Advertisement
ACTIVE CROSSOVER SYSTEM
RADIO
ACTIVE CROSSOVE
6 dBlOctave
PASSIVE CROSSOVER
12 dBlOctave
Sound is created by the movement of the woofer cone back and forth. If a woofer cone moves
forward creating a positive pressure wave, this same motion creates a negative pressure at the
back of the woofer. If these t\iiro waves combine due to the lack of a wall separating the front of
the speaker sound from the back, the output from the woofer is effectively canceled thus
substantially reducing the bass output of the speaker. This wall is absolutely necessary and is
referred to as an acoustical "baffle". It can be accomplished using a box of some kind or simply
the rear package shelf of an automobile to isolate the front and back waves of the speaker.
THIELE-SMALL PARAMETERS
Every woofer has its own electromechanical characteristics which are called THIELE-SMALL
parameters. The three most important parameters include RESONANT FREQUENCY ("fs" -
the frequency where the speaker moves with the least mecha'nical resistance), TOTAL 0
VOLUMETRIC COMPLIANCE Was" - the equivalent volume of air that the woofer cone can
displace for a given power input). Using these parameters we can then calculate an
optimum box volume for a particular woofer and reasonably predict its frequency response.
a
OUTPUT
FREQUENCY
Inductor Value
80
100
150
200
9.0
100
150
6.0
200
4.5
8.0
6.4
4.2
3.2
140
Advertisement
