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Electrostatic Loudspeaker

Electrostatic Loudspeaker. Bret Spencer ECE 5320 - Mechatronics. http://www.hometheaterhifi.com/images/stories/speaker_product_reviews/home_theater_speakers/2007-08-final-sound-1000i-speakers-90ht-system-product-reviews.jpg. History – Early Patents.

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Electrostatic Loudspeaker

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  1. Electrostatic Loudspeaker Bret Spencer ECE 5320 - Mechatronics http://www.hometheaterhifi.com/images/stories/speaker_product_reviews/home_theater_speakers/2007-08-final-sound-1000i-speakers-90ht-system-product-reviews.jpg

  2. History – Early Patents • In 1929, E.W. Kellogg filed for a patent for an early magnetically driven electrostatic speaker • In 1953, Arthur Janszen • was granted a patent for a • high-frequency • electrostatic speaker http://www.virtualdj.com/image/oldblog/95/23138/image.jpg

  3. History – On the Market • In 1957, first full-range electrostatic speaker put on market by Quad ESL based on Kellogg’s patent design • In the early 1960’s, Arthur Janszen, with KLH loudspeakers, introduced a rival electrostatic loudspeaker to Quad ESL

  4. Vs. Janszen Electrostatic Speaker Quad ESL Design Photos courtesy of http://www.martinlogan.com/learn/electrostatic-loudspeaker-history.php

  5. Electrostatic Speakers Today • Electrostatic technology has steadily increased • New materials and new techniques have improved electrostatic loudspeakers http://media.audiojunkies.com/martinlogan-spire-martin-logan-loudspeaker-electrostatic-speaker-subwoofer-audiophile-audio.jpg

  6. Types of Electrostatic Speakers Static film charge Dynamic film current

  7. Static Film Charge • Center film has a very high, constant charge • Outer plates are driven with input signal • Front and back plates are driven in anti-phase Electric Field

  8. Static Film Charge • Changing electric field causes inner film to move • Rapid changes cause vibrations and sound is produced Diagram courtesy of Wikimedia Commons

  9. Dynamic Film Current • Outer plates have a very high, constant voltage • Current is driven through center film

  10. Dynamic Film Current Illustration courtesy of www.howstuffworks.com

  11. Dynamic Film Current • A constant electric field is generated by the outer plates • The change in charge on the diaphragm causes it to move and vibrate within the electric field

  12. Diaphragm Construction • A very early design used pig intestine with gold leaf coating as the diaphragm • Plastics coated in conductive substance were a standard diaphragm material • Polyester films, such as Mylar, are commonly used today

  13. Speaker Construction http://free-hosting.infodiv.com/geocities-quad_esl63/images/home/esl63exposed.jpg

  14. Advantages • Very low sound distortion levels • Excellent frequency response due to low diaphragm mass • Sound carries further because of increased sound producing surface area

  15. Linear Sound Emitter • Electrostatic Speaker is a linear sound emitter • Sound is produced along the whole length of the diaphragm • Sound carries longer distances

  16. Linear Sound Emitter • Conventional speakers have greater spread • Electrostatic speakers are concentrated in a single direction Electrostatic speaker Top View Conventional Speaker

  17. Disadvantages • Poor low frequency response • Thin diaphragms are very fragile • Highly directional • Much more expensive than conventional speakers • High impedance input • Requires use of amplifier

  18. Low Frequency Response • The poor low frequency response can be countered with adding a conventional magnetically driven cone loudspeaker, a woofer http://gizmodo.com/assets/resources/2007/10/martinlogan_speaks.jpg

  19. Alternative: Magnetic Coil • Most common type of loudspeaker today • Uses electromagnetics to drive a conical diaphragm • Size can be altered for a wide array of frequencies • Durable • Low impedance input Photo courtesy of Wikimedia Commons

  20. Alternative: Magnetic Coil http://www.virtualdj.com/image/oldblog/103/23138/image.jpg

  21. Alternative: Ribbon Magnetic • Very similar to electrostatic loudspeakers • Uses an electrically charged metallic ribbon placed in a strong magnetic field • Can be more fragile than electrostatic diaphragms http://www.ariesmotor.com/products/neopro5i.jpg

  22. Cost & Availability • From $500 to over $6000 • Several companies available worldwide produce electrostatic speakers • A variety of designs • Floor standing • Wall mount • Wide or narrow dispersion

  23. High End Electrostatic Speaker • http://www.audioadvisor.com/prodinfo.asp?number=MLSUMX%20%20%20%20BLKBLK • Frequency Response 24 – 23,000Hz • 30° Horizontal Dispersion • 400 Watts total power • Just over 5 feet tall • $7,000

  24. Low End Electrostatic Speaker • http://www.cowboom.com/store/productDetails.cfm?contentID=218663 • Frequency Response 41 – 23,000Hz • 200 Watts total power • $539

  25. Sources http://www.martinlogan.com/learn/electrostatic-loudspeaker-history.php http://history.sandiego.edu/GEN/recording/loudspeaker.html http://www.howstuffworks.com/speaker11.htm http://www.quadesl.org/History/Quad_History/quad_history.html

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