1 Crossovers Manual Reference Pages 222 – 227 Manual Reference Pages 222 – 227

2 What is a Crossover? Audio crossovers are a class of electronic filters designed specifically for use in audio applications Audio crossovers are a class of electronic filters designed specifically for use in audio applications Crossovers serve the purpose of splitting an audio signal into separate frequency bands which can be handled by individual loudspeaker drivers optimized for those bands. Crossovers serve the purpose of splitting an audio signal into separate frequency bands which can be handled by individual loudspeaker drivers optimized for those bands.

3 What is a Crossover? They are generally described according to the number of frequency bands available (two-way, three-way and four-way). They are generally described according to the number of frequency bands available (two-way, three-way and four-way).

4 How it works It uses bandwidth limiting filters to separate the input signal into multiple outputs, each of which has a steep cut-off below and/or above its range (24dB/octave is typical). In some, the cut-off slope (and in some of those, even the type of filter: Bessel/Butterworth/Linkwitz-Riley, etc.) is user-determined. It uses bandwidth limiting filters to separate the input signal into multiple outputs, each of which has a steep cut-off below and/or above its range (24dB/octave is typical). In some, the cut-off slope (and in some of those, even the type of filter: Bessel/Butterworth/Linkwitz-Riley, etc.) is user-determined.

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9 3 types of crossover filters High-pass High-pass Low-pass Low-pass Band-pass Band-pass

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A high-pass filter will block low frequencies A high-pass filter will block low frequencies A low-pass will block high frequencies A low-pass will block high frequencies A band-pass will block low and high frequencies below and above crossover points. A band-pass will block low and high frequencies below and above crossover points.

13 Slope Slope is expressed as decibels per octave. Slope is expressed as decibels per octave. The rate of attenuation for every octave away from the crossover frequency The rate of attenuation for every octave away from the crossover frequency Crossovers do not block undesired frequencies completely (unless you are using digital crossovers) Crossovers do not block undesired frequencies completely (unless you are using digital crossovers) Crossovers cut frequencies progressively Crossovers cut frequencies progressively A crossover "slope" describes how effective a crossover is in blocking frequencies A crossover "slope" describes how effective a crossover is in blocking frequencies

14 Slope A 6dB per octave crossover reduces signal level by 6dB in every octave starting at the crossover point. A 6dB per octave crossover reduces signal level by 6dB in every octave starting at the crossover point.

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20 - 6db

21 - 6db - 12db

db - 6db - 18db

db - 18db - 24db - 6db

24 1st order filters have a 6 dB/octave slope 1st order filters have a 6 dB/octave slope 2nd order filters have a 12 dB/octave slope 2nd order filters have a 12 dB/octave slope 3rd order filters have an 18 dB/octave slope 3rd order filters have an 18 dB/octave slope 4 th order filters have a 24 dB/octave slope 4 th order filters have a 24 dB/octave slope 5 th order filters have a 48 dB/octave slope 5 th order filters have a 48 dB/octave slope

25 - 6db - 12db - 18db - 24db - 48db 500hz250Khz125hz1Khz63hz

26 Crossover Point The nominal dividing line between frequencies sent to two different speaker drivers. The nominal dividing line between frequencies sent to two different speaker drivers. In a crossover network, the frequency at which the audio signal is directed to the appropriate driver (low frequencies to the woofer, high frequencies to the tweeter). In a crossover network, the frequency at which the audio signal is directed to the appropriate driver (low frequencies to the woofer, high frequencies to the tweeter). The single frequency at which both filters of a crossover network are down 3dB. The single frequency at which both filters of a crossover network are down 3dB. The frequency at which an audio signal is divided. The frequency at which an audio signal is divided.

28 Cutoff Frequency The "corner point" of a filter, usually the point where the response is down -3dB compared to the midband signal level. The "corner point" of a filter, usually the point where the response is down -3dB compared to the midband signal level. The signal frequency output of a filter that marks the transition from no attenuation to attenuation. Usually it is defined as the point at which the amplitude of the signal is reduced by 3 dB after passing through the filter. The signal frequency output of a filter that marks the transition from no attenuation to attenuation. Usually it is defined as the point at which the amplitude of the signal is reduced by 3 dB after passing through the filter.

There is 1 crossover point in a 2 way crossover There is 1 crossover point in a 2 way crossover There are 2 crossover points in a 3 way crossover There are 2 crossover points in a 3 way crossover There are 3 crossover points in a 4 way crossover There are 3 crossover points in a 4 way crossover

32 Types of Filters Butterworth filter Butterworth filter Chebyshev filter Chebyshev filter Linkwitz-Riley (L-R) filter Linkwitz-Riley (L-R) filter Elliptic filter Elliptic filter Bessel filter Bessel filter Legendre filter Legendre filter Gaussian filter Gaussian filter

33 Butterworth filter It is designed to have a frequency response which is as flat as mathematically possible in the passband It is designed to have a frequency response which is as flat as mathematically possible in the passband

35 Linkwitz-Riley filter The filters are usually designed by cascading two Butterworth filters, each of which has −3 dB gain at the cut-off frequency. The resulting Linkwitz- Riley filter has a −6 dB gain at the cutoff frequency. This means that summing the low-pass and high-pass outputs, the gain at the crossover frequency will be 0 dB, so the crossover behaves like an all-pass filter, having a flat amplitude response with a smoothly changing phas response. This is the biggest advantage of L-R crossovers compared to Butterworth crossovers The filters are usually designed by cascading two Butterworth filters, each of which has −3 dB gain at the cut-off frequency. The resulting Linkwitz- Riley filter has a −6 dB gain at the cutoff frequency. This means that summing the low-pass and high-pass outputs, the gain at the crossover frequency will be 0 dB, so the crossover behaves like an all-pass filter, having a flat amplitude response with a smoothly changing phas response. This is the biggest advantage of L-R crossovers compared to Butterworth crossovers

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Linkwitz-Riley filter

38 2 Types of Crossovers Active Active Passive Passive

39 Passive Passive crossovers are usually built into speaker cabinets (typically in the form of a printed circuit board with one or more capacitors and/or resistors and/or inductors mounted on it) Passive crossovers are usually built into speaker cabinets (typically in the form of a printed circuit board with one or more capacitors and/or resistors and/or inductors mounted on it) A passive crossover appears in the circuit after the amplifiers, and divides the signal that then goes to your speakers. A passive crossover appears in the circuit after the amplifiers, and divides the signal that then goes to your speakers. A passive crossover has no power, ground, or turn-on leads and are rather inexpensive. But, they tend to be inefficient and can even add some distortion. A passive crossover has no power, ground, or turn-on leads and are rather inexpensive. But, they tend to be inefficient and can even add some distortion.

44 Advantages of Passive Crossovers Less Amplification needed compared to active Less Amplification needed compared to active Less Expensive Less Expensive No ac power required to operate nothing to turn on. No ac power required to operate nothing to turn on.

45 Disadvantages of Passive Crossovers Less Efficient Less Efficient More Distortion More Distortion Fixed crossover point Fixed crossover point No level control for individual frequency ranges No level control for individual frequency ranges

46 Active Crossover Active crossovers usually come in the form of a 19" 1U rack-mounted box with knobs or buttons and some sort of menu display on the front. Some - usually with system- specific EQ settings, delay and limiting functions - are described as controllers. Active crossovers usually come in the form of a 19" 1U rack-mounted box with knobs or buttons and some sort of menu display on the front. Some - usually with system- specific EQ settings, delay and limiting functions - are described as controllers.

47 Active Crossover Most active crossovers allow adjustment of the crossover points, as well as independent control of the output level of each frequency band. Most active crossovers allow adjustment of the crossover points, as well as independent control of the output level of each frequency band. An active, or electronic, crossover does its job pre-amp (taking the signal directly from the mixer before it gets to the amplifier) An active, or electronic, crossover does its job pre-amp (taking the signal directly from the mixer before it gets to the amplifier) Needs an external power source. Needs an external power source.

48 Active Crossover Active crossovers give you control over which frequencies you want to use as the crossover points for bass mid and treble Active crossovers give you control over which frequencies you want to use as the crossover points for bass mid and treble Some active crossovers allow you to customize the crossover slope as well as the crossover point Some active crossovers allow you to customize the crossover slope as well as the crossover point Because they filter frequencies before the signal is amplified, active crossovers ensure that the amp gives its full attention to the filtered signal, which is very efficient Because they filter frequencies before the signal is amplified, active crossovers ensure that the amp gives its full attention to the filtered signal, which is very efficient

BSS

ASHLY

54 RANE

55 Advantages of Active Crossovers Selectable Crossover Points Selectable Crossover Points Level Control of each band Level Control of each band Better system efficiency Better system efficiency Driver Delay control Driver Delay control Less Distortion Less Distortion Signal is not affected as much as with passive crossovers, since everything is done at low voltages. Signal is not affected as much as with passive crossovers, since everything is done at low voltages.

56 Disadvantages of Active Crossovers Need separate amps for each band of frequencies Need separate amps for each band of frequencies Increasing systems expense dramatically Increasing systems expense dramatically More complex setup More complex setup

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58 Active & Passive

60 How To Choose Crossover Points Choose your crossover points and crossover slopes by consulting the frequency response measurement on your speaker specs. Choose your crossover points and crossover slopes by consulting the frequency response measurement on your speaker specs. The frequency response is the range of frequencies that the speaker can successfully reproduce. The frequency response is the range of frequencies that the speaker can successfully reproduce. The frequency response of two separate speakers (woofer and midrange, for example) must overlap a little, or you will hear a "gap" in the sound. The frequency response of two separate speakers (woofer and midrange, for example) must overlap a little, or you will hear a "gap" in the sound. The crossover point appears within this overlap The crossover point appears within this overlap

61 Typical Crossover Points Two way ( 1.6 khz ) Two way ( 1.6 khz ) Three way ( 125 hz – 1.6 Khz ) Three way ( 125 hz – 1.6 Khz ) Four way ( 80 hz – 250 hz – 1.6 Khz ) Four way ( 80 hz – 250 hz – 1.6 Khz )

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64 18” Driver

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66 12” Driver

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68 1" Line Array High Frequency Driver Freq. Range - 500Hz to 20kHz Freq. Range - 500Hz to 20kHz

69 DSP Digital Signal Processor Digital Signal Processor

70 Digital Crosovers Also known as loudspeaker management systems Also known as loudspeaker management systems Give us complete control of all elements of loud speaker system including: EQ, Crossover points, Delay, Compression, Limiting, all in one unit. Give us complete control of all elements of loud speaker system including: EQ, Crossover points, Delay, Compression, Limiting, all in one unit. Storable programs and setups ie: stereo 4 way or 4 x 2way etc. Storable programs and setups ie: stereo 4 way or 4 x 2way etc. BSS Omni Drive is one example of this type of unit BSS Omni Drive is one example of this type of unit

72 Many processes that would traditionally be achieved by using many units can now be incorporated into one crossover system providing an integrated solution. A digital unit is not simply a crossover; it is a complete Loudspeaker Management System As well as the crossover, functions are provided for limiting, time delay and equalisation. Because the unit is completely controlled by a microprocessor, each unit can store many programs internally. The same DSP can be used for many different speaker configurations Perhaps the most important crossovers is the provision of driver alignment. The integration of delay into a digital crossover enables the benefits of driver alignment to be easily achieved without great expense.

73 Behinger DCX2496

74 XTA Loudspeaker Management

75 XTA Loudspeaker Management

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LAKE PROCESSOR

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