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 loudspeaker with a pair of speaker units and a manifold chamber between the speaker units for combining the sound from both speaker units. The manifold chamber is formed by walls having an exit opening and a pair of rectangular apertures, the apertures confronting each other on opposite sides of the chamber and the exit opening being disposed normal to a plane centrally between the apertures, and the apertures and exit opening having parallel axes of elongation. One of the speaker units is coupled to each of the apertures to direct sound into the manifold chamber, and the manifold chamber is provided with a wedge confronting the apertures to direct sound parallel to the central plane between the apertures toward the exit opening. In one construction, a horn is coupled to the exit opening to conduct sound from the manifold chamber.

Abstract: A siren having one or more stacked speakers, each speaker having a substantially circular lower horn member having an upwardly facing surface including a substantially convex annular portion and a substantially concave central cavity portion. A substantially circular upper horn member having a downwardly facing surface including a substantially convex annular outer portion and a central opening, is spaced above the lower horn member, thereby defining an annular, radially outwardly diverging sound director between the upper and lower horn members. A diffuser horn is coupled to a central opening in the upper horn member and projects downwardly into the cavity portion of the lower horn member. A siren driver is mounted in the upper horn member adjacent to the central opening for projecting a sound wave through the diffuser horn into the cavity, where the sound wave is reflected upwardly out of the cavity into the sound director, through which the sound is projected horizontally in a 360.degree. pattern.

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: An omnidirectional speaker unit includes a housing having a plurality of twelve identical sides each having a speaker mounted therein and equally spaced around and directed outward from a common point with all speakers connected to operate in unison to provide a spherical dispersal of sound. A preferred embodiment of the invention is the intersection of six equi-distant identical hyperboloids of two sheets creating horns that merge at unique saddle-like curves between adjacent horns of the enclosure with each speaker placed at the end of a long hyperboloid horn.

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: An improved method for transmitting sound at high power levels over a wide angle zone of dispersion without distortion, comprising the step of emitting sound waves from a plurality of individual sources, each characterized by a relatively narrow, wedge-shaped envelope of sound projection, such that adjacent edges of respective sound projection envelopes are in substantial alignment and do not overlap, whereby the absence of interference between sounds emitted from different sources precludes sound distortion and enables uniform sound dispersion and high sound quality throughout the zone. The sound waves are preferably emitted from electroacoustical loudspeakers having loudspeaker enclosures shaped to conform to the edges of their respective sound envelopes.

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 loudspeaker and enclosure assembly, comprising: a load bearing member exhibiting good thermal conductivity; at least one loudspeaker mounted on the load bearing member and in thermal engagement therewith; and, an enclosure having walls formed of rigid light-weight material mounted on the load bearing member to enclose the at least one loudspeaker, whereby the assembly is easily moved and mounted and thermal energy generated by operation of the loudspeaker is effectively dissipated through the load bearing member. The enclosure may be a rigid foam-filled member defining a generally funnel-shaped bore therein to form a horn for the loudspeaker, whereby a modular construction of interchangeable integrally formed enclosures and horns can be achieved.

Abstract: The invention concerns a loudspeaker housing (1), particularly for rendition of the deep and middle tone ranges, having a loudspeaker (27) and a folded flare (14; 20, 21, 15, 16; 6). The front side of this loudspeaker housing (1) has an upper area, in which the loudspeaker (27) is located, as well as a lower area, which represents the end of the folded flare. The tones with higher frequency are thus radiated directly from the loudspeaker (9, 27) forwards, while the low frequency tones are radiated via the folded flare, whereby this flare guides the sound waves generated by the loudspeaker (9, 27) towards the rear wall of the loudspeaker housing (1). Hereby, the flare is formed by an opening (18) in an intermediate wall (17), an arch (14), two guide spacers (20, 21), two arches (15, 16) above the guide spacers (20, 21), and one exponentially curved wall (6) (FIG. 2).

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: An ultrasonic rangefinder capable of detecting a distance between a vehicle and an object with high accuracy is shown. The measurements for microphones for transmitting and receiving ultrasonic waves are chosen so that detour waves are restricted.

Abstract: A loudspeaker system for low frequencies has a manifold chamber into which oppositely mounted and aligned woofer units radiate sound. The chamber radiates the sound perpendicularly to the woofer axes, either directly into space or into a horn. An additional back woofer may radiate directly in the perpendicular direction.

Abstract: High quality single or multiple channel sound dispersal is obtained through the arrangement of a plurality of similar speakers divergently mounted in an airtight frame with integral horns formed therein such that the central axis of each speaker is coaxial with a line normal to and projected from the center of each face of a polyhedron characterized by the tetrahedron, the hexahedron, the octahedron, the dodecahedron and the icosahedron. When the speakers thus arranged are excited in phase, a series of infinite acoustic baffles are created between adjacent speakers creating a series of exponential horns which disperse the sound energy as if from a point source to the walls, ceiling and floor of the listening room and then by reflection to the listener. The frame/horn component is manufactured of universal parts.

Abstract: A cabinet for a loudspeaker is disclosed, which has a duct communicating the inside and outside of the cabinet. The duct includes a first duct section open to the inside of the cabinet and having a substantially constant sectional area and a second duct section extending from the first duct section toward the outside of the cabinet, the sectional area of the second duct section being gradually increased from the first duct section toward the outside of the cabinet.

Abstract: A loudspeaker horn having side wall members which converge to a throat and then diverge at a controlled horizontal dispersion angle allows horizontal dispersion from a bass driver to be maintained up to 4 KHz, permitting higher crossover frequencies and therefore use with lighter and more responsive high frequency units.

Abstract: A speaker cabinet of the type used in stereo systems. A horizontal wall partitions the interior of the cabinet into an upper portion within which is positioned a full range speaker member, and a lower portion within which is positioned a low range speaker member. A pair of laterally spaced ports are formed in the partition wall to allow sound emanating from the low range speaker to enter into the upper portion of the cabinet. A horn associated with the full range speaker is spaced apart therefrom, in non-attached relation thereto to define a space between the full range speaker and the horn. Sound from the low range speaker and from the full range speaker enters into the space between the full range speaker and the horn and mixes so that the sound emanating from the horn is a full-bodied sound characterized by minimal distortion and substantial absence of unpleasing sounds of the type associated with speakers of the prior art.

Abstract: A multiple driver manifold for coupling four high frequency drivers to a single horn. Two drivers are mounted in a "Y" or "skewed" configuration, and two additional drivers are mounted so as to be directly opposed to one another along a line perpendicular to both the horn throat on-axis direction and the general plane of the "Y" configuration. Sound radiated transverse to the horn on-axis direction by the opposed drivers is "ray-reflected" by a unique ray-reflection summation plug located at the internal hub of the four acoustic paths.

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

Abstract: A loudspeaker is provided for high-quality stereophonic loudspeaker systems intended to be positioned on the floor close to a vertical wall of a room. The aim is to reduce distortion due to that part of the reflected sound which arrives from substantially the same direction as the direct sound. Therefore the sound radiating surfaces and the loudspeaker casing are so arranged that the reflected sound from the floor and the wall arrives substantially in phase with the direct sound up to at least 800 Hz.The loudspeaker has a casing with a side wall (2), a top wall (4) and a bottom wall (6). A loudspeaker unit (7) in the side wall (2) is the sound source for at least the range from 50 to 150 Hz. A loudspeaker unit (9) mounted in a horn-type casing structure close to the bottom wall (6) is the sound source for at least the range from 300 to 800 Hz.

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: 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: 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 acoustic assembly adapted to receive a loudspeaker comprising an enclosed housing having an area defining a loudspeaker port and an area defining at least one sound port, the loudspeaker port being adapted to mount the loudspeaker substantially outside of the housing in a sealed relationship to the front of the housing, the loudspeaker directing sound into the housing, and, each of the sound ports having a cross-sectional area less than the cross-sectional area of the loudspeaker port so that the pressure of the sound energy emitted at the loudspeaker becomes increased when emitted through at least one of the sound ports.

Abstract: A loudspeaker includes, in an enclosure, a motor and a diaphragm coupled thereto. An inverted horn couples the surface of the diaphragm through the enclosure. The diaphragm is located in the enclosure with the center line which is parallel to but offset from a center line of the inverted horn.

Abstract: A loudspeaker enclosure with precisely dimensioned chambers to control and develop loudspeaker back wave energies almost exclusively as acoustical tensions. Focusing of these acoustical tensions is accomplished within each chamber so as to localize the several points of acoustical energy concentration optimally at the aperture positions between chambers. The second and also a third chamber operate to maintain proper load levels throughout the complex acoustical air column until eventual release into the listening space, the third, as well, creating essential reverberation and depth.

Abstract: A miniaturized cone driven reentrant loudspeaker is provided. A cone spea is positioned within a housing. The housing includes a front wall for radiating sound and a side wall. The cone speaker is directed towards a reflector back plate having a generally spherical surface which protrudes into the cone speaker for directing sound waves towards sidewalls of the housing to define a miniaturized cone driven reentrant loudspeaker.

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: A loud-speaker of a closed or a bass-reflex type, wherein a plurality of speaker units are intensively arranged behind an opening of a baffle board or a throat of a sounding horn with the sound wave radiating direction thereof being concentrated toward the center axis of the opening of throat, and the total area of the entire diaphragms of the speaker units is made substantially equal to, or larger than, the area of the opening or throat.

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: The upper peak impedance of a speaker or woofer that is mounted in a base reflex or ported enclosure is dampened by designing the enclosure so that the speaker is mounted in the upper end of a horn formed in the housing, for example, by inclining its front wall to the vertical, so that its upper edge is located closer to the rear wall of the housing than its lower edge. The interior of the housing between the speaker and the housing port thus has a cross sectional area which increases progressively from the upper to the lower end of the housing, and thereby functions as an acoustical transformer, which dampens the cone of the speaker particularly in the area of its upper resonant frequency.

Abstract: An improved speaker enclosure apparatus re-radiates biphase sound emanating from a speaker supported therein. When connected to receive a differential sound signal, the sound produced complements the direct sound radiating from "right" and "left" speakers. The enclosure is of compliant material, such that at low frequencies the entire enclosure expands and contracts with the expansion and contraction of the speaker diaphragm, responsive to volume expansion and contraction of the air enclosed in the enclosure. At high frequencies, only thinned portions of the enclosure expand and contract, responsive to the higher frequency sound wavefronts emanating from the speaker. The ability to mold the enclosure and the thinned portions provides a method of controlling the radiated wavefront to a desired shape to be propagated into the listening environment.

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 system for radiating acoustic output throughout 360.degree. in generally horizontal planes, comprising an enclosure having low frequency (woofer) and high frequency (tweeter) radiators mounted in spaced relation on a common vertical axis. The horn loaded compression driver tweeter is the upper of the two and has a diaphragm radiating axially upwardly into a flaring horn, preferably exponential, including an intermediate annular section which abruptly reflects sound waves approximately 90.degree. into a radial outlet section of the horn radiating approximately horizontally through 360.degree., providing the known advantages of horn loaded compression drivers in a radically more compact form than conventional horn speakers. The woofer radiates axially downwardly, and a conical plug spaced downwardly from the speaker cone serves to load the cone for higher efficiency and smoother response, and to deflect acoustic output of the cone generally horizontally through 360.degree. in a 2.pi.

Abstract: An improved, compact speaker system for production of the full range of sound audible to the human ear, the sound radiating from the speaker being omnidirectional with the speaker including an outer cabinet shell and a defined chamber configuration within the shell. High and low frequency speakers are mounted within the cabinet shell with an acoustical path being defined within the cabinet for the low frequency wavelengths with the low frequency tones traveling within the cabinet for a distance of 1/12 the wavelength of the natural free air resonance of the low frequency speaker. The high frequency speaker having a slug of pre-determined surface configuration to permit omnidirectional sound radiation without distortion.

Abstract: A loudspeaker comprises a horn having an open throat from which a pair of outwardly curved side walls extend. A cone driven speaker is mounted in the horn throat, and the horn with attached speaker is mounted in a base reflex enclosure which forms a chamber therebetween. A compression driven tweeter is mounted in one of the curved horn side walls, and a port is disposed through the other horn side wall and communicates with the chamber to vent back waves.

Abstract: A folded-horn loudspeaker system adapted for high-power audio applications. The system preferably comprises a rigid enclosure of generally cubicle dimensions and an integral, exponentially curved horn projecting outwardly from the enclosure toward the listening area. A transducer housed within a sealed chamber interiorly of the enclosure communicates through an aperture into a waveguide system of substantially rectangular dimensions. A baffle plate system deflects sound energy from the waveguide into the throat of the horn. The baffle plate system is positioned to avoid the reflection of sound waves back into the waveguide to thereby minimize distortion.

Abstract: A loudspeaker unit having an improved quality of bass reproduction for use in a stereo system with a second unit, which is a mirror image of it, to provide a better three-dimensional feeling on hearing the reproduced sound and to provide an increase in the area of the sound producer or source which includes a bass or woofer loudspeaker housed in a chamber, whose volume, together with the properties of the loudspeaker, is so designed that a desired resonant frequency is produced. An exponential horn is placed at an opening of the chamber, whose design is based on a Helmholtz resonator, whose captive air volume takes over the function of an active diaphragm, and the resonant frequency of the horn resonator has a specific relation to the resonant frequency of the chamber and the loudspeaker.

Abstract: A loudspeaker enclosure for housing a basic speaker and providing a conduit for channeling the sound waves emitted from the back surface of the basic speaker so that the sound waves are shifted in phase and emerge from a port in the enclosure and add to, rather than acoustically cancel, the sound waves emitted from the front surface of the basic speaker. The sound waves from the back surface of the speaker travel through the length of the conduit which is folded through several 45.degree. angles upon itself. These sound waves are directed through the conduit by striking and reflecting from a plurality of at least six reflector panels which are mounted at 45.degree. angles. In this manner, due to the nature of reflections at 45.degree. angles, each portion of a sound wave impulse travels the same distance as each other portion and the impulse emerges from the port basically intact. The enclosure has a unique shape because of the several foldings of the conduit through 45.degree. angles.

Abstract: Loudspeaker equipment embodying a speaker, an enclosure for the speaker which is substantially closed except for the speaker opening and which is formed of walls which are thin and therefore capable of excitation and consequent sound generating vibrations under the influence of the speaker, the speaker equipment further including a reflector surrounding the speaker enclosure and having an open front through which the speaker is exposed, the walls of the reflector being spaced from the walls of the speaker enclosure to provide a passage through which sound generated by the walls of the speaker enclosure is reflected forwardly. The side walls of the reflector include a plurality of wall elements with adjacent edges spaced from each other and having a thickness dimension sufficiently small to provide for excitation and sound generation under the influence of the speaker enclosure within the reflector.

Abstract: A bass sound projection system comprises a cabinet containing at least one bass loudspeaker operating into a sound channel. The sound channel converges forwardly, relative to the direction of propagation of sound waves, of the loudspeaker to a throat and then diverges forwardly, relative to the direction of propagation of sound waves, of the throat to an acoustically open front end of the cabinet. The system may include a further bass loudspeaker and sound channel arranged as a mirror image of the first bass loudspeaker and sound channel, and the or each sound channel may be folded.

Abstract: A loudspeaker enclosure comprising a cabinet to be located adjacent to a wall and having a horn contained therein driven by two loudspeakers oriented at right angles to the axis of the throat portion of the horn in which they are located and on opposite sides thereof, the speakers being substantially aligned in close mutual proximity and driven out-of-phase to provide adequate drive to the horn while tending to damp each other's excursions, and the horn having an internal expansion air column which extends into an external expansion air column bounded by the cabinet and by the wall and floor of the room, the external air column having a catenoidal rate of expansion which terminates in very rapid flaring closely matching the high expansion rate of the air column into the room which results from placing the horn at a mid-wall location, as distinguished from a corner-wall location.

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.