Amp/Sub - Power

[Raz316]

Right this afternoon i put a phoenix gold qx2180 amp and a 12" JL sub in my car.

Basically when the sub is active the backlight of my cd player dims slightly. Its very noticeable with a track that has a bass drum. Is this something I should worry about, does this mean my battery is too weak?

cheers!

[Ant]

hmm, recharge and re-asses dude.

does it still do it engine running ?


if it does this regardless of engine state then I might suggest a power cap would be a good call to cure this woe.

[Dom]

It's not a powerful amp so I'd say power cap is overkill. Sounds like the battery is lacking a bit.

[amit325i]

It shouldn't do that because you have an amp, unless your pumping the unit more, and the headunit is not powerful enough to drive the normal speakers in your car.

[Kedge]

Could someone tell me what a power cap does because i've been contemplating getting one of these.

The way i understand it is that it gains a charge of the battery and when the amp needs the extra power it takes it from the capacitor, is this about right?

[billgatese30]

sounds right to me mate

[Dom]

Could someone tell me what a power cap does because i've been contemplating getting one of these.

The way i understand it is that it gains a charge of the battery and when the amp needs the extra power it takes it from the capacitor, is this about right?

essentially it is a second battery... the idea is that when a big bass note comes in the juice is sucked from the capacitor and then recharged at the normal speed thus avoiding dimming lights etc.

[A1BMW325iSport]

buy a cap and run on the power feed to the amp

[placey]

raz

bear in mind that a power cap can only charge itself as fast as your battery can supply it and that it has it's own overhead. before fitting a cap consider the following carefully:

when your bass comes in it's obviously drawing more power than the car can spare - hence other power draws suffer. this situation cannot be continued over any length of time without something failing, probably your battery and probably on a cold day when you really need the car.

on the most simple level ensure that the power cables to your amp are plenty large enough and propery terminated. small or poorly terminated cables cause no end of strange problems.

what you don't state is whether this happens engine running or stopped. put simply if the engine is running it's the alternator supplying power, if stopped it's your battery.

the factory alternator for 316i is 65 amps with about 10 amps headroom, 15 amps max. how big is the fuse on the amp? bigger than 10 amps and this will explain your troubles. 95 amp alternators, giving you 40 amps for your system, are about 100 exchange from euro car parts. fit in about 15 minutes. you can go larger but the cost goes larger too.

a much larger battery than the factory standard unit fits in the 316 battery tray. go for the largest diesel car or truck battery you can fit in there, budget about 90 retail. avoid the dedicated car hi-fi batteries for single battery use as they don't much like engine starting duties, they are for more serious setups and steady slow current drains, thus giving extended car park system times. diesel batteries are designed for starting diesels with pre-warming duties etc so nice and strong.

if you do these upgrades and still have troubles then you'll need to upgrade some of the car's cables under the bonnet, bit this is unlikely to be necessary as bmw fitted reasonable quality cabling from the off.

paul

[Kedge]

Cool, might have to get one. What is the farad rating, is it the amount of current that it can hold?

[Sextons_Cardiff]

Not knowing a few things about the situation ill take a stab in the dark here...

what gauge (size) is the wiring your using for the amp?

What other speakers is the Head Unit running aswell as supplying the pre-outs?

A power cap isnt like a second battery, more like a power resevoir, which can be used when the bass drops very low and hard, and the amp needs that extra boost to cope with it....

But its not advisable to run an amped system with the engine off as the battery can only act as a power source for a short period with the system running at mid/high volume as it will have a high draw from the battery...

Plus if you add a power cap, remember that it also needs to draw power from the battery to recharge itself during and after its been used....

If your planning a serious install and will be upgrading your battery, may i suggest either replacing your battery with a one thats more designed for audiophiles such as a Stinger battery or spiralcell battery like Optima...

The easiest way to explain Farad ratings is... the higher the RMS output of your system, then the higher the Farad needs to be...


Im at the start of collecting bits and pieces for my next install, and im unsure whether to get a 15 farad or 30 farad PowerCore, or fit a SplitCharge system.... its when you get to this point that you have to sit back and really think if its worth all the hassle!! lol

[Raz316]

Wow, thanks for the usefu replies people.

When i was testing it, it was with the engine off. I charged the battery last night and will find out what it's like with the engine running.

Ill post back later today.

[Dom]

In that case you shouldn't have any problems with the engine running. It's only a low power amp.

If you do have problems with the engine running then as suggested check the wiring and upgrading where necessary. Upgrading the battery to a diesel model will also help.

The last thing I'd be doing in this scenario is adding a power cap, seems an unjustified expense for an 180 watt amp.