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Monday, 6 September 2021

Electrostatic Loudspeaker Working

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)

Placement: 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).

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