To Cap, or not to Cap?

[filthgrinder]

Hey guys, after having all of my system stolen from my car i'm finally starting to get a new one together. I have run 1/0 gauge from the battery to my boot. There it splits to two 4 gauge wires to each of my amps. These are Rockford Fosgate T4004 and T10001 amps.
The monoblock will be running 2 RF T112D4 subwoofers (600W RMS, 1200 Peak)

I have read that a capacitor will be unnecessary in alot of threads and was wondering if this would still be the case running this gear? If so would I put the capacitor before the power distribution block or afterwards on the monoblocks wire?

Thanks heaps for any help you can provide

[daron]

ya dont really need caps
if ya running the correct size wiring from battery youll be fine
a good battery and alt will be fine

[filthgrinder]

What are the stock VT alts? Good enough?

[1991_Vn2nV]

For that setup, the stock VT alternator should be fine but there are higher output alternators available from Bosch I believe. I think stock is 85amp, you can get up to 120amp but i'd be looking at the battery before the alternator.

With 0 guage to distribution block, then 4 guage to amps, i'd say you should be fine running 1200wrms. If you wanted, you could run 2 guage wire to the mono as it is meant to take up to 0 guage wire for power and ground I believe.

[roon_VR]

Buy a better and more beefy battery and upgrade your earth points in your engine bay and you should be good to go without having to install a cap or a new alternator. I always assumed commodore alternators were pretty good.

[| evaN |]

Caps are pretty much there for looks and do nothing.
A better choice would be to upgrade the wires in the engine bay. Remember theres no point have 0 gauge wire coming from the positive terminal if the negative side has like 8 gauge wire.
Do that first and then upgrade the battery afterwards if its not up to the task.

[filthgrinder]

So its looking like just upgrading the big 3 with 0 gauge wire?

[kopper69]

Caps are pretty much there for looks and do nothing.

Caps do have a purpose in some cases, just not all.

[filthgrinder]

Caps do have a purpose in some cases, just not all.

Thats what I thought, just needed to know if this was one of those cases as will be running some pretty nice (thirsty) stuff

[| evaN |]

My most infamous test results, back from the Great Bin In The Sky. Enjoy. Keep any replies clean & on topic.

The Test System:

1x Ford Festiva Trio
1x JBL W15GTi subwoofer (DVC 6ohm, wired for 3ohm)
Street enclosure tuned to 48hz
1x JBL A1201GTi 1200WRMS Monoblock
2x SuperCharge Gold 900CCA batteries
1x Stock 60A alt.
1x 0g wiring harness
1x Lightening Audio Competition Series 1.0 Farad Cap
1x Alpine headunit (5V subout, unclipped)

Test Equipment:
1x DMM
1x Goldline DSP-30 RTA

Test Method:
Amp hooked up to CRO, gains adjusted @ 60hz until clipping, then backed off. LP Xovers set to 80hz using CRO & DMM.
Enclosure strapped Street Beater style, ports blocked by tail gate, filler pack in wheel well and false floor installed (this gear is normally removed for SPL).
Engine idling @ 800RPM. Tests run with voltage on amp terminals showing @ 14.1V idle.
15 minutes cool down between runs.
Run some tones, find the "mad note" @ 51hz and commence testing.

(Quick Note: This system doesn't suffer from typical power issues such as blinking headlamps at night.. its a stout power supply)

No Rear Battery, No Capacitor.
Voltage On Burp: 12.8V (1.3V Drop)
Output: 140.7dB, 140.7dB, 140.6dB

No Rear Battery, 1 Capacitor.
Voltage On Burp: 12.6V (1.5V Drop)
Output: 140.5dB, 140.4dB, 140.3dB

Both Batteries, No Capacitor.
Voltage On Burp: 13.8V (0.3V Drop)
Output: 141.0dB, 141.0dB, 140.9dB

Both Batteries, 1 Capacitor.
Voltage On Burp: 13.2V (1.2V Drop)
Output: 141.0dB, 141.0dB, 140.9dB

if it doesn't help in high current applications like this then its a waste of money IMO

[StoneX]

All that test is showing is that a capacitor can't sustain a constant current draw, which is just common sense if you know how a capacitor works. People don't listen to test tones and if they do, they need more than a capacitor to fix their mental problems

Music is dynamic, so the current draw by the amplifiers will be up and down all the time and will not draw anywhere near the current of a test tone.

I'm not a fan of capacitors because people recommend them for the wrong reasons, but the theory of a capacitor "filtering" out voltage fluctuation in a system playing music is completely correct. But can you see or hear the effects? I don't think you can hear the effects but i'm sure you'll see the effects when it reduces headlight dimming... And that is the only application i'd recommend them for.

[UNKNOWN]

Caps are pretty much there for looks and do nothing.
A better choice would be to upgrade the wires in the engine bay. Remember theres no point have 0 gauge wire coming from the positive terminal if the negative side has like 8 gauge wire.
Do that first and then upgrade the battery afterwards if its not up to the task.

If they did nothing why do people run them in sound off cars?
Mate has a sound off Camira with 0 gauge wiring and he still needs a cap...

[| evaN |]

Mate has a sound off Camira with 0 gauge wiring and he still needs a cap...

i was running over 3000wrms using one battery up front and my headlights never dimmed which is the only reason ppl use caps as StoneX mentioned. If you were to upgrade the wires up front properly then there wouldn't as big of a voltage drop to cause your headlights to dim.

[| evaN |]

Music is dynamic, so the current draw by the amplifiers will be up and down all the time and will not draw anywhere near the current of a test tone.

actually im pretty sure its the other way around. you draw more current with music then a test tone. why do you think ppl use test tones for spl? because with the same current, you'll be louder with a test tone

[stocky]

If they did nothing why do people run them in sound off cars?
Mate has a sound off Camira with 0 gauge wiring and he still needs a cap...

cause as he said, theyre there for looks

[StoneX]

If they did nothing why do people run them in sound off cars?
Mate has a sound off Camira with 0 gauge wiring and he still needs a cap...

They do nothing for SPL cars and people who know what they'r doing in SPL don't use them. The results from the above test show that and any electronics knowledge would tell you that too.

actually im pretty sure its the other way around. you draw more current with music then a test tone. why do you think ppl use test tones for spl? because with the same current, you'll be louder with a test tone

It's not the other way around. A full power sine wave (test tone) uses a massive amount of power. Music sound waves are varying in frequency and volume constantly even when the volume is at max, music varies.

People use test tones to match the resonant frequency of their car. They use test tone sweeps to find the resonant frequencies of their car. Do some research into SPL if you wish to know what resonant frequencies are and why they're important to match.

[1991_Vn2nV]

Thats what I thought, just needed to know if this was one of those cases as will be running some pretty nice (thirsty) stuff

A 1000wrms amp is not that thirsty when you look at what is out there.

[vs-6]

Hey guys im an electrician and therefore i have done a fair bit to do with caps (capacitors).
Alot of people seem to be miss guided by other's on here.
Capacitors up the voltage and so when your sitting at the lights with your lights on and your music blaring and you can see your lights dimming this can mean your need a cap but before you would put in a capacitor you would up the calbes going to your amps, put in a higher output alternator run some bigger cables from your alternator to you battery which is overlooked in most half decent installs and get a good battery if not run 2 batterys something like a deep cycle dry cell battery.
If all of this doesnt work it would be time to install a capacitor.
Another reason capacitors are used is because in a big coil of wire (a sub contains a huge amount of wire all coiled up) you can get things call induced emf's and power factor which can effect the way your car used power, a capacitor can counteract this problem.

[filthgrinder]

Cool, thanks for the feedback. I will just hold off and leave it as a last resort if I experience any problems with dimming AFTER battery and alternator replacement (if necessary)!

Just didn't want to waste money that I can use to help pay for the subs I'm after if it wasn't needed.

[daron]

dont watse ya time wiht new alt unless yours maybe be slow/buggerd make sure battery is fine
in my vt i run 3 1000 watt amps (not crappy ones:P ) and lights dim a little bit now cause battery is going to go soon but when battery is fine theres no lights dimming
like everyone says good cables good earths youll be fine in a vt

[filthgrinder]

Excellent, thats what I wanna hear! Thanks

[Joe Peeps]

I love how BlackIce's test is repeatedly brought up to demonstrate that caps are useless, i remember when i used to believe everything on CAA aswell!

Look anywhere and you'll find that the benefits of a cap are negated in SPL as stoneX has pointed out - musical applications however, or another story - although the necessary size cap vs cost vs benefits is a different matter altogether.

[filthgrinder]

Well I was looking at trying to do some SPL, though I have been told i'd get nowhere with a Commodore and lose sound quality, thats why I'm going with the T1's instead of the T'2 now.

[1991_Vn2nV]

Running 2 of the 12" T2 woofers in a decent setup would make some very nice SPL numbers. Obviously they'd make larger numbers in a hatch, but you'd still do well in a commodore and retain decent sound quality with the right subs. It depends how serious you want to get, running 2 rockford subs of any sort won't break records as RF don't have any major SPL subs compared to what is available from brands like DD (or even Pioneer), but you'd still do well in local car shows and sound offs.