Electrical audio signal processing systems and devices – Electro-acoustic audio transducer – Having acoustic wave modifying structure
Reexamination Certificate
2000-03-28
2003-11-04
Isen, Forester W. (Department: 2644)
Electrical audio signal processing systems and devices
Electro-acoustic audio transducer
Having acoustic wave modifying structure
C381S335000, C181S144000, C181S199000
Reexamination Certificate
active
06643379
ABSTRACT:
FIELD OF INVENTION
The present invention relates to a stereophonic speaker system and more particularly to an improved and unique speaker system in which uniquely constructed spaced true left and right speaker assemblies are preferably positioned such that a speaker assembly is located to the left and right front sides of a room or listening area thus effectively recreating the sound characteristics of a sound stage.
BACKGROUND OF THE INVENTION
Faithful reproduction of sound (music and/or speech) has been the goal of many in the audio industry. Stereophonic reproduction of sound has been with us for over fifty (50) years and is still the basis for most sound reproducing equipment for home entertainment. Introduced in the early sixties was quadraphonic sound, utilizing four discreet channels and four separate speakers. The goal was to immerse the listener in a soundstage environment by surrounding the listener at or in a theater by the four channel sound source. More recently, surround sound for home or theaters in various different forms has been introduced. The surround sound uses multiple speakers positioned in different locations in an attempt, as close as possible, to recreate as close as possible the original performance of the sound stage. Again, the object was to immerse the listener in sound, mimicking the sound characteristics of a sound stage.
In a typical sound stage for recording a stereophonic sound, the stage usually consists of two microphones, each located in the front left and front right of the source of the sound, as shown diagrammatically in FIG.
1
and which will be described further. The listener is to the front of the microphones and between the two, as shown. Multi-microphone techniques have evolves over the years enabling the recording engineer to re-locate the positions of the various musicians and/or vocalists to different places on the sound stage in an attempt to emulate the kind and quality of sound which the engineer seeks. The techniques for creating and arranging the sound stage using multiple microphones are well known and discussion thereof is beyond the scope of this invention. However, it is the case that the listener at a sound stage hears a sound reproduction as close as possible to the original performance.
The typical prior art stereophonic model is illustrated diagrammatically in FIG.
2
and will be described further below. In its basic form, the system includes two channels of sound information reproduced by a left and right speaker, as shown. The listener in front of and between the two speakers hears an illusionary sound stage between the two speakers, up front and up to the rear wall at the back of the speakers' location. Due to room boundary reflections, speaker cabinet diffraction, and reflection and psychoacoustic effect, the illusion of a sound stage would appear to be centrally located only in front of the spaced speakers. Various forms of signal processing, such as DSP, have been developed to counteract the effects of diffraction and room boundary reflections. These techniques were successful, to some extent, but due to the difference in room layouts, differing acoustic properties of floors, walls and ceilings, the desired result of reliably replicating the sound in a sound stage was not reasonably achieved. Furthermore, the introduction of signal processing in the signal path may produce undesirable artifacts in the electrical signals.
It is thus apparent that a need exists for a relatively simple speaker system which emulates the sound characteristics of a sound stage and compensates for the differing acoustic properties of floors, ceilings, walls and room geometry.
It is an object of this invention to preserve the original signal in its purest form as generated at the sound stage by utilizing the room boundary reflections and the acoustical blending of R-L and L-R stereo information by the use of a unique speaker system which effectively recreates the sound stage.
It is also an object of this invention to provide an improved speaker system including true left and true right speaker assemblies, each having a plurality of axially aligned speakers and a side wall with spaced cutouts in alignment with some of said speakers.
Another object of this invention is to provide a relatively simple stereophonic speaker assembly which includes a true left and true right speaker assembly, the left unit receiving left channel information and the right unit receiving right channel information.
Yet another object of this invention is to recreate a sound stage reproduction of sound by the use of left and right speaker assemblies, each having facing side walls with apertures therein for faithful reproduction of such sound.
BRIEF DESCRIPTION OF THE INVENTION
The above and other objects of this invention are achieved through the use of a pair of unique stereo speakers which effectively recreates the original sound stage acoustics.
In accordance with this invention, each speaker assembly consists of seven full range drivers vertically mounted, one above the other, with a tweeter located between selected drivers. The speakers are mounted on a tubular column which may be square or circular or other shape having a front and side faces. In a preferred form, the column is constructed of a flexible material such as {fraction (1/16)} inch structural polyvinyl plastic. The column configuration of the drivers creates a diffraction-free baffle board. In a preferred form, the seven drivers are housed in five different and separate chambers. The first three drivers are housed in a single chamber while drivers four through seven are each housed in four separate chambers. The result is the creation of and the provision of a spherical sound field, encompassing the left and right speakers, much like a sound stage.
In addition, the chamber containing the first three drivers and the single chambers of the fifth and seventh driver include axial and horizontally disposed cutouts. These cutouts are intended to optimize the sound stage effect and performance of the drivers. In a preferred form each cutout is positioned perpendicular to the forward axis of the drivers and in a side face or wall of the support so that it faces the other speaker assembly on the other side of the listening area. In effect, there is a true right and a true left speaker assembly, each spaced from the other. These cutouts are intended to perform the following functions.
In the case of the left speaker assembly, there is cancellation of a certain band of audio frequencies (300 Hz to 3000 Hz) to move the virtual sound source of the left speaker assembly towards the rear and to the left of the speaker assembly. The cutouts in the left speaker also project an opposite polarity sound towards the right speaker assembly, creating a negative-left minus right sound information at the intended sound stage area. The cutouts in the left speaker assembly also effectively reduce enclosure resonance which minimizes sound coloration.
In the case of the right speaker assembly, the cutouts cancel a certain band of audio frequencies (300 Hz to 3000 Hz) to move the virtual sound source of the right speaker assembly towards the rear and to the left of the speaker assembly. The cutouts in right speaker assembly also project an opposite polarity sound towards the left speaker assembly, creating a negative-right minus left sound information at the intended sound stage area. Again, the cutouts in the right speaker assembly also effectively reduce enclosure resonance which minimizes sound coloration.
Accordingly, the cutouts create a centrally located sound stage behind both speaker assemblies.
The present invention is also unique in that there is a true right speaker assembly and a true left speaker assembly; these speaker assemblies are not interchangeable either electrically or physically. Electrically reversing the left and right channel information will produce a detrimental effect on the sound stage; localization of the performers will be skewed. Mechanically reversing the speakers (left to right and r
Balasco David A.
Belasco Jacobs & Townsley LLP
Isen Forester W.
Pendleton Brian T.
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