U.S. Philips Corporation

Georgius B Sanders

Joris A Nieuwendijk

Wilhelmus D Van Gijsel

Jacob M Van Nieuwland

Cornelis D Van Dijk

Johannes W Bax

Adrianus J Kaizer

Franciscus J Op De Beek

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 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

Georgius B Sanders