iain atkins

Chiark

Thanks for responding

It happens when actually going along, when a big bass note hits. If it is the alternator then do you know of an uprated one that will fit? Or shall I try the battery first.....I also thought about running a bigger cable from the alternator to the battery

Cheers


Iain

iain atkins

I have a MY97 turbo and whenever the tunes are cranked up all my lights dim whilst driving(looking like a mobile friking disco). I have a phoenix gold xs 2500 driving to perfect 10's (bridged to 2ohm, so amp seeing 1ohm) and a sony xm3040 bridged to stereo driving the 6" infinity components up front.

Is it the alternator being too weak or the battery giving up. I have been told to try an Optima D1050 dry battery or an Oddessy PC1250, as it is thought that would clear things up.

Any other ideas???

Much appreciated


Iain

chiark

Does it do this when actually driving along? Mine dims at a big bass hit when idling, but when running at a decent engine speed this doesn't seem obvious.

If think that it may be the alternator, as when idling you're only on just over 12V and the alternator's not doing anything. At decent revs, your system should be 14-15V.

You should be able to check this fairly easily with a multimeter, or alternatively your dealer can do a load test on your alternator, I believe.

chiark

Try cable first, and maybe consider upgrading your cable from the chassis to the battery. Dunno if this will do anything.

Alternators are expensive! You may want to get everything checked out by an auto electrical specialist first, and they may be able to rewind your alternator to correct the problem - if it is that which is the problem.

A second battery may help, though dimming sugests to me that you're probably dropping from 14 down to 12v.

I think that I'd stick a multimeter somewhere and keep an eye on where the voltages were actually going. Is that possible?

rockin'Ru

Iain,you need a bigger alt.Not sure what your car is but it's probably a 60 amp Fuji.I burned up 3 of these in one summer in my car running 4 MTX 6000's on a USAcoustics 1000F and a bridged MTX 4300x on my comps up front.I also run two massive Exide batteries.Both in the car[89 Suby hatchback 4wd]behind the seats on the floor boards,no battery under the hood.But I listen to music with the engine off alot and that's the ONLY reason for running multiple batteries.
You can put 10 batteries in your car,but the lights will still dim.Batts only put out 12.5 volts,no more.Alternators put out 14.4 volts.Your lights dim because the alt can't put out enough ampage to feed everything so it drops from the 14.4 down to the 12.5 volts.
Here's a simple way to show you the difference.Park your car in front of a wall or garage door or what ever[at night]and shut the car off.Now turn on the lights.While watching the lights reflection,start the car.You'll find they get considerably brighter.That's the diff between 12.5 and 14.4 volts.
I didn't have any luck finding a larger Fuji alt,so I used a Delco.It's a GM,but this is a BIG alt.It came from a 74 Caddy.It has the same mounting brackets that the Fuji had,but it was just bigger.It took me about an hour to convert it in.140 amps.No problems.
Skip the battery and go with the alt upgradeany way you can.It's the only way to solve the dimming lights problem.

Scooby Doc

Would it not be better to get your ears syringed and run at lower volume?

kryten

Before you try to upgrade the altenator which may be problematic (please post if you find an upgrade that fits!):

What guage cable do you having running from the battery to the amps and also from the battery to the chassis. Both are important!

What sort of power are your amps kicking out?

What size fuses are you using?

Also, measure the voltage across the battery and across the amp - these should be almost identical, otherwise you need larger cables.

A stiffening capacitor _may_ help - does in some cases and not in others!

A second battery will probably do you no good at all. Batteries are very slow at supplying power. Adding a second one will allow you to run for longer with the engine off but will not increase the voltage available with the engine running.

RonaldoH

Ian, invest in a lightening cap. This holds 12 volts constant stored from the battery and will surge power to the amp from the cap to the amp without hitting the alternators power output-thus affecting the lighting

Battery-(high guage live wire)---fuse---lightning cap---amp

This way your using power when the amps are drawing for a real influx of bass.
Friend of mine who is now th UK SPL amateur champion (148db) is running 4 12" MTX subs off a vauxhall omega battery with a lightening cap and he had no dimming and no lighting problems when holding a real low bass frequency for a long duration

Hope this helps.

[This message has been edited by RonaldoH (edited 11 November 2000).]

rockin'Ru

I run 4 MTX 12",1000 watts rms and then some and my lights don't dim,and I use NO cap.You also lose the amps dynamic power running only 14.4 volts.It's not a huge difference,but think of the lights.Which would you rather have.
Also,anything under 14.4 volts is below max alt voltage and when the cap discharges it has to recharge,dimming your lights on the off-beat.You STILL have a huge power consumtion.Caps are a crutch for SQ systems with weak charging systems.The cap draws power from the cars electrical system to feed the amplifier.
You can try the cap and other battery if you want.Please let us know the results.

rockin'Ru

Excuse me,you lose the amps dynamic power below 14.4 volts,not AT 14.4.My bad.

Scooby Doc

The fact that your lights dim suggests that your amp is drawing too much current. Surely this suggests that the cabling from your battery to your amp is OK but that it is a supply problem. I had loads of trouble with an alternator in my old citroen ax (but then it was French and made out of balsa wood and tissue paper).

Have you not got your voltmeter out yet. Its 10am on a Saturday. Come on, tell us the answer....

I am sorry abouth the ears thing - I am just jealous, but I do have a mate with a Clio Williams with a stratospheric amount of ICE who is deaf in one ear. I get quit a lot of wax myself and feel that a good clear out.....

Martin

PS His car was broken into in our local hospital car park, but the tealeaves were disturbed. He couldn't park his car there again.
Martin

Ederijke

Hi Iain

Are you sure that the XS2500 is running on a mono 2ohm load (1 ohm load per channel)?
According to the brochure I have this amp is only 2 ohm stable (so 4 ohm load in bridged mode). On 1 ohm it would use an enormous amount of current (and possibly get very hot) .

Maybe you could try to change the wiring to stereo bass (although SPL would decrease), or try a BIG capacitor.

Eric

Scooby Doc

Iain

I think Ederijke might have nailed it for you. A 1 ohm load is huge and the flashing lights probably represent near melt down.

Do you have any way of altereing the impedance on the amp in bridged mode. You should not need to switch to stereo.

Martin

iain atkins

Thanks for the suggestions guys, I fitted the lightning cap that used to be in my williams 3 and that has helped a bit. I also made another box (non isobarik) so I have the benefit of two drivers moving twice the amount of air. The next thing i'm gunna try is running the amp in stereo mode to bring the impeadence down. I will keep you posted, in the meantime if anyone has any further suggesions or has a part number of a bigger alternator that will fit please let me know (volt meter did show 14.8v when engine is running and dropping to 12.8v when a bass note hits).

Thanks so far....

iain

PS. I was going to replace the standard battery with a dry cell and get this to run the lot

Ederijke

Concerning the stereo or mono issue,

you could try stereo which is 4 ohm load to each channel (as each sub is 4 ohm).
Or you could try mono with the 2 subs in series to get 8 ohm load in bridged mode. Thats also 4 ohm load per channel.
So that would be a change from parallel (=2 ohm) to series (=8 ohm) connection.

Both (stereo or 'in series' mono) should get you the same power-output (but it's lower than with the parallel connection).

Eric

PS I was told once that a Legacy alternator should also fit an Impreza and should get you 90 ampere instead of 75.
It's super expensive though.

[This message has been edited by Ederijke (edited 12 November 2000).]

Scooby Doc

Iain

I presume your subs are in series and thus would pose an 8 ohm load. Current is inversely proportinal to resistance, so if your subs were in parallel then your resistance would be 4 ohms and the current drawn twice that in series.

How have you connected them up?

Martin

DrEvil

Iain,

You need to make sure the power cable from the battery is the right wattage.. plus you may find a capacitor (1 ferra) might help..

I found running two amps (F407 V12 & PT201) needed a 0.5 Ferra capacitor to stop the lights dimming when driving.. note the dash lights will flicker (well the clock at least) when the indicators are used regardless of what stereo system is installed (in my experience with two UK turbos).

Hope this helps.

Rgds, Alex

Rgds, Alex

iain atkins

Martin,

They are wired in parallel so the amp is seeing a 1 ohm load......maybe a have to sacrifice some power, shame though as they sound spot on with all that power going into them

DrEvil

Ermm.. where I put PT201, I meant KAC-X201T ... doh!

Scooby Doc

Iain
I have gone looking for my O grade physics text book. Informative website from Richard at

Nigel Bowles

Iain,
I had the same problem when I installed a pair of 250m rockfords driving a DVC seeing 1ohm and pushing silly power.
The first step to cure it is very simple, CHARGE THE BATTERY !!!
Then to stop the hammering the battery will be getting put a Cap in the system to provide power for the big hits.
I have a dry cell yellow top battery but have not needed to fit it yet.

rockin'Ru

Gentlmen,I'm not trying to be disrespectful in any way,but I'm a mechanic and can tell you that the battery's only purpose in a running car is 0.It's only there to start the engine and supply what power it can with the engine off.This has been the case since the dawn of alternators.All the caps and batteries won't help on heavy bass notes.The alternators supplied with a car from the factory are meant to cover the demands of that particular vehicles' electrical system,period.Throwing a high powered stereo onto the electrical system[or driving lights,or any other power consumer]will result in a deficiency in the entire system and cause dimming lights and early retirement of the alt.
It's like trying to power an entire city with a little hydro-electric science project.
Bigger alt,no problems.I've seen it time and again.Just 30 or 40 more amps will cure the problem.

chiark

RockinRU: You're right. The battery is there for starting, and occasionally for when the alternator isn't fully charging like at idle.

However, I think it would be worth checking wiring and all the other stuff first, as a new alternator is serious money over here (megabucks), and even a rewind of the existing one can cost a shedload. I don't understand why a cap should help, but I have seen and heard systems where they really have made a difference. No, I don't understand it.

Iain: have you tried running your amp in a less current hungry mode? Any joy? Checked the wiring?

Most importantly, <B>Have you upgraded the cable from alternator to battery and from battery to ground and alternator to ground?</B> This may be a cheap way of mitigating the problem... Maybe

Any luck with a multimeter yet? I think that that may reveal the problem. Erm.

(Very good thread this one, and a definite for the FAQ when we get some form of way forward )

iain atkins

Chiark

I have been told that the alt is 70A, so in theroy it should be ok (the alt on my Williams 3 was also 70A and there was no problem what so ever with dimming lights). Checked with a voltmeter - 14.8v when running (and no sounds), 12.8v when bass note hits (sometimes as low as 12 when really working it).

I'm going to try and upgrade the wiring at some point, can't do it this weekend or next (cuz of the rally - who else is going??). Tonight I might try and run it in stereo and up the gain a bit, shame though because they sound amazing with huge amounts of power (2 perfect 10's).

Rockin ru - I do understand where youre coming from but surely a bigger battery will help??

Cheers


Iain

chiark

That's very interesting... Where did you take the measurements for voltage? (ie at battery, alternator, fuse block, ?)

The output for your amp at 2 ohm mono isn't stated (http://www.phoenixgold.com/xs2500.html), but for 4 ohm mono its 500W, so let's guess at 750W for 2 ohm mono as it'll have some current limiting stuff in there somewhere. This may be wide of the mark as max quoted power is given at 4 ohm mono, so 2 ohm may be restricted due to current limiting circuitry...

Efficiency isn't quoted, so I'll assume 75%. That means input power = 1000W. At 14V, that's 71 Amps, which equals shedloads of current (Imperial shedloads too, not the smaller US shedloads ). More than the alternator can supply when your lights are on. Something will give.

What fuse are you using on the amp?

Dropping down to 2x4ohm will take you to 125W per sub. Quite a drop. Given that doubling the power gives a 3dB increase output and that a 10dB increase is generally taken to be a doubling in perceived loudness, you'll be losing quite a bit of output. On the bright side, your losses in speaker cable will be less .

I'd start with upgrading the wiring between alternator & battery, and alternator/battery/car. Worth a shot.

How have you earthed your amps at the moment? If you've got a multimeter handy, can you check the resistance between your ground point and battery negative, or alternator ground. If it's large, it may be time to look for another earthing point.

Might be worth checking the resistance of your power cable from battery to amp too.

What style fuse are you using? The least resistive is the flat blade style.

After all this, it may be worth trying to find a recently scrapped legacy and "yee-haw"ing the alternator into the Impreza...

My thinking cap most definitely "on" now...

[This message has been edited by chiark (edited 15 November 2000).]

rockin'Ru

chiark,you're right on the wiring.It all should be heavy duty.As an example,here's some of my screw-ups.
After burning up 3 60 amp alts,$99 a pop,I "shoe-horned" in the Delco and KNEW I should upgrade the power wire to it,but didn't have the cash on hand and wouldn't for a few days,so I just ran it.And I knew I should've gone easy on it but...one night on the way home,jammin hard,the voltage dropped down to around 9 or 10.I shut it down and took a look and found the fusable link box melted.Lucky I didnt burn the car.
So,like an idiot,I bypassed the box and ran it right to the battery.The very next night,I lost power again.This time the wire from the alt just disintergrated.The clip and first 10" of wire were just gone.Lucky again.
Things are good now with 4 gauge power wire from the alt.
Ian,if you're drawing power from the battery while the engine's running,a bigger battery will help solidify your 12.5 voltsbut the poor alt has to recharge the battery and still try to bring the volts up to 14.4.It's going to die.Look for black soot under the hood above the alt.That's the brushes burning up.The cap will keep the amplifiers supplied,but the rest of the system suffers.
Where I work,we have huge 240 volt motors that have caps the size of 16oz beer cans,and when you turn one on,the motor starts turning instantly and a second later the lights dim,when the cap recharges.Not when the motor starts.Just an example.
I just don't want to see another person spend 3 or 400 dollars on every other option possible except the source.
You'd have a good start on a bigger alt if you don't get a cap,but as chiark said,a rewire is in order regardless.
Good luck Ian.

iain atkins

Chiark & Rockin Ru,

The main fuse (for both amps) is a flat blade rockford 60A (AGU 60Amp), and until now has never blown, does it takes a lot more than 60A to blow it?

The suggestion about the legacy alt sounds very interesting, does it go straight on?? The only other one suggested was an AC Delco.

The volt tests were done at the battery, I will try it from the amp end in the next few days.

Thanks for your help so far guys


Iain

rockin'Ru

Iain,the fuses usually don't blow unless there's a surge.Like when the power wire comes in contact with ground.All available power in front of this wire is discharged through the wire to the ground[path of least resistance]and the fuse keeps the car from burning up.
I don't know about the alternator.I'm very familiar with the old,but not the new,so it's kinda out of my league,but all charging systems are alike,and a compitent mechanic can retrofit any alt into your car,regardless of make.
Look at the casing of your alt and go to the parts store and ask about an alt that will fit your aproximate year with every available option.Power everything including heated seats.You may be suprised.

Ederijke

One more thought

When connecting amps to the battery, also upgrade the connection between the chassis and the negative pin (pole?) of the battery.
Because the current needs to flow through the battery. Too small a negative wire on the battery will also cause loss in voltage.

Eric