Capacitor needed with a sub?
Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
I'm gonna finally put in my 12in sony sub this weekend, and I guy I know told me that I should get a capacitor to make sure my headlights don't dim. I know the electrical system on my renix probably isn't the greatest, so is there anything I should worry about when doing the installation? I already read up on charging and discharging the capacitor safely. I'm just not sure if I should even go through with it if my electrical system won't handle it. I'll be running the sub off of a 500w single channel alpine amp. The sub is rated at 300w and the peak power is 1100w. Is that too much power to run?
Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
My headlights dim when the transmission downshifts, I think I should run a capacitor. haha. A new alternator is planned for the future, but I don't have that kind of money.
Senior Member
Joined: Mar 2011
Posts: 651
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From: Norway
Year: 1993
Model: Grand Cherokee
Engine: 4.0L I6
There isnt any battery today that could deliver power the same way as a capacitor. Go for a capacitor as close to the amp as possible, i dont think it will fix your dim problem 100%, but you would hear big difference on the sound if its a good sound system.
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Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
See, this is why I made up the thread. I keep getting mixed info on whether to get one or not. I'm getting one because I can get a good deal, but I wanted to see what people thought of it. I'm also iffy on the old electrical system. It could probably handle it, but I'm just wondering.
CF Veteran
Joined: Feb 2012
Posts: 1,206
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From: Southern Oregon
Year: 1990
Model: Cherokee
Engine: 4.0
I run a 1200w pioneer sub and 1200w dual amp (unfortunately from wally-world) in my 90' (renix also) with no capacitor and have no real problems even with the car off just sitting and listening to music before work for 30-45 min at a volume that makes me slightly deaf for a min or two after and there are no problems, i do sometimes notice at a stop light at night my headlights will dim slightly when the sub hits but nothing serious.
Also there are days where my sub SEEMS to hit harder or softer which I understand a capacitor could fix.
So, in conclusion, you CAN run a sub and amp without a capacitor, but if I had the money at the time to purchase one i would have just as a safety precaution. and maybe someday i will. Hope this helps you.
Either way rock on man, rock on.
Also there are days where my sub SEEMS to hit harder or softer which I understand a capacitor could fix.
So, in conclusion, you CAN run a sub and amp without a capacitor, but if I had the money at the time to purchase one i would have just as a safety precaution. and maybe someday i will. Hope this helps you.
Either way rock on man, rock on.
Last edited by PNWjeeper; Oct 5, 2012 at 02:36 PM.
Junior Member
Joined: Mar 2012
Posts: 75
Likes: 0
From: San Antonio
Year: 2001
Model: Cherokee
Engine: 4.0 I6
I ran a 1 farad cap in an old system with a optima red top and factory alternator with no dimming. I did have headlight dim pre-cap running 2 12's with a 500w amp.
Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
I run a 1200w pioneer sub and 1200w dual amp (unfortunately from wally-world) in my 90' (renix also) with no capacitor and have no real problems even with the car off just sitting and listening to music before work for 30-45 min at a volume that makes me slightly deaf for a min or two after and there are no problems, i do sometimes notice at a stop light at night my headlights will dim slightly when the sub hits but nothing serious.
Also there are days where my sub SEEMS to hit harder or softer which I understand a capacitor could fix.
So, in conclusion, you CAN run a sub and amp without a capacitor, but if I had the money at the time to purchase one i would have just as a safety precaution. and maybe someday i will. Hope this helps you.
Either way rock on man, rock on.
Also there are days where my sub SEEMS to hit harder or softer which I understand a capacitor could fix.
So, in conclusion, you CAN run a sub and amp without a capacitor, but if I had the money at the time to purchase one i would have just as a safety precaution. and maybe someday i will. Hope this helps you.
Either way rock on man, rock on.

I might have to put things on hold though, cuz I'm getting a case of the renix woes again. My electric fan won't kick on so it leaves me running hot whenever I stop.
Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
Kinda why I want to get a cap. Just in case I do upgrade with another 12 eventually. Plus it just helps to have things regulated. The guy I got my sub off of said his headlights would dim every time it hit, so I don't want the same to happen to me.
Seasoned Member
Joined: Oct 2012
Posts: 378
Likes: 1
From: spring grove il
Year: 2001
Model: Cherokee
this is one topic i know about capacitors are useless and dangerous. my dad owns a starter and alternator rebuild shop and iv done all of his high end stuff for the past 10 years. caps. can be explosive seen it a few times. your best bet is to do a duel battery setup safer and more practical for winches, lights ect. and the same price as a good cap.
Thread Starter
CF Veteran
Joined: Jan 2012
Posts: 1,057
Likes: 2
From: Nazareth/Pen Argyl, Pennsylvania
Year: 1989
Model: Cherokee
Engine: 4.0L 242ci I6
I can get a deal on a cap for about $50 only. A second battery will run me at least $80. I'm not looking to spend much on my setup as of now. Once I get roof lights and bumper lights, I'll upgrade the alternator and add a second battery. I heard that you just have to use a cap properly to avoid any danger.


