Crossover vs gain

Discussion in 'OT Technology' started by notaniceperson, May 14, 2009.

  1. notaniceperson

    notaniceperson -I'm an ASSHOLE!

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    Just wired up an amp in my car and need a quick tutorial on crossover vs gain.
     
  2. avctechsupp

    avctechsupp New Member

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    go on. . .
    ?
     
  3. JRock10

    JRock10 Active Member

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    what do you want to know? gain is the adjustment for input levels, crossover is used to limit frequencies in the range of the crossover's adjustability
     
  4. notaniceperson

    notaniceperson -I'm an ASSHOLE!

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    Ok i just needdd it in plain english. Thanks.
     
  5. popsnbeer

    popsnbeer New Member

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    lol....

    gain: to you this might sound like how loud your system is, however do not use this as a volume knob. To adjust my gain I will turn up my deck (receiver in car w/ CD player and what not) to abou 80% of maximum volume and then put the gain just below the point to where it starts to sound distorted/bad.

    crossover: this is not meant to be used as a volume knob either. the crossover essentially sets the threshold at which your amp will put sound to your speakers. for example high pitched noises have a higher frequency number than lower deeper sounds (usually observed in subwoofer with car audio). I would check your manufactuers website on the speakers you have for the correct crossover adjustments.

    :dunno: keep in mind I am not an audiophile, but just the guy who installs them occasionally in his garage. I might get yelled at in here for my recommendations. but at least they are in "plain english"
     
  6. lawngn0me

    lawngn0me In every wish and dream and happy home, you will f

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    that's pretty much how it goes. However, many people still don't understand what sounds "clean" and what sounds "distorted". I've always set my gains using a digital multimeter. I set the volume to the highest I would possibly listen to it. Play a sine wave on repeat for the appropriate speakers you would like to set. for a sub, usually a 50 hz sine wave. disconnect the speakers you will be setting. Use ohms law.

    sqrt(power * resistance) = voltage

    in other words: sqrt (watts rms * impedance the amp is "seeing") = voltage. adjust the voltage until the number on the dmm matches whatever the voltage you get from this equation.
     
  7. Kieffer87

    Kieffer87 Orly OT Supporter

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    How would this even work? You don't know exactly what wattage your amp is putting out, a lot of amps on the market may claim 500watts rms for example but probably never reach it. So are you then assuming a gain of 50% on a 500 watt rms amp would be putting out 250 rms? This just doesn't sound like a very efficient way of doing this but I could be wrong.
     
  8. lawngn0me

    lawngn0me In every wish and dream and happy home, you will f

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    many amps are pretty much in the ballpark of their rms wattage. don't ever pay attention to peak wattage. you may be getting the 2 mixed up.
     
  9. JRock10

    JRock10 Active Member

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    as far as wattage ratings on an amp go, I look at the fusing in the amps and figure about 100 watts for every 10 amps of fusing. This isn't always accurate b/c some amps are pretty efficient in their power use and get better than 100w per 10a. But it's a decent rule of thumb.

    For example: you have an amp with a 30 amp fuse, you can generally figure that amp will produce about 300 watts.
     
  10. twistid

    twistid Banged By Super Models Moderator

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    current X voltage can get you in the ballpark... though some amps are more efficient, some are less.

    30amp fuse should make a 400watt amp... but it's not a sure thing.
     
  11. JRock10

    JRock10 Active Member

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    we'll call it an ok ball-park power estimator :mamoru:
     
  12. GammaRadiation

    GammaRadiation Active Member

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    Avg Class D amp is in the 70% efficiency range. Avg A/B is in the 50-60% efficiency range. However, you have to know the amps. For instance, the JL slash series are about 50% efficient even though they are class D. Also, some companies use slow blow fuses. My USamps MD2D used a slow blow IIRC. A better ball park is to get a DMM with a clamp ammeter that can read RMS measurements and measure the current and voltage at around 60Hz. RMS Current * RMS Voltage = Apparent Power. As long as you dont have a lot of impedeance rise, apparent power is just a little larger than actual power.

    [​IMG]
    img courtesy of Wikipedia.org

    Every other question: www.bcae1.com
     
    Last edited: May 20, 2009
  13. JRock10

    JRock10 Active Member

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    get the fuck out with that logic shit.
     
  14. GammaRadiation

    GammaRadiation Active Member

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  15. twistid

    twistid Banged By Super Models Moderator

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    :werd: again someone steps in, and takes the fun out of things.
     
  16. JRock10

    JRock10 Active Member

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