Higher Order Analog (Butterworth) Filter Design Calculators
- Make sure you have Java turned on in your browser.
- Enter high and low pass speaker impedances.
- Enter desired crossover frequency.
- On the second-order crossover calculator you must select type of crossover.
- Click on the "calculate" button to get the answers.
- Impedance is the nominal resistance of the speaker (typically 4 Ohms).
- Enter frequency in Hertz (not kHz).
- Capacitor value(s) are given in millionths of a Farad (µF).
- Inductor value(s) are given in thousands of a Henry (mH).
- For the Zobel circuit, enter inductance in Henries (not mH).
- First Order Crossover (6db/octave).
- Second Order Crossover (12db/octave).
- Third Order Crossover (18db/octave).
- Fourth Order Crossover (24db/octave).
- Zobel Circuit (Impedance Stabilization).
- L-pad Circuit (Speaker Attenuation).
First Order (6db/octave) Two-Way Crossover
- Phase shift on a first-order crossover is 90 degrees.
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).
Third Order (18db/octave) Two-Way Crossover
- Phase shift on a third-order crossover is 270 degrees (-90 degrees).
Fourth order (24dB/octave) Two-Way Crossover
- The phase shift on a fourth-order crossover is 360 degrees = 0 degrees (no phase shift).
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.
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.