Matsushita Electric Industrial Co., Ltd.

Katsuaki Satoh

Seiichi Ishikawa

Masaharu Matsumoto

Akihisa Kawamura

Hiroyuki Takewa

Shuichi Obata

Shuji Saiki

Satoshi Takayama

Mitsuhiko Serikawa

Kousaku Murata

Kazue Sato

Tsuneo Tanaka

Akira Kurozuka

Katsuji Hattori

Kenichi Terai

Sawako Usuki

Yasutoshi Nakama

Tadashi Tamura

Michiko Ogawa

Yoichi Kimura

Kosaku Murata

Youichi Kimura

Hikari Hashimoto

Yoichi Kumura

Mituhiko Serikawa

A speaker which is thin but which is capable of providing high-fidelity reproduction and ensuring a suitable level of sound pressure even when it is brought close to a wall. A closed chamber is formed behind one part of a disphragm mounted in an enclosure, and an open chamber is formed behind another part of the diaphragm. At least one voice coil driver unit is connected to the diaphragm. The phase difference between sounds radiated from the front and rear surfaces of the diaphragm is increased as large as possible by using an acoustic duct for the sound radiated through the open chamber, thereby minimizing cancellation of sounds and improving the sound pressure level.

Thin speaker having an enclosure with an open portion and a closed

A transfer function is determined in accordance with an amplitude characteristic and a phase characteristic. The transfer function is subjected to inverse Fourier transform. An imaginary part of a result of the inverse Fourier transform is set to zero and thereby the result of the inverse Fourier transform is converted into a converted result. The converted result is subjected to Fourier transform. The amplitude characteristic and the phase characteristic are updated in accordance with a result of the Fourier transform. Such processes are reiterated. A primary desired amplitude characteristic is corrected in accordance with the finally-obtained amplitude characteristic so that the primary desired amplitude characteristic is converted into a final desired amplitude characteristic. A final desired phase characteristic is determined in accordance with the finally-obtained phase characteristic. A second transfer function is determined in accordance with the final desired amplitude characteristic and the final desired phase characteristic. The second transfer function is subjected to inverse Fourier transform. Filter factors are calculated from a real part of a result of the inverse Fourier transform of the second transfer function. The calculated filter factors are set in a FIR digital filter.

Method and apparatus for calculating filter factors

A speaker system has an acoustic diaphragm and an image projection screen provided on a surface of the diaphragm integrally therewith so as to enable the user to enjoy both realistic image on the screen and powerful sound reproduced through the diaphragm. The rear surface of the diaphragm is closed at a peripheral portion thereof while the central portion of the rear surface of the diaphragm is opened to the exterior, so that the speaker system can provide a high level of reproduced sound pressure in low-pitched region, while the thickness of the speaker is reduced remarkably. The diaphgram can be driven by a plurality of driving units so that the speaker system can operate only with an ordinary stereophonic amplifier. The diaphragm can be composed of a pair of diaphragm elements capable of vibrating independently of each other and the screen may be integrally and commonly attached to the surfaces of these diaphragm elements in such a manner as to allow the diaphragm elements to vibrate independently of each other, whereby the speaker system can operate in stereophonic mode. Any variation in the acoustic characteristic attributable to variation in the condition of installation is compensated for by a change in the ratio of the opened area of the rear surface of the diaphragm to the whole effective vibration area or by a selective provision of a sound absorbing member on the rear side of the cabinet.

Speaker system with image projection screen

An apparatus for changing a sound field, comprising at least two signal processing means, which can smoothly and continuously switch a sound field into an arbitrary sound field without a break of signals by alternately switching one of the signal processing means into the other.

Apparatus for changing a sound field

A sound reproducing apparatus for use in a vehicle having a speaker system constituted by at least one acoustic duct and a speaker unit disposed at a throat of the acoustic duct, an opening formed at the other end of the acoustic duct facing the passenger compartment of a vehicle. The apparatus is arranged such that, F0 and Fs are substantially equal to each other. Where Fs is the lowest frequency in a frequency range within which the imaginary part of the acoustic impedance at the sound radiating surface of the speaker system in the direction of the space within the passsenger compartment is zero and F0 is the low-range resonance frequency of the speaker system itself in the free space.

Sound reproducing apparatus for use in vehicle

An apparatus for calculating a filter factor for a digital filter which can be simply constructed and in which the time period for calculation can be shortened as compared with conventional techniques. The apparatus has an input circuit for inputting a desirable frequency property, a division circuit for dividing the inputted frequency property into a plurality of frequency bands, and a calculating circuit for obtaining filter factors for realizing a frequency property of each of the divided frequency bands. The input circuit inputs the frequency property with a frequency resolution corresponding to the number of the filter factors. The division circuit performs a correction for a division so that the frequency property becomes zero from a frequency over the high cut-off frequency of a band-pass filter toward the Nyquist frequency of the frequency band corresponding to the transversal filter, the Nyquist frequency being 1/2 of the sampling frequency. The calculating circuit has a transformation unit for performing a Hilbert transformation or a linear phase transformation with respect to the respective frequency properties divided by the division circuit.

Calculation of filter factors for digital filter

A digital equalizer for audio system applications is based on a FIR (finite impulse response) digital filter whose amplitude and phase/frequency characteristics can be respectively independently established in accordance with input data representing an arbitrary amplitude/frequency characteristic and input phase data from which an arbitrary phase/frequency characteristic for the filter can be derived. In addition to audio frequency response equalization, the apparatus can be provided with a microphone howl suppression function.

Digital equalizer apparatus enabling separate phase and amplitude

A multi-layer block to be developed into a disk having a honeycomb construction is initially developed into a columnar block, and then the bottom of the columnar block is radially developed for obtaining a core of a speaker diaphragm. A suitable circular thin layer is attached to the top and bottom of the core to complete a diaphragm. The columnar block may be developed by means of a cone-shaped tool into a truncated cone, and this truncated cone may be further developed into a flat disk by applying a force to the top thereof. Since the forces on development are applied to the block uniformly, the density of hexagonal sections of the honeycomb construction is uniform throughout the entire circumference of the core providing superior speaker characteristics.

Method of manufacturing a speaker diaphragm

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Osaka, Japan

Katsuaki Satoh