Loudspeaker- direct radiating type and horn type.pptx

loudspeaker, characteristics of loudspeaker, direct radiating type loudspeaker, permanent magnet type, cone type loudspeaker, moving coil type loudspeaker, dynamic loudspeaker, electrodynamic loudspeaker, horn loudspeaker

1. Dr. Priyanka Tabhane Department of Physics Rashtrasant Tukadoji Maharaj Nagpur University , Nagpur Loudspeaker Direct Radiating Type Moving Coil Loudspeaker Electrodynamic Loudspeaker Horn Loudspeaker

2. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Loudspeakers have been used for many years to convert electrical signals into audio sound waves. It is a type of Transducer. The job of a Loudspeaker is to set up vibrations in the air which are acoustic representations of the waveforms of the electrical signals that are being supplied to the input terminals. A loudspeaker is therefore an electro-mechanic-acoustic transducer. There are several different technologies and approaches used within loudspeakers. As a result there are several different types of loudspeaker that can be used . Loudspeaker systems vary enormously. Some only have a single drive unit or loudspeaker unit, but often these single speaker systems have limited response at the low and high frequency ends of the frequency spectrum. As a result many systems consist of two or even three different loudspeaker drive units, each targeted at covering a different frequency range.

3. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Most audio systems include several loudspeaker drivers to reproduce both low frequencies (LF) and high frequencies (HF). the most common types of drivers are woofers, mid-range and tweeter . The voltage applied to the loudspeaker voice coil is AC voltage, which means it has two defining characteristics: frequency and magnitude. The frequency fed controls pitch while the magnitude determines how loud the sound will be.

4. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Loudspeaker drive units :   The loudspeaker units themselves are of paramount importance as they convert the electrical currents into sound waves. Hi-Fi loudspeakers may have one or more loudspeakers of the different types mentioned below. For free standing systems two and sometimes there speakers with different ranges are used . Cross-over unit :   If multiple speakers are used, then it helps to have the required frequencies routed to the relevant speakers. Traditionally crossover units tended to consist of inductor and capacitors and many still do today. Modern amplifiers sometimes have different outputs for low end and top end speakers, so into in case the crossover unit is effectively contained within the amplifier . Cabinet :   There are many different types of loudspeaker cabinet. Often an infinite baffle system is used, that consists of a closed box. This needs to be as rigid and airtight as possible to ensure that the only vibrations come from the loudspeakers themselves. Accordingly these boxes are made from very rigid wood or other material . Internal sound absorbed material :   To prevent resonances being set up inside the loudspeaker cabinet, sound absorbed material is used within the infinite baffle systems

5. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Characteristics of loudspeaker Efficiency : It is defined as the ratio of output sound power to the input audio(electrical power). Noise : The unwanted sound, not contained in the input signal but present in the output of the loudspeaker is called noise. the signal to noise ratio (S/N) which is defined as the ratio of ‘signal output’ to the ‘output of noise in the absence of signal’. Distortion : Any change in the frequency, phase and amplitude complexion of the output sound as compared to the input audio signal is called distortion. Impedance : Input impedance of the loudspeaker is represented in ohms and its matching with the impedance of source amplifier is necessary. Power handling capacity : A loudspeaker can handle some maximum power (in watts) for which it is designed. Power more than the maximum will damage the speaker.

6. Direct Radiating Type loudspeaker In this Loudspeaker the vibrations of the coil are transmitted to attached cone which creates the sound in the air for the listener. Radiate sound energy directly to the air. There are two types of Direct radiating Loudspeaker. 1. Moving Coil Loudspeaker/typical cone speaker/permanent magnet type loudspeaker 2. Electrodynamic Loudspeaker Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

7. Moving Coil Loudspeaker Typical Cone Loudspeaker/moving coil/permanent magnet is a loudspeaker in which the vibrating diaphragm is large and conical and usually made of paper, no horn being used. Principle : The moving coil loudspeaker works on the principle of interaction between magnetic field and current. A coil, called voice coil, is placed in a uniform magnetic field. When audio current passes through the voice coil, there is an interaction between the magnetic field and the coil, resulting in a force working on the movable coil. This force is proportional to the audio current and hence causes vibratory motion in the coil, which makes a conical paper diaphragm to vibrate and produce pressure variations in air, resulting in sound waves. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

8. The force in Newtons on the coil due to interaction between current through the coil and magnetic field is given by , F=BIL Sin θ Where, F= force in newton B= flux density in wb /m 2 (or tesla) L = length of coil wire in meter I = current in ampere θ = angle between the coil and field, Normally, θ = 90 o , and hence, F=BIL Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

9. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

10. Construction The moving coil loudspeaker consist of voice coil , wound on a cardboard or fiber cylinder. Audio current is fed to it through two terminals. The coil is placed in a magnetic field. The magnet is a pot type permanent magnet which has a central pole (south pole) and peripheral pole (north pole ). The magnet is made of high grade magnetic material, like Al,Ni,Co . The coil is attached to a conical diaphragm, made of paper .It is called ‘paper cone’. The spider springs are used to support the complete diaphragm and also provide the required stiffness to restrain the motion. The spiders also keep the coil centered so that the motion is vertical and linear. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

11. Working: When audio current flows through the voice placed in a magnetic field, a force equal to BIL N acts on the coil and moves it to and fro. The paper cone attached to the coil also moves and causes compression and rarefaction cycles in the air. Thus, audio current is finally converted into sound waves. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

12. Characteristics of the cone-type speaker Efficiency : The efficiency of a cone speaker is quite low , about 5 to 10 percent only. The poor efficiency is due to the fact that it acts as a direct radiator . Signal to noise ratio : It is 30 db. or better. Frequency response : It is restricted to mid frequencies only. Frequency response drops at low and high audio frequencies for typical loudspeaker. Frequency response of a typical speaker is 200 Hz to 5000 Hz. Low frequency woofer speakers with baffles will give frequency response up to 40 Hz. High frequency tweeters extend the frequency response to 10 KHz or even higher . Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

13. Distortion: Non-linear distortion due to non-uniformity in the magnetic flux density causes severe distortion up to about 10 %. Directivity: Basically the loudspeaker is Omni-directional. But baffles and enclosures modify the directivity so that most of the power is in the front. Impedance: The effective impedance taking into account the mechanical and acoustical loads varies from 2 Ω to 32 Ω. the common impedances in commercial speakers are 4,8 or 16 ohm . Power handling capacity : Power range of speakers lies between a few mW (for 2 cm speaker) to about 25 W for large size speakers. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

14. Applications: Broadcast Studio Houses of worship Sports Venues Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

15. Electrodynamic /dynamic Loudspeaker To provide very strong magnetic field for high wattage speakers, electromagnet is used instead of permanent magnet. The moving coil loudspeaker works on the principle of interaction between magnetic field and current. Loudspeaker of more than 25 W and up to a few hundred watts are of electrodynamic type. The strong and steady magnetic field is produced by a large field coil wrapped around a core. This shape of magnet is pot type with south pole in the center and north pole in the periphery. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

16. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

17. The special shape of the core allows magnetic flux to remain concentrated in the annular gap between pole pieces . The voice coil is wound on fibre or aluminium (to keep it light in weight). It is placed in the annular gap . The audio signal is given to voice coil. The audio signal from the amplifier's output transformer is applied to the voice coil. This signal causes a varying magnetic field. The resultant interaction between the magnetic fields, one due to electromagnet and the other due to audio current in the voice coil, produces mechanical vibrations (motor action) in the coil assembly , which correspond to the audio signals. The vibrations of the coil are transmitted to the attached cone which create sound waves in the air and hence radiate sound energy directly. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

18. Advantages Higher power can be obtained Frequency response is better (40 Hz to 5000 Hz) Disadvantages Power supply needed for field coil Heavier weight for the same amount of magnetic field Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

19. Applications Broadcast studio PA Systems Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

20. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur A horn loudspeaker is a loudspeaker element which uses an acoustic horn to increase the overall efficiency of the driving elements. A horn loudspeaker use moving coil They are indirect Radiating Loudspeaker A horn loudspeaker, which uses an acoustic horn to increase overall efficiency of driving elements. Acoustic horn is an acoustic transformer that provides impedance matching between relatively dense diaphragm material & less dense air. Acoustic horn acts as a high pass filter. At High frequency, distance of different points on the diaphragm from the horn will be equal, causing phase difference & resultant cancellation. To overcome this difficulty, special chambers have been designed.

21. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Horn loudspeaker

22. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur

23. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Working Principle Current Flows in voice coil which generates magnetic field Magnetic field of magnet & magnetic field of voice coil interacts, causing voice coil moves and resulting in vibrating diaphragm which generates sound

24. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Characteristics Efficiency - the efficiency of loudspeaker is given by the ratio of output sound power to input audio power. Efficiency of horn loudspeaker is more than 40% Noise - Noise is an unwanted signal which is not present in electrical i/p but appears in its o/p. Noise determines the SNR of Loudspeaker. SNR of horn loudspeaker is more than 40 dB

25. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Distortion Any change in o/p frequency, phase or amplitude complexion is called as 'distortion'. In case of horn loudspeaker there is non-linear distortion which is less than 5 %. Impedance It should be taken cone of which connecting, for proper impedance matching. (T/F or emitter follower ) use. Input impedance is about 15 ohm. Directivity It can be Unidirectional, Bidirectional or Omnidirectional In case of horn loudspeaker directivity is different at different frequency. Frequency Response Frequency Response indicates the response of loudspeaker for audio range & it required to be flat for the whole audio range. Frequency response for horn loudspeaker is about 25 Hz - 10 KHz.

26. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur Advantages More efficiency More sound power Disadvantages Frequency Response is more uneven. Application PA system Megaphones Sports stadium Cinema halls

27. Dr. Priyanka Tabhane Dpartment of Physics, RTM nagpur University, Nagpur