Abstract: A ceiling-mounted loudspeaker includes upper and lower sound-directing structures having walls acting as a radial horn to provide a wide included angle of coverage for sound energy generated by a loudspeaker driver assembly having a piston for directing generated sound energy upwardly into the horn. The lower structure further has a continuously convex bottom configured and dimensioned to define a diffraction path for at least some of the sound energy exiting the output mouth of the radial horn, so that the convex bottom acts as a downwardly-directed diffractor. The radial horn and convex bottom together produce an oblate spheroid of sound energy affording a substantially uniform amplitude of sound within a large finite horizontal plane at the level of a listener.

Abstract: A loudspeaker system is arranged to house an electromagnetic loudspeaker driver of the type having both front and back acoustic waves. The loudspeaker driver is reversed mounted such that its weaker back waves are emitted directly to the outside, while its stronger front waves are directed through an internal passageway of the loudspeaker enclosure before adding in phase and exiting with the back waves. The front waves are phase-shifted by half a wavelength through the internal passageway which acts as a transmission line. The attenuation suffered through the transmission line is offset somewhat by the stronger front waves such that the differential amplitudes of the front and back exiting waves are minimized. Throughout the transmission line, the flow of the sound waves is kept circular and laminar in order to maintain coherence and to further minimize loss of energy due to turbulence. These are accomplished by the use of a cylindrical passageway, a streamlining reflecting cone, and an outer reflecting ring.

Abstract: An audio loudspeaker system is provided which consists of an enclosure having a front wall, a rear wall with a plurality of circular openings, a pair of side wall, a top wall and a bottom wall. A plurality of loudspeaker components are supported on the front wall of the enclosure for radiating sound energy therethrough and having varying frequency ranges. A plurality of tubular ducts are supported in the circular openings in the rear wall and extend inwardly into the enclosure to exhibit a tuned acoustic frequency to the loudspeaker components having the lowest frequency ranges.

Abstract: A loudspeaker system for use as a subwoofer or other bass speaker system utilizes an enclosure with at least one speaker mounted therein and a port to form a bass reflex system. The bass reflex system is tuned to a selected low frequency range so that the acoustical output within such low range of the frequency spectrum of the loudspeaker system is enhanced while minimizing speaker cone excursion and distortion. Whereas the bass reflex speaker system loads the speaker at the selected low frequency range, a waveguide in the form of a quarterwave resonator is included in the loudspeaker system for loading the speaker at a higher frequency range which is still within the frequency range of the speaker system, so that acoustical output is enhanced and speaker cone excursion and distortion are minimized at the upper end of the frequency range. The resonator is designed to function as a quarterwave resonator within the upper frequency range.

Abstract: A loudspeaker apparatus for an electronic keyboard musical instrument has a shelf board constituting a casing of the musical instrument. The shelf board has a sound emission opening. A loudspeaker is mounted on the shelf board in alignment with a fringe of the sound emission opening. A speaker box is mounted on the shelf board so as to enclose the loudspeaker.

Abstract: An audio speaker in a cabinet is provided having an internal baffle movable on a track and driven by a motor. The movement of the internal baffle is controlled externally by controls mounted on the speaker cabinet. Selective movement of the internal baffle results in a change of the resonant frequency of the speaker/cabinet combination thereby selectively changing the characteristic of the reproduced sound.

Abstract: A loudspeaker system and a loudspeaker housing system uses a plurality of smaller rated loudspeakers to generate a high-level output. Specifically, the plurality of loudspeakers are housed in a corresponding number of substantially cylindrical sound collecting tubes, one tube for each loudspeaker. Sound waves, which are generated toward the rear of each loudspeaker and which are otherwise attenuated by the insulation material or reflected by baffles and/or walls and ultimately dissipate, instead travel through the tube, the tube forming a sound traveling path. Each tube converge and merge smoothly into a single substantially cylindrical tube. The sound waves traveling through the individual tubes are merged at the converged tube. The outlet of the single converged tube is connected to or is integral with a conventional or specialized sound concentrating horn to direct the captured sound to a desired direction.

Abstract: A sub-woofer arrangement for the reproduction of bass tones is provided in an armrest of a seat of a passenger car. The sub-woofer arrangement has a sound outlet orifice positioned so as to face a dashboard when lowered in a first position and be unobstructed when raised into a second position in a recess within the seat.

Abstract: A speaker tube structure formed of a semi-cylindrical first side wall portion and a planar second side wall portion, with the second side wall portion including speaker members mounted therewithin, having a tuning port orthogonally directed into the second side wall portion extending into the speaker tube cavity in a spaced adjacency relative to the tube axis. The tuning port is arranged to receive a plurality of inserts to permit tuning of the speaker tube.

Abstract: A fluid damped acoustic enclosure system for a loudspeaker is provided. An enclosure defines first and second chambers separated by a common wall in which the loudspeaker is sealably mounted. The first chamber is airtight and the second chamber has a port in a wall thereof communicating with the exterior of the enclosure. A flexible bladder is filled with a fluid and maintained in the first chamber a given distance from the loudspeaker. The bladder receives acoustic pressure waves generated by the loudspeaker. The bladder is further mechanically coupled to a portion of at least one wall of the first chamber that communicates with the exterior of the enclosure.

Abstract: A multiple speaker loudspeaker system wherein an internal baffle extends the full length of the interior volume dividing the interior volume into two unequal portions. The baffle has folded portions, which is not parallel to the walls of the enclosure. Loudspeakers are mounted onto the folded portions within a first volume. The loudspeakers radiate sound into a second volume. One of the first and second volume is ported in a bandpass configuration, to the outside of the enclosure. Thus, the non-parallel portions of the baffle reduce unwanted peaks and/or cancellations in the sound emanating from the enclosure. Additionally, the baffle is secured along its width to top and bottom walls of the enclosure, thus also providing extra rigidity to the enclosure.

Abstract: A loudspeaker system including a cabinet and at least one loudspeaker mounted on the cabinet which includes a movable speaker element for directing acoustical wave energy to the ambient atmosphere and to the interior of the cabinet. A passive radiator is mounted on the cabinet at a location spaced from the loudspeaker. A panel mounted within the cabinet interior vibrates at a free end when impacted by the acoustical wave energy from the loudspeaker. The panel generates acoustical wave energy which is directed to the passive radiator and causes the passive radiator to move and to direct sound externally of the cabinet.

Abstract: A loudspeaker system 10 and a method for disbursing sound waves are disclosed. The loudspeaker system 10 has a reflector screen 12 which is provided with a concave reflective surface 14. The reflective surface 14 is a complex curve having a central axis 16. A first speaker 18 is positioned in front of the reflective surface 14 a longitudinal distance along the central axis 16 less than a pre-determined distance x. The first speaker 18 projects sound waves above a pre-determined frequency toward the reflective surface 14 to be reflected and disbursed into a listening area. A second speaker 20 is positioned to project sound waves below the pre-determined frequency into the listening area generally. A frame 24 supports the first and second speakers 18,20. A method for disbursing sound waves is also disclosed including the steps of providing a reflector screen 12 having a concave reflective surface 14 and positioning first and second speakers 18,20.

Abstract: This invention relates to a loudspeaker having at least one sound collecting tubes attached to the rear of the speaker frame or the sound collecting tubes forming the speaker frame for collecting and directing sound waves emitted from the rear of the speaker diaphragm. The sound collecting tube is particularly useful for directing and boosting sound waves emitted from the rear of the speaker which is otherwise dissipated or absorbed by the loudspeaker housing material or insulation. In addition, conventional or specialized sound horns may be readily attached to the outlet end of the sound collecting tubes which can direct sound waves emitted by the speaker to any desired direction.

Abstract: A synchronous common polar resonant wall type speaker cabinet comprises a speaker fixed to its front board, and one or more resonance means on the other wall boards, in which each resonance means includes an air pressure compensation chamber surrounded by a rigid conductive hood, a compensation resonance chamber surrounded by a rigid wall board, a resonance plate between the air pressure compensation chamber and the compensation resonance chamber, a soft expansion gasket located between the resonance plate and the rigid conductive hood, and another soft expansion gasket between the rigid conductive hood and the rigid back board so that the resonance plate can oscillate by changing of air pressure in the air pressure compensation chamber, and hence a surrounding sound effect superior to that available from matrix speaker system is obtained with only a speaker without any increase of driving power.

Abstract: A low sound loudspeaker system is constructed of an acoustic pipe extending from the back side of a loudspeaker unit, an air chamber provided at the front side of the loudspeaker unit, and a bass reflex port provided within the air chamber. The acoustic pipe communicates with the air chamber via the aperture of the acoustic pipe.

Abstract: A tube speaker system having a pair of cylinder bass speakers aligned end to end with closed or blind ends in mutual juxtaposition and with speakers mounted in the other open ends which are opposite each other. A support is secured beneath the coaxially aligned speaker cylinders to prevent the cylinders from rolling on their cylindrical walls. Also, the system is provided with means for forming a laterally enclosed sound tunnel that extends the lengths of the speakers in communication with radial openings in the cylindrical walls thereof. The support may take the form of channel-shaped stand atop the sides of which the tubular speakers are mounted. Alternatively, the sound tunnel may be formed by a larger diameter cylinder within which the cylindrical tube speakers are located. In this embodiment the stand may be formed by a flat slab atop which both the larger diameter cylinder and the cylindrical tube speakers are mounted.

Abstract: An acoustic apparatus comprises an inner cabinet, a vibrator mounted thereon and an outer cabinet. The inner cabinet and the outer cabinet constitute an acoustic cabinet having a closed cavity. The outer cabinet covers the inner cabinet with a predetermined gap formed between the inner peripheral surface of the outer cabinet and the outer peripheral surface of the inner cabinet and has an opening causing the gap to communicate with the external region of the acoustic cabinet and to function as a resonance port. The resonance port and the closed cavity constitute a resonator. The vibrator is provided so as to face the closed cavity. The resonator radiates a resonant sound from the open end of the gap, i.e., the resonance port, upon being driven by the vibrator.

Abstract: Coiled exponential bass/midrange/high frequency horn loudspeakers which are 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, a coiled or convoluted, exponentially flared sound passage extending from the air chamber to the top of the cabinet and a high frequency horn mounted in the cabinet near the open top to extend the audio range of the loudspeaker system, which high frequency horn is attached to a corresponding high frequency driver by means of a time adjustable acoustic delay line. The combination of a high frequency acoustically delayed horn and a low frequency driver separated by a continuously exponentially expanding or flared, coiled or convoluted, multi-tapered sound passage chamber, enables the sound waves from both horns to exit the cabinet at substantially the same time.

Abstract: A loudspeaker (34,134) excites a quarter wave resonant air column that is folded forward on itself. The column is closed at one end and has an output port located at the other. The output port (20,120) is in line with the speaker so that the one speaker can excite air both at the output port and at the closed end of the resonant column. At resonance, the column loads the speaker, and the speaker regeneratively drives the column output. At other frequencies output from the port is partially from vibration of the air column and partially from the speaker. At resonance the direct speaker output regeneratively reinforces and combines with the output of the resonant column, which has a length of one-quarter of the wavelength of sound propagated in air at the resonant frequency.

Abstract: A compact acoustic apparatus in which a vibrator is arranged in a Helmholtz resonator having a resonance port, and is driven to radiate a resonant acoustic wave so as to perform lower bass sound reproduction, is characterized in that a cabinet is reduced in size by externally projecting the resonance port from the cabinet, and/or a boundary condition change buffer means is arranged at an opening portion of the resonance port to prevent noise caused by an air flow flowing through the resonance port.

Abstract: A bass reflex speaker system with a ducted port which can be made without coloration in the mid frequency band of the speaker caused by standing wave resonances in the duct. The system includes one or more openings in the wall of the duct between the ends of the duct, and covering the openings with a deflectable membrane, such as a film of latex-like material, or a rigid membrane with a flexible surround. The additional openings prevent pressure build-up at a quarter wavelength location of undesirable standing waves, and thereby cancels the standing waves, but they do not affect the operation of the duct at the Helmholtz frequency of the bass reflex system.

Abstract: In a speaker system, the rearward area of a diaphragm is separated into two acoustic regions. One of the two acoustic regions is a rear opening type and the other is a base-reflex type. An acoustic mass, such as a port or a passive radiator, is located between the first and second acoustic regions for providing a phase inversion characteristic.

Abstract: A subwoofer system for providing acoustic energy is provided. The subwoofer or full-range speaker enclosure is divided into at least three chambers. A first speaker acoustically couples the first chamber with the third chamber. A second speaker acoustically couples the second chamber with the third chamber. A first port acoustically couples the first chamber to the exterior of the enclosure. A second port acoustically couples the second chamber to either the first chamber or the exterior of the enclosure. The speakers are driven out-of-phase with respect to the third chamber so as to maintain the third chamber in a substantially constant-pressure state.

Abstract: An active muffler for use in motor vehicles comprises a sensor, an electronic control responsive to the signal generated by the sensor for producing a drive signal delivered to a transducer which emits cancellation pulses phased 180.degree. from the sound pressure pulses passing through a conduit, where both front and rear sides of the transducer are acoustically coupled to the conduit to improve the efficiency of the transducer operation. Preferably, the acoustic coupling comprises an enclosed chamber including a port for communicating with the conduit which can be tuned to resonate at predetermined frequencies. When both sides of the transducer are so coupled to the conduit, the transducer has increased efficiency over a broad band of frequencies, and the frequency band can be broadened at the low end as required to accommodate the frequencies generated by a source of noise.

Abstract: In an audio speaker system and speaker-cabinet combination, a speaker positioned in a cabinet is mounted to the cabinet by a mounting assembly made of non-resonant material and clamping a flange of the speaker so as to prevent contact of the speaker with the cabinet wall, and at the same time flush with the front panel of the cabinet. The cabinet is substantially non-resonant and may be made of plywood or plastic.

Abstract: The present invention relates to a so-called bass-reflex electroacoustic transducing apparatus, wherein a plurality of sound ducts (ports) having the same equivalent mass and different lengths are provided in communication with a housing which incorporates therein an electroacoustic transducing element. Thus, resonance and antiresonance generated in respective sound ducts cancel each other out, thereby preventing a tone quality of a reproduced sound from being deteriorated.

Abstract: A loudspeaker enclosure accommodates at least one speaker in the front wall of the enclosure. The interior of the enclosure is divided into at least 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 a 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 are 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: An isosceles shaped sound reproduction speaker 70 is illustrated in the accompanying drawings and described in the specification. The speaker has isosceles sides that extend upward from an apex 86 at an internal angle of between 74.5.degree. and 79.degree. and preferably 78.4.degree.. The width of the enclosure is substantially equal to the circumference of the piston diameter of the primary dynamic, direct radiation diaphragm, low-to-mid frequency range driver 94 mounted in the front wall. The height "C" of the enclosure 71 is substantially equal to or less than the width "B" of the enclosure. The speaker 70 has a secondary dynamic diaphragm driver 98 mounted in the rear wall that is connected electrically in series with the front wall driver 94. The enclosure 71 has an upper fundamental resonance frequency of 2978 Hz.+-.3%. The front and rear drivers 94 and 98 have free air resonance frequencies that are 55 Hz.+-.3%.

Abstract: A speaker housing arrangement which uniquely combines a number of acoustic functions is disclosed in both a simple embodiment and in a more complex embodiment. Each embodiment utilizes a pair of angular deflectors in a tubular or pipe type enclosure to directionally co-align the sound product from both sides of the speaker cone. A slight interval in time of egress between the pressure opposite signals provides sonic contrast and hence sharp imaging. In the simpler embodiment linearity and signal integrity is preserved throughout the sound spectrum. In the more complex embodiment part of the bass signal is momentarily retained for purposes of co-phasing in a partial bass reflex arrangement. Either embodiment permits the production of sound of unusual quality and quantity in relation to input energy and to cost and grade of components. Secondary improvements in high frequency linearity and in overall spectral equalization in the region of the speaker itself are also disclosed.

Abstract: A subcompact woofer speaker cabinet system provides high volume low frequency response, long speaker life without overload and sound projection over considerable distances. This is achieved by mounting a damped speaker diaphragm within a cabinet enclosure having a single projection opening for soundwaves expanded by an internal panel forming a common wall between substantially an exponentially diverging output horn and a converging pathway from the speaker front into the output horn, wherein the panel first compresses the wavefront from the speaker diaphragm into the horn and then expands the wavefront to project low frequency audio outwardly from the cabinet system. Lower audio frequencies in the order of 100 Hz or less are faithfully reproduced and projected in a cabinet having major dimensions only slightly larger than the diameter of the speaker.

Abstract: A tuned-port rigid baffle panel which mounts to the side opposite the beater drumhead membrane side of acoustic drums and is used by musicians to enhance the live acoustic sound of these drum type percussion instruments by adding low-frequency punch to their performance. This low-frequency response enhancement is achieved by treating the drum as a bass-reflex enclosure and tuning the port of the rigid baffle panel to the appropriate percentage of the free-air resonant frequency of the beater drumhead membrane in order to control the peak amplitude of the beater drumhead membrane at resonance and extend the low-frequency response of the acoustic drum.

Abstract: A loudspeaker system has at least a first electroacoustical transducer having a vibratable diaphragm for converting an input electrical signal into a corresponding acoustic output signal. An enclosure is divided into at least first, second and third subchambers by at least first and second dividing walls. The first dividing wall supports and coacts with the first electrical transducer to bound the first and second subchambers. At least a first passive radiator intercouples the first and third subchambers. At least a second passive radiator intercouples at least one of the second and third subchambers with the region outside the enclosure. Each passive radiator is characterized by acoustic mass. Each subchamber is characterized by acoustic compliance. The acoustic mass and acoustic compliances coact to establish at least three spaced frequencies in the passband of the loudspeaker system at which the deflection characteristic of the vibratable diaphragm as a function of frequency has a minimum.

Abstract: A loudspeaker of the present invention includes a loudspeaker cabinet and at least one loudspeaker element having a loudspeaker membrane. A plurality of sound passages define a cavity in a wall of the cabinet, and each sound passage terminates on one end in a proximal aperture acoustically coupled to the loudspeaker element and on the other end in a distal aperture acoustically coupled with exterior surrounding of the cabinet. In this way, the loudspeaker membrane is acoustically coupled with the exterior surroundings of the cabinet. The distal aperture of a one sound passage communicates with a distal aperture of another sound passage, and the sectional area of the distal aperture of the first sound passage is different from the distal aperture of the second sound passage. The first and second sound passages have different lengths.

Abstract: A speaker system installable in a narrow space and capable of efficiently reproducing sounds of frequencies of up to about 45 Hz. The system comprises a speaker, and a speaker cabinet having a first chamber enclosing the rear side of the speaker and a second chamber enclosing the front side of the speaker. The first chamber is provided with at least one duct communicating at its forward end with a port portion in the cabinet. The second chamber has an aperture or apertures which are 0.02 to 0.25 in opening degree, i.e., in the ratio of the combined opening area of the aperture to the inside volume of the second chamber.

Abstract: Stereo electroacoustical transducing apparatus for providing acoustical reproduction in a room at least partially bounded by a room bounding surface including a floor, sidewalls, and a ceiling, the apparatus including a nonlocalizable woofer module that is mounted outside of the room and communicates with an opening in the room bounding surface, upper frequency drivers located within the room, and electronics for providing audio electrical signals to the nonlocalizable woofer module and the upper frequency drivers.

Abstract: A loudspeaker system has an enclosure with a baffle dividing the interior into first and second subchambers. The smaller subchamber is directly coupled to the region outside the enclosure by a port tube. The larger subchamber is coupled to the region outside the enclosure via the smaller subchamber by a port tube. The dividing baffle carries a woofer.

Abstract: This invention relates to a loudspeaker having a plurality of sound collecting tubes attached to the rear of the speaker frame or the sound collecting tubes forming the speaker frame for collecting and directing sound waves emitted toward the rear of the speaker diaphragm. The sound collecting tubes are particularly useful for directing and boosting sound waves emitted from the rear of the speaker which is otherwise dissipated or absorbed by the loudspeaker housing material or insulation. In addition, conventional or specialized sound horns may be readily attached to the outlet end of the sound collecting tubes which can direct sound waves emitted by the speaker to any desired direction.

Abstract: An enclosure (10) for mounting two transducers (12, 14) includes a wall (20, 22) defining an enclosure (10) interior. The enclosure (10) also includes a wall (54 and/or 56) for dividing the enclosure (10) interior into a first portion (16) and a second portion (18). The enclosure (10) wall (20 and/or 22) includes a vent (52) for venting one of the first (16) and second (18) portions outside the enclosure (10), and a vent (74) for venting the other of the first (16) and second (18) portions outside the enclosure (10). The enclosure (10) further comprises a step (38) for mounting a transducer (12) perimetral edge. The step (38) extends inwardly from the enclosure (10) wall (20 and/or 22) into the enclosure (10) interior. The vent (52) for venting one of the first (16) and second ( 18) enclosure portions is provided between the step (38) and the back of the enclosure (10).

Abstract: In an acoustic apparatus in which a vibrator is arranged in a Helmholtz's resonator having an open duct port, and the vibrator is driven to radiate a resonant acoustic wave, a duct resonance absorbing means is provided to the open duct port constituting the Helmholtz's resonator so as to remove an unnecessary resonant sound other than a Helmholz's resonant sound caused when the Helmholtz's resonator is driven, thereby removing noise in a radiated acoustic wave and improving distortion characteristics.

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: An acoustic apparatus comprises a plurality of resonators having different resonance frequencies, each of which is constituted by a closed cavity and acoustic mass for causing the cavity to acoustically communicate with an external region. A housing enclosing the plurality cavities is integrally formed. Resonance acoustic radiation portions of the resonators are arranged adjacent to each other on one side of the housing, whereby sound sources which correspond to the acoustic mass can be concentrated.

Abstract: An acoustic apparatus for improved bass sound reproduction comprises a resonator, a vibrator, and a vibrator drive means. The resonator has a resonance radiation unit for radiating an acoustic wave by resonance, the vibrator has a diaphragm disposed in the resonator, the vibrator drive means has a motional feedback (MFB) means for detecting the movement of the diaphragm and negatively feeding back a motional signal corresponding to the movement of the diaphragm to the input side of the circuit, and the counteraction of the resonator on the diagram is canceled upon driving of the resonator whereby the vibrator may be invalidated as viewed from the resonator, and the vibrator and the resonator can be independently designed.

Abstract: An acoustic apparatus for improved bass sound reproduction comprising a resonator, a vibrator, and a vibrator drive means, the resnoator having a passive diaphragm serving as a resonance radiation unit for radiating an acoustic wave by resonance, the vibrator having an active diaphragm provided for the resonator, and the vibrator drive means having a drive control means for controlling a drive condition so as to cancel atmospheric counteraction of said resonator at the time of driving of the resonator, whereby the vibrator may be invalidated as viewed from the resonator, and the vibrator and the resonator can be independently designed.

Abstract: In an acoustic apparatus in which a vibrator which drives a Helmholtz resonator having an open port by one surface thereof and directly radiates an acoustic wave from the other surface thereof is arranged in the Helmholtz resonator, the open port is arranged coaxially with the vibrator, and the vibrator is driven to cancel an air counteraction from the resonator when the resonator is driven. According to this construction, the acoustic apparatus can be rendered compact and the clear sound localization can be realized.

Abstract: An acoustic reproduction range expanding apparatus includes a closed or bass-reflex speaker system which has a low-frequency drive speaker and can reproduce a sound to a predetermined lowest frequeny. A port portion adapter consists of a mounting portion attached to an openng formed in a closed cabinet or a bass-reflex port of a bass-reflex cabinet, and a port portion. The port portion constitutes a Helmholtz's resonator together with the cabinet when the port portion is attached to the cabinet, and has a port shape so that a resonance frequency becomes lower than the lowest frequency. A drive portion adapter consists of an amplifier for driving the low-frequency drive speaker, and eliminates or invalidates an internal impedance inherent to the low-frequency drive speaker. The amplifier generates a negative impedance component in an output impedance.

Abstract: An acoustic apparatus has a Helmholtz resonator having an open duct port and cavity and a vibrator disposed in the Helmholtz resonator. An opening portion of the open duct port is extended in a horn-like shape, so that the open duct port communicates with a port mounting surface with a smooth curvature. An air-flow diffusing body corresponding to the shape of the port opening portion is provided at the center of the extended port opening portion, so that an effective sectional area of the air-flow path defined by the opening portion and the diffusing body is substantially equal to a sectional area of the open duct port excluding the opening portion.

Abstract: Disclosed is a compact, wide-range acoustic apparatus which can perform lower bass sound reproduction and is free from noise or distortion components. Spatially separated first and second chambers are formed. The first and second chambers communicate with each other through a port, so that the first chamber and a resonance port constitute a Helmholtz resonator. An open port is formed in or a passive vibrating body is arranged on the outer wall surface of the second chamber, so that the second chamber and the opening or the passive vibrating body constitute an essential low-pass type acoustic filter. A vibrator is attached to the outer wall surface of the first chamber, so that the Helmholtz resonator is driven at the inner surface side of the vibrating body of the vibrator, and an acoustic radiation is directly performed from its outer surface side. The vibrator is driven to cancel an air counteraction from the resonator when the Helmholtz resonator is driven.

Abstract: A waterproof ground audio speaker apparatus has a speaker housing having a cylindrical sidewall, one open end and a closed end. A hollow cylindrical inner housing has a pair of open ends and is attached to the speaker housing with its walls in a spaced relationship to the walls of the speaker housing to form a passageway between the walls of the inner housing and the walls of the speaker housing. A loud speaker is mounted in the hollow inner housing facing one open end thereof for directing acoustical energy out the open end of the speaker housing and directing the backwave of the speaker through the hollow inner housing and through the passageway between the inner housing and the speaker housing to the open end of the speaker housing. A rigid domed supporting cover extends over the opening of the speaker housing and a filter membrane cover covers the open end of the speaker housing to protect the inside of the speaker enclosure.

Abstract: A loudspeaker cabinet in which an elongated enclosure has a driver mounted internally in one wall thereof in facing, open communication with the exterior of the enclosure and an outlet sound port positioned in spaced relation to the driver in another wall of the enclosure remote from the one wall. An audio transmission passage extends longitudinally at right angles to the axis of the driver and is defined by baffles extending in equally spaced parallel relation to one another to divide the passage into a plurality of communicating folded passage sections extending from open communication with the driver to terminate in the outlet sound port. The total length of the passage through its cross-sectional area is on the order of from 8:1 to 16:1 so that at low frequencies air pulses delivered by the driver will remain in phase throughout the length of the transmission passage.