MULTIWAY SPEAKER SYSTEM BY HARSH MEHTA GIUDE BY Prof. ANKIT SUTHAR ELECTRONICS AND COMMUNICATION A. D. PATEL INSTITUTE OF TECHNOLOGY, NEW V. V. NAGAR

Contents Introduction to loudspeaker Different types of loudspeaker Multi way speaker system Woofer Tweeter References

What is Loudspeaker? A loudspeaker is an electroacoustic transducer; a device which converts an electrical audio signal into a corresponding sound. Loudspeaker’s performance is measured by following characteristics: Efficiency Noise Frequency response Distortion Directivity Impedance

There are many different types of loudspeaker as follows: Moving coil loudspeaker Electrodynamic loudspeaker Horn type loudspeaker Baffles Multiway speaker system(Woofers & Tweeters)

Multi-way Speaker System A single loudspeaker cant have flat response for the whole audio frequency range from 16 Hz to 20000 Hz & not even for practical Hi-Fi range of 40 Hz to 15000 Hz. Low frequencies are weakened by back sound waves of reverse phase in open speaker. In closed box(enclosure) , the compliance of entrapped air comes in series with the compliance of the cone system and hence increases resonance frequency of loudspeaker. The loss at high frequencies is due to mass of diaphragm , thus a single speaker can’t produce both, good solid bass & smooth crisp treble. The best of them can only produce just acceptable bass and treble which will not satisfy Hi-Fi requirements.

To solve the problem , the audio frequency spectrum is divided into at least 2 and preferably 3 parts. Separate speakers are designed for each part so that each speaker has to cover only a small range of frequency. The speakers which cover low frequencies from 16 Hz to 1000 Hz are called ‘woofers’. The speakers which cover higher frequencies are called ‘tweeters’. Many a time , a third speaker called squawker is used for mid frequency range from 500- 5000 Hz and in that case woofer works up to 500 Hz and tweeter from 5000 Hz onwards. Woofer & tweeters can either be separate speakers mounted in a common enclosure or there can be a dual cone loudspeaker.

Woofers A woofer is a slang term for loudspeaker driver designed to produce low frequency sounds, typically from around 40hertz up to about a kilohertz or higher. The most common design for a woofer is the electrodynamic driver, which typically uses a stiff paper cone, driven by a voice coil which is surrounded by a magnetic field. The voice coil is attached by adhesives to the back of the speaker cone. The voice coil and magnet form a linear electric motor.

When current flows through the voice coil, the coil moves in relation to the frame according to Fleming's left hand rule, causing the coil to push or pull on the driver cone in a piston-like way. The resulting motion of the cone creates sound waves as it moves in and out. At ordinary sound pressure levels (SPL), most humans can hear down to about 20 Hz.  Woofers are generally used to cover the lowest octaves of a loudspeaker's frequency range. In two-way loudspeaker systems, the drivers handling the lower frequencies are also obliged to cover a substantial part of the midrange, often as high as 2000 to 5000 Hz; such drivers are commonly termed mid woofers.

Since the 1990s, a type of woofer (termed subwoofer), which is designed for very low frequencies only, has come to be commonly used in home theatre systems and PA systems to augment the bass response; they usually handle the very lowest two or three octaves (i.e., from as low as 20 to perhaps 80 or 120 Hz).

Tweeter A tweeter is a special type of loudspeaker (usually dome or horn-type) that is designed to produce high audio frequencies, typically from around 2,000 Hz to 20,000 Hz (generally considered to be the upper limit of human hearing). Specialty tweeters can deliver high frequencies up to 100 kHz.  Cutaway view of a dynamic tweeter 

Nearly all tweeters are electrodynamic drivers, using a voice coil suspended within a fixed magnetic field. These designs operate by applying current from the output of an amplifier circuit to a coil of wire, called a voice coil. The voice coil produces a varying magnetic field, which works against the fixed magnetic field of a magnet around which the cylindrical voice coil is suspended, forcing the voice coil and the diaphragm attached to it to move. This mechanical movement exactly resembles the waveform of the electronic signal supplied from the amplifier's output to the voice coil. Since the coil is attached to a diaphragm, the vibratory motion of the voice coil transmits to the diaphragm; the diaphragm in turn vibrates the air thus creating air motions or audio waves, which we hear as high sounds.

Most tweeters are designed to reproduce frequencies up to the formally defined upper limit of the human hearing range (typically listed as 20 kHz); some operate at frequencies up to approximately 30 kHz.

References Websites- www.Wikipedia.org Books- Audio & video systems by R. G. Gupta