It is a class of digital filters, these slides will give you brief knowledge that how bass, voice and other sounds are separated

1. Crossovers
By
Shahbaz Ali Khidri
Shakir Hussain Memon

2. Outline
• What is a Crossover
• How Crossover works
• Crossover filter types
• Slope & Crossover Point
• Cut-off frequency
• Active & Passive crossovers
• Choosing crossover points

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

4. How Crossover 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).
• Steep cut-off is also called as Slope.

5. Example

6. Crossover Filter Types
• High-pass
• Low-pass
• Band-pass

7. Crossover Filter Types
• A high-pass filter will block low frequencies.
• A low-pass will block high frequencies.
• A band-pass will block low and high frequencies
below and above crossover points.

8. Slope
• Slope is expressed as decibels per octave.
• 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 cut frequencies progressively.
• A crossover "slope" describes how effective a
crossover is in blocking frequencies.
• A 6dB per octave crossover reduces signal level
by 6dB in every octave starting at the crossover
point.

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

10. Slope

11. Crossover Point
• 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).
• The frequency at which an audio signal is divided.

12. Crossover Point
• There is 1 crossover point in a 2 way crossover.
• There are 2 crossover points in a 3 way crossover.
• There are 3 crossover points in a 4 way crossover.

13. Cut-off Frequency
• The "corner point" of a filter, usually the point
where the response is down -3dB compared to
the mid-band 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.

14. Cut-off Frequency

15. PASSIVE AND ACTIVE CROSSOVERS

16. Passive Crossovers
• 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 appears in the circuit after the
amplifiers, and divides the signal that then goes to
your speakers.
• 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)

19. Advantages of Passive crossover
• Less Amplification needed compared to
active
• Less Expensive
• No ac power required to operate nothing to
turn on.

20. Disadvantages of Passive Crossover
• Less Efficient
• More Distortion
• Fixed crossover point
• No level control for individual frequency
ranges

21. Active Crossover
• Needs an external power source.
• 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)

22. Active crossover
• 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
• 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

23. Active crossover

24. Advantages & Disadvantages of
Active Crossovers
Advantages
• Selectable Crossover Points
• Level Control of each band
• Better system efficiency
Disadvantage
• Need separate amps for each band of frequencies
• Increasing systems expense dramatically
• More complex setup

25. How To Choose Crossover Points
• 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.