This specification describes a horn loudspeaker with gain shading.
In one aspect of the specification, a horn loudspeaker includes an acoustic horn. The acoustic horn includes side walls, for determining the horizontal dispersion angle of the acoustic horn; top and bottom walls, for determining the vertical dispersion angle of the acoustic horn; a plurality of acoustic drivers coupled to the acoustic horn by a diffraction slot having segments, each of the segments separated from the adjacent segments by less than one half of the wavelength of the highest frequency of the operational range of the horn loudspeaker; and circuitry for transmitting an audio signal to the plurality of acoustic drivers. The circuitry includes a first signal attenuation element electrically coupling an audio signal input element and a first of the acoustic drivers. The circuitry may further include a second signal attenuation element coupling the acoustic signal input element and a second of the acoustic drivers. The circuitry may be configured so that the signal attenuation element electrically couples the audio signal input element and a second of the acoustic drivers. The acoustic may further include a second signal attenuation element coupling the acoustic signal input element and a third and a fourth of the acoustic drivers. The circuitry may include a single amplifier. The circuitry may include a step-down transformer. The step-down transformer may include more than two taps. Each of the plurality of acoustic drivers may be alternatively coupleable to each of the plurality of taps. Each of the segments may be separated from the adjacent segments by less than 0.81 cm.
In another aspect of the specification, an acoustic system includes an acoustic horn. The acoustic horn includes side walls and top and bottom walls, joined to form a single mouth; a plurality of acoustic drivers, acoustically coupled to the acoustic horn by respective acoustic ducts, each of the acoustic ducts having a inlet end and an outlet end. The outlet ends are coupled to form a single diffraction slot. The acoustic system further includes circuitry for providing an audio signal to the plurality of acoustic drivers. The circuitry includes a signal attenuator coupling a signal input element and at least one of the acoustic drivers. The single diffraction slot may be a segmented diffraction slot. The plurality of elongated ends may be aligned along an arc. The signal attenuator may include a step-down transformer. The circuitry may include a path that bypasses the signal attenuator. The circuitry may include a second signal attenuator coupling the signal input element and a second of the acoustic drivers. The first signal attenuator and the second signal attenuator may be incorporated in a single transformer. The single transformer may include a plurality of taps so that the attenuation of the first signal attenuator and the second signal attenuator are selectable. The circuitry may be configured so that the amplitude of the audio signal provided to the second of the acoustic drivers are substantially the same as the amplitude of the audio signal provided to a third of the acoustic drivers.
In a third aspect of the specification, an acoustic horn loudspeaker includes an acoustic horn; a plurality of acoustic drivers, acoustically coupled to the acoustic horn; and circuitry for coupling an audio signal source to the plurality of acoustic horn. The circuitry includes a step-down transformer for attenuating the audio signal provided to at least one of the acoustic drivers. The step-down transformer may include a plurality of taps so that the amount of attenuation applied to each of the plurality of acoustic drivers may be adjustable. Each of the taps may be coupleable to each of the acoustic drivers.
Other features, objects, and advantages will become apparent from the following detailed description, when read in connection with the following drawing, in which:
Though the elements of several views of the drawing may be shown and described as discrete elements in a block diagram and may be referred to as “circuitry”, unless otherwise indicated, the elements may be implemented as one of, or a combination of, analog circuitry, digital circuitry, or one or more microprocessors executing software instructions.
This specification describes a horn loudspeaker. “Horn loudspeaker” as used herein includes one or more acoustic drivers (typically compression drivers) that radiate pressure waves into an acoustic horn, typically through a diffraction slot. The horn has side walls and top and bottom walls (or the equivalent, in case the horn has a non-rectangular shape in the cross section in the X-Z plane as shown in the coordinate system of
Line arrays may or may not be acoustically coupled to horns. The vertical dispersion angle of straight line arrays that are not coupled to horns is substantially zero, so that the vertical dispersion of a line array not acoustically coupled to a horn is determined principally by the length of the line array, the curve of the line array, or a time delay equivalent of the curve of the line array. The vertical dispersion angle of a horn is determined principally by the dispersion angle upper and lower walls of the horn.
A plurality, in this example four, of acoustic drivers 12 are acoustically coupled to a horn at the horn throat end 13 by acoustic ducts 16. The duct outlet end (that is, the end of the duct that is acoustically coupled to the horn) may be mechanically coupled to the horn directly. Alternatively, the outlet ends of the ducts may be combined into a manifold which is acoustically coupled to the horn. The outlet ends of the ducts may be elongated in a vertical direction relative to the front and side views. The elongated outlet openings of the acoustic ducts or the outlet of the manifold may be aligned in the direction of elongation at the horn to form a diffraction slot. The diffraction slot may be segmented, with no segment separated from an adjacent section by more than one half wavelength of the highest frequency of interest. In one implementation segments are separated from the adjacent segments by no more than ⅜ (0.375) wavelength of 16 kHz (with a corresponding wavelength of about 2.15 cm) so that the segments are separated by no more than 0.375×2.15=0.81 cm (approx 0.3 inches). The horn includes horn side walls 18A and 18B and top and bottom walls 20A and 20B. In order to show details of the side walls 18A and 18B, top and bottom walls 20A and 20B are not shown in the top view. The side walls 18A and 18B flare outwardly. In some implementations, the walls may flare outwardly linearly. In other implementations, such as the implementation of
In operation, the acoustic drivers transduce electrical energy into acoustic energy, which is conducted to the horn. The acoustic energy enters the horn at the horn at the throat end 13 and exits the horn at the mouth 17 in a controlled and predictable radiation pattern, with the vertical dispersion angle (that is, the dispersion angle in the Y-Z plane of the coordinate system of
As stated above, sometimes two or more horn loudspeakers are assembled into a single enclosure.
The assembly of
Further details of the operation and configuration of the horn loudspeaker of FIGS. 2-6 may be found in U.S. patent application Ser. No. 12/898,947.
In the situation of
In a first configuration, the horn 100A includes a plurality of modules, each module including an acoustic driver 12-1 . . . 12-n (in this example n=6) and an acoustic duct acoustically coupling the corresponding compression driver with a diffraction slot. An audio signal source is coupled to an amplifier 22. The amplifier is coupled to each of the acoustic drivers 12-1-12-n through signal attenuators 36-1-36-n, respectively
In operation, the amplifier 22 amplifies an audio signal from an audio signal source to an amplitude that results in adequate SPL at the location farthest from the horn loudspeaker. The amplitudes of the signal to the acoustic drivers are attenuated so that the acoustic energy toward the most distant listening location is attenuated little or not at all and the signal to the nearest listening location is attenuated so it does not receive excessive acoustic energy. The signal to each of the other acoustic drivers is attenuated by an amount (a . . . n; in this example n=f) that results in SPL at the location 210 not being significantly greater than the SPL at location 212.
Referring again to
Numerous uses of and departures from the specific apparatus and techniques disclosed herein may be made without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features disclosed herein and limited only by the spirit and scope of the appended claims.
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