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.
Two-way, 4th Order
(24 dB/Octave) Filters
Note: -12 dB Pad and CD Horn EQ |
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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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