|Crossover 101 - Page 5
The high pass section of a passive crossover in a loudspeaker system that employs a constant directivity high frequency horn provides two additional functions beyond that of the high pass filtering circuitry. The first additional function is the necessary pad or attenuation to match the sensitivity of the paper cone loudspeaker. Function two is the equalization necessary to allow the driver to have a flat response in the last two octaves. How is the equalization or boost of high frequencies accomplished in a "passive" crossover? Essentially there is a primary crossover circuit that crosses over the audio signal at the designated crossover frequency and provides the proper amount of attenuation. Then a secondary crossover circuit uses the voltage window of the un-attenuated high pass signal to provide an additional signal path for the high frequencies with less and less attenuation as the frequency rises.
Without the proper Pad and CD horn EQ, the loudspeaker system is very honky or mid range sounding (due to the mid-band efficiency); and the highest frequencies, such as those produced by a high hat or cymbals, are buried due to the roll off characteristic of the (non-equalized) driver/horn.
This is the conclusion of this first paper of a three part series on crossovers. Part II, Crossovers 102, will cover Electronic Crossovers, and the filter types available. Part III, Crossovers 2001+, will cover DSP (digital signal processor) electronic crossovers.
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