First Order (6db/octave) Two-Way Crossover

High Pass Impedance: Ohms
Low Pass Impedance: Ohms
Frequency Hz


6dB Crossover Diagram     C1= F




  L1= mH

Phase shift on a first-order crossover is 90 degrees.


Second Order (12db/octave) Two-Way Crossover

Linkwitz-Riley Butterworth Bessel

High Pass Impedance: Ohms
Low Pass Impedance: Ohms
Frequency Hz



12dB Crossover Diagram     C1 = F

  L1 = mH


  C2 = F

  L2 = mH

- 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).


Third Order (18db/octave) Two-Way Crossover

High Pass Impedance: Ohms
Low Pass Impedance: Ohms
Frequency Hz



18dB Crossover Diagram     C1 = F
  C2 = F
  L1 = mH

  L2 = mH
  L3 = mH
  C3 = F

Phase shift on a third-order crossover is 270 degrees (-90 degrees).


Fourth order (24dB/octave) Two-Way Crossover

High Pass Impedance: Ohms
Low Pass Impedance: Ohms
Frequency Hz



24dB Crossover Diagram     C1 = F
  C2 = F
  L1 = mH
  L2 = mH

  C3 = F
  C4 = F
  L3 = mH
  L4 = mH

The phase shift on a fourth-order crossover is 360 degrees = 0 degrees (no phase shift).


Zobel Circuit (Impedance Stabilization)

DC resistance (Re): Ohms
Inductive Equivalent (Le): Henries



Zobel Circuit Diagram     C1= F


  R1= Ohms

- 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.


L-pad (Speaker Attenuation)

Driver Impedance = Ohms
Desired Attenuation = dB



l-pad.gif (1013 bytes)     R1 = Ohms


  R2 = Ohms

- 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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