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  1. #1
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    Default Subwoofers and 'Power Drain'

    Yes, i'm posting another topic, sorry about that!


    Basically i am planning on putting some subwoofers into the Roadster now, but bit concerned about draining too much power 'when the bass kicks in', im sure i read that it can put it into limp mode or something?


    Really i don't want to spend money on a new/used system and that as i've got an old system from a previous car that works fine.


    The system:
    Sony Xplod 1600W Amplifier (12V, 90A) (20mm˛ cable)
    2x 1200W Sony Xplod Subwoofers

    These are peak power values by the way
    Not i'm not expecting to run the system at full power, but maybe half power or something would be nice?



    Basically, does anyone know what sort of power draw i could allow before wreaking havok with the cars electrix?
    Last of a dying breed

  2. #2
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    Default Re: Subwoofers and 'Power Drain'

    It's volt drop on the system that can interfere with the system as you draw the heavy current..

    You'd be advised to get a higher capacity (diesel) battery and maybe a diesel alternator to help keep the supply up at (or closer to) 12V during peaks.
    fq101.co.uk

  3. #3
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    Default Re: Subwoofers and 'Power Drain'

    Ah yeah i get that its the volt-drop that causes the issues, maybe i should of worded it better

    Based on the standard Roadster battery and alternator, is the system going to be too big? I mean i can always whack the gain down to very low.


    Could i cause any lasting damage to the ECU or SAM etc if i overload it?
    Obviously the battery and alternator probably won't enjoy the extra load...

    When i had it in my Celica the lights would dim with the bass but that was the only issue, that i can live with
    Last of a dying breed

  4. #4
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    Default Re: Subwoofers and 'Power Drain'

    You could always monitor how much volt drop you're causing with a meter ...

    You're not overloading the ECU/SAM, you're just providing it with a fluctuating supply by having it on the same 12v system, it will have safeguards in place for some level of protection..but if you really want to beef the system up to cope with the power demand, upgrade battery, alternator and wiring ... and think about adding a 2nd battery nearer the amp.
    I.e. upgrade the cars 'system' before adding the audio system.
    fq101.co.uk

  5. #5
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    Default Re: Subwoofers and 'Power Drain'

    Quote Originally Posted by TheAlmostInvisibleMan View Post

    You're not overloading the ECU/SAM
    I.e. upgrade the cars 'system' before adding the audio system.
    Again not very well worded by me!
    I meant if i overload the Smart's power system with too much bass and that haha, and meant if i give the ECU/SAM a dodgy power supply (fluctuating sounds better) could that cause either of them lasting damage do you reckon?

    Could i say does anyone know what volt drop would be allowable on the Smart without damaging ECU/SAM/Alternator?
    I might just connect it all up outside the car and stick a multimeter on it like you suggested

    I do actually have Foundation Degree in Electrical and Electronic Engineering, although i do sound like a novice!


    Last resort would be to upgrade battery or alternator...
    Last of a dying breed

  6. #6
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    Default Re: Subwoofers and 'Power Drain'

    Quote Originally Posted by Danohosko View Post
    Could i say does anyone know what volt drop would be allowable on the Smart without damaging ECU/SAM/Alternator?
    There is no 'safe allowable volt drop data before you damage it' , it's a car and it has to cope with the massive voltdrop encountered on cranking (but the car sheds load so it can concentrate on cranking...)

    ... but you're suggesting subjecting it to it all the time when other ancillaries are being used too ... you might be 'okay' with the basic alternator and stock battery but it's hardly ideal....

    Common sense would suggest you beef up the system by errr ....upgrading alternator and beefing up storage (bigger and/or) 2 batteries and the wiring.... I think I'm repeating myself ...
    Upgrade and do a proper job ! or suffer with it.

    If the sub is big enough and you want to play it loud, the 1st resort would be to do the upgrades OK
    fq101.co.uk

  7. #7
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    Default Re: Subwoofers and 'Power Drain'

    I hear ya i hear ya

    Thanks for the advice man, i shall look into alternators and put the subwoofers on the shelf for a little longer, at some point in the future i'll probably start an 'alternator upgrade' thread haha

    Cheers again!
    Last of a dying breed

  8. #8

    Default Re: Subwoofers and 'Power Drain'

    I really doubt the equipment you have will have any bad effect on the battery or the system.

    Make sure you use at least 4 gauge power and earth cable, also for good measure upgrade the battery and engine earth, if possible do the alternator cable.

    As the alt will charge at 14.4v you should have no issues when engine running, if u wish to use with engine off then maybe you will need extra battery, but no harm in getting a bigger normal battery, my car has a nice big Volvo battery and I have never had any charging or power issues from my system.

  9. #9
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    Default Re: Subwoofers and 'Power Drain'

    The alternator will have a finite power output I. E. Current at that particular voltage) , load it too much and you may well burn it out if not just add considerable noise to its output.
    fq101.co.uk

  10. #10

    Default Re: Subwoofers and 'Power Drain'

    Quote Originally Posted by TheAlmostInvisibleMan View Post
    and maybe a diesel alternator to help keep the supply up at (or closer to) 12V during peaks.
    The diesel alternator will not plug in and will not work.

    Peak powers are usually 4 times what you'll normal get at full whack. If you have AC then just leaving it turned off when you are running the system at full pelt will be fine. Chances are, you'll mainly run it at sensible power because 2 subs and a big amp are overkill in a car with such a small cabin and a soft top roof. So the standard AC ready alternator will be fine even with the AC running and the subs going.

    Do upgrade the battery to a diesel one. It will take longer to charge though. Maybe consider a split charge system with a separate battery.

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