To cap or not to cap?

[Junglist]

What's the benefit of a capacitor, do I need one and what rating do I need if so?

I have a 60w x 4 (26w x 4 RMS) alpine head with direct feed from battery powering the 4 speakers, a bridged 2x100w RMS amp powering the 500w max sub (I'm guessing 150-200w RMS) powered direct from the battery and I have a big 250 battery (90ah) charging off a 90amp alternator which pushes out 14.2 volts at idle under no load. I'm about to fit 100w RMS (300w max) infinity speakers in the back and power them independently from another alpine amp that gives 50w per channel RMS (2 channel).

Will a capacitor improve anything? Sound quality's a priority for me and I do like my music reasonably loud. I like my bass to be as clear as possible and don't want any distortion or loss, degredation, etc.

[Nate]

does it make your headlights dim with the bass when you crank it up? if yes, you need one.

[Junglist]

No. Just feel as though certain sections of music aren't quite as clear as they could be. Maybe I'm imagining it though.

[Nate]

Just feel as though certain sections of music aren't quite as clear as they could be

as i've said before, a car is more or less the worst possible environment for hi-fi sound ;)

[Junglist]

I'm aware of that! Just want to get it the best i can without compromising the car's originality. If there are any improvements i can make, i'll make them.

[fonzooorooo]

I doubt you're drawing enough power to need a cap.
If it were me, i'd be looking at the box your sub's in... check the internal volume, then get the tech specs of your sub, and pop them into one of the box calculators online... chances are that if you're using a generic "sub box for X" sub" it'll be the wrong size and MUCH too weak. I've just built a box for a 15" paper cone bass driver (for PA use - sounds awesome in the car though!!!) that's 36mm thick (2 boards of 18mm chipboard) which sounds a monumental amount better than the original box (15mm thick, with a big plastic plate housing the low-pass filter and input sockets straight in the centre of the back of the box!)

Time spent reinforcing the the box is well spent, as the air pressure created by the movement of the driver deflects the walls of the box, resulting in wasted effort, and the box being out of phase with the driver, resulting in phase cancellation. Also consider wadding inside the box. Legend has it that this can lower the low frequency response of a cabinet by 10 Hz. If audio places are charging silly money for wadding, or not stocking it at all, wander into a haberdashers [bet that word's never been on this forum before!] as it's the same stuff that's used in cushion covers etc.

Is your box ported, or sealed? A ported box tends to accent frequencies just above the resonant frequency of the driver, (gives the impression of a "bassier" sound, but at the expense of efficiency) whereas a sealed box rolls off much more gradually (smoother response across the frequency range, hence likely to integrate better to your tops). Sealed boxes that are too small are often used for car subs, as the air compressing inside supports the driver, meaning the driver's less likely to fail under extreme load conditions. When doing the maths for my 15", a sealed box would need to be about 4 feet high, 2 feet wide, 18" deep... a ported box worked out at less than 1/2 that size.

Funny, I say all this, but I'm running a 10" sub i got for 15 quid in a generic sub box in the car... with the amount of road noise, I really can't be bothered to change it!

[Junglist]

sealed box, thin walls of MDF, speaker terminals in the side screwed on by a plastic housing. Inside the box, there's no padding - just wires going from the terminals on the wall of the box to the terminals on the sub itself. box is roughly a foot high, a foot deep, a foot and a half wide angled so you can tuck it against the rear seats (which I have done). How would you feel about making me a better box and how much money would you want to do it? I think the sub's a 10 inch one. It's Alpine and it's 500 watt "max" running off a bridged 2x100 watt RMS amp screwed to the other side of the box from the terminals.

[jbo]

One thing that can really kill the sound in a car is not having your speakers in phase. Make sure all the wiring is correct IE + to + and - to -.

If its not it can really through it out.

Jason

[Jay4424]

I doubt you're drawing enough power to need a cap.
If it were me, i'd be looking at the box your sub's in... check the internal volume, then get the tech specs of your sub, and pop them into one of the box calculators online... chances are that if you're using a generic "sub box for X" sub" it'll be the wrong size and MUCH too weak. I've just built a box for a 15" paper cone bass driver (for PA use - sounds awesome in the car though!!!) that's 36mm thick (2 boards of 18mm chipboard) which sounds a monumental amount better than the original box (15mm thick, with a big plastic plate housing the low-pass filter and input sockets straight in the centre of the back of the box!)

Time spent reinforcing the the box is well spent, as the air pressure created by the movement of the driver deflects the walls of the box, resulting in wasted effort, and the box being out of phase with the driver, resulting in phase cancellation. Also consider wadding inside the box. Legend has it that this can lower the low frequency response of a cabinet by 10 Hz. If audio places are charging silly money for wadding, or not stocking it at all, wander into a haberdashers [bet that word's never been on this forum before!] as it's the same stuff that's used in cushion covers etc.

Is your box ported, or sealed? A ported box tends to accent frequencies just above the resonant frequency of the driver, (gives the impression of a "bassier" sound, but at the expense of efficiency) whereas a sealed box rolls off much more gradually (smoother response across the frequency range, hence likely to integrate better to your tops). Sealed boxes that are too small are often used for car subs, as the air compressing inside supports the driver, meaning the driver's less likely to fail under extreme load conditions. When doing the maths for my 15", a sealed box would need to be about 4 feet high, 2 feet wide, 18" deep... a ported box worked out at less than 1/2 that size.

Funny, I say all this, but I'm running a 10" sub i got for 15 quid in a generic sub box in the car... with the amount of road noise, I really can't be bothered to change it!

We salute you sir!

[Funky Diver]

I vote fonzooorooo does a "Complete Guide to ICE for Numptys" (aka me!!)

Like when to use stuff and when not to. The thought of picking out a nice pink dress to have a bit of cross-over in my car is scaring me...

[fonzooorooo]

Let me be the first to dispel any ideas that i'm any kind of ICE guru... ICE is specialist, and my knowledge is general off the back of research building simple cabinets for PA/bass guitar and years of mucking about with home studio type stuff.

This is as far as my "guide to ICE" will get - Box design and building in 1 easy paragraph:
To find out about optimum cabinet sizes, you'd need the model number of your sub, then google it to get the "thiele small parameters" specific to that driver. The act of googling something along the lines of "speaker box size calculator" will find you some freeware which you can plonk some of the list of meaningless numbers into, and which'll give you an internal volume for a cabinet. A bit of maths'll tell you how big the cab has to be, then get the board cut to size at your local timber yard. That's the easy (and cheap!) way... cuts are all straight and square, so you should just be able to glue it together... (use plenty of glue - joints have to be air tight!) Screw the driver in using every screw hole. Finish to suit.

My own ICE:
After killing a fair number of speakers by clipping them by running underpowered headunits, I've gone down the path of amp-ing everything in my car... 2 channel amp driving the fronts, with high pass filter in, and a 4 ch. amp running the rear speakers and sub. (high pass on the tops, and low pass on the sub) headunit's an alpine, amps are cheapos(mutant and boschmann(!)), speakers are JBL and sub's a real cheapo! All set up so it sounds balanced with the EQ flat on the headunit, then increase the dB on the sub to drown out the roadnoise. No pink dress for me!