Abstract: A loudspeaker system includes an enclosure (1) which accommodates a loudspeaker device (3) and a bass-reflex port (5) having two open ends (5b, 5c). The port has a longitudinal axis (5a) and a length (L) defined by the two open ends, and has a passage which flares towards the two open ends. This provides flared portions (5d, 5e) which extend over a substantial part of the length of the port. In order to minimize undesirable noises and distortions, the flared portions, in a longitudinal section of the port, have bounding lines (7) which extend at an angle .alpha. having a value of between 3.degree. and 12.degree. with respect to the longitudinal axis of the port.

Abstract: A passive radiator comprising a chassis, a mass element suspended within the chassis, and a suspension means for flexibly suspending the mass element from the chassis. In order to obtain a large amplitude of the mass element, a sub-chassis extends between the chassis and the mass element, first flexible connecting elements connecting the mass element to the sub-chassis, and second flexible connecting elements connecting the sub-chassis to the chassis.

Abstract: An extensible speaker assembly for use in a motor vehicle including an enclosed hollow chamber for receiving sound waves from a speaker, the hollow chamber having a first hollow tubular cylinder rigidly connected thereto for receiving sound waves generated from a speaker, a second hollow tubular cylinder rigidly connected to the first hollow tubular cylinder for transmitting sound waves received from the first tubular cylinder to a third tubular cylinder, the first tubular cylinder and the second tubular cylinder having an opening at both ends, and a third hollow tubular cylinder slidably connected to the second hollow tubular cylinder, the hollow chamber having a speaker connected thereto for generating sound waves.

Abstract: In an omni-directional sound system such as a sound-light combination arrangement having at least one loudspeaker and optionally at least one light source, a bass loudspeaker arrangement includes a cylindrical casing having end walls at which are installed a bass loudspeaker and an insert casing respectively. The insert casing forms one or more bass reflection spaces within the casing. A sound deflection cone is arranged with its tip opposite the bass loudspeaker.

Abstract: A speaker assembly is disclosed. The speaker assembly employs a unique design permitting reduction in the size and weight of the speaker assembly, while maintaining high fidelity sound. The speaker incorporates inverted midranges, with opposed tweeters to produce high fidelity stereo sound. The speaker assembly also includes a strain relief member which reduces the weight of the speaker assembly. The speaker assembly also includes a pair of inductors with securing bolts running therethrough to increase the efficiency of the induction coils and permit the inductors to function as structural spacer.

Abstract: A speaker enclosure including a pair of tubular cylinders, one of which is slidable inside the other, the first of the tubular cylinders having one end closed, one end open, and an opening in the wall thereof, the second of the tubular cylinders having one end open and a speaker located in the other end thereof. The speaker enclosure may also include a pair of tubular cylinders, one of which is slidable inside the other, the first of the tubular cylinders having one end closed, one end open, a speaker in the open end, and an opening in the wall thereof, the second of the tubular cylinders having both ends open.

Abstract: An electrodynamic loudspeaker comprising a chassis, a diaphragm, and an actuator. The diaphragm is disposed within the chassis and has a front part and a back part. The actuator comprises a first actuator part connected to the diaphragm and a second actuator part connected to the chassis to cooperate with the first actuator part via an air gap. In order to obtain a large amplitude of the diaphragm a sub-chassis extends between the chassis and the diaphragm, a first flexible connecting element connecting the diaphragm to the sub-chassis, and a second flexible connecting element connecting the sub-chassis to the chassis.

Abstract: A speaker propagating sound waves in the manner of a point source. The speaker includes high, medium, and low range drivers vertically arranged within a vertically arranged tubular support member having sound escape openings in its lateral wall. The high and medium range drivers project sound upwardly, and the low range driver projects sound downwardly. The speaker has a truncated obeliskoid housing including a chamber disposed below the low range speaker. This chamber is muffled to absorb non-coherent sound, and has a vertical air tube for managing air flow within the chamber and conducting sound waves downwardly from the housing. The high range driver is exposed above the housing, so that sound projects upwardly therefrom. Sound produced by the medium range driver passes through the openings in the tubular support member. The housing is supported on casters for mobility.

Abstract: A speaker enclosure with at least one woofer and one mid-range speaker with associated parallel sound channels and ports for direction of the back waves generated by the speakers. The woofer and mid-range speaker are in a spaced relationship with the sound channel ports for the woofer speaker in close proximity to the mid-range speaker and the mid-range sound channel port in close proximity to the woofer speaker. The sound channels for the mid-range and woofer speakers are adjacent and parallel to each other. The back waves generated by the speakers travel along the sound channels which form a sound traveling path. The ports are located at a distance from the speakers generating the sound waves, but adjacent to other speakers, resulting in a life-like and rich sound.

Abstract: A sound radiated from the back of a speaker unit passes through a three-dimensional spiral sound passage formed by a coaxial dual-tube structure of an outer tube and an inner tube, and by a spiral partition plate provided to bridge a gap between the outer tube and the inner tube before exiting the speaker system. The cross-sectional area of the spiral sound passage may continuously expand or remain constant.

Abstract: The present acoustic system produces sounds over a broad range of frequencies, and includes an enclosure, a speaker acoustically connected to the enclosure, for generating, almost simultaneously, two sounds, a forward sound, and a rearward sound. It further includes a waveguide enclosed at least partly within the enclosure, and acoustically connected to the speaker, for defining an acoustic path along which the rearward sound travels. The waveguide includes a plurality of inner panels that are positioned inside the enclosure for optimizing the length of the travel path. The inner panels and the enclosure define a plurality of inner passageways having generally similar cross-sectional surface areas, and a plurality of inner openings, for causing a selective cancellation of sounds at predetermined frequencies, while preserving sounds at other frequencies.

Abstract: A vent loudspeaker system is provided which has at least one active driver and a port opening in a speaker cabinet. Disks or baffle plates are mounted a predetermined distance to and concentric to the port opening, resulting in a vented system achieving an equivalent performance as would result from a flared, ducted port, but with several performance advantages and simpler construction.

Abstract: Noise attenuation apparatus comprising an enclosure having a wall separating an interior and an exterior. The enclosure defines a volume. The volume is characterized by an acoustic compliance and includes a device producing noise. The noise has spectral components predominantly in a noise frequency range. A first port has a first acoustic mass. The port passes through the wall between the interior and the exterior wherein the acoustic compliance and the first acoustic mass are configured to establish a resonant frequency outside the noise frequency range.

Abstract: This disclosure relates to a sound system that provides high quality sound notwithstanding extreme background noise. Preferably implemented in amusement ride vehicles, such as roller coasters, the present sound system mounts left and right channel sets of speakers in each seat back, one on each side of a center section that supports the passenger's back. These speakers are mounted in a wing-back relationship, such that they direct their sound away from one another and toward laterally extending arms that extend forward from the seat back, outside of the speakers. These arms mount an inward-facing spherical reflector, which reflects and disperses sound toward a range of positions associated with height variance of the passenger. Using this arrangement, all passengers will experience the same high quality sound, whatever the passenger's height. The left and right channels speakers are each coaxially-mounted, two-way speakers.

Abstract: A television receiver has a subwoofer box situated inside the cabinet of the television receiver. The subwoofer box has a loudspeaker arranged in a chamber and mounted in such a manner that it is situated outside the space enclosed by the subwoofer box. The chamber is dimensioned so as to accommodate the loudspeaker. This enables the volume of the subwoofer box to be optimized in view of the space available inside the cabinet of the television receiver. Moreover, mounting of the loudspeaker and the wiring thereof is simplified considerably.

Abstract: The surface of an acoustic reflector faces the source, and has a plurality (N) of wells, where N is an odd prime number. Each well has a depth D.sub.n =(n.sup.2 rem N)* unit depth (0<=N<=N-1), governed by a Quadratic Residue Sequence. Acoustic energy directed from the source to the reflector, and reflected along a length direction of the reflector, has substantially equal acoustic energy in all angular directions from the reflector within plus and minus .pi./2 from the direction of radiation. The surface above can be used for the surface of a loudspeaker, where either it is the surface of the loudspeaker or has speakers positioned at the bottom of the wells. The surface above can also be used for drag reduction in moving vehicles when it is positioned either at the front or rear of the vehicle.

Abstract: A loudspeaker system comprises a housing consisting of three interconnected sealed enclosures. The primary sealed enclosure has an aperture in it in which a loudspeaker is mounted in a sealed relationship. This enclosure is interconnected with an intermediate sealed enclosure located between it and a third or output enclosure. The intermediate sealed enclosure has an aperture communicating between it and the interior of the primary sealed enclosure. A first passive plate is movably mounted in this aperture in sealed relationship. A second passive plate is movably mounted in an aperture between the second enclosure and the output enclosure in sealed relationship to form a sealed airspace between the first and second passive plates. The output enclosure has a port in it for communication with the air surrounding the enclosures.

Abstract: A speaker system includes a vertically oriented elongated tube supported on a ground surface, and open at upper and lower ends thereof; a woofer, mid-range speaker and tweeter mounted at a lower end of the tube, the woofer having a front driving face with an effective driving area, the woofer providing an in-phase audio signal directed upwardly through the tube and an out-of-phase ground wave audio signal directed in an opposite direction therefrom; an enclosure enclosing the woofer and mounting the tube on the ground surface; a restricted open area formed between a lower edge of the enclosure and the ground surface and being less than the effective driving area, the restricted open area being arranged to transmit the out-of-phase ground wave audio signal from the woofer in a direction transverse to the axial direction; and a driving circuit for driving the woofer and including a power amplifier for amplifying an input signal with a variable gain and supplying the amplified input signal to the woofer, a circu

Abstract: Interference between sound waves of different frequencies in a speaker system having a woofer and associated transmission tube are eliminated by securing a sound absorbing diaphragm to the output end of the tube to absorb sharp and high frequency sound waves while permitting low frequency sound waves to be transmitted through the diaphragm.

Abstract: Attempts to achieve fidelity of sound produced by speaker systems has led to often large, relatively complicated and expensive speaker cabinets, particularly for reproducing sound in the lower acoustic frequencies. A simple solution to the problem is a speaker assembly including a housing divided by a partition into a speaker chamber containing a speaker and a sound outlet chamber. The sound outlet chamber contains a sound outlet box remote from an opening in the partition connecting the speaker chamber to the sound outlet chamber. A sound outlet tube extends through the box and one wall of the housing. The interior of the box and at least a portion of the area around the box are filled with sand or another solid material for eliminating vibration or at least reducing vibration to a minimum.

Abstract: Disclosed is a sub-woofer module which has a simple construction and provides a good low-frequency bass in compliance with an audience's taste. The sub-woofer module has an enclosure, a baffle board which separates the enclosure into first and second chambers, and a speaker coupled to the baffle board. The baffle board is engaged with a screw shaft and moves upward and backward along the screw shaft to vary the volume of the first and second chambers. A reverse-conical cap is disposed above the enclosure to permit the upwardly projected sound to be projected in 360 degrees, and a conical base is disposed below the enclosure to permit the downwardly projected sound to be projected in 360 degrees. The audience can listen to sound of the same quality regardless their position in relation to the sub-woofer module.

Abstract: A loudspeaker enclosure has an inside volume. At least one port characterized by predetermined mass intercouples the inside volume and the region outside the enclosure. Each port has a smoothly flared input end within the inside volume and smoothly flared output end adjacent to the region outside the inside volume. The port defines a boundary between the acoustic mass therein and the inside volume, the boundary typically being defined by an ellipse, and in a particular form by the rotation of an ellipse about the axis of a port. Typically, the length of the port corresponds substantially to the major diameter of the ellipse.

Abstract: A television set speaker system includes first and second acoustic waveguides arranged respectively in the front surface parts of respective diaphragms of left channel and right channel speakers so as to radiate sounds. First and second directional reflectors are arranged respectively in the rear surface parts of the respective diaphragms of the left channel and right channel speakers so as to forcibly reflect the sound radiated from the respective rear surface diaphragms respectively in the left and right side surface part directions and to radiate the sound out of the television set through first and second radiating ports provided respectively in the left and right surface parts of the television set.

Abstract: A high quality sound system for installation into the bay of an existing computer including a front panel supporting a pair of speakers. A sound focussing isolation unit having a mouth opening up on the front panel is positioned between the speakers and has a throat communicating with a reverberating chamber provided by a housing located in the bay of the computer. The focussing isolation unit is constructed to prevent sound waves generated by one speaker from destructively interfering with sound waves generated by the other speaker. It also dampens mechanical vibrations of the front panel. The focussing isolation unit also focusses sound from the reverberating channel located in the bay space out through a mouth located in the front channel. Each channel is provided with an individual amplifier for two channel reception. Power to the amplifiers is provided from the computer power supplies which is first filtered to reduce noise to the amplifier circuits.

Abstract: A Helmholtz resonator loudspeaker having a capsule shape that may be truncated at one or both ends. When the housing is truncated, dampening material may be added at the truncated portion. Legs or a stand aid in the physical stability and to further assist the acoustics. The resonator tube is located on the interior of the housing chamber with one end opening into the interior concentric with an axis running along the length of the capsule and the other end exiting the housing below the speaker.

Abstract: A bass-reflex loudspeaker system includes a number of ports configured to reduce acoustic depth mode re-radiation associated with the loudspeaker cabinet during use. The length of a first port is dependent upon the interior depth of the loudspeaker cabinet and the first port is configured such that the half-wavelength resonance of the first port coincides with the half-wavelength depth mode resonance of the loudspeaker cabinet. The length of a second port is less than the length of the first port and the cross sectional area of the first port is approximately equal to the cross sectional area of the second port.

Abstract: The present invention discloses a method of constructing a loud speaker system and a loud speaker enclosure itself that is ducted. Based upon a selected speaker base which is needed, the ideal duct diameter is determined to ensure maximum low frequency or bass, and punch, from the cabinet. Using the ideal duct diameter, the actual duct diameter is then determined. Based upon the ideal duct diameter, the speaker, and the desired cabinet depth, the cabinet height and width dimensions are determined. The length of the actual duct is then determined.

Abstract: As the front surface diaphragm of the speaker is provided with a first acoustic waveguide and the rear surface diaphragm is provided with a back cavity reflecting sound waves and a second acoustic waveguide guiding the reflected sound waves, a mass of air by the first acoustic waveguide will be applied to the front surface diaphragm, substantially the same load as to the rear surface diaphragm, the acoustic loads in the front and rear of the diaphragm will be balanced, the sound waves of the low frequency ranges will be able to be efficiently discharged on substantially the same level from both acoustic waveguides and sounds having an expansion and presence will be able to be obtained.

Abstract: A loudspeaker system has specific exterior dimensions and specific interior dimensional correlations which has at least a first electroacoustical transducer having a vibratable diaphragm for converting an input electrical signal into a corresponding acoustic output signal. A speaker 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, and each subchamber is characterized by acoustic compliance.

Abstract: A combination of computer mainframe housing, sound producing unit, and mainframe unit, including a housing separated into a front sound chamber and a rear receiving chamber by a vertical partition board, a sound producing unit mounted inside the rear receiving chamber which includes a woofer mounted in a hole on the vertical partition board facing the sound chamber, a sound producing circuit board fixed to the back panel of the housing and connected to the woofer by an electric wire, and a sound tube having one end fastened to a hole on the back panel of the housing and an opposite end facing the vertical partition board, and a mainframe unit mounted inside the rear receiving chamber of the housing which includes a mother board having a plurality of expansion card slots, and a plurality of expansion cards respectively mounted in the expansion card slots.

Abstract: A speaker box with improved low frequency response. Three chambers of specified proportion are provided which allow vibration of both front-cone and rear-cone sound waves projected from an internally installed low frequency speaker. Housing is provided for one or more higher frequency speakers, further providing rear covers to protect the speakers from low frequency sound wave interference. Ports are also provided for rear-cone sound wave emission.

Abstract: A speaker enclosure including a pair of tubular cylinders, one of which is slidable inside the other, the first of the tubular cylinders having one end closed, one end open, and an opening in the wall thereof, the second of the tubular cylinders having one end open and a speaker located in the other end thereof. The speaker enclosure may also include a pair of tubular cylinders, one of which is slidable inside the other, the first of the tubular cylinders having one end closed, one end open, a speaker in the open end, and an opening in the wall thereof, the second of the tubular cylinders having both ends open.

Abstract: A speaker apparatus includes a cabinet divided by a partition plate into a front compartment and a rear compartment, a speaker unit mounted on the partition plate so that the sound radiating direction is towards said front compartment, an internal passive radiator mounted on the partition plate, and a duct formed on an outer wall section of the front compartment for extending in the same direction as the sound radiating direction of the speaker unit. The speaker unit and the internal passive radiator mounted on the partition plate dividing the cabinet into a front compartment and a rear compartment render the rear compartment into a hermetically sealed box and constitute a resonance circuit. The sound is radiated via a duct formed on the outer wall section of the front compartment.

Abstract: A modular port turning kit for tuning a speaker enclosure. Two flared sections, a straight section, and a pair of cylindrical connectors are included in a kit. The straight section is cut to length to configure the port to have an enclosed volume of a size needed to tune a particular speaker enclosure. The straight section has a wall thickness and profile size which forms a butt junction with the junction end of the flared section. The connectors fit over the cylindrical peripheries to provide an interference fit when the sections are joined. The sections are all of thermoplastic material to provide sufficient rigidity. After testing, adhesive can be used to secure the butt junctions to form a permanent installation.

Abstract: A speaker system with an anion generator and a television set using the speaker system. The speaker system includes an anion generator provided within a speaker box. Sound pressure is used to help spread the generated anions outside the speaker box. An antistatic agent may optionally be provided on one or more surfaces of the speaker box to prevent static charge build-up within the speaker box.

Abstract: A bass reflex loud speaker system for use in high power applications which includes an enclosure with at least two, and preferably three, cone drivers mounted in front of separate and acoustically isolated bass reflex chambers. Each bass reflex chamber is tuned to a separate octave such that the bass reflex modules formed by each bass reflex chamber and its associate cone driver produces a complex acoustical signal comprised of different frequency components in the low frequency range at high sound pressure levels, but with minimum driver cone excursion and distortion.

Abstract: A duct is provided in a cabinet for radiating sound pressure emitted from a speaker unit. The duct comprises a first duct and a second duct. The first duct extends in a direction perpendicular to a radiating direction of the sound pressure radiated from a front side of the speaker unit. The second duct is connected to an end of the first duct. An inner end of of the second duct is communicated with the cabinet. The speaker unit is disposed at a connection of the first and second ducts.

Abstract: A tube-annexed speaker cabinet has a connecting device disposed on an opening at the bottom wall. A tube assembly which composes of one or more than one tubes engages with the connecting device. The other end of tube assembly engages with a pedestal which is a platform or a hollow box to support the cabinet from falling. A venting hole is optionally disposed on the bottom wall and each said wall of the hollow box and on the tube assembly respectively. A horizontal platform and a friction pad are disposed on the upper end of tube assembly to hold the cabinet. Tube assembly and pedestal box expands the volume of cabinet. Speaker cabinet can also be disposed on the rear shelf of car trunk with tube assembly extending downward into the trunk. The bottom wall of tube assembly is close or has a venting hole formed therein. Thus forming an increase interior volume of speaker cabinet to generate better resonant effect.

Abstract: According to the state of the art, double chamber bass reflex boxes are constructed so that the housing is separated by a partition wall into two spaces (13, 14). A loudspeaker (19) is inserted into the partition wall. One of the two spaces (13, 14) is equipped with an outlet opening, into which a so-called bass reflex tube is inserted for tuning the box. If complicated housing shapes are to be manufactured, it is not possible to build the bass reflex tube and the wall to which it is connected, in one piece. In such instances it is rather necessary to insert the so-called bass reflex tube into an opening in the wall, and to attach it by means of suitable sealing and connecting means. For that reason the invention has the task of presenting a housing for double chamber bass reflex boxes (10) which is especially easy to produce.

Abstract: A speaker system comprises a speaker for reproducing a sound, a main acoustic radiation housing for transferring the reproduced sound forwardly radiated from the speaker toward a listening location, and an auxiliary acoustic radiation duct attached to a rear portion of the radiation housing for collecting the reproduced sound backwardly emanating from the speaker and transferring it toward the listening location. The radiation housing includes a plurality of axially parallel partitions formed therein for providing acoustic waveguides corresponding to the number of notes of an octave. The waveguides are provided with acoustic separating holes formed at a side wall of the radiation housing, which are serially arranged in conformity with the notes of the octave.

Abstract: A vented loudspeaker system is provided which has at least one active driver and a port opening in a speaker cabinet, Disks or baffle plates are mounted a predetermined distance to and concentric to the port opening, resulting in a vented system achieving an equivalent performance as would result from a flared, ducted port, but with several performance advantages and simpler construction. Flow guides are provided, attached to the disks or baffle plates, extending back into the port to block areas of stagnant air and enhance laminar air flow.

Abstract: The present invention relates to a reflex compression valve--divided chamber speaker cabinet which improves acoustic frequencies emanating from the speaker cabinet by specially designed and positioned ports located frontally and rearwardly within the speaker cabinet. The speaker cabinet greatly reduces reverb or lag caused by uncontrolled reflecting air within a standard baffle chamber resulting from the speaker cabinet design and electrical passive crossover network.

Abstract: A speaker enclosure has three chambers sub-divided from one other, each chamber being ported by its own separate acoustic port to the ambient. An electro-acoustic transducer is mounted in communication with two of the chambers, and the third chamber being is isolated from the transducer except for an acoustic port communicating between the third chamber and one of the other two chambers.

Abstract: A loudspeaker enclosure for mounting on a vehicle rear deck includes a main chamber, and at least one subchamber adjacent to the main chamber. At least one support intercouples the main chamber and the at least one subchamber. The acoustic mass of the at least one subport and the acoustic compliance of the at least one subchamber establish a mass-compliance resonant frequency of the order of substantially 250 Hz.

Abstract: The speaker apparatus of the invention having a speaker for radiating sound waves, an acoustic pipe having a slender opening and a rectangular form, with the front opening joined to the outer wall side of a cathode-ray tube and inner wall side of a cabinet of television receiver, being disposed at the front side of the speaker, and a sound leading part composed of a hollow part surrounded between the outer wall side of the cathode-ray tube and the inner wall side of the cabinet, from the junction to the opening of the cabinet, for guiding the sound waves radiated from the acoustic pipe to the front side of the television receiver, thereby realizing acoustic reproduction of high sound quality and high sound pressure, when applied in the television receiver, in spite of small size and slim shape.

Abstract: A speaker system includes a speaker unit, a cabinet, and a pair of ducts. The cabinet has a baffle plate. The speaker unit is mounted on the baffle plate. The pair of ducts have parallel axes. Each of the ducts has a first end mounted on the baffle plate and a second end disposed in the cabinet. The first end of each duct defines an outer opening formed in a plane parallel to a surface of the baffle plate, and the second end of each duct defines an inner opening at least a part of which is formed in a plane not parallel to the plane forming the outer opening. Each duct has a shape such that a sectional area of each duct is gradually reduced from one of the inner and outer openings to the other opening.

Abstract: A speaker unit includes a speaker housing having a lower portion and an upper portion. A drive unit is housed in the upper portion for producing and outputting sound, with the drive unit having a central axis, and a sound mirror is housed in the lower portion for reflecting the sound output by the drive unit. The mirror has a generally conical surface facing the drive unit for redirecting sound therefrom into a generally horizontal direction and a cone shape, with an apex of the cone being closest to the drive unit. A supporter supports the drive unit in a cantilever type manner above the sound mirror, and the center axis of the drive unit is offset from the apex of the sound mirror, with the drive unit supporter positioned at substantially the opposite side of the apex than the center of the drive unit.

Abstract: A speaker enclosure assembly (10) having an enclosure cabinet (11) in which a speaker (26) is mounted. The speaker (26) creates an airflow within the enclosure cabinet (11) as the speaker (26) is vibrated for the transmission of sound. The airflow tends to resonate as it is bounced off of the upper, lower, front, rear, and side and end panels (14, 16, 17, and 18) of the enclosure cabinet (11), and is directed into a first baffle duct (31). The airflow is redirected by the first baffle duct (31) into a smaller second baffle duct (55) wherein the airflow is compressed to increase the resistance of the airflow, which exits the enclosure cabinet through an audio port (70) formed in the enclosure cabinet (11) to reinforce the sound from the front of the speaker (26).

Abstract: A high fidelity loudspeaker having a driver, e.g., a woofer in a housing, is rear-loaded by a folded passage, i.e., a transmission line, closed at one end by a loudspeaker and open to the environment at the other end. The line has a length equal to the quarter-wave length of the lowest desired frequency. Angled 45.degree. reflectors are used in the transmission line whereby an advancing planar wave from the rear of the speaker is produced from the rear hemispherical wave. The transmission line is conventionally stuffed with fibrous material, such as long fiber wool, which attenuates resonances, absorbs high frequencies and acts as a low pass filter. The acoustic output at the open end of the transmission line has high frequencies filtered out and a low frequency planar wave at maximum possible amplitude emitted in close phase with the front wave of the loudspeaker.

Abstract: A passive radiator baffle 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 percussion instruments by adding low-frequency punch to their performance. This low-frequency response is achieved by selecting the mass of an acoustically suspended piston to provide tuning the drum enclosure to a selected frequency.