134:. They also outlined criteria for the design of the channels in the plug and suggested a path-length based design approach to maximize the bandwidth. Significantly, their plug moves the coupling point between the cavity and horn away from the axis of rotation. This change significantly improves the transducer response as the effect of the acoustical resonances in compression cavity is reduced. The paper described the first generation compression driver with a field coil magnet and phase plug, It used an aluminum diaphragm with an edge wound aluminum ribbon voice coil.
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97:, a widening duct which serves to radiate the sound efficiently into the air. It works in a "compression" mode; the area of the loudspeaker diaphragm is significantly larger than the throat aperture of the horn so that it provides high sound pressures. Horn-loaded compression drivers can achieve very high efficiencies, around 10 times the efficiency of direct-radiating cone loudspeakers. They are used as
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methodology to suppress the resonances by careful positioning and sizing of channels in the phase-plug. This work was largely ignored by his contemporaries and was only later popularized by
Fancher Murray. Today the majority of compression drivers, either by inheritance or design, are based on the guidelines outlined by Smith.
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in the radiation resistance (and therefore increased efficiency), because the loading mismatch between the vibrating transducer surface and air is largely corrected, thus allowing for much better energy transfer. In the Hanna and
Slepian proposal the compression cavity is directly connected to the throat of the horn.
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The suppression technique of Smith has been recently extended using a more accurate analytical acoustical model of the compression driver geometry. From this work improved phase plug design guidelines have been deduced to eliminate all traces of acoustical resonance in the compression cavity. In this
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The next innovation came from E. C. Wente and A. L. Thuras in "A High-Efficiency
Receiver for a Horn-Type Loudspeaker of Large Power capacity" in the Bell System Technical Journal, 1928. They devised a plug placed in front of a radiating diaphragm to control the transition from compression
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In 1953 Bob Smith made the most significant contribution to modern phase-plug, and hence compression driver design, with his paper published in the
Journal of the Acoustical Society of America in which Smith analyzed the acoustical resonances occurring in the compression cavity and devised a design
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In 1924 C. R. Hanna and J. Slepian were the first to discuss the benefits of using a large radiating diaphragm with a horn of smaller throat area as a means of increasing the efficiency of horn loudspeaker drivers. They correctly surmised that this arrangement results in a significant increase
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and others is a light bulb placed in series with the driver to act as a variable resistor. The resistance of the bulb filament is proportional to its temperature which increases as current flow through the filament increases. The net effect is that as the power increases the filament consumes an
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the high frequency drivers are protected from damage by current sensing self-resetting circuit breakers. When too much power is dissipated by the driver, the circuit breaker interrupts the flow of electric current. The circuit breaker resets itself after a brief interval. An older circuit
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The first commercial compression driver was introduced 1933 when Bell Labs added a
Western Electric No. 555 compression driver as a mid-range driver to their two-way "divided range" loudspeaker which was developed in 1931.
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Dodd, M.; Oclee-Brown, J. (October 2007). "A New
Methodology for the Acoustic Design of Compression Driver Phase-Plugs with Concentric Annular Channels".
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Wente, E.; Thuras, A. (March 1978) . "A High-Efficiency
Receiver for a Horn-Type Loudspeaker of Large Power Capacity (reprint)".
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cavity to horn throat. They found that the bandwidth of the transducer could be extended to higher frequencies using their
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Hanna, C. R.; Slepian, J. (September 1977) . "The
Function and Design of Horns for Loudspeakers (Reprint)".
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increasing share of the total power thus limiting the power available to the compression driver.
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370:"Adjustable high-speed audio transducer protection circuit - US Patent 6201680 Description"
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Smith, B. (March 1953). "An
Investigation Of The Air Chamber Of Horn Type Loudspeakers".
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Murray, Fancher (October 1978). "An
Application Of Bob Smith's Phasing Plug".
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Presented at the 123rd Convention of the Audio Engineering Society
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Presented at the 61st Convention of the Audio Engineering Society
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vibrated by the audio signal current in a coil of wire
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on a midrange horn speaker used in a home audio system
70:. The sound waves pass out through an acoustic horn
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in a horn loudspeaker consists of a metal diaphragm
283:The Journal of the Acoustical Society of America
109:, and in reflex or folded-horn loudspeakers in
339:"Sea & Land's Speaker Protection Devices"
260:"The Short History of Audio/Video Technology"
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146:work Smith's derivation is confirmed using
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64:between the poles of a cylindrical magnet
222:Journal of the Audio Engineering Society
203:Journal of the Audio Engineering Society
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241:"More references on horn loudspeakers"
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270:from the original on Mar 14, 2022.
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85:is a small specialized diaphragm
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89:which generates the sound in a
258:Plummer, Gregg (May 2, 2007).
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167:protection technique used by
154:Compression driver protection
403:"WESTERN ELECTRIC speakers"
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32:(cylindrical box at rear)
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148:finite element analysis
424:Loudspeaker technology
115:public address systems
105:drivers in high power
48:A compression driver
30:A compression driver
160:sound reinforcement
16:Type of loudspeaker
83:compression driver
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181:Cerwin Vega
87:loudspeaker
384:2009-01-17
355:2009-01-17
264:Ampliozone
228:: 139–144.
209:: 573–585.
188:References
132:phase plug
111:megaphones
173:Community
418:Category
268:Archived
158:In some
99:midrange
121:History
103:tweeter
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