Horn Impedance

Discussion in 'Amps and Cabs [BG]' started by david_l_perry, Sep 15, 2003.

  1. Question for the technical minded guys...
    why does the Impedance of a high frequency Horn in a bass cab not effect the overall resistance of the cab..?

    ie a 2x10 4ohm cab (2 8ohm 10" drivers) have the same 8ohm horn as an 8ohm 4x10 cab and the same 8ohm horn as a 4ohm 6x10..?

    Any takers ?
  2. Steve


    Aug 10, 2001
    The ohmage of drivers fluctuate depending on the frequency they are reproducing.

    The frequencies of horns are high enough that the resistance loading they add to the circuit is not significant.
  3. Hmm, that's not quite accurate.

    The first part is right, but the second part is only valid for piezo horns. They have a very high impedance (=AC resistance) of around 1,000 ohms, therefor the effect on the total cabinet impedance is negligable.

    Voice coil horns, however, require a crossover. A very complicated circuit that devides the frequencies into 2 bands, high and low. That way the impedances of both woofers and tweeters match.
  4. Exactly. At low frequencies the amp only "sees" the impedance of the woofer because the components in the crossover make the horn seem like an open circuit in parallel with the woofer. At high frequencies the opposite happens. And in between it's a combination of both and the math gets very complex. The impedance quoted in specs is the nominal impedance averaged over the frequency range of the cab.