U.S. Philips Corporation

Joris A Nieuwendijk

Nicolaas G Vink

Werner A Heijnemans

Johannes W Bax

Georgius B Sanders

Wilhelmus D Van Gijsel

Jacob M Van Nieuwland

Albertus A Sluijterman

Martinus P Van Den Thillart

Piet G Barten

Jan Gerritsen

Willem M Van Alphen

Nicolaas Bernardus Roozen

Franciscus C De Haas

Cornelis D Van Dijk

Franciscus J Op De Beek

Adrianus J Kaizer

Guido O D'Hoogh

Jozef E Vael

Adrianus Hubertus Kantelberg

Frans A Westra

Gerrit F De Poortere

Henricus H Roelofs

Martinus P Van De Thillart

Johannes Van Den Boogert

Cornelis J Oepkes

Johannes J Kamphues

Andre J De Wachter

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.

Loudspeaker system having a bass-reflex port

A sound-reproducing apparatus comprises an acoustic horn which terminates in an opening in the wall of the apparatus. An obstacle is arranged in the acoustic duct of the horn, which provides a better frequency response.

Sound-reproducing apparatus comprising an acoustic horn, and acoustic

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 electrodynamic transducer (1) comprises a diaphragm with a central part (2) and a peripheral part (3) and a voice-coil device (9, 10) coupled to the central part (2). The diaphragm (2, 3) cooperates with an enclosed volume (6), the enclosed volume being such that ##EQU1## where f.sub.o and f.sub.o ' are the anti-resonance frequencies of a transducer respectively with or without the enclosed volume behind the diaphragm. These frequencies each correspond to a local minimum situated between two maxima (f.sub.1 and f.sub.1 ' respectively, and f.sub.2 and f.sub.2 ' respectively) in the input impedance curves Z.sub.1 in the case of a transducer with the enclosed volume and in the case of a transducer without the enclosed volume. The maxima correspond to the two resonance frequencies for which the central part of the peripheral part move in phase and in phase opposition relative to one another, and S.sub.1 and S.sub.2 are the surface areas of the central part and the peripheral part, respectively, where S.sub.2 /S.sub.1 .gtoreq.2.

Electrodynamic transducer comprising a two-part diaphragm

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.

Electrodynamic transducer of the isophase or ribbon type

A combination of a monochrome cathode-ray tube with a deflection unit for applications which require high resolution. The deflection unit produces a magnetic field having a six-pole component which is positive on the screen side to minimize raster distortion and which, in the deflection center, has a strength and polarity sufficient to minimize spot distortion. Preferably the effective length 1 of the deflection field satisfies the conditon

Combination of a monochrome cathode-ray tube and a deflection unit

An electrodynamic transducer (1) for use in a loudspeaker system for converting an n-bit digitized electric signal (11) into an acoustic signal comprises n voice-coil devices (4.1, 4.2, . . . 4.n) which cooperate with a magnet system (3). The voice-coil devices each comprise a conductor whose length is the same for all the voice-coil devices. The areas of the perpendicular cross-sections of the conductors increase each time by a factor of two starting from the voice-coil device (4.n) corresponding to the least significant bit and going to voice-coil devices corresponding to consecutive more significant bits. The invention enables the transducer to be constructed in a simple manner if the transducer is a moving-coil loudspeaker or if it is a ribbon-type loudspeaker.

Loudspeaker system for converting a digitized electric signal into an

A loudspeaker system for converting an n-bit digitized electric signal (11) into an acoustic signal comprises an electrodynamic loudspeaker (1) with n voice-coil sections (4.1, 4.2, . . . 4.n) which cooperate with a magnet system (3). The loudspeaker system further comprises means (18.1, 18.2, . . . 18.n) for short-circuiting a voice-coil section if the value of the bit corresponding to the voice-coil section is such that the relevant voice-coil section is not driven.

Loudspeaker system and loudspeaker for use in a loud-speaker system for

In a loudspeaker system for converting an n-bit digitized electric signal (6) into an acoustic signal a plurality of sections (voice coils 14.1, 14.2, 14.3, 14.p) of a digital loudspeaker (1) are driven directly by the p most significant bits of the n-bit digitized electric signal (6). The loudspeaker (1) comprises at least one additional section (14.p+1). This (p+1).sup.th voice coil receives a signal from a digital-to-analog converter (5), the input signal of the digital-to-analog converter comprising at least the n-p least significant bits (FIG. 2). In a different embodiment the digital-to-analog converter (5) receives all the n bits of the digitized electric signal as the input signal. At least the p sections (14.1 to 14.p) which correspond to the p most significant bits are provided with means (the resistances r) for producing a signal which is a measure of the sum of their instantaneous drive signals and for applying the said signal to a signal combination unit (32) arranged in the line (10) from the output of the digital-to-analog converter (5) to the (p+1).sup.th section (R.sub.1). By means of this correction circuit the distortion in the loudspeaker system can be reduced substantially (FIG. 3b).

Hybrid loudspeaker system for converting digital signals to acoustic

An electroacoustic transducer comprises a diaphragm (1), a magnet system (4) and a voice coil (3) arranged on a voice-coil former (2) in an air gap (5) of the magnet system. The movement is transmitted between the voice-coil former and the diaphragm via a lever mechanism comprising n lever devices (6) arranged at an angle relative to each other (n.gtoreq.2). A lever device (6) comprises a lever arm (9) coupled to a fulcrum (11) at the location of a first position (10) on the lever arm, to the voice-coil former (2) at the location of a second position (13), and to the diaphragm (1) at the location of a third position (14). The lever mechanism multiplies the excursion of the voice-coil former by a factor greater than unity. This results in an electroacoustic transducer with a long stroke which provides large excursions of the diaphragm. The lever mechanism may also be employed in other types of transducer, such as piezo-ceramic transducers. A compliant element (25) formed as a zigzag bellows secured both to the outer circumference of the diaphragm and to the chassis (26) to permit the large excursion of the diaphragm, is constructed so as to reduce the acoustic contribution of the compliant element to the transducer output signal, which contribution forms a distortion component in the output signal.

Large-excursion electroacoustic transducer

A ribbon-type electro-acoustic transducer comprising a magnet system having a pole plate (2, 3) and a center pole (1) between which at least one air gap (8) is formed with a diaphragm (7) arranged in the air gap (8). The diaphragm comprises at least two foils (10, 11) which extend substantially parallel to each other in the diaphragm plane, every two adjacent foils being joined to each other at their circumference in an air-tight manner so that a volume (12) is enclosed. A conductor (9, 18) is arranged on each of the foils. Preferably the volume enclosed between two foils contains a damping material (22).

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Eindhoven, Netherlands

Joris A Nieuwendijk