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Thread: 4 Subwoofers for Home use

  1. #11
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    Ah I've just looked up and I think I now understand what you mean.

    For e.g. if I run a 500W mono @ 2Ohm, to my subs. I'll need around 42A (500/12)worth of current towards the amp in order to provide it with maximum power. Otherwise it will be underpowered, so those videos are just really underpowered car subs that aren't giving it their best potential unless they invested in a PSU that provided them with sufficient current? I actually studied electronics haha, can't believe I didn't work it out. But wouldn't including a capacitor between psu and car amp accomodate for such low current draw?

  2. #12
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    remember, a capacitor can discharge very fast, but takes a long time to recharge-- so a capacitor wired in parallel to the amp will help, but only for the first 'boom', maybe the second if there is adequate time for the cap to charge, but very likely, by the time the amp needs to send a signal to teh sub again, the capacitor will still be charging-- which will be a extra load on the power supply, and will hurt the amp because it is siphoning off part of the voltage to charge up.

    there have been numerous debates in car audio forums on this-- and most car audio competitiors agree that caps only hurt a audio system. in spl comps, most gain loudness by removing their caps.

  3. #13
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    Why do people argue that 12V @ 20A on rails of a PSU is sufficient enough to power a car amp? I would have thought car amps would never reach that much current draw, say 42A.

  4. #14
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  5. #15
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    warning: rambling ahead!

    Quote Originally Posted by soloxp View Post


    Quote Originally Posted by wonga View Post
    Why do people argue that 12V @ 20A on rails of a PSU is sufficient enough to power a car amp? I would have thought car amps would never reach that much current draw, say 42A.
    it depends entirely on the amp-- a small 4 channel 'motorcyle' amps will not draw much more than 5-10 amps, mostly becuase they have a very small, cheap, components in the amplifier circuit.

    higher quality amps use better components that sometimes take more juice becaue they have better frequency range, and better sound quality.

    one of the best pieces of advise i have heard when looking at amps is to look at the fuse size-- cheap amps might say they have 1000 watt output, but only have a 20 amp fuse-if you do the math, it would never get even 500 watts with a fuse that size. they do this by doing things that would void the warranty for end users-- they could be using 24 volt system, a 18 volt rca line input, or test using one frequency.

    higher quality amps will have much larger fuse sizes(fuse size will also be larger with larger amps), because the amp circuit is designed much better-- for both efficiency, and for sound quality.

    for cheap, small projects, or just when your are screwing around with some ideas, computer power supplies work great. but when you need a dedicated power supply for something that you need to work, or need more than a 5-10 amps, they are a poor choice.

    i currently have 2 projects that i use one in-- a large ipod speaker with a very small motorcycle amp-- powers with no problem- the whole project cost me about $10-- $3 for the box, and $5-6 for the amp...

    i also have a bazooka bass tube (i think they are about 50 watts max) powered off one, for a basic home theater. it started as a temporary solution, and, sadly seems to be sticking around-- i got a box for a new one, just haven't followed through yet (2 jl audio 6-w3's, and a small sub amp )...so far, the bass tube cost me $5 for a bargin bin power supply-- the tube was free, i just had to hack a 20 pin molex to work with it.

    for me, once i reach $30-50 cost on a speaker project, there is no reason anymore to try to do it cheaply, becuase then i will need to fix it later, and usually for double the cost of whatever i was trying to cheap out on.

  6. #16
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    Thanks for all the advice guys, I'm looking to go on the cheap here :P.
    Since I'm still experimenting it's best if I experiance both types of setups. I've just bought an Alpine Class D monoblock @ 500W RMS 4Ohm. And a Mourdaunt Short sub amp @ only 150W RMS, because it was cheap and the only one I could find with the correct mains voltage.

    I'll try both, and sell the amp I'm not comfortable with. Because even if I'm underpowering the subs, if it gets too powerful for me to bear, then what's the point of having that power.
    Thanks guys. I'll keep posted when I receive and set it all up.

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