U.S. Philips Corporation

Johannes W Bax

Joris A Nieuwendijk

Martinus P Van Den Thillart

Franciscus C De Haas

Georgius B Sanders

Frans A Westra

Henricus H Roelofs

Cornelis J Oepkes

Johannes J Kamphues

Andre J De Wachter

An enclosure (35) of a loudspeaker (37) is provided with a plurality of tubes (43) of different length via which the sound is emitted in order to achieve frequency spreading of resonance peaks in the SPL (sound pressure level) curve. The side walls (46, 47) of the tubes (43) have openings (63) via which the tubes are coupled to common Helmholtz resonators (59, 61) in order to suppress undesirable resonances in the tubes (43). By spreading the resonance peaks it is possible to use Helmholtz resonators of smaller dimensions than in the case that the sound would emanate via a single tube. This results in a loudspeaker system (33) with more compact and cheaper Helmholtz resonators (59, 61).

Loudspeaker system

An audio or video apparatus has a housing, a loud-speaker and an acoustic channel. The loud-speaker acoustically cooperates with the channel. One end of the channel opens into an aperture in a side of the apparatus. The dimensions of the loud-speaker and acoustic channel and the positioning thereof within the housing are chosen so as to provide an apparatus that is compact and at the same time produces improved audio reproduction.

Audio or video apparatus with a built-in loudspeaker

A silencer arrangement for a combustion engine (1) whose exhaust gases are discharged via an exhaust pipe (3) comprises a microphone (9), a tachometer (11) for the engine speed, a control unit (13) and a loudspeaker enclosure (19). The loudspeaker enclosure accommodates two loudspeakers (15, 17) secured to a partition (21). The partition divides the volume of the loudspeaker enclosure into two subvolumes (23, 25). The subvolumes communicate with one another via a tube (27) in order to reduce the electric power required to obtain the desired acoustic power of the sound emitted by the loudspeaker enclosure. One of the subvolumes (25) is acoustically coupled to a tube (33). One end (35) of the tube is situated near the end (7) of the exhaust pipe (3). The sound issuing from the loudspeaker enclosure via the tube interferes with the exhaust-gas sound. A Helmholtz resonator (41) is acoustically coupled to the tube (33) in order to suppress undesired resonances in the tube (33). The Helmholtz resonator contains such an amount of an acoustic damping material (43) in the form of glass wool or rock wool that the quality factor Q.sub.Helmh. of the Helmholtz resonator lies between the values 1 and 3.

Silencer arrangement for combustion engines

A loudspeaker system includes a housing (1) having therein at least one loudspeaker (3) which divides the volume of the housing into two parts (V.sub.1, V.sub.2). The first volume (V.sub.1) is coupled, via an aperture in the housing (1), to an acoustic tube (5) which includes a damping element (6). The first volume part (V.sub.1) has a smaller volume than the second volume part (V.sub.2). The damping element is in the form of a Helmholtz resonator.

Loudspeaker system comprising a helmholtz resonator coupled to an

An electrodynamic loudspeaker (1) has a diaphragm comprising a central part (2) and a peripheral part (3), and a voice-coil device (9, 10) coupled to the central part (2). The surface ratio S.sub.2 /S.sub.1 complies with the relationship 0.5.ltoreq.S.sub.2 /S.sub.1 .ltoreq.6, where S.sub.1 and S.sub.2 are the surface areas of the central part (2) and the peripheral part (3) respectively. The mass ratio m.sub.2 /m.sub.1 complies with the relationship 0.5.ltoreq.m.sub.2 /m.sub.1 .ltoreq.8 where m.sub.1 and m.sub.2 are the mass of the central part (2) and the voice-coil device (9, 10) and the mass of the peripheral part (3) respectively. Further, the stiffness imposed on the diaphragm by the space (6, 6') defined by the diaphragm (2, 3) and the chassis (4) and/or the magnet system (7) is smaller than the stiffness of the diaphragm itself. Thus it is possible to derive a car loudspeaker which has a specific dip in its frequency response characteristic P (FIG. 2a), measured in an anechoic room.

Loudspeaker having a two-part diaphragm for use as a car loudspeaker

An electro-dynamic transducer of the isophase or ribbon type includes a vibratile diaphragm (7) arranged in the air gap of the transducer magnet system and having a current conductor (9) arranged thereon. An additional layer (23, 24) of material is arranged on at least one part of the diaphragm, e.g. in a space (11) between the pole plates. In order to extend the operating frequency range of the transducer, the additional layer is divided into sections (25, 26) with the area of each section being at least an order of mangitude smaller than the area of the one part of the diaphragm. These sections are distributed more or less uniformly over the one part of the diaphragm. It is possible to reduce distortion and increase the sensitivity of the transducer.

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Eindhoven, Netherlands

Johannes W Bax