First Order (6db/octave) Two-Way
Crossover
- Phase shift on a first-order crossover is 90 degrees.
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Second Order (12db/octave) Two-Way
Crossover
- Linkwitz-Riley crossovers match attenuation slopes so that
system response is flat at crossover point.
- Butterworth crossovers yield to a peak at the crossover
frequency.
- Bessel crossovers have a frequency response between
Linkwitz-Riley and Butterworth crossovers.
- The phase shift on a second-order crossover is 180 degrees
(reversed polarity).
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Third Order (18db/octave) Two-Way
Crossover
- Phase shift on a third-order crossover is 270 degrees (-90
degrees).
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Fourth order (24dB/octave) Two-Way
Crossover
- The phase shift on a fourth-order crossover is 360 degrees =
0 degrees (no phase shift).
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Zobel Circuit (Impedance
Stabilization)
- Even though speakers are rated at a certain
"resistance" (i.e. 4 Ohms), the actual impedance varies with frequency (speakers
have inductance). To compensate for the non-linearity of speakers (on mainly subwoofers),
Zobel circuits are used.
- Re is the DC resistance of the woofer (can be measured with
an ohmmeter)
- Le (or Lces) is the electrical inductive equivalent of the
driver.
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L-pad (Speaker Attenuation)
- An L-pad circuit will attenuate a speaker.
- L-pads keep the load "seen" by the amplifier
constant, affecting only the power delivered to the speaker. The power delivered by
the amplifier remains constant.
- Since L-pads are made from resistors, it does not induce any
phase shifts, or affect frequency response.
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