ECE5320 Mechatronics Assignment#01: Literature Survey on Sensors and Actuators Topic: Loudspeakers

1. ECE5320 MechatronicsAssignment#01: Literature Survey on Sensors and Actuators Topic: Loudspeakers Prepared by: Balaji Ravindran Dept. of Electrical and Computer Engineering Utah State University 3/7/2008

2. Outline • Reference list • To probe further • Major applications • Basic working principle illustrated • Design Classifications • Major specifications • A typical sample configuration in application (application notes) • How/Where to Purchase ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

3. Reference list • http://hyperphysics.phy-astr.gsu.edu/hbase/audio/spk.html#c1 • http://melhuish.org/audio/theory.html • http://en.wikipedia.org/wiki/Loudspeaker#Full_range_drivers • http://www.trueaudio.com/st_diff1.htm • http://www.teamrocs.com/technical/pages/vented_enclosures.htm • http://www.silcom.com/~aludwig/Loudspeaker_construction.html ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

4. To explore further (survival pointers of web references etc) • http://history.sandiego.edu/GEN/recording/loudspeaker.html • http://en.wikipedia.org/wiki/Woofer • www.bolo-digital.com/pages/surround/surround.html • http://bdsays.files.wordpress.com/2007/02/rahman_control.jpg • http://www.sweetwater.com/ • http://www.mcsquared.com/speakers1.htm ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

5. Major applications • Recording Studios / Home Theatre, • Telephones / Mobile / Voice Communication, • Hearing Aids, • Motion Pictures • University / Public / Private Conferences • Computers • Space Applications • Medical Applications ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

6. Basic working principle illustrated • Electromechanical transducer • Electrical signal to Sound • History • Siemens - nonmagnetic parchment diaphragm as the sound radiator of a moving-coil transducer, loudspeaker horn that would be used on most phonographs players in the acoustic era ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

7. Design Classification – Dynamic LS ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

8. Design Classification • Horn Loudspeakers • Oldest Loudspeakers • Shaped waveguide – to increase directivity and transform small diameter high pressure to large diameter low pressure at the mouth of horn • A horn loaded speaker can have a sensitivity as high as 110 dB @ 2.83volts • Majorly used during WWII era ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

9. Design Classification • Piezo-Electric Loudspeakers • Resistant to overloads • inherently capacitive electrical load • Disadvantage • amplifiers can oscillate when driving capacitive loads, which results in distortion or damage to the amplifier • Piezoelectric speakers can have extended high frequency output • Used in watches(beeps) or in computers ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

10. Major Specifications • Speaker or Driver type • Full Range Driver • Center Cap – normal cone with dome center cap • Whizzer cone – 1 large cone and 1 small whizzer cone • Figure – Axiom 180 LS • High efficiency, low excursion, and a frequency response graph that shows lowered sound pressure levels at medium to low bass • Low efficiency one’s have flatter frequency response. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

11. Major Specifications • Woofer • useful for augmenting main loudspeakers by providing playback of low bass frequencies at high levels • Electro-dynamic Driver • These use a cone, driven by a voice coil surrounded by a magnetic field. 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 voice coil is attached by adhesives to the back of the speaker cone. The resulting motion of the cone creates sound waves as it moves in and out ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

12. Major Specifications • Rated Power • peak power a loudspeaker can handle before thermally destroying the loudspeaker • A driver may be damaged at much less than its rated power if driven past its mechanical limits at lower frequencies. • Sensitivity • The sound pressure level produced by a loudspeaker, (in dB), measured at 1 meter with an input of 1 watt ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

13. Major Specifications • Impedance • typically 4 Ω (ohms), 8 Ω, • Frequency Response • The measured, or specified, output over a specified range of frequencies for a constant input level varied across those frequencies(usually +/- 2.5dB) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

14. Major Specifications • Enclosure types • cabinet designed to transmit sound to the listener via mounted loudspeaker drive units. • prevent the out of phase sound waves from the rear of the speaker from combining with the in-phase sound waves from the front of the speaker • Major problem - Diffraction Loss and Compensation • occurs in the low frequency range of loudspeakers in enclosures that are located in the open, away from walls or other surfaces • Because the "energy density" at low frequencies is reduced there is a loss of bass – (Figure – 6dB Step Reduction Ckt) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

15. Major Specifications • Enclosure types • Vented Enclosure • "bass-reflex" enclosures require special construction due to the large forces that can be developed by the drivers installed inside that act on them. • Two Primary Functions • the separation of vibrations from the front and rear of the loudspeakers, • containment of air so that the air can act as a resonating elastic medium inside the enclosure • analogous to the way a bottle will behave as a whistle. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

16. Major Specifications • Enclosure Types • Factor determining good enclosure design • Is air-tight • Has walls that do not vibrate a lot • Does not have strong internal resonances • Isolates each driver from the others • Has a geometry compatible with good sound reproduction ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

17. Major Specifications • Directivity • the directivity is an indication of how effective the speaker is at taking the sound it produces and sending it in one particular direction instead of all directions • Loudspeaker - high directivity device - "long throw" device • Speaker - low directivity device - “short throw" device • Bass frequencies have very long wavelengths which make it difficult to control the direction they travel • For a loudspeaker to have moderate control of directivity at 40Hz would require a physical size greater than 18 feet (6m) square. ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

18. Sample Configuration • Typical Studio with Different Loudspeaker Systems • High End/Commercial Studio – with typical loudspeaker placement (Image Courtesy – A.M Studio., Chennai, India) ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

19. Sample Configuration • Dolby 5.1 Surround Placement • Used basically for small and household uses ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators

20. How/Where to Purchase • Analyze the requirement • Analyze the surrounding environment(make sure neighbor's are kind enough!) • Best Place to buy that I would suggest based on experience and if you are concerned on high enf loudspeakers - http://www.sweetwater.com/ • Normal Loudspeakers – For domestic use and if quality is not a priority • www.amazon.com • www.bestbuy.com ECE5320 Mechatronics. Assignment#1 Survey on sensors and actuators