IB sub in the trunk - Capacitor ??

This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
Hey all :)

... been a while ... I recently got a new (to me) car. 97 maxima reconstructed with parts from my old 97 maxima.

I've currently got a 15" dayton IB Sub in a custom mount that'll be going into the trunk. I'm using an early to mid nineties Earthquake amp bridged mono for it.

I had the 15" dayton IB Sub juiced with only around 100watts but it would still dim my lights majority of the time. I had a brand new interstate battery and alternator put in and it would still dim them out ...

The newer car has the newer battery in it right now.

My uncle who was into car stereo nearly 20 years ago recommended getting a capacitor to prevent the lights dimming.

Does this sound like the thing to do?

If so is there a specific type I should get? I have zero experience with capacitors ...


PS. I'm also looking for any recommendations on a 4 channel amp for the 4 Alpine SPS-600, 2way speakers already installed by the previous owner.

AND i'm looking at upgrading the current Kenwood to this kenwood :


Thoughts , Comments and Advice are all welcome :)
Last edited:
What size power wire are you running to your amp?? I always made it a point to run at least 4 gauge wire minimum for power and ground. Also make sure you run the same size ground from your battery to the car frame. (same size as your power wire for the amp) It sounds like you have a bad ground or not big enough power wire. One hundred watts, could dim the lights (depending on the brand of amp) But in most cases it should not.

As for caps, (To me) they are a waste of money. So I would say no to the cap..
I agree. Caps are generally useless for light dimming.

If the lights dim and stay dimmed on long bass notes, the alternator isn't producing sufficient current.

If they only dim for a fraction of a second at the beginning of a long bass note but they recover after that fraction of a second, the alternator isnt' responding quickly enough to prevent the lights from diming but is capable of supplying the required current. There's not much you can do about that.

If they only dim at idle (not at higher engine RPMs), it's due to the reduced output capacity of the alternator at low RPMs. A different pulley on the alternator can make it a bit better but can also be harder on the alternator at highway speeds.

You should also check the charging voltage. If the alternator is overcharging (producing too much voltage), it won't be able to maintain it as it could if it were producing the standard 13.8v.

There are various ways to stop the headlights from dimming (although they're generally too expensive for most people). You can replace your headlights with HIDs. You can use two alternators (one for the vehicle and one for the audio system). You could also use a regulator for the headlight power supply but that would be complex and there may be safety issues if not done properly.
@ Warped

Hi ... thanks for your help :)

I'm currently running this kit here which says its 4 gauge for both:

StreetWires PSK04B Amp Installation Kits - Audio/Video Accessories at Onlinecarstereo.com

The earthquake amp (american made - high current) 2channel (700w RMS) is bridged mono running 350w RMS @ 8ohms with the gain set to around 100w.

Going off of your suggestions ... I'm guessing the main issues might be these here ---->

... where the 4 gauge ground wire plugs into the amp it is a very small hole. The spot on the amp where the 4 gauge goes into is probably 30-40% the size of the actual wire so the wire was trimmed off to make it fit ( I had a buddy do a half-assed installation) ... My guess is that it probably should be connected to a spade terminal , ring terminal or some other terminal that'll take a 4gauge input and then down size it to fit into the ground input on the amp??

Also the other end of the ground wire was only screwed into the sheet metal interior of the trunk.

And lastly ... If there wasn't another 4gauge grounding wire supplied in the kit then i'm almost sure there was no ground wire attached directly to the negative terminal on the battery , with the other end attached to the frame.

There was a ground from the amp to the sheet metal in the trunk and a ground from the deck to the frame and that was it , I'm pretty sure.

@ Perry

Thanks for your help too :)

I've yet to put the stereo into my NEWer 97 maxima with 99k on the clock.

The older maxima had around 150k on the clock when I put this system in 2 years ago. It killed the original alternator and battery within a couple of months. I then had a brand new battery and alternator installed. As far as I can remember it would dim mainly at the beginning of the notes ... although I believe there were times when a long drawn out bass boOoOoooOoOoommmmm would hit and they would stay dim much longer than just a blink.

And in the names of education and curiosity...

Then what exactly is the true performance purpose of a capacitor ??

hahaha ... I'm very much a beginner with this stuff if you couldn't already tell :D
Last edited:
The large 1F capacitors are used to smooth/reduce ripple in the power supply voltage. When used in the commonly recommended ratio of 1F/1000w, their essentially useless. The relatively high ESR of most of the electrolytic caps sold further reduces their effectiveness. I know of no local shop that sells them. There were too many complaints that the caps failed to stop the lights from dimming.
Also class D amps are more efficient and less likely to dim lights, that is why I mostly only use those now for bass. Check the grounds on the headlights too, and check ground battery to body. IB does not take as much power, you must have a problem or that amp is a real hog. Maybe your alternator is not working right? Mine is 125A and have a 500rms alpine class D on two 15s, I don't know if the amp is near clipping but it has to be really thunderous to find any dimming at all, at idle. Had a kicker 700.5 in there before that would dim a little, but not bad really. I clamped that to 74A peaks but that was clipping the subs and I never used it that way for music.
@ Richie ... just did a search on "big 3" ... time to get to work I suppose.

Someone mentioned getting 4 gauge "welding wire" as it is basically the same thing but much cheaper than the kits.

@ Jol50 - Hey man! Not sure if you remember me or not but you helped me out tons in my quest for an IB in the trunk!

Big thanks to you as always :)

Over here at maxima.org there's a post on the big 3 ... after reading through it , it seems I should start with an alternator replacement.
Last edited:
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.