INTRODUCTIONINTRODUCTION An electro-acoustic transducer that converts An electro-acoustic transducer that converts

electrical signals into sounds loud enough to electrical signals into sounds loud enough to be heard at a distance. Non-electrical be heard at a distance. Non-electrical loudspeakers were developed as loudspeakers were developed as accessories to telephone systems, but accessories to telephone systems, but electronic amplification by vacuum electronic amplification by vacuum tube made loudspeakers more generally tube made loudspeakers more generally useful. The most common form of useful. The most common form of loudspeaker uses a paper cone supporting loudspeaker uses a paper cone supporting a voice coil electromagnet acting on a a voice coil electromagnet acting on a permanent magnet.permanent magnet.

HISTORYHISTORY The standard dynamic loudspeaker that we The standard dynamic loudspeaker that we

know of today was developed in the 1920's know of today was developed in the 1920's and uses a magnetic field to move a coil or and uses a magnetic field to move a coil or magnet which is connected to a diaphragm. magnet which is connected to a diaphragm. The dynamic loudspeaker outperforms The dynamic loudspeaker outperforms many other types of speakers, and is lower many other types of speakers, and is lower cost to produce. For these reasons it is the cost to produce. For these reasons it is the most popular.   most popular.  

TYPESTYPES

►HornsHorns►Electrodynamic Loudspeaker Electrodynamic Loudspeaker ►Flat Panel SpeakersFlat Panel Speakers►Diaphragm SpeakersDiaphragm Speakers►Plasma Arc SpeakersPlasma Arc Speakers►Piezoelectric SpeakersPiezoelectric Speakers

HORNSHORNS Horns were the earliest form Horns were the earliest form

of amplification.Horns do of amplification.Horns do not use electricity. The not use electricity. The problem with horns is that problem with horns is that they could not amplify the they could not amplify the sound very much.Horns sound very much.Horns remain a novelty for remain a novelty for collectors today. Audio collectors today. Audio Recording for Recording for entertainment and entertainment and recorded keeping, later on recorded keeping, later on for voice radio for voice radio

ELECTRODYNAMIC ELECTRODYNAMIC LOUDSPEAKERLOUDSPEAKER

This is a device that uses This is a device that uses an electromagnetic coil an electromagnetic coil and diaphragm to and diaphragm to create sound. It uses create sound. It uses an electromagnet to an electromagnet to turn electric signals of turn electric signals of varying strength into varying strength into movement. This is the movement. This is the most common type of most common type of speaker in the world speaker in the world today. today.

FLATPANEL SPEAKERSFLATPANEL SPEAKERSFlat Panel Speakers use Flat Panel Speakers use

voice coils mounted to voice coils mounted to flat panels to act as the flat panels to act as the source of sound. The source of sound. The flat panel acts as a flat panel acts as a diaphragm. Different diaphragm. Different materials can be used materials can be used as a diaphragm from as a diaphragm from vinyl to Styrofoam vinyl to Styrofoam .Types of flat panel .Types of flat panel speakers: Ribbon speakers: Ribbon speaker, Planar speaker, Planar magnetic, magnetic, Electrostatic. Electrostatic.

DIAPHRAGM SPEAKERDIAPHRAGM SPEAKER

Diaphragm Speaker is Diaphragm Speaker is related to the related to the electrodynamic electrodynamic loudspeaker in that it loudspeaker in that it uses magnetic fields to uses magnetic fields to move an element. This move an element. This speaker has the coil speaker has the coil directly mounted on the directly mounted on the diaphragm. diaphragm.

PLASMA ARC SPEAKERPLASMA ARC SPEAKERPlasma is ionized gas, or Plasma is ionized gas, or

current sent through a current sent through a gas. Plasma is gas. Plasma is responsive to electrical responsive to electrical fields, therefore you fields, therefore you can turn electric signal can turn electric signal of sound into an of sound into an electric field which electric field which manipulates the manipulates the plasma.This kind of plasma.This kind of speaker is interesting speaker is interesting but limited in sound but limited in sound quality.  quality. 

Piezoelectric SpeakersPiezoelectric Speakers

Piezoelectric speakers Piezoelectric speakers are limited in are limited in frequency response frequency response therefore they are only therefore they are only used as tweeters or in used as tweeters or in small electrical devices small electrical devices like watches/clocks to like watches/clocks to make simple sounds. make simple sounds.

S C A N N E RS C A N N E RComputer peripheral device that converts Computer peripheral device that converts

a document, film, graphic, or photograph to a document, film, graphic, or photograph to a digital image, manipulate through an a digital image, manipulate through an appropriate software. When used with appropriate software. When used with an optical character recognition an optical character recognition (OCR) software, a scanner can convert (OCR) software, a scanner can convert printed, typewritten text into a digital file that printed, typewritten text into a digital file that can be read by a word processor.can be read by a word processor.

TYPES TYPES ►Flatbed ScannersFlatbed Scanners

►Photo ScannersPhoto Scanners

►Sheet fed ScannersSheet fed Scanners

►Portable ScannersPortable Scanners

FLATBED SCANNERFLATBED SCANNERFlatbed scanners will Flatbed scanners will

take up some desktop take up some desktop space. They look like space. They look like miniature printers with miniature printers with a flip-up cover a flip-up cover protecting the glass protecting the glass platen These scanners platen These scanners are good for scanning are good for scanning the newspaper, book, the newspaper, book, photograph;or for scan photograph;or for scan bulky items.  bulky items. 

PHOTO SCANNERSPHOTO SCANNERS

Photo scanners include Photo scanners include specialized technology specialized technology so that they can deal so that they can deal with slides and with slides and negatives; they also negatives; they also have built-in software have built-in software to clean up old photos. to clean up old photos. Many all-purpose Many all-purpose scanners can also scanners can also scan photos. scan photos.

SHEETFED SCANNERSHEETFED SCANNER

Sheet fed scanners are Sheet fed scanners are smaller than flatbed smaller than flatbed scanners. You feed a scanners. You feed a document or photo into document or photo into the scanner rather the scanner rather than place it on top. In than place it on top. In these the output these the output resolution in the resolution in the process is not good.process is not good.

PORTABLE SCANNERPORTABLE SCANNER

Portable scanners are Portable scanners are small enough to  carry small enough to  carry with us. Some are with us. Some are small enough like small enough like fountain pen. These fountain pen. These scanner scan scanner scan document line by line. document line by line. so they are not good so they are not good for scanning photos or for scanning photos or other high class result.other high class result.