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  Answer ID  
8
  Product  
Amplifiers
  Category  
General Product Info
  Date Created  
09/25/2001 03:15 PM
  Date Updated  
02/06/2003 10:44 PM

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  What are crossovers used for?
  Question
  What is a crossover used for and why do I need them in my system?
What difference will a crossover make in my system?
What is the difference between passive and active crossovers?
  Answer
  A crossover is a key element in the overall design of a multiple-driver system. It is designed to filter sound into frequency ranges the way a prism filters light into colors. There are two common types of crossovers, "passive" and "active". Both types of crossovers consist of a single (or group) of electronic parts responsible for dividing or "blocking" frequencies. Once the frequencies are divided or "blocked", they are routed to the correct speakers.

Passive Crossovers
Passive crossovers are non-powered components. They consist of capacitors (and/or) inductors placed in-line with the speaker leads located between the amplifier and the speaker.

Active Crossovers
Active crossovers are powered components. They are typically electronically powered "black boxes" placed in-line with the RCA signal cables located between the source unit and the amplifier(s). Crossovers built into amplifiers are this type.

General Requirements for Crossover Selection
The first consideration when designing a crossover system is to address the most vulnerable of all speakers, the tweeter. Since tweeters have small, fragile voice coils, they can be over-driven very easily. Choose a tweeter that can begin reproducing frequencies where the midrange stops (avoid gaps in the tweeter-to-midrange transition.) Second, select a crossover frequency that allows the response of each driver to remain flat on either side of the crossover frequency. Try to select a crossover frequency at least one octave away from the speaker's resonant frequency. This is very important for tweeters because they can sound "harsh" if frequencies near the Fs (resonant frequency) are reproduced.

2-Way Crossovers
2-way Crossover Systems are typically used with tweeter / midrange combinations. In a 2-way speaker system, high frequencies go to the tweeter and low frequencies to the midrange. 2-Way Systems are great for people want good music reproduction and want to add a subwoofer in the future. You may notice most "component systems" already come supplied with a "ready-made" crossover. These 2-way crossovers are designed for the specific type of tweeter / midrange combination. Higher quality models usually have additional impedance compensation and attenuation networks that provide a "flatter" frequency response.


*see below for graph explanations

3-Way Crossovers
3-way Crossover Systems are typically used with tweeter / midrange / woofer combinations. A 3-way crossover divides the signal into three different frequency bands: low-pass, bandpass, and high-pass. 3-Way Systems give the listener awesome sonic performance because of their ability to properly reproduce all frequencies in the human hearing range (20Hz to 20kHz.) One reason to use three speakers in a system is the appetite for more bass. You'll need larger diameter speakers (woofers) to move the large amounts of air required to reproduce low frequencies (i.e.: 20Hz to 80Hz.)


*see below for graph explanations

*Graph Explanations
dB: A logarithmic scale used to denote a change in the relative strength of an electrical signal or acoustic wave.
Hz: A unit of frequency equal to one cycle per second. Humans hear in a relatively narrow frequency band from about 20Hz to 20,000Hz (expressed as 20kHz).
FLC: Low-Frequency Crossover point
FHC: High-Frequency Crossover point
 
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