Sub questions.

RAMpant1500 · Feb 9, 2017

So I've got two 10" JBL subs in a custom enclosure stretching across the entire back seat, taking up both under seat storage areas. Subs are rated at 125w RMS - 500w peak @ 4 ohms. Not sure what the volume of the box is. Subs are powered by a JL JX 500/1 - rated @ 300w RMS x 1 @ 4 ohms. I didn't install everything and I'm a novice when it comes to car audio so I have a few questions. I messed with the gain and bass boost on the amp and it seems to distort pretty quickly when you turn the levels up. Is that a sub problem or amp problem? Also, since it's a single channel amp, how did they send it to 2 subs? Am I underpowering the subs or pushing them too hard?

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Eestee70 · Feb 9, 2017

That amp is meant to power one speaker, also the gain is not for volume it is used to set the proper voltage output so the amp is running with maximum power without distortion. With JL Audio you should have gotten a booklet that shows speaker ohms to voltage output. Find the one that fits to your speaker ohms and use a volt meter to set the gains. ( if you have a volt meter).

RAMpant1500 · Feb 9, 2017

Okay, I'll take a meter to it later. Can you explain why the amp has 4 speaker outputs (2 neg and 2 pos)? Since it's only meant to power one sub.

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Eestee70 · Feb 9, 2017

My bad I was thinking of a different amp. My hunch is that your amp and head unit are not
Level matched. It's an easy process. Do you have the manual for your amp? If not I can take a pic of the page you need for setting the voltage and level matching. Do you have a bass knob. How is you amp connected to your system?

RAMpant1500 · Feb 9, 2017

Eestee70 said:
My bad I was thinking of a different amp. My hunch is that your amp and head unit are not
Level matched. It's an easy process. Do you have the manual for your amp? If not I can take a pic of the page you need for setting the voltage and level matching. Do you have a bass knob. How is you amp connected to your system?

I have a PDF version of the manual. And you were right to say it is for a single sub; that's what the manual says. But for some reason it has two neg and two pos terminals for speaker out. It even says "mono" next to the terminals. I just don't understand how a "mono" amp is powering two subs; and is it bad practice to hook up like that. I also found how to adjust the sensitivity. 50hz and I should be getting around 34 VDC.

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Eestee70 · Feb 9, 2017

Also to answer your other questions too. Once you connect two subs it cuts the power in half so each sub is getting 150watts of power, that may not be enough bass for what you want. Is that the reasons you tried to adjust the gains?

RAMpant1500 · Feb 9, 2017

Eestee70 said:
Also to answer your other questions too. Once you connect two subs it cuts the power in half so each sub is getting 150watts of power, that may not be enough bass for what you want. Is that the reasons you tried to adjust the gains?

It was purely out of curiosity. Just to see what it would do. I'm happy with the sound I'm getting. 10x better than the factory Alpine sub. I was thinking that I might end up swapping some components later down the road and I'm just curious as to how my current configuration functions.

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Eestee70 · Feb 9, 2017

Gotcha, will you be amping the components?

RAMpant1500 · Feb 9, 2017

I'm not sure. I definitely would if I had the base audio. But I don't like dealing with upgraded systems because of all the bypassing and rewiring, not to mention special harnesses. I'm not at all familiar with how the Alpine system is set up so if I did upgrade the rest of it I'd probably gut it and start from scratch.

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14hemiexpress · Feb 9, 2017

So the mono with dual sub terminals seems to be a Rockford fosgate thing. The main thing is you need to match the ohms of your sub and your amp. There are multiple ways to wire amps. What you need to do is find out what ohm your subs run at and what ohm your amp puts out. Look up wiring diagrams to make sure your subs are properly wired to your amp. If you have 4ohm subs and running them at 2 ohm you could be easily over powering them. And your amp is little big for those subs 125 per 2 subs is 250 and your amp puts out 300 not a huge deal you just cant crank it all the way up. If you need help finding. Diagram after you figure out the ohms on your sub and amp send me a pm. I'm no audio expert but I have wired my fair share of systems up. I used to run a fosgate prime 500r1 with 2 12s and now a co worker powered 2 10s with it. My dad runs a 5 channel 4x60 and 1x200 or 300 cant remember but we push 2 10s clean off it.

Eestee70 · Feb 9, 2017

I'm gonna shoot you some pics of my setup. It's not as difficult as some people make it out to be. With a little patience and planning you can do a really nice setup in your truck. I keep my factory head unit as you can see. You can add a really nice system to your truck and keep your dash looking factory.

Damion · Feb 9, 2017

With both subs connected to your amp, they are giving your amp a 2 ohm load. Which would make the output handy to 500w. ( should be in the specs for your amp ). Your amp and subs are fairly well matched.

The gains aren't a volume for your subs but a level control. To set it turn the gain all the way down, turn the volume on the head unit up until the speakers just begin to distort, then turn the gain up until your subs just start to distort as well. This will get you close to being level matched. ( well the quick and dirty way anyway ). The bass boost just adjust to your liking.

If your subs aren't in a proper volume box, it can make them distort a bit sooner than they normally would. More so at lower frequencies. Hope this helps

Sub questions.

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