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Resistor power requirements in car system

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  • Resistor power requirements in car system

    I'd like to put some resistors in series with the front tweeters in my car stereo system to pad down the highs somewhat. The resistor(s) will be connected between the hot lead from the radio and the crossover cap. Assuming a 4Ω tweeter, a 2khz crossover frequency and a head unit with 15watts/channel, what should my resistor's power ratings be? I'm estimating I'll need 50Ω or less.

  • #2
    You should use an L-pad configuration with 2 resistors and they should go between the crossover and driver, see the link to determine what resistor values you need.. L pad calculator - attenuation dB damping impedance decibel loudspeaker speaker voltage divider - sengpielaudio Sengpiel Berlin
    5w resistors will be sufficient if you do it this way.
    Paul O

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    • #3
      If I don't care about maintaining a specific impedance, what's the advantage of an L-pad over just a simple series resistor?

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      • #4
        Originally posted by swechsler View Post
        If I don't care about maintaining a specific impedance, what's the advantage of an L-pad over just a simple series resistor?
        More consistent attenuation across frequency. The parallel resistor damps the driver resonance peak a bit.
        Electronics engineer, woofer enthusiast, and musician.
        Wogg Music
        Published projects: PPA100 Bass Guitar Amp, ISO El-Cheapo Sub, Indy 8 2.1 powered sub, MicroSat, SuperNova Minimus

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        • #5
          Originally posted by swechsler View Post
          If I don't care about maintaining a specific impedance, what's the advantage of an L-pad over just a simple series resistor?
          You should care about maintaining a specific impedance. By placing attenuating resistors after the high pass cap it reduces their power handing requirement by some 75%. But if you just put a series resistor after the cap the filter frequency goes down, which is bad news for the tweeter.
          www.billfitzmaurice.com
          www.billfitzmaurice.info/forum

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