Abstract: A vehicle warning system (1) is disclosed. The device includes a main housing (2) to which is attached a sound generator (7), a lighting system (4), a mounting bracket (4) which is used to attach the device to an emergency vehicle, and a trim ring (6) which conceals the structure for mounting the device. As a sound signal is produced by the generator (7) it passes through a nozzle (9) and an aperture (14) into a deflector means (3) which is designed to expand and direct the sound signal through carefully proportioned chambers (30) and (33) of the deflector (3) so as to direct the sound signal against the closed portion (15) of expander horn (16) and out the open portion of the expander horn (16). In operation the sound generating system is attached to an amplifier of well known design and is capable of producing a variety of sound signals.

Abstract: A wave guide fitted at the output of a loudspeaker, in front of the membrane or in front of the orifice of a compression chamber, along the axis of the transducer being considered, and comprising a conduit which expands from its input to its output. The area of the output orifice of the wave guide is planar and oblong, that its conduit comprises a passage between the input orifice and the output area, adapted to guide the waves along a general direction from which the shortest paths allowed in the one or more passages are all of lengths which are practically identical from the input orifice to the output orifice of the conduit. The invention is for use in providing sound to large areas.

Abstract: An improved compression driver has a phasing plug with air passages coupling the compression region of the loudspeaker to the throat of the loudspeaker. An auxiliary air passage combines with a plurality of inner primary passages, which may be of the annular, radial or saltshaker form, to couple variations in pressure from the region around the voice coil to the throat of the speaker.

Abstract: A speaker system comprises an acoustic panel. The acoustic panel is constructed of a plurality of thin plate-like sound absorbing panels provided close to the loudspeaker and arranged such that major surfaces thereof are disposed with a predetermined space therebetween so that the front space of the loudspeaker is opened for guiding a sound wave forwardly to radiate along the surface of the panels, while components of the sound wave having a radiation direction oblique to the major central axis of the sound absorbing panels are attenuated due to propagation through the sound absorbing panels. The sound absorbing panels are made of a porous sound absorbing material in which metal powders of Al, Ni, Cu, and others are sintered. In the case where one side of the acoustic panel is opened, it is preferable to provide a sound absorbing material at least at that opening and to further enclose the periphery of the sound absorbing material with a sound insulating material.

Abstract: A horn-equipped loudspeaker is provided which has an electro-acoustic transducer to convert electrical signals into acoustical signals, a coil with input terminals for receiving the electrical signals and at least one movable diaphragm for the emission of acoustical signals. The loudspeaker also includes a horn with walls arranged facing each other. The separation between the horn walls progressively increases from a small input area, or throat, to a large output region, or mouth. The loudspeaker diaphragm is formed of a portion of one of the walls of the input area of the horn.

Abstract: A vehicle horn has a shield which covers the mouth of the horn's bell to prevent debris from entering the bell. A front sound opening beyond the bell mouth perimeter allows sound to project forwards while still protecting the bell and a rear sound opening aligned with the front sound opening allows debris to pass through both openings without collecting within the space between the bell mouth and the shield. A side surface shields that space and includes a bottom cutout which allows any debris collected to fall out of the space. A vehicle horn has a bell constructed of two tubular sections, the end of each section having a mating flange which fits into a specially adapted clamp. As the clamp is tightened, the tube sections are drawn together until they butt against each other. The clamp is tightened by securing mating collar portions against each other. A pedestal and a rear mounting base are used to connect the horn to a vehicle. The rear mounting base and a mounting bolt are connected to the vehicle.

Abstract: A loudspeaker enclosure accommodates at least one speaker in the front wall of the enclosure. The interior of the enclosure is divided into two smaller chambers by means of a partition inclined with respect to the front and rear walls. One such chamber is adjacent to the speaker, while the second or rear chamber is separated from the front chamber by the partition. Below the speaker is a vent or port in communication with the rear chamber. Sound waves emanating from the rear of the speaker are reflected by the inclined partition and reflected upwardly toward the top of the speaker enclosure. The partition does not extend to the top wall of the enclosure, thereby allowing sound waves to reflect off of the top wall and enter the rear chamber. The sound waves then exit the enclosure through the port below the speaker. The rear waves are thus delayed with respect to the front waves from the speaker to achieve the desired tuning of the speaker system.

Abstract: A loudspeaker including a diaphragm for generating sound waves, the diaphragm being comprised of a peripheral conical portion adjacent to and surrounding a central domed portion, a flared horn adjacent to the diaphragm for receiving and projecting the sound waves into an acoustical space, a phasing plug intermediate the diaphragm and the horn defining sound pathways for impedance matching of the diaphragm and the horn. A plurality of sound channels extend through the phasing plug from the peripheral conical portion and the central domed portion of the diaphragm to the horn. The plurality of sound channels provide time compensated paths of equal length for the sound waves generated at both the peripheral conical portion and the central domed portion of the diaphragm.

Abstract: A grille is attached to a woofer, and a tweeter is further mounted on the grille to mutually face the woofer and be at least partially disposed in a cavity defined by the woofer and grille to define a compact loudspeaker structure. The grille and a back of the tweeter face an environment to which sound is to be directed, and both contain structures and are arranged to allow sound from the tweeter and woofer to communicate with the environment, while resisting water from contaminating the woofer and tweeter. Further, the rim of the grille and a frame define a component storage space in which elements which constitute a dividing network or other discrete electronic components of the loudspeaker are housed.

Abstract: A loudspeaker system which comprises a loudspeaker unit for radiating a first sound, a horn unit having a throat coupled to the back of the loudspeaker for radiating a second sound, and an acoustic filter provided in the horn for causing an acoustic impedance of the horn unit to be discontinuous. When the minimum frequency of cyclic dales of the sound pressure observed in the characteristic curves of a sound pressure of a composite of the first and second sounds as a result of a phase delay brought about by the length of the horn unit is expressed by fd, a primary harmonic resonance can be produced between the loudspeaker unit and the acoustic filter which is similar to that produced by a straight acoustic tube having its opposite ends closed, thereby to render the frequency of the primary resonance to be generally equal to the frequency fd.

Abstract: A speaker system which has a speaker unit with a diaphragm and an acoustic path provided on the front side of the diaphragm so as to guide sound waves emitted from the diaphragm. The acoustic path is defined by a sound absorbing member. The space in the acoustic path and the sound absorbing member is separated by a partition member which is disposed in such a manner that at least a portion of the sound absorbing member is exposed to the space in the acoustic path, except that the portion of the sound absorbing member just adjacent the diaphragm is not exposed to the acoustic path. This arrangement eliminates peaks and troughs of resonance determined by the length of the acoustic path, so that flat sound pressure frequency characteristics can be obtained over a wide range up to high-pitch tone region.

Abstract: A dual diverging manifold loudspeaker system includes a generally cubically-shaped outer horn housing and an inner dome-like cap member for encapsulating therebetween a compression driver assembly. The loudspeaker system includes a back plate member which is secured adjacent to the rear end of the housing. The back plate member includes a first diverter member for diverting a planar sound wavefront into two diverging sound wavefronts, a pair of second diverter members for splitting the two diverging sound wavefronts into four separate planar wavefronts, and reflector members for deflecting forwardly the four separate planar wavefronts toward an open mouth of the housing. A manifold formed by the inner surfaces of the housing and the inner cap member is used to recombine the four separate planar wavefronts back into a single composite wavefront emanating from the open mouth of the housing.

Abstract: A speaker enclosure assembly is disclosed, which comprises an enclosure provided with a baffle plate, to which a speaker unit is attached, characterized in that the enclosure is provided with a bellows-like sound pressure buffer member.

Abstract: Disclosed is an acoustic horn to aid in bulk powdered material handling particularly from trucks and railroad cars. Such acoustic horn is comprised of an external cone having a driver affix thereto. There is also an inverted internal cone contained within the external cone. There is a cylindrical throat communicating with the acoustic wave driver which extends into the internal cone, the combination of the throat extending into the internal cone contained within the external cone creates a folded horn arrangement wherein a horn of relative shortened length can achieve the desired low fundamental frequencies needed for bulk powdered material handling.Extending radially from the mouth of the external cone is a flange. Means are provided to detachably affix said flange from the flange on existing manways present on trucks and railroad cars.

Abstract: A low frequency loud speaker is disclosed for use in a room at the intersection of two, mutually perpendicular planes, such as a ceiling and a wall, a floor and a wall or two walls. The speaker has a back air chamber within which an electrically-driven diaphragm, centered on and facing a vent cut through the chamber's rear surface, projects low frequency sound waves into the throat of a compact, bifurcated, exponential horn folded around the sides of the chamber to the mouth of the horn at the back of the speaker. The back air chamber receives sound waves from the rear face of the diaphragm and causes these back waves to acoustically activate the air in the vent above and below the diaphragm.

Abstract: Electroacoustic apparatus for reproducing lowest to medium frequencies being provided with a housing wherein a folded exponential horn combined with a loudspeaker is defined having five horn element walls lengthening the horn with good exponential form toward its throat and bent horn element walls provided in the area ending in the horn mouth and at foldings above the mouth and forming the horn with high approximation to an exponential function. The horn element walls are arranged so that undesired reflections are substantially avoided and no sharp break points exist in the course of the horn which is advantageously prolongated toward its throat, and a high characteristic acoustic impedance as well as a linear frequency reproduction characteristic over a wide range are achieved.

Abstract: One or more up-firing woofer loudspeakers (12 or 22) are mounted atop a truncated pyramidal enclosure (1 or 21). A down-firing tweeter (5 or 25) is aligned above the woofer. A sound-reflecting sphere (4 or 24) is disposed between the woofer and the tweeter. When the sphere is aligned there-between omni-directional sound is radiated in both horizontal and vertical planes. When the sphere is positioned to the rear, a medium to high frequency forward hemispherical pattern is obtained. This pattern is desirable when the loudspeaker structure is positioned against a wall. Duct ports (3) or a folded horn (20) within the enclosure enhance very low frequency sound.

Abstract: An improved sound reinforcement enclosure is disclosed which incorporates a cone-type loudspeaker operating into a generally cylindrical channel extending from the perimeter of the cone to free air. A central member is coaxially mounted within this channel, the central member having rear surfaces substantially parallel to the surface of the cone and external surfaces which, with the internal surfaces of the channel form an annular region, the central member also having at least one coaxial internal passage forming a concentric horn flare. Methods of coaxially mounting a high-frequency compression driver behind the magnet assembly of the loudpseaker and of mounting a second loudspeaker internally in an enclosure are also disclosed.

Abstract: A tone generator of the type in which a housing defines a pair of communicating chambers one of which is closed except for an area of communication with the other chamber. A thin flat diaphragm of circular configuration is mounted in an operative position over the area of communication between the chambers in engagement with a flat annular surface defining the same. An annular diaphragm retaining member is mounted in an operative position in superposed relation to the diaphragm in fixedly secured relation within the housing. An improved mounting for the diaphragm is provided which includes a plurality of annularly spaced transversely extending diaphragm engaging lugs formed on the retaining member. The lugs extend in engagement with the diaphragm so that when the retaining member is in its operative position the engagement of the lugs with the diaphragm serves to retain the diaphragm in its operative position.

Abstract: A device having two sets of oppositely facing corresponding resonance cavities; i.e., an upper and a lower resonance cavity. Each of the resonance cavities include a piezo-electric type diaphragm consisting of a vibration diaphragm and a start-up plate. Electric signals cause the piezo-electric type diaphragm to vibrate back and forth and produce sound waves from the upper and lower resonance cavity.

Abstract: In a sound emitter including an emitting piston powered by a three phase asynchronous electric motor, the torque curve of the motor may be adjusted to suit any temperature, causing variations in the emitted resonance frequency by using a motor having its maximum torque at less than half the maximum speed. This may be done by using an alloy of silicon and aluminum in the rotor winding.

Abstract: Coiled Exponential Bass Midrange Horn Loudspeakers which are each characterized by a rigid cabinet of selected size having a sealed air chamber in the base thereof for receiving a low frequency speaker, or driver, and a coiled or convoluted, exponentially flared sound passage extending from the air chamber to the top of the cabinet. In a most preferred embodiment, a high frequency horn is mounted in the cabinet near the open top to extend the audio range of the loudspeaker system. The combination of a low frequency driver and a high frequency horn separated by a continuously exponentially expanding or flared, coiled or convoluted, multi-tapered sound passage chamber eliminates the need for a midrange speaker or horn.

Abstract: A sound projection system for use in diffusing sound of a frequency ranging from 160 Hz up to 5 KHz over a relatively long distance with a substantially constant distribution of the sound over a wide diffusion angle, whereby the quality and intensity of the sound transmitted by the system remain substantially constant for a listener even if this person is substantially offset from the general direction and orientation of the projection system. The system which is advantageously compact in size, comprises a cabinet defining an enclosure in which a loudspeaker is mounted. An acoustic channel of rectangular cross-section is connected to the cabinet in alignment with the loudspeaker.

Abstract: A speaker system including a frusto-conical diaphragm, and a phase plug mounted within the volume formed by the diaphragm, the phase plug including a pair of substantially diametric open slots extending across the diaphragm and through the phase plug, with each of the slots having substantially rectangular cross sections transverse to the axis of the diaphragm.

Abstract: An electroacoustic motor for association with a horn comprising, in combination, a direct radiation speaker including a chassis, the speaker including a movable diaphragm, an acoustic wave transmitting means comprising an output orifice at the end thereof remote from said diaphragm, and passage means in the acoustic wave transmitting means communicating acoustic waves from the diaphragm to the output orifice. The acoustic wave transmitting means is a separate unit which is detachably secured to the speaker chassis by a fluid-tight connection. The acoustic wave transmitting means comprises a hollow truncated conical member of smaller diameter at the output orifice end thereof than at the end thereof contiguous the diaphragm. A phase adjustment element is positioned in the hollow interior of the truncated conical member, the phase adjustment element being in facing relation at one end thereof to the diaphragm and at the opposite end thereof to the output orifice of the truncated conical member.

Abstract: A loudspeaker system has an elliptical stepped mid-range horn above and coplanar with a flared mid-bass horn having disposed therein a pair of tweeters on sidewalls thereof and a woofer in a backwall thereof. The back of the woofer communicates with a folded low frequency bass horn such that low frequency response is loaded from the rear of the diaphram for the woofer driver, thereby eliminating the necessity for further amplification and drivers to obtain fidelity in low frequency response. The low frequency bass section defines a convoluted path for the sound which comes from the interior structure of a folded horn thus creating an acoustical boost for low frequency sound.

Abstract: A horn loudspeaker with a convex diaphragm in which the throat of the horn is formed by an assembly including the diaphragm, a cover plate for the diaphragm, a tapered plug, and a base, the plug and cover forming linear channels of equal length confronting different portions of the convex dome of the diaphragm.

Abstract: This invention relates to low-frequency speaker enclosures in general, and more specifically to a dual cabinet construction, wherein each of the cabinet structures contains a portion of a generally semi-circular uniform diameter horn passageway, formed by contoured foam elements that provide redirection and amplification of rear-cone sound wave energy, through the forward face of the combined cabinet construction.

Abstract: A radial high-frequency, high-efficiency orthospectral loudspeaker is disclosed in which a horn-loaded, electro-acoustic driver is used and the horn configuration is radial and annular to give a 360.degree. lateral dispersion of the sound generated by the loudspeaker, the output being frequency and amplitude equalized over the desired high frequency band.

Abstract: An electric diaphragm horn includes a housing having a diaphragm mounted thereon defining a chamber, the chamber being vented to the atmosphere through the diaphragm.

Abstract: The invention pertains to electric horns for automobiles wherein a metal horn motor housing is assembled to a sound projector formed of synthetic plastic. A metal insert is molded into the projector having a metal flange extending from the projector adjacent a projector mounting surface whereby the insert flange is deformed upon the motor housing to produce an effective mechanical interconnection and assembly of the motor housing and projector.

Abstract: There is disclosed a method for making horn loudspeakers, of the sectorial diffusion type, characterized by the transformation, in order to operate under predetermined sectorial diffusion conditions, of a horn loudspeaker, predisposed for circular diffusion, comprising a horn provided with opposite walls the distances whereof increase according to a given law, from the axis of the horn on which the electroacoustic transducer is located, the transformation being carried out by neutralizing the space included between the walls and about the compression chamber associated with the transducer, and in the directions in which the diffusion is not desired, by using a substantially fibrous material and effective to absorb or deaden the acoustic energy or power.

Abstract: A loudspeaker horn is described, which produces good coupling of sound to the atmosphere, while avoiding perturbations in magnitude and phase that would produce large narrow-frequency losses or transient distortions. The horn includes a major sound-reflective portion of typical horn shape, and also includes a buffer extending around the large end of the horn. The buffer has a sound absorption coefficient about halfway between the almost zero absorption coefficient of the major portion of the boundary walls of the horn and the 100% absorption coefficient of the ambient atmosphere, to couple sound to the atmosphere more efficiently, and with an efficiency that is relatively constant with frequency. A horn of largely rectangular cross-section, has corner regions covered with highly sound absorbing material, to minimize transient distortions such as "ringing".

Abstract: A loudspeaker and horn combination having desirable sound clarity characteristics and having a desirable per unit of electric power input to per unit of sound output ratio can be constructed using a horn body of one or more parts of a rigid, closed cell polyurethane foam material having a smooth exterior skin or surface shaped so as to include an internal horn cavity. A speaker is located so that its diaphragm extends across an entrance end of the cavity. The cavity is shaped in a bilaterally symmetrical manner so as to include a sound chamber region adjacent to and leading from the speaker diaphragm, this sound chamber region having a restricted throat located intermediate its ends and having a continuous curvature between its ends, a flare region diverging outwardly from the end of the sound cavity region remote from the speaker and a transitional region located generally between the flare and sound cavity regions so as to connect the adjacent surfaces of these regions.

Abstract: An acoustical transformer or "phasing plug" for coupling the sound from an annular diaphragm to the throat of a compression-type loudspeaker. The phasing plug in the invention has the general shape of a doubly-truncated cone with an annular surface located on the larger end of the truncated cone and positioned adjacent to the diaphragm. The conical surface of the cone has spaced radial slots or channels formed therein connecting the truncated surfaces of the cone. These channels form air passageways for propagation of sound waves. The walls of the slots or channels are tapered such that the cross-sectional areas of the channels increase from their inlet ends near the speaker diaphragm, towards the outlet ends, positioned at the throat of the horn. The phasing plug provides an improved impedance match between the output of the annular diaphragm and the input of the horn.

Abstract: A speaker horn is adapted for coupling to a speaker drive assembly and for dispersing incident sound energy in a 360.degree. radial pattern. The horn includes two sound-dispersing structures for making a passageway generally symmetrical about a longitudinal axis. An inserted structure restricts the movement of the incident energy in one axial direction and includes a plug which is nested in close proximity to a wall of a receiving structure at the input end of the receiving structure. The receiving structure restricts the propagation of the sound energy in the other axial direction to cooperate with the inserted structure in defining the passageway in a radial pattern between the two structures. The plug includes a concave face perpendicular to the longitudinal axis for receiving incident energy. The plug, in cooperation with the inner walls of the receiving structure, effects a change in phase of sound energy encountering the plug, and acts as an intensity amplifier for incident sound energy.

Abstract: An electroacoustic transducer which includes a vibratile diaphragm operating at resonance has its narrow band width response characteristic increased by an order of magnitude by the use of a uniquely designed acoustic coupler in combination with the resonant diaphragm. The acoustic resistane presented to the resonant diaphragm by the acoustic coupler dominates the motional impedance characteristic of the transducer in the resonant frequency region of the vibratile diaphragm. The use of the inventive acoustic coupler reduces the Q of the vibrating system from a value in the order of 30 or more to the order of 8 or less.

Abstract: A low frequency loudspeaker apparatus includes a folded exponential horn which is divided to provide a bifurcated curved sound path from at least one electroacoustic transducer that is positioned at the throat of the horn to a volume into which sound waves are radiated that is located at the bifurcated mouth of the horn. The mean length of the folded exponential horn is such that, at an exponential rate of expansion between the throat and the bifurcated mouth, the area of the mouth is adequate for reproduction of low frequencies in the audible range. An illustrative embodiment of the low frequency loudspeaker apparatus has an effective low end cut-off frequency of 38 Hz. and affords 99 dB SPL output at three meters with one watt input which corresponds to about 20% efficiency measured in free space. Presence of a single boundary surface, such as a stage floor adjacent the mouth of the folded exponential horn, improves amplitude response by 3 to 6 dB.

Abstract: An electrically driven loudspeaker is coupled to the atmosphere, which is to carry sound to the human ear, through a hollow coupler the inlet end of which has a cross sectional area comparable to the effective area of the loudspeaker, said cross sectional area decreasing progressively from said inlet end to an outlet end of substantially smaller cross sectional area. In a specific embodiment of the invention, an exponential horn is formed within the confines of a loudspeaker cabinet enclosure, and the inlet end of the horn is coupled to the electrically driven loudspeaker by means of the hollow coupler also formed within the cabinet enclosure. The outlet end of the coupler has the same cross sectional area and shape as the inlet end of the horn.

Abstract: An acoustic transducer for reproduction of sound over a wide frequency band. The transducer consists of an elongated partially enclosed chamber having a sound source at one end and wherein the cross-sectional area of the chamber is decreased with distance along the length of the chamber away from the sound source. A curved wall is included in the chamber to serve as an expanding horn, the lower end of which is provided with an elongated slot aperture which widens exponentially as a function of the length of the chamber through which sound energy is delivered to the aperture of the horn.

Abstract: A sound projection system comprising means defining a longitudinally extending acoustic channel which is acoustically open at a front end of the channel and acoustically closed at a rear end and at sides of the channel, a loudspeaker having a cone diaphragm operating into the channel at the rear end of the channel, and a longitudinally extending member mounted within the channel directly in front of, and in alignment with, the loudspeaker so as to restrict the free space within the channel, the cross-sectional area of said member varying along its length.

Abstract: A dual loudspeaker is set up to handle separately high frequency and low frequency sounds in the same piece of equipment. The apparatus comprises a single housing having a vertical partition dividing the housing into two chambers. A high-frequency driver in one chamber feeds into a relatively short horn path to a high frequency bell. A low-frequency driver in the other chamber feeds into a relatively longer horn path to a low-frequency bell. The high-frequency and low-frequency bells are located side by side on opposite sides of a partition and feed into a progressively expanding horn which serves simultaneously the output of both drivers.

Abstract: A springless diaphragm-type air horn provided with fixed structure for controlling the amplitude of diaphragm oscillation to thereby enable manufacturing of the horn without necessity for any adjustment of parts to achieve tone control.

Abstract: The present adapter is an annular body with a top portion of very pronounced oblong configuration to match the usual oblong speaker opening in the rear deck of a car between the rear seat and rear window. The adapter tapers down to a bottom portion of more nearly circular configuration, for supporting a speaker of similar configuration spaced below the rear deck.

Abstract: A cone speaker is mounted to a horn within a reflex chamber behind a forward opening through the chamber, and the forward end of a horn is attached to the opening. The speaker is connected in the entrance discharging rearwardly into the chamber, and forwardly into the horn. The horn includes a restriction between the forward end of the horn and the speaker, and ports are formed through the horn, entering the restriction.

Abstract: A phase plug structure is described which is an intermediate element between a conventional fiber cone loudspeaker and an exponential horn. The purpose of the phase plug is to equalize acoustical path lengths and thereby minimize high-frequency cancellations caused by phase differences. The design of the phase plug is based upon an analysis of both low-frequency and high-frequency horn behavior. A usable bandwidth of four octaves is obtained over a sharply-defined angle of radiation.In accordance with another embodiment of the invention, an enclosure is provided having a first exponential radiator, of relatively small size attached to the front of the speaker, and a relatively large exponential radiator coupled to the rear surface of the speaker for improved base response.

Abstract: An acoustical horn speaker for producing low distortion sound comprised of a casing assembly having a voice coil gap and a magnetic source and return circuit for providing a constant magnetic field across the gap, a current-carrying voice coil disposed in said gap, and a voice diaphragm in rigid attachment with the voice coil, said voice diaphragm being suspended from the casing assembly by a relatively flexible, high compliance suspension member. An acoustical horn having a throat resistance sufficiently high to substantially dominate the radiation resistance of the diaphragm is air coupled at its throat end to the voice diaphragm suspended from said casing, while the compliance of the voice diaphragm suspension is relatively high such that in the presence of the dominating throat resistance of the horn the diaphragm vibratory movement is characterized by substantially force determinative excursions as opposed to substantially linear constant displacement excursions.

Abstract: A driver unit for a horn type loudspeaker is disclosed. The driver unit comprises a dome-shaped diaphragm and an equalizer positioned on the concave side of the diaphragm. The equalizer has a convex surface adjacent the diaphragm and a plurality of slits extending from the convex surface to an interior, outwardly opening throat. The slits are disposed in equal angular pitch with the outermost slits being located at the edge of the convex surface of the equalizer. The outermost slits are approximately one half the width of the remaining slits, the remaining slits being of equal width.

Abstract: The present adapter is an annular body with a top flange of very pronounced oblong configuration to match the usual oblong speaker opening in the rear deck of a car between the rear seat and rear window. The adapter tapers down to a bottom flange of more nearly circular configuration, for supporting a speaker of similar configuration spaced below the rear deck.

Abstract: A sound projection system comprising means defining a longitudinally extending acoustic channel which is acoustically open at a front end of the channel and acoustically closed at a rear end and at sides of the channel, a loudspeaker having a cone diaphragm operating into the channel at the rear end of the channel, and a longitudinally extending member mounted within the channel directly in front of, and in alignment with, the loudspeaker so as to restrict the free space within the channel, the cross-sectional area of said member varying along its length.