2-Way Crossover Calculator |
Speaker Definition | ||
---|---|---|
Tweeter (RH) Ω |
Woofer (RL) Ω |
X-Over Freq. (f): Hz |
Cross-Over Type/Order | ||
Butterworth: 1st 2nd 3rd 4th | ||
Linkwitz-Riley: 2nd 4th 6th | ||
Bessel: 2nd 3rd 4th | ||
Solen Split: 1st | Chebyshev, Q=1: 2nd | |
Legendre: 4th | Gaussian: 4th | Linear Phase: 4th |
It's common to have multiple speakers in any kind of audio system. But some of those speakers may be more efficient at low frequencies and other at high frequencies. A 2-Way Cross-Over filter is then employed to steer the audio to the speakers that can reproduce the audio better.
The simplest form of a 2-Way Cross-Over would be the 1st Order filter, which only employes one capacitor and one inductor. The capacitor is used in series with the high frequency speaker and the indictor is used in series with the low frequency speaker. When the audio is below the Cross-Over frequency, the capacitor has a high impedance and effectively reduces the audio energy from reaching the high frequency speaker. But as the frequency goes up, past the Cross-Over frequency, the capacitors reactance decreases and the inductors reactance increases. This then sends more audio energy to the high frequency speaker.
The drawing also contains the equations needed to calculate the value for the capacitors and inductors. The equations are slightly different depending on which type of Cross-Over required. These equations are simplifications of the actual equations. For example, the actual equations for a 1st Order Butterworth Cross-Over is C1 = 1/[2·PI·RH·f], and L1 = [2·PI·RL]/f. But simplified, they work out to C1 = 0.1590/[RH·f] and L1 = 0.1592·RL/f. The same is true for all of the other equations.
Note: The values are in Ohms for RH and RL, Micro-Farads (µF) or Farads for C1 to Cn, and Micro-Henries (µH), Mili-Henries (mH), or Henries for L1 to Ln, and Hertz for f.
3-Way Crossover |
Speaker Definition | ||
---|---|---|
Tweeter (RH) Ω |
Midrange (RM) Ω |
Woofer (RL) Ω |
Frequency Spread (fH/fL) | Cross-Over Frequency | |
10 (3.4 Octaves) 8 (3 Octaves) |
Low (fL) Hz |
High (fH) Hz |
Bandpass Gain = 0 dB | 1st Order, Normal Polarity |
2nd Order, Reverse Polarity | 3rd Order, Normal Polarity |
3rd Order, Reverse Polarity | 4th Order, Normal Polarity |
The calculator on the right is for determining the component values for a 3-Way "All-Pass Crossover".
In the calculator, Cross-Over Frequencies are dependent on the Frequency Spread selected. If you change the Frequency Spread, fL or fH will automatically be adjusted to match the current Frequency Spread. For example, if you have 8 (3 Octaves) selected, and then set fL, the calculator will set a fH that is 3 Octaves above fL.
Note: The values are in Ohms for RH, RM and RL, Micro-Farads (µF) or Farads for C1 to Cn, and Micro-Henries (µH), Mili-Henries (mH), or Henries for L1 to Ln, and Hertz for fH, fM, fL.
3-Way, 1st Order, APC, FS = 8 (3 Octaves) C1 = 0.1590/(RH×fH) = 6.6 uF C2 = 0.5070/(RM×fM) = 66.8 uF L1 = 0.0500×RM/fM = 421.64 uH L2 = 0.1592×RL/fL = 4.25 mH 3-Way, 1st Order, APC, FS = 10 (3.4 Octaves) C1 = 0.1590/(RH×fH) = 6.6 uF C2 = 0.5540/(RM×fM) = 66.8 uF L1 = 0.0458×RM/fM = 421.64 uH L2 = 0.1592×RL/fL = 4.25 mH |
Crossover Characteristics |
Below are some brief descriptions of the various cross-over types. Generally, Butterworth and Linkwitz-Riley filters are described in detail and the rest included differences from the others.
Butterworth - Some of the characteristics (Pro and Con) are listed below.
- Monotonic amplitude response in both passband and stopband.
- Quick roll-off around the cutoff frequency, which improves with increasing order.
- Considerable overshoot and ringing in step response, which worsens with increasing order.
- Slightly non-linear phase response.
Linkwitz-Riley
- Absolutely flat amplitude response throughout the passband with a steep 24 dB/octave rolloff rate after the crossover point.
- The acoustic sum of the two driver responses is unity at crossover. (Amplitude response of each is -6 dB at crossover, i.e., there is no peaking in the summed acoustic output.)
- Zero phase difference between drivers at crossover. (Lobing error equals zero, i.e., no tilt to the polar radiation pattern.) In addition, the phase difference of zero degrees through crossover places the lobe of the summed acoustic output on axis at all frequencies.
- The low pass and high pass outputs are everywhere in phase. (This guarantees symmetry of the polar response about the crossover point.)
- All drivers are always wired the same (in phase).
- Not "Linear Phase", meaning that, the amount of phase shift is a function of frequency. Or, put into time domain terms, the amount of time delay through the filter is not constant for all frequencies, which means that some frequencies are delayed more than others.
Bessel - A Bessel filter is a type of analog linear filter with a maximally flat group/phase delay (maximally linear phase response), which preserves the wave shape of filtered signals in the passband. This make the Bessel filter well suited for audio crossover networks.
Solen Split - Theoretically, the Butterworth will have more overlap around crossover frequency,
so there will be "bump" at 4kHz, may be 3dB. OTOH, the other one has less bump, could be 0dB or -3dB at 4kHz.
As 4kHz is usually the location of breakups, and our ears are very sensitive to this frequency,
and the filter is too simple, it is better to lower the response around this frequency, so I
will prefer the "Solen Split", or even much lesser bump.
Legendre
Chebyshev - having a steeper roll-off and more passband ripple (type I) or stopband ripple (type II) than Butterworth filters. Chebyshev filters have the property that they minimize the error between the idealized and the actual filter characteristic over the range of the filter,[citation needed] but with ripples in the passband.
Gaussian - a Gaussian filter is a filter whose impulse response is a Gaussian function (or an approximation to it). Gaussian filters have the properties of having no overshoot to a step function input while minimizing the rise and fall time. This behavior is closely connected to the fact that the Gaussian filter has the minimum possible group delay. It is considered the ideal time domain filter, just as the sinc is the ideal frequency domain filter.[1] These properties are important in areas such as oscilloscopes[2] and digital telecommunication systems.
Linear Phase - Linear phase is a property of a filter, where the phase response of the filter is a linear function of frequency. The result is that all frequency components of the input signal are shifted in time (usually delayed) by the same constant amount, which is referred to as the phase delay. And consequently, there is no phase distortion due to the time delay of frequencies relative to one another.