Electrostatic Loudspeaker Working and Construction:
An electrostatic loudspeaker is a type of loudspeaker that generates sound by applying force to a membrane that is kept in an electrostatic field.
Figure: Electro Static Loudspeaker
Construction: The figure represents the
construction and connections of an electrostatic loudspeaker. The electrostatic
loudspeaker is made out of a thin flat diaphragm and two conducting grids (or
stators). The diaphragm is placed between two electrically conducting grids,
with a tiny air gap between the diaphragm and grids. The diaphragm is typically
constructed of a polyester sheet (thickness 2 to 20 m) with outstanding
mechanical characteristics. The grids are just perforated metal sheets.
Working: The diaphragm is kept at a DC
potential of several kilovolts to the grids by the conductive coating and an
external high voltage source. The audio signal controls the grids. The front
and rear grids are driven in opposite directions. As a consequence, a
homogeneous electrostatic field proportionate to the audio stream is created
between both grids. This exerts a force on the charged diaphragm, and the
ensuing movement pushes the air on each side of it. It is a high impedance
gadget. As a result, impedance matching is required to utilize a standard
amplifier. A transformer is most commonly utilized. It must maintain a
consistent transformation ratio throughout the audio frequency spectrum to
avoid distortion.
Advantages:
1. The
diaphragm's extremely low weight and has a great frequency response
2. Improved
stereo recording reproduction.
Disadvantages:
1. Poor
bass response
2.
Sensitivity to the amount of humidity in the surrounding environment.
HIGH
FIDELITY (HI-FI) ELECTROSTATIC SPEAKER:
The
definition of hi-fi sound is a reproduced sound that has a similarity to the
original or direct sound launched from the source and has undergone some
conversion through the system or multiple systems. Hi-fidelity is considered to
be attained when the published sound contains unnoticeable distortion from the
original, when there is little external noise, and when the volume levels and
acoustic effects of the room are readily audible. This replicated sound may be
more pleasant to the listener at the system output than the original live sound
at the source.
(A) WOOFER,
MIDRANGE, AND TWEETER:
The capacity of a receiver to reproduce distinct frequency components is known as its fidelity. A single speaker cannot accurately replicate all frequency components.
Figure: Connection of Hi-Fi Speakers
(or) Two Way Cross Over Network
Woofer:
i) Woofer is
a cone with a huge diameter that is used to reproduce low-frequency signals.
Tweeter:
ii) Tweeter
is a device used to recreate high-frequency signals with a tiny cone-diameter.
Driver or
Squawker:
iii) The
driver or squawker loudspeakers are located between the tweeter and woofer to
reproduce mid frequencies ranging from 300Hz to 5000Hz.
The diagram
represents the connecting of woofer and tweeter loudspeakers. It is a
bidirectional cross-over network.
Frequency
Response Characteristics:
The figure represents the frequency response of the woofer, tweeter, and squawker.
Figure. Frequency Response Characteristics
(B)
SPECIFICATION AND RANGE OF WOOFERS AND TWEETERS:
Loudspeakers
come in a variety of forms, including round, oval, and hexagonal. The speakers
are identified by the letter The speakers are identified by:
a. Speaker
frame's diameter
b. Type.
c. Power consumption.
d. The
impedance of the voice coil.
CROSS
OVER NETWORK:
Several control circuits are employed to enhance the quality and performance of amplifiers and radio receivers. Cross over network refers to these circuits. In multi-way speaker systems, cross-over networks are utilized to divide the input sound into several frequency bands. The figure depicts a three-way cross-over network.
Figure: Three-Way Cross over Network
The
mid-frequency range is a band that exists between the low and high pass
frequencies. An inductor L1 serves as the low pass filter, while a capacitor C2
serves as the high pass filter. An inductor L2 and a capacitor C1 comprise the
bandpass filter. The capacitor C2, which is linked in series with the tweeter,
prevents low and mid-frequency sounds from reaching the tweeter. Similarly,
putting inductance L1 in series with the woofer prevents high frequencies from
reaching it. Inductance L2 and capacitor C1 connected in series with the
squawker circuit keep low and high frequencies from reaching the squawker.
SURROUND
SOUND SYSTEM TYPES
Surround
sound, which utilizes Multichannel audio, refers to a set of techniques for
improving (extending and deepening) the quality of sound reproduction from a
recorded source. The additional recorded sound channels are replicated in this
system by employing additional discrete speakers. With audio channels above and
below the listener, the three-dimensional (3D) sphere of human hearing may be
practically realized. Surround sound technology is utilized in both cinema and
home theatre systems, as well as video game consoles and personal computers.
1.
Creating Surround Sound:
Surround
sound, which utilizes Multichannel audio, refers to a set of techniques for
improving (expanding and deepening) the quality of sound reproduction from a
recorded source. The additional recorded sound channels are replicated in this
system by employing additional discrete speakers. With audio channels above and
below the listener, the three-dimensional (3D) sphere of human hearing may be
practically realized. Surround sound technology is utilized in both cinema and
home theatre systems, as well as video game consoles and personal computers.
2. Mapping
Channels to Speakers:
Surround
sound systems depend on each source channel being assigned to its own set of
loudspeakers. The number and content of the source channels are recovered and
applied to the appropriate loudspeakers using matrix systems. The transmission
medium of a discrete surround system supports (at least) the same number of
source and destination channels. One-to-one channel-to-speaker mapping is not
the sole technique to provide surround sound signals.
3. Bass
Management:
Bass
management may be used in surround sound systems. The basic concept is that
bass content in the incoming signal, regardless of channel, should be sent
exclusively to loudspeakers capable of handling it.
4.
Surround Sound Specification:
The number of
channels, not the number of speakers, can be represented by each
specification description. The many channel surround systems are described
here.
5. Low-Frequency
Effects (LEF) Channel:
It was
designed to transmit incredibly low sub – bass' cinematic sound effects on its
channel. The LFE was originally a separate channel supplied to one or more
subwoofers in the original movie theatre installation.
Types of
Surround Sound System:
(A) 3.0
Channel Surround (Analog multiplexed, Dolby Surround): This method extracts
three audio channels from a two-channel source that has been specifically
encoded.
·
Two
channels – left (L) and right (R) – for the front speakers (R)
· One channel for a surround speaker or a rear-facing speaker – surround (S)
Three identical speakers are arranged equidistantly around a central listening point. If two back speakers are utilized, they should be placed somewhat behind the listening position, above ear height.(B) 4.0
Channel Surround (Analog Multiplexed / Discrete, Quadraphonic): In this method,
four audio channels are retrieved from either a specifically encoded
two-channel source or a four-channel source.
·
There
are two channels for front-facing speakers – left (L) and right (R) (R)
·
There
are two channels for rear surround speakers – surround right (RS) and surround
left (LS) (LS)
· Describes the early matrixes system and discrete quadraphonic surround systems.
Placement:
This method is solely used for music. All speakers should be angled at 45
degrees. All speakers should be placed above the level of the ear.
(C) 5.1
Channel Surround (3-2 Stereo) (Analog Matrixed, Dolby Pro Logic – II):
Five audio
channels and one LFE channel are derived from a specially encoded two-channel
or stereo source in this system. 5.1 Surround sound can also be referred to as
3-2 stereo. The phrase 3-2 refers to three front speakers and two back
speakers.
·
Front-facing
speakers with two channels – left (L) and right (R) (R)
·
One
channel for a speaker in the center - (C)
·
Two
channels for rear surround speakers – surround left (LS) and surround right
(SR) (RS)
·
One
low-frequency effects channel (LFE).
· Describes the Dolby Pro Logic – II matrixed surround system.
Placement:
The left and right speakers are angled at ± 30°. The rear speakers should
be angled around ± 110°.
(D) 6.1
Channel Surround:
This method
extracts six audio channels and one LFE channel from a specifically encoded
two-channel or stereo source.
·
Front
speakers have two channels: left (L) and right (R) (R)
·
One
channel for the center speaker - center (C), side left (LS), and side right
(SR) (RS)
·
Two
channels for side surround speakers – side left (LS) and side right (SR) (RS)
·
One
channel for rear surround speakers - back surround channel (BS)
· One low-frequency channel for driving a subwoofer (SW)
(E). 7.1
Channel Surround:
This method
extracts seven audio channels from an eight-channel source. This system is
employed in the home entertainment system.
·
Front speakers have two channels: left (L) and right (R) (R)
·
ONE
CHANNEL FOR THE CENTER SPEAKER – CENTER (C)
·
Two
channels for side surround speakers – left surround (LS) and right surround
(RS) (RS)
· There is just one low-frequency effect (LFE) channel.
(F). 10.2 Channel Surround:10.2 Channel
Surround has 14 distinct channels.
·
Five
front speakers are available: left wide, left, center, right, and right wide.
·
There
are five surround channels: left surround diffuse, direct, rear surround, right
surround diffuse, and direct.
·
Two
LFE channels (LFE left and LFE right) and two height channels (LFE left and LFE
right).