test your amp.

3.)  If the amp is good, have them completely reinstall it for you with a brand new wiring kit.

4.)  If the amp is bad, either buy a new amp from the shop or just have the old amp removed and go back to running your speakers off deck power for awhile.

5.) Have the shop do a write up of exactly what's wrong with the amp and everything that was done incorrectly on the original install.

6.) Bring the old amp and all the wiring back to the guy that sold it to you, show him the write up from the shop,  and tell him in a calm and professional manner that you want your money back.  If he refuses, tell him that you are ready to take legal action.  If he still refuses, then leave quietly and file a claim.  If he threatens you, then tack that onto the complaint as well.

I dont' know how much you paid for the amp and the installation, but if you decide that it's not worth the aggravation and want to skip step No. 6,  that's your call, but do yourself a favor and at least take steps 1 to 5.  If you have issues with your power wire and fuse, you could end up having much bigger problems than an amp with a lame channel.