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CrossoversCrossovers

Manual Reference Pages 222 – 227Manual Reference Pages 222 – 227

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What is a Crossover?What is a Crossover? Audio crossoversAudio crossovers are a class of are a class of

electronic filters designed electronic filters designed specifically for use in audio specifically for use in audio applications applications

CrossoversCrossovers serve the purpose of serve the purpose of splitting an audio signal into splitting an audio signal into separate frequency bands which can separate frequency bands which can be handled by individual be handled by individual loudspeaker drivers optimized for loudspeaker drivers optimized for those bands.those bands.

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What is a Crossover?What is a Crossover? They are generally described They are generally described

according to the number of according to the number of frequency bands available (two-frequency bands available (two-way, three-way and four-way).way, three-way and four-way).

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How it worksHow it works It uses bandwidth limiting filters It uses bandwidth limiting filters

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

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3 types of crossover 3 types of crossover filtersfilters

High-passHigh-pass Low-passLow-pass Band-passBand-pass

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AA high-pass high-pass filter will block low filter will block low frequenciesfrequencies

AA low-pass low-pass will block high will block high frequenciesfrequencies

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

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SlopeSlope Slope is expressed as decibels per Slope is expressed as decibels per

octave.octave. The rate of attenuation for every octave The rate of attenuation for every octave

away from the crossover frequencyaway from the crossover frequency Crossovers do not block undesired Crossovers do not block undesired

frequencies completely (unless you are frequencies completely (unless you are using digital crossovers) using digital crossovers)

Crossovers cut frequencies Crossovers cut frequencies progressivelyprogressively

A crossover "slope" describes how A crossover "slope" describes how effective a crossover is in blocking effective a crossover is in blocking frequenciesfrequencies

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SlopeSlope

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

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- 6db

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- 6db

- 12db

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- 12db

- 6db

- 18db

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- 12db

- 18db- 24db

- 6db

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1st order filters have a 6 dB/octave 1st order filters have a 6 dB/octave slopeslope

2nd order filters have a 12 dB/octave 2nd order filters have a 12 dB/octave slopeslope

3rd order filters have an 18 dB/octave 3rd order filters have an 18 dB/octave slopeslope

44thth order filters have a 24 dB/octave order filters have a 24 dB/octave slopeslope

55thth order filters have a 48 dB/octave order filters have a 48 dB/octave slopeslope

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- 6db

- 12db

- 18db

- 24db

- 48db500hz250Khz125hz 1Khz63hz

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Crossover PointCrossover Point

The nominal dividing line between The nominal dividing line between frequencies sent to two different speaker frequencies sent to two different speaker drivers.drivers.

In a crossover network, the frequency at In a crossover network, the frequency at which the audio signal is directed to the which the audio signal is directed to the appropriate driver (low frequencies to the appropriate driver (low frequencies to the woofer, high frequencies to the tweeter).woofer, high frequencies to the tweeter).

The single frequency at which both filters The single frequency at which both filters of a crossover network are down 3dB.of a crossover network are down 3dB.

The frequency at which an audio signal is The frequency at which an audio signal is divided.divided.

There is 1 crossover point in a 2 There is 1 crossover point in a 2 way crossoverway crossover

There are 2 crossover points in a There are 2 crossover points in a 3 way crossover3 way crossover

There are 3 crossover points in a There are 3 crossover points in a 4 way crossover4 way crossover

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Types of FiltersTypes of Filters

Butterworth filterButterworth filter Chebyshev filterChebyshev filter Linkwitz-Riley (L-R) filterLinkwitz-Riley (L-R) filter Elliptic filterElliptic filter Bessel filterBessel filter Legendre filterLegendre filter Gaussian filterGaussian filter

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Butterworth filterButterworth filter

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

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Linkwitz-Riley filterLinkwitz-Riley filter

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2 Types of 2 Types of CrossoversCrossovers

ActiveActivePassivePassive

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PassivePassive Passive crossovers are usually built Passive crossovers are usually built

into speaker cabinets (typically in the into speaker cabinets (typically in the form of a printed circuit board with form of a printed circuit board with one or more capacitors and/or resistors one or more capacitors and/or resistors and/or inductors mounted on it)and/or inductors mounted on it)

A passive crossover appears in the A passive crossover appears in the circuit circuit after the amplifiersafter the amplifiers, and divides , and divides the signal that then goes to your the signal that then goes to your speakers. speakers.

A passive crossover has no power, A passive crossover has no power, ground, or turn-on leads and are ground, or turn-on leads and are rather inexpensive. But, they tend to rather inexpensive. But, they tend to be inefficient and can even add some be inefficient and can even add some distortion.distortion.

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Advantages of Passive Advantages of Passive CrossoversCrossovers

Less Amplification needed Less Amplification needed compared to activecompared to active

Less ExpensiveLess Expensive No ac power required to operate No ac power required to operate

nothing to turn on. nothing to turn on.

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Disadvantages of Passive Disadvantages of Passive CrossoversCrossovers

Less EfficientLess Efficient More DistortionMore Distortion Fixed crossover pointFixed crossover point No level control for individual No level control for individual

frequency rangesfrequency ranges

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Active CrossoverActive Crossover

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

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Active CrossoverActive Crossover

Most active crossovers allow Most active crossovers allow adjustment of the crossover points, adjustment of the crossover points, as well as independent control of the as well as independent control of the output level of each frequency band.output level of each frequency band.

An active, or electronic, crossover An active, or electronic, crossover does its job pre-amp (taking the does its job pre-amp (taking the signal directly from the mixer before signal directly from the mixer before it gets to the amplifier)it gets to the amplifier)

Needs an external power source.Needs an external power source.

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Active CrossoverActive Crossover Active crossovers give you control Active crossovers give you control

over which frequencies you want to over which frequencies you want to use as the crossover points for bass use as the crossover points for bass mid and treblemid and treble

Some active crossovers allow you to Some active crossovers allow you to customize the crossover slope as well customize the crossover slope as well as the crossover point as the crossover point

Because they filter frequencies Because they filter frequencies before the signal is amplified, active before the signal is amplified, active crossovers ensure that the amp gives crossovers ensure that the amp gives its full attention to the filtered its full attention to the filtered signal, which is very efficientsignal, which is very efficient

BSSBSS

ASHLYASHLY

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RANERANE

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AdvantagesAdvantages of Active of Active CrossoversCrossovers Selectable Crossover PointsSelectable Crossover Points

Level Control of each bandLevel Control of each band Better system efficiency Better system efficiency Driver Delay controlDriver Delay control Less DistortionLess Distortion Signal is not affected as much as Signal is not affected as much as

with passive crossovers, since with passive crossovers, since everything is done at low everything is done at low voltages.voltages.

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DisadvantagesDisadvantages of Active of Active CrossoversCrossovers

Need separate amps for each Need separate amps for each band of frequenciesband of frequencies

Increasing systems expense Increasing systems expense dramaticallydramatically

More complex setupMore complex setup

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Active & PassiveActive & Passive

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How To Choose How To Choose Crossover PointsCrossover Points Choose your crossover points and Choose your crossover points and

crossover slopes by consulting the crossover slopes by consulting the frequency response measurement on frequency response measurement on your speaker specs.your speaker specs.

The frequency response is the range The frequency response is the range of frequencies that the speaker can of frequencies that the speaker can successfully reproduce.successfully reproduce.

The frequency response of two The frequency response of two separate speakers (woofer and separate speakers (woofer and midrange, for example) must overlap midrange, for example) must overlap a little, or you will hear a "gap" in the a little, or you will hear a "gap" in the sound.sound.

The crossover point appears within The crossover point appears within this overlapthis overlap

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18” Driver18” Driver

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12” Driver12” Driver

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1" Line Array High 1" Line Array High Frequency DriverFrequency Driver

Freq. Range - 500Hz to 20kHzFreq. Range - 500Hz to 20kHz

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DSPDSP

Digital Signal ProcessorDigital Signal Processor

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Digital CrosoversDigital Crosovers

Also known as loudspeaker Also known as loudspeaker management systemsmanagement systems

Give us complete control of all Give us complete control of all elements of loud speaker system elements of loud speaker system including: EQ, Crossover points, including: EQ, Crossover points, Delay, Compression, Limiting, all Delay, Compression, Limiting, all in one unit.in one unit.

Storable programs and setups ie: Storable programs and setups ie: stereo 4 way or 4 x 2way etc.stereo 4 way or 4 x 2way etc.

BSS Omni Drive is one example of BSS Omni Drive is one example of this type of unitthis type of unit

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Behinger DCX2496 Behinger DCX2496

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XTA Loudspeaker XTA Loudspeaker ManagementManagement

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XTA Loudspeaker XTA Loudspeaker Management Management

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LAKE PROCESSORLAKE PROCESSOR

LAKE PROCESSORLAKE PROCESSOR

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