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On the top of this page you can find an overview of all brands that supply crossovers.



To dedicate each driver to a particular frequency range, the speaker system first needs to break the audio signal into different pieces -- low frequency, high frequency and sometimes mid-range frequencies. This is the job of the speaker crossover.

The most common type of crossover is passive, meaning it doesn't need an external power source because it is activated by the audio signal passing through it. This sort of crossover uses inductors, capacitors and sometimes other circuitry components. Capacitors and inductors only become good conductors under certain conditions. A crossover capacitor will conduct the current very well when the frequency exceeds a certain level, but will conduct poorly when the frequency is below that level. A crossover inductor acts in the reverse manner -- it is only a good conductor when the frequency is below a certain level.

The typical crossover unit from a loudspeaker. The frequency is divided up by inductors and capacitors and then sent on to the woofer, tweeter and mid-range driver.

When the electrical audio signal travels through the speaker wire to the speaker, it passes through the crossover units for each driver. To flow to the tweeter, the current will have to pass through a capacitor. So for the most part, the high frequency part of the signal will flow on to the tweeter voice coil. To flow to the woofer, the current passes through an inductor, so the driver will mainly respond to low frequencies. A crossover for the mid-range driver will conduct the current through a capacitor and an inductor, to set an upper and lower cutoff point.

There are also active crossovers. Active crossovers are electronic devices that pick out the different frequency ranges in an audio signal before it goes on to the amplifier (you use an amplifier circuit for each driver). They have several advantages over passive crossovers, the main one being that you can easily adjust the frequency ranges. Passive crossover ranges are determined by the individual circuitry components -- to change them, you need to install new capacitors and inductors. Active crossovers aren't as widely used as passive crossovers, however, because the equipment is much more expensive and you need multiple amplifier outputs for your speakers.

Crossovers and drivers can be installed as separate components in a sound system, but most people end up buying speaker units that house the crossover and multiple drivers in one box. In the next section, we'll find out what these speaker enclosures do and how they affect the speaker's sound quality.

Questions and answers

X-over point? (K. Haselberger)

Waslo Berg EQ/Active filter (John Hodgson)

K. Haselberger (April 2002): Dear ESL Circuit Team, in Ronald Wagners book you find on page 145 that a resistor in series with the stator forms a high pass filter also Audio-Static uses this form of x-over. Unfortualty I can not find how tho calculate the x-over point of that kind of filter. I would be verry pleased if you can give me some support. Thanks a milliion. K. Haselberger

Mike Beck (May 2002): Electrical segmentation using a series resistor connection to the stators forms a low pass voltage network to attenuate the high frequency drive to the segment. This has been used by Audiostatic, Acoustat (Spectra series), Quad (ESL57), and others. Arthur Janszen featured this in his 1953 US patent #2,631,196.

Electrical segmentation provides a more benign load to the amplifier and improves dispersion of the upper frequencies while allowing the overall response to be more easily equalized. The idea is to drive a narrow tweeter section full range, then have one or more sections filtered to progressively remove the high frequencies. The result is that the driven panel area increases as the frequency decreases. The roll off 3dB point can be calculated by:

  • F=1/(2*pi*R*C)
  • Where C is the stator to diaphragm capacitance of the segment or strip area in farads, And R is the resistance in ohms.
  • You can calculate the stator/diaphragm capacitance using the formula: C=8.85E-12*A/D
  • Where C is in farads, A is stator area in meters, D is the stator to diaphragm spacing in meters
  • If you use the total stator to stator capacitance then use: F=1/(4*pi*R*C) since it is half the stator to diaphragm value.
  • Place equal value resistors in each stator. Bear in mind the resistors will see half the secondary voltage at high frequencies so they must be able to handle the power (P=Vrms squared/R watts) and have a high voltage rating

Good experimenting! Mike Beck, Thales Mackay Radio, Inc. (formerly Mackay Radio Systems) If you can provide an additional answer please contact The Audio Circuit

John Hodgson (November 2000): I would very much like to contact for technical discussion any constructors of the Waslo Berg EQ/Active filter from the Associated Electronics projects of Barry Waldron's ESL Information Exchange Thanks. John. If you can provide an answer please contact The Audio Circuit