A loudspeaker is an electro acoustic transducer; a device which converts an electrical audio signal into a corresponding sound. (Electrical energy to acoustical energy)

1. AUDIOGRAPHY
UNIT – 2 - Loudsperkers
PREPARED BY
SANKARANARAYANAN K. B
ASST. PROFESSOR
DEPARTMENT OF VISUAL COMMUNICATION
NEHRU ARTS AND SCIENCE COLLEGE(Autonomous)
COIMBATORE

2. Expected outcomes
 Students will be able to understand about the
various loudspeakers, its type and design.
 Students will be able to remember the working
patterns and principles of different loudspeaker
types.
 Students will be able to choose the right speakers
according to their purpose.
 Students will know about the characteristics of each
loudspeakers.

3. Introduction
 A loudspeaker is an electro
acoustic transducer; a device which converts an
electrical audio signal into a
corresponding sound. (Electrical energy to
acoustical energy)
 The most widely used type of speaker
is invented in 1924 by Edward W.
Kellogg and Chester W. Rice.

4. Operating Principle
 The dynamic speaker operates on the same basic
principle as a dynamic microphone, but in reverse, to
produce sound from an electrical signal.
 When an alternating current (AC) electrical audio
signal is applied to its voice coil, a coil of wire
suspended in a circular gap between the poles of
a permanent magnet, the coil is forced to move rapidly
back and forth due to Faraday's law of induction,
which causes a diaphragm (usually conically shaped)
attached to the coil to move back and forth, pushing on
the air to create sound waves.

5. Driver design: dynamic loudspeakers
 Cutaway view of a dynamic loudspeaker
1. Magnet
2. Voice coil
3. Suspension
4. Diaphragm

6. Image Source: https://www.ht-audio.com/images/Basics15.gif

7. Diaphragm
 The diaphragm is usually manufactured with a
cone- or dome-shaped profile. A variety of
different materials may be used, but the most
common are paper, plastic, and metal. The ideal
material would
 1) be rigid, to prevent uncontrolled cone
motions;
 2) have low mass, to minimize starting force
requirements and energy storage issues;
 3) be well damped, to reduce vibrations
continuing after the signal has stopped with little
or no audible ringing due to
its resonance frequency as determined by its
usage.

8. Working
 Dynamic loudspeaker, uses a lightweight diaphragm, or cone,
connected to a rigid basket, or frame, via a flexible
suspension, commonly called a spider, that constrains a voice
coil to move axially through a cylindrical magnetic gap. A
protective cap glued in the cone's center prevents dust,
especially iron filings, from entering the gap. When an
electrical signal is applied to the voice coil, a magnetic field is
created by the electric current in the voice coil, making it a
variable electromagnet.

9. Other Parts
 Basket
 The chassis, frame, or basket, is designed to be
rigid, preventing deformation that could change
critical alignments with the magnet gap, perhaps
allowing the voice coil to rub against the magnet
around the gap. Chassis are typically cast from
aluminum alloy, in heavier magnet-structure
speakers; or stamped from thin sheet steel in
lighter-structure drivers.
 Cone materials
 The cone surround can be rubber or
polyester foam, treated paper or a ring of
corrugated, resin coated fabric; it is attached to
both the outer cone circumference and to the
upper frame.

10. Driver types
 Individual electro dynamic drivers provide their best
performance within a limited frequency range.
Multiple drivers (e.g., subwoofers, woofers, mid-
range drivers, and tweeters) are generally
combined into a complete loudspeaker system to
provide performance beyond that constraint. The
three most commonly used sound radiation systems
are the cone, dome and horn type drivers.

11. Speaker drivers
 Loudspeaker for home use with three types
1. Mid-range driver(Squawker)
2. Tweeter
3. Woofers
 The hole below the lowest woofer is a port
for a bass reflex system.

12. Full-range drivers
 A full-range driver is a speaker designed to be
used alone to reproduce an audio channel
without the help of other drivers, and therefore
must cover the entire audio frequency range.
 Full-range (or more accurately, wide-range)
drivers are most commonly heard in public
address systems, in televisions (although some
models are suitable for hi-fi listening), small
radios, intercoms, some computer speakers, etc.
 In hi-fi speaker systems, the use of wide-range
drive units can avoid undesirable interactions
between multiple drivers caused by non-
coincident driver location or crossover network
issues.

13. Subwoofer
 A subwoofer is a woofer driver used
only for the lowest-pitched part of the
audio spectrum: typically below
200 Hz for consumer systems below
100 Hz for professional live sound.
 Since sound in this frequency range
can easily bend around corners
by diffraction, the speaker aperture
does not have to face the audience,
and subwoofers can be mounted in
the bottom of the enclosure, facing
the floor. Image Source : https://www.canalsoundlight.com/wp-content/uploads/2013/08/p-24746-SUB-
8006-AS-RIGHT-NO-GRILL.jpg

14. Woofer
 A woofer is a driver that reproduces low frequencies.
The driver works with the characteristics of the
enclosure to produce suitable low frequencies. Some
loudspeaker systems use a woofer for the lowest
frequencies, sometimes well enough that a subwoofer
is not needed. Additionally, some loudspeakers use
the woofer to handle middle frequencies, eliminating
the mid-range driver. This can be accomplished with
the selection of a tweeter that can work low enough
that, combined with a woofer that responds high
enough, the two drivers add coherently in the middle
frequencies.

15. Mid-range driver
 A mid-range speaker is a loudspeaker driver that
reproduces a band of frequencies generally between
1–6 kHz, otherwise known as the 'mid' frequencies
(between the woofer and tweeter).
 Mid-range driver diaphragms can be made of paper
or composite materials, and can be direct radiation
drivers (rather like smaller woofers) or they can
be compression drivers (rather like some tweeter
designs).

16. Tweeter
 A tweeter is a high-frequency driver that
reproduces the highest frequencies in a speaker
system. A major problem in tweeter design is
achieving wide angular sound coverage (off-axis
response), since high frequency sound tends to leave
the speaker in narrow beams. Soft-dome tweeters
are widely found in home stereo systems, and horn-
loaded compression drivers are common in
professional sound reinforcement.

17. Coaxial drivers
 A coaxial driver is a loudspeaker driver with two or
several combined concentric drivers.
Image Source: https://www.madisoundspeakerstore.com/images/products/integra-624.jpg Image Source: https://cdn.shopify.com/s/files/1/1577/7605/products/new_coax-
15_pair_a0e3f47e-6daf-4bdd-9e16-05f96e66cccd_1024x1024.jpg?v=1510262356

18. Active(Powered) and Passive speakers
 Passive speaker doesn’t have a amplifier that is Built-
in. An amplifier is needed to power the speaker
through normal speaker wire. This speaker signal
level will be amplified to drive the speakers
sufficiently.
 Active speakers, have a built-in amplifier and are
supplied by a low-level (line-level) signal from the
mixer or interface. Since the amplifier is inside the
speakers it needs power, and you have to power them
externally.
More Info: https://www.youtube.com/watch?v=kApwnPm3RNU

19. Image Source: https://www.astounded.com/wp-content/uploads/Passive-Active-Speakers-.png

20. System design
 Crossover
 Enclosures
 Wiring connections
 Wireless speakers

21. Crossover
 Used in multi-driver speaker systems, the crossover
is an assembly of filters that separate the input
signal into different frequency ranges (i.e.
"bands"), according to the requirements of each
driver. Crossovers can be passive or active.
 A passive crossover is an electronic circuit that uses
a combination of one or more resistors, inductors, or
non-polar capacitors. These components are
combined to form a filter network and are most
often placed between the full frequency-range
power amplifier and the loudspeaker drivers to
divide the amplifier's signal into the necessary
frequency bands before being delivered to the
individual drivers.
 An active crossover is an electronic filter circuit that
divides the signal into individual frequency
bands before power amplification, thus requiring at
least one power amplifier for each band pass.

22. Enclosures
 Most loudspeaker systems consist of drivers
mounted in an enclosure, or cabinet. The role of the
enclosure is to prevent sound waves emanating from
the back of a driver from interfering destructively
with those from the front. most enclosures function
by containing the rear radiation from the moving
diaphragm.
 A sealed enclosure prevents transmission of the
sound emitted from the rear of the loudspeaker by
confining the sound in a rigid and airtight box.
Techniques used to reduce transmission of sound
through the walls of the cabinet include thicker
cabinet walls, lossy wall material, internal bracing,
curved cabinet walls—or more rarely, visco-
elastic materials (e.g., mineral-loaded bitumen)
or thin lead sheeting applied to the interior
enclosure walls.

23. Wiring connections
 Most home hi-fi loudspeakers use
two wiring points to connect to
the source of the signal (for
example, to the audio amplifier
or receiver).
 With sound reinforcement
system, PA system and instrument
amplifier speaker enclosures,
cables and some type of jack or
connector are typically used.
 Speakon connectors are
considered to be safer for high
wattage amplifiers, because the
connector is designed so that
human users cannot touch the
connectors.

24. Specifications
 Speaker or driver type (individual units only) – Full-range, woofer, tweeter, or mid-range.
 Size of individual drivers. (Voice-coil diameter may also be specified.)
 Rated Power - Nominal (or even continuous) power, and peak (or maximum short-term) power
a loudspeaker can handle.
 Impedance – typically 4 Ω (ohms), 8 Ω, etc
 Baffle or enclosure type (enclosed systems only) – Sealed, bass reflex, etc.
 Number of drivers (complete speaker systems only) – two-way, three-way, etc.
 Class of loudspeaker: Class 1, 2, 3, 4.
 Frequency response : measured, or specified, output over a specified range of frequencies
for a constant input level varied across those frequencies.
 Sensitivity : sound pressure level produced by a loudspeaker in a non-reverberant
environment, often specified in dB and measured at 1 meter with an input of 1 watt
 Maximum sound pressure level : highest output the loudspeaker can manage

25. Other speaker designs
 Moving-iron loudspeakers
 Piezoelectric speakers
For More Info: https://en.wikipedia.org/wiki/Loudspeaker#Other_speaker_designs

26. MCQs / Assessment
 Multiple Choice Questions Link will be shared in
Quizziz.com
Model Question :
 What is the operating principle of a transducer in Moving Coil
loudspeaker?
a) Electromagnetic Induction b) Electrostatic Principle
c) None of the Above d) Both a & b

27. Summary
 A loudspeaker is an electro acoustic transducer, a
device which converts an electrical audio signal into
a corresponding sound.
 Mainly there are three type of Speaker drivers: Full
range, Mid-range and woofers.
 Speakers are of two types : Active and Passive
 Speakers can be classified according to its baffle
design, power output, enclosure, and
sensitivty/frequency response.
 The placement and directivity of speakers are
essential for hearing good quality sound.

28. Points to Remember
 Loaudspeakers work opposite to the working
pattern of microphone.
 Electrical energy is converted into acoustical energy.
 Major Driver types are :Full-range drivers,
Subwoofer, Woofer, Mid-range driver, Tweeter,
Coaxial drivers.
 The system design of speakers are classified into
crossover types used, enclosure, wiring and
transmission of loudspeakers.

29. Source for Reference
1.https://youtu.be/mD6P39t8obo
2.https://www.youtube.com/watch?v=048tBZMt3eY
3.https://www.crunchreviews.com/blog/different-
types-of-speakers/
4.https://blog.landr.com/how-do-speakers-work/
5.https://www.youtube.com/watch?v=fpGlz_HpnmY

30. Introduction of Next Session
 Amplifiers
 Types and designs
 Uses and applications
 Audio chain

31. Thank You
SANKARANARAYANAN K. B
ASST. PROFESSOR
DEPARTMENT OF VISUAL COMMUNICATION
NEHRU ARTS AND SCIENCE COLLEGE(Autonomous)
COIMBATORE
Mail Id: nascsankaranarayanan@nehrucolleges.com