Large Capacitors for Car Audio

Discussion in 'Electronics & Electrics' started by @rt, Dec 5, 2010.

  1. HairyMerkin

    HairyMerkin Member

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    Do you headlights dim on large bass hits?
     
  2. OP
    OP
    @rt

    @rt Member

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    Definitely not, although only two of the three amplifiers are in use at the moment.
    Next pay I get the last pair of speakers to finish it off.

    My Falcon with a single 4x4 battery handled the three amp install
    without any dimming of lights, so I can only assume the Surf will.
     
  3. mtma

    mtma Member

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    Dimming lights is not a good test. The reason for this is because dimming lights only shows you that the circuits shared by the headlamps and amplifier (i.e something between the alt and fusebox) is deficient.

    A crude 'wiring is ok' test would be to check if a lamp connected right at the terminals of the amplifier will dim or not during heavy operation. Of course a definitive answer is to oscilloscope the shit out of every power node along the system, but it depends on your target and available equipment as to how worthwhile the extra information would be.
     
  4. m0n4g3

    m0n4g3 Member

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    Actually Lost... i'm completely against you here, SPECIALLY on big powered systems.

    I run an mr2 with 7kw worth of power for amps (2x Digital Design M3's (3000wrms each), 1x Digital Design C4a (100wrmsx4) and 1x Digital Designs C2a (200wrmsx2).

    So according to your 1kw = 1farad ruling there, you would need 7farad. This will equal about 700--1050 (assuming that the caps are 100-150 bucks each).

    You would be MUCH better off using a dual battery setup (in a normal sedan using a sealed AGM or Gel something like an Odyssey 2150 or an Optima Yellowtop battery in the boot), and short runs of 0awg cable.

    Not only would you be able to run your system for a lot longer than having the caps in there... you are miles ahead in terms of money, and can spend more money on decent amps/speakers.

    The mr2 can run it's system for approximately 2-3 hours and only THEN does it start to get to the scary low voltage (11-11.2v). Anything lower than that the car needs to either get charged or run without the stereo.

    BTW the car audio in this is setup for IASCA SQ Intermediate classes, and also DBDrag Racing Super Street 3-4.

    I personally don't recommend the caps as you have better value for money with proper sealed AGM or Gel batteries, and using appropriate power cables for it.

    *PS just as a note for you... 145.9db in an mr2 reading of a TermLab*
     
  5. xc351

    xc351 Member

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    u are much better of getting a super cap like 500-600 farad a guy at work bought one handles the job great. but yes a 2nd batt would be good get a large 4wd batt should only be $120 (presdent 780cca n70zzh battery)
    why do u need a cap any way. $5 says u are running a doggey set up run bigger c ables i used 95mm2 cable in my old xr6 and still ran 3 batteys but unless u are running 5000wrms+ (yes that rules out any stuff u get from supercheap or repco) get what set up are u running.

    For reference i was runninga DD9915 with dual .5ohm coild running in parrall to a modded earthquake phd10000 with quad 0 gauge inputs
     
  6. tumutbound

    tumutbound Member

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    Large capacitors as a 'power reserve' have no place in a car.

    Those capacitors should be used for projects like these.

    Sparks! burning metal! what more could you ask? :thumbup:

    Warning: Do not use while driving!
     
  7. Ulan

    Ulan Member

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    I read a rather large analysis on a car audio forum about these 1-2 farad car audio caps involving pages of maths basically saying what you guys are also saying - that they're worthless.
     
  8. m0n4g3

    m0n4g3 Member

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    I have read such articles over and over, and they all say the samething, for the price you may aswell invest in a decent sized deepcycle battery and enjoy the benefits of extra current ontap aswell as longer runtimes!

    :)
     
  9. OP
    OP
    @rt

    @rt Member

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    Another question, related to in car audio....

    I have three Pioneer amplifiers, one is high quality running a sub,
    the other two are the lower shelf units marked as 300 Watt max power.
    On the sticker underneath,
    these amps say 60 Watt (probably RMS) into two 4 Ohm speakers.

    I have one of the cheaper amps running a pair of 6x9s in the back and all is well,
    The other is ready to go into the car.

    I have (not yet installed) a pair of 4 inch speakers for the dash,
    and a set of high quality ($399 retail) 6 inch splits for the doors.
    If I use the left over amp for the splits, and then use an output from the head unit
    for the 4 inch speakers in the dash, will the 4 inch speakers clip before the rest of the stuff?


    The head unit is Pioneer DEH-4250SD which claims 22 Watt x 4 channel output
    (says 50 Watt x 4 on the front face which I assume is peak power).
    Cheers, Art.
     
  10. xc351

    xc351 Member

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    @rt
    i ahve run similar set ups. its all a bit iffy but u can adjust all teh level so its no real drammas eg. if 4" slip at arround 25% turn down there gain.

    pioner gear is not my fav i like company that will advertise there RMS values.

    u also need to know what u want DB or SQ. make sure u sound deaden your doors even if its just flash tac from bunnings.

    id also get rid of teh 6x9"s as thease are a jack of all trades master of none.
     
  11. OP
    OP
    @rt

    @rt Member

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    Too late to get rid of the 6x9s, they are in the back of a 4WD wagon anyway,
    I don't think I'd even percieve any stereo separation from them.

    I don't see how I can turn down the gain of the 4 inch speakers if they are
    powered directly from the head unit other than turning down the volume
    which would in turn, lower the volume of everything else connected to amplifiers.

    The goal is to drive all of the speakers without any clipping using the equipment I have.
     
  12. atmo

    atmo Member

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    Here's a theory regarding the headlight dimming I heard from an old school car audio & electrical guy I knew a few years back. It seemed to make sense.

    The alternator & regulator in a car will usually output 13.8 to 14.4v, but they don't react particularly quickly under sudden transient load conditions. The most that a fully charged regular car battery with no load can produce is around 12.5-12.6v. Dropping the voltage to the headlights from 14.4v to 12.5v is enough to notice some dimming (which is why older cars headlights aren't as bright at idle as they are when the engine's revving higher). Dropping the voltage from 14.4 to below 12v would be much more noticeable.

    Let's say for example, you had an audio system capable of drawing 70A (500w at 12v, 60% efficient). Let's also say the battery is in decent condition and of sufficient capacity that it could deal with the 70A load without dropping below 12v.

    If you're playing a dynamic piece of music (loudly, so the peaks are close to clipping) the load could cause the voltage to drop from 14.4v to 12v for those brief moments, as the charging system wouldn't adjust fast enough to support the transient load. In this case, the battery is enough to support the load from causing it to drop below 12v, so more batteries wouldn't have any much effect.

    If the audio system could draw 200A or more, it would be a hard ask for any single battery to deal with that sort of load and still provide 12v, so additional batteries would help.

    In either system, if an external capacitor was able to smooth out the transients, providing enough current at a full 14.4v to the amp when needed and a more consistent load for the alternator/regulator it would possibly prevent the dimming. That's a big if though, for reasons that have already been highlighted in this thread.
     
  13. m0n4g3

    m0n4g3 Member

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    There really is no way of stopping the 4" speakers from clipping unless you turn everything else down to match the inbuilt amp on the headunit.

    Why did you purchase the 4" speaker if you don't mind me asking?

    If you are looking to get a 3-way front stage the best thing to do is look for a 3way cross over so that you are able to power all 3 speakers per side.

    Either that or ditch the 6x9's (horrible speaker design but i digress), and use the 4" splits in the rears.
     
  14. OP
    OP
    @rt

    @rt Member

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    The vehicle provides for mounting 4 inch speakers in the dash and that's
    the only reason. I haven't opened them, and they might go back for refund.

    If I use the 6 inch woofers I have to cut holes in the door trim and hope the well is deep enough.
    They are actually 6 3/4 inch woofers, and don't fit into 6 inch pods which would
    normally solve any depth problem :(

    I'm about to pull the trim off a door and check it out now.
    THere's no factory speakers in the doors.
     
  15. Foliage

    Foliage Member

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    most head units have a separate gain control for the sub outputs so that they can be adjusted quieter or louder than the rest, you can usually also set the equaliser settings for every speaker bar the sub, that way you can tune all the bass out of your side speakers and leave the sub to do it all, meaning less clipping at the same volume.

    that is what I did with mine anyway, was a cheap as chips headunit as well.
     
  16. OP
    OP
    @rt

    @rt Member

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    It appears that one set of RCA outputs respond to the settings applied to the
    front speakers, so one amplifier (and in the end, two of three amplifiers) will be affected
    by what I try to do to the head unit's speaker outputs.. that's the problem.


    Re getting rid of the 6x9s... I don't think there's any going back from this:
    [​IMG]

    Not cheaply anyway.

    EDIT,,,
    I have the door trim off, and as absurd as it sounds,
    I think I have to forgo the highest quality component (6 3/4 inch drivers)
    and use the 4 inch speakers as the woofer connected to the crossover network.
    I just can't see how the 6/34 inch woofers could be mounted in the door.
     
    Last edited: Dec 17, 2010
  17. m0n4g3

    m0n4g3 Member

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    LIES! there's always a way! if i can fit 4x10" subs, 2x 7" midbass, 2x 4" mids and 2x 1.1" tweets in an mr2.... i'm sure you can do something to ur 4wd wagon! :D
     
  18. OP
    OP
    @rt

    @rt Member

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    Well I'm sure there's something I can do, but not this weekend.
    I'll see how things sound when I get this together,
    then I can always disconnect the 4 inch pair and add
    the real woofers later if I'm prepared to get someone to make pods for the door.
     
  19. ener

    ener Member

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    fixed for you :p
     
  20. xc351

    xc351 Member

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    cool so u are ina 4wd wagon.
    dont use the 4" return them. my hiluxes dont get used either.
    Deffinly get a 2nda battery and put it in a battery box as its great to have a 2nd batt in a 4wd, autobahn has special boxes that have inputs on the box for ciggy lighter and a anderson plug connection. This will solve all ya cap/voltage drop then all u will need is a 4wd battery controller and smaller cables going to back as they will only be charge cables (id still grapa large off teh shef amp wiring kit as its best back for ya buck)

    u will need a sealed battery though so no fume sget into ya cab $200 will do it.

    6x9's will do then lets face it its a big cab and not a sq car.

    i have 3.7 cubic ft 15" sub box and DD9915 (designed built by digital designs australia) sub if u want it $1000
     

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