KR20000067321A - A broadband, acoustical wave shaping and control system of loudspeaker - Google Patents

Abstract

PURPOSE: A system for shaping a wideband acoustic wave of a speaker is provided to make a true hemispherical acoustical polar pattern by controlling/shaping a maximum acoustic wave front. CONSTITUTION: A wideband acoustic wave shaping system includes a reflective plate, and an acoustic sound diffusion plate(10). The reflective plate reflects a high-frequency sound effect wave generated from acoustic sound source. The acoustic diffusion plate performs a variable impedance diffusion filtering about the acoustic sound wave in order to maintain a balance between a high frequency acoustic wave and a low frequency acoustic wave. The acoustic wave shaping/controlling part distributes acoustic energy of a speaker driver, and provides acoustic energy field of a true hemispherical acoustical polar pattern within a power bandwidth of a system at an adding point of a diameter of acoustic sound source.

Description

Broadband Acoustic Wave Shaping and Control System for Speakers {A BROADBAND, ACOUSTICAL WAVE SHAPING AND CONTROL SYSTEM OF LOUDSPEAKER}

The present invention relates to a speaker system, and more particularly, to achieve a true hemispherical acoustical polar pattern from a single overhead sound source in a low ceiling environment. The present invention relates to a wideband acoustic wave shaping and control system for a speaker that is equally applicable to multiple drivers and a single sound source system.

Speakers are widely used for voice and sound transmission for various purposes in various spaces. The speaker function is particularly important and the space where it is difficult to show is a large assembly space. In such large spaces, the use of conventional directional speakers is common, but it is difficult to use due to the directional characteristics of sound projection. Therefore, in the case of directional speakers, a plurality of speakers should be installed in order to secure the maximum possible sound diffusion range, but the sound projection range of each speaker overlaps with each other. A sophisticated technical approach is required to secure a desired diffused sound field. It can be expensive.

In order to reduce the necessity of installing a large number of such directional speakers, hemispherical diffusion type speakers have been developed. Although these hemispherical speakers have a wider audible range in sound or voice transmission than directional speakers, many difficulties have arisen in producing practical products that can secure the entire frequency band from an overhead single sound source in all directions.

The existing known speaker systems all have various problems as follows.

1. Since the audio frequency essentially occupies eleven octaves of the electromagnetic spectrum, the acoustic wavelength varies over a ratio of 2000: 1 or more (or approximately 113 feet to 1/2 inch or more). For practical purposes, the ratio of 1000: 1 is a reasonable and feasible number (56 feet to 0.68 inches). In either case, the wave energy at these extremes requires the application and utilization of very different bands and aspects of physical phenomena.

2. The low frequencies of the audio spectrum tend to be fluid in nature and thus create spherical waves that are difficult to control shaping and directing.

3. The high frequencies of the audio spectrum show linearity and, by their nature, generate plane waves that are not easily spread or spread in a wider coverage pattern.

4. The midband frequencies of the audio spectrum produce the variable combination forms of 2 and 3 above.

5. The low ceiling structure provides a shorter linear distance between the sound source and the listener's ears compared to the high ceiling structure, thus exacerbating the problem of acoustic polar distribution for overhead speaker systems [where the "low ceiling" Is general and variable, but limited to height between 8 and 15 feet. Practically, the finishing ceiling height and interior ceiling height of a multistory building about 10 feet each floor is between 8 and 9 feet]. Due to this condition, the listener must be located within the acoustic near field of the system, in which some but not all of the acoustic components of the speaker are at any given point in space. In contrast, the boundary of the far feild marks the beginning of a spatial field where the summation wave shows all the properties of the system design. The acoustic pattern shaping effects of other true hemispherical coverage speaker systems do not exist in the near field, but in proper form and function in the far field. Speakers using concave progressive-curve reflectors that achieve true hemispherical pole coverage should be at least eight times the listening distance of the reflectors. For example, an 18-inch reflector requires 12 feet of listening distance.

6. In order to achieve a true hemispherical spatial response, conventionally all of the above reasons are designed to compromise. This led to some or all of the following shortcomings.

A. The high intensity lobes of acoustic energy applied directly on the axis including the reflector are typically around 30 to 60 degrees around the central axis of the system.

B. At higher points in the coverage pattern, high frequency energy distribution is severely reduced, usually starting at 45 degrees and ending at 90 degrees from the central axis.

C. The phase distortion is greatly increased due to undesirable multiple reflections between the sound source and the reflector.

D. For one sound wave, the intermodulation distortion is greatly increased due to remodulation by other sound waves of different frequencies due to the effect of "C" described above.

E. Frequency-selective distribution of playback signals causes bandwidth loss, low-fidelity state, and secondary loss of clear audio representation and comprehension.

F. Generates spectral imbalances in the distribution pattern, ie, unequal levels of low, intermediate and high frequencies at various angles within the 180 degree coverage pattern.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art as described above and, when positioned around the speaker driver, controls and shapes the highest acoustic wave front to provide hemispherical pole coverage over the entire power bandwidth of the system. It is an object of the present invention to provide a wideband acoustic wave shaping and control system for a speaker that allows the pattern to start at a distance approximately three times the diameter of the sound source (eg 2 feet for an 8 inch speaker).

1 (a) is a schematic cross-sectional view of a wideband acoustic wave shaping and control system of a speaker according to the present invention;

1 (b) is a schematic plan view of the diffuser and reflector cone of FIG. 1 (a),

2 (a) and 2 (b) are diagrams for explaining an acoustic ray pattern in an incident / simultaneous reflection mode in which acoustic waves are incident / simultaneously reflected by the present invention;

3 (a) and 3 (b) are diagrams for explaining the acoustic ray pattern of the surface / edge diffraction mode in which acoustic waves are surface / edge diffraction according to the present invention;

4 (a) and 4 (b) are diagrams for explaining an acoustic ray pattern in a control variable impedance diffusion filtering mode in which acoustic waves are diffusely filtered according to the present invention;

5 (a) and 5 (b) are diagrams for explaining an acoustic ray pattern in an aperture reflection mode in which acoustic waves are aperture reflected according to the present invention;

6 (a) and 6 (b) are diagrams for comprehensively explaining the reflection, diffraction, diffusion and aperture reflection of acoustic waves according to the present invention.

<Description of the code | symbol about the principal part of drawing>

10 cone of low frequency driver 12 high frequency driver

14 diffuser 16: reflector cone

14A: Slot

The present invention for achieving the above object is a wideband acoustic wave shaping, which is a waveform shaping and control device designed to be attached to a speaker cabinet required for a low ceiling overhead sound system, and comprising one or more drivers or speaker motors; Provide a control system.

The shaping and control system is designed to distribute the acoustic energy of the speaker driver to provide a true spherical pattern of acoustic energy field at a point of summation approximately three times the diameter of the sound source within the power bandwidth of the system. do.

The shaping and control system is rigidly mechanically attached to the front or baffles of the speaker enclosure, or otherwise installed in the enclosure structure during fabrication or molding into homogeneous or integrated components. The geometry of the shaping and control system is designed and positioned in an important acoustical fashion to influence the hemispherical pole coverage pattern.

The shaping and control system is a combination of a single acoustic shaping device and a sound distribution device, each of which is individually designed to control a particular sub-band of the audio spectrum. Their individual function is the factor of the final acoustic addition product, the shaping and control system.

Hereinafter, a wideband acoustic wave shaping and control system of a speaker according to the present invention will be described in detail with reference to the accompanying drawings.

Figure 1 (a) is a schematic cross-sectional view of a wideband acoustic wave shaping and control system of a speaker according to the present invention, Figure 1 (b) is a schematic plan view of the diffuser and reflector cone of Figure 1 (a).

In the figure, reference numeral 10 denotes a cone of a low frequency driver, 12 denotes a high frequency driver, 14 denotes a diffuser plate, 16 denotes a reflector plate installed on the diffuser plate 14, and 14A denotes on the diffuser plate 14. Slots of exponential shape formed.

The system of the present invention includes a diffuser plate 14 which is a controlled variable impedance diffusion filter (CID) for balancing the cone 10 and the high frequency driver 12 of a low frequency driver as an active sound source, It consists of a reflector plate cone 16 which is an incident / coincidence acoustic reflector (ICR) provided at the center of the diffuser plate 14.

The reflecting plate reflects, or otherwise distributes, the upper intermediate frequency and high frequency pressure waves, first through incident / simultaneous reflection and secondly through surface / edge diffraction according to the desired radiation pole pattern (or acoustic profile ( profile)]. The reflecting plate is geometrically enlarged in its (acoustic virtual) cross section and (acoustic real) surface area, and preferably formed in a cone shape like the reflecting plate cone 16 in the figure. In the present invention, in order to achieve the desired effect of the reflecting plate, the basic physical law regarding the sound phenomenon and the reflection and diffraction sound wave action are used.

The diffusion filter (diffusion plate) 14 is designed to control the distribution of the upper low and lower intermediate frequencies, via controlled variable impedance acoustic (pressure) diffusion and aperture reflection. The diffuser plate 14 is not linear in its actual cross-sectional profile, but is a geometry defining a pair of exponentially increasing slots 14A and baffles, which complement each other's acoustical functions. . The shape of these slots and baffles extends radially toward the edge or to the outer periphery of the diffuser plate, starting at the outer periphery of the reflecting plate. The mathematical and geometric curves defining their shape are radially and annularly symmetrical about the periphery of the reflecting plate. In order to achieve the desired effect of the diffuser plate, two basic laws of physics relating to acoustic shape for aperture impedance and reflection are used.

Next, the effect by the synergistic effect of said reflecting plate and a diffuser plate is demonstrated.

The augmentation form of the reflector exhibits a form-factor that is acoustically complementary to the desired ray pattern of the driver's natural upper intermediate frequency and high frequency plane wave dispersion.

The augmentation form of the diffuser plate also defines the inverse of the natural exponential pressure distribution of the square wave at the upper bass and lower intermediate frequencies.

The diaphragm of the driver (moving mass of the speaker motor) has a fixed diameter and shape, and all of its acoustic, mechanical and dimensional parameters have finite properties. Thus, these values establish a reference baseline for profile calculation of the diffuser and reflector plates. Thus, the exponential shape constituting the shape of the diffuser plate and the shape of the reflector plate must be variable-specific and relative to the diaphragm in order to realize the desired design goals.

The acoustic properties of the reflector and diffuser plate are algebraically combined to provide a variety of acoustics that in turn define the highest target performance, acoustic spatial wave shaping representing a true hemispherical pole coverage pattern of acoustic pressure waves, and consequently acoustic power (energy) distribution Calculate the control product. This characteristic occurs in front of the speaker over the system over the entire system's full power bandwidth at spaces that are roughly three times the linear distance of the sound source's diameter beyond the near-field, ie at the far peak of the far field.

In essence, the five physical factors of acoustic phenomena are described by each component of the system. That is, incident / simultaneous reflection and surface / edge diffraction are performed by the reflector cone 16, controlled variable impedance diffusion filtering and aperture reflection by the diffuser plate 14, and synergistic addition by the entire system. .

2 (a) schematically illustrates an acoustic ray pattern in an incident / simultaneous reflection mode in which acoustic waves by the high frequency driver 12 are incident / simultaneously reflected by the reflector cone 16. FIG. 3A schematically illustrates the acoustic ray pattern of the surface / edge diffraction mode in which acoustic waves by the low frequency driver 10 and the high frequency driver 12 are surface / edge diffracted by the reflector cone 16.

FIG. 4A shows the acoustic ray pattern of the control variable impedance diffusion filtering mode in which acoustic waves by the low frequency driver 10 are controlled variable impedance diffusion filtered by the diffusion plate 14. In the same figure, the high energy ray of the acoustic wave is incident outside of the diffusion plate 14 of FIG. 4 (b), and the low energy ray is incident inside of the diffusion plate 14. Accordingly, the high energy ray diffuses through the wider portion 14A-1 on the outside in the slot 14A, and the low energy ray passes through the narrow portion 14A-2 on the inner side of the slot 14A. Pass through and spread. At this time, due to the shape of the slot 14A, the amount of diffusion is higher in the case of the high energy ray than in the case of the low energy ray.

FIG. 5A illustrates an acoustic ray pattern in an aperture reflection mode in which acoustic waves by the low frequency driver 10 are aperturely reflected by the diffuser plate 14. In this case, the acoustic wave hits the edge of the slot 14A and reflects through the slot.

6 (a), the acoustic waves generated by the low frequency driver 10 and the high frequency driver 12 are reflected by the broadband acoustic wave shaping and control system according to the present invention (1 in the figure) and diffraction (2 in the figure). , Diffused (3 in the drawing) and aperture reflection (4 in the drawing) are shown collectively.

The overall physical and acoustical characteristics of the acoustic wave shaping and control system of the present invention are defined in connection with the design of the present invention. That is, the resulting wave representing the acoustic addition of all of the above factors determines the shape of the final or peak wave.

In general, the diffusion plate and the reflector may be made of the same material as the configuration of the enclosure, it is preferable to use a specific type and shape of the material as follows. That is, the diffuser plate and reflector plate are selected from the group consisting of glass fibers, plastics, structural foams, various processed resins such as molds, aluminum bonded to specific sound dampening materials, steel bonded to specific sound dampening materials, and the like. It consists of either. The plastic is any one selected from the group consisting of acrylic, styrene, PVC, and polycarbonate / polypropylene series.

All of the above materials are limited in their intrinsic characteristics, acoustic properties and / or structural preservation. Density, thickness, hardness and stiffness are the basic characteristics to consider in determining the suitability of a material.

In addition, in the above description, "power bandwidth" means a variation within, for example, approximately +/- 3 dB (6 dB = 4: 1 power ratio in total), and "semi-spherical", "pole pattern", " "Polar response", "spatial pattern", "spatial response", and "coverage pattern" all mean that the sound pressure level (amplitude or intensity) boundary is below +/- 3dB (6dB = 4: 1 power ratio), for example. It means a hemispherical pattern of fluctuating true meaning. In addition, the " addition wave " means a point in space where all acoustic wave shaping effects are integrated into one single wavehead. The above "boundary" means a line indicated by an acoustic addition point.

In addition, this invention is not limited to the above-mentioned specific embodiment, A various deformation | transformation and correction can be implemented in the range which does not deviate from the summary and range of this invention.

As described above, according to the present invention, a reflection plate reflecting high frequency acoustic waves emitted from an acoustic source, and a variable impedance diffusion filtering of the acoustic waves in order to maintain a balance between the high frequency acoustic waves emitted from the acoustic source and the low frequency acoustic waves By providing a diffuser plate, it is possible to achieve a true hemispherical acoustic pole pattern from a single overhead sound source in a low ceiling environment.

Claims (9)

In a speaker system, Sound acoustic shaping and control means for distributing acoustic energy of the speaker driver to provide a true spherical pattern of acoustic energy field at approximately three times the diameter of the sound source within the power bandwidth of the system; Speaker system. The method of claim 1, The acoustic wave shaping and control means is attached to the front or baffle of the speaker enclosure. The method of claim 1, The acoustic wave shaping and control means are integrally configured in the enclosure structure by molding. A speaker system having at least one sound source, Sound reflecting means for reflecting high frequency acoustic waves emitted from the sound source; And widespreading means for variable impedance spreading filtering the acoustic wave in order to maintain a balance between the low frequency acoustic wave and the low frequency acoustic wave radiated from the acoustic source. The method of claim 4, wherein The reflecting means is a wideband acoustic wave shaping and control system, characterized in that the conical shape installed in the center of the system. The method of claim 4, wherein The spreading means is a wideband acoustic wave shaping and control system, characterized in that the geometric shape defining a slot and baffle that increases exponentially. The method of claim 6, The slot is disposed radially with respect to the center of the diffusion means, and the wideband acoustic wave shaping and control system, characterized in that the shape is increased as the width advances to the outside. The method according to any one of claims 4 to 7, The diffusing means and the reflecting means is a broadband, characterized in that any one selected from the group consisting of glass fiber, plastic, structural foam, resin, aluminum bonded to a specific sound damping material, steel bonded to a specific sound damping material Acoustic Wave Shaping and Control System. The method of claim 8, The plastic is any one selected from the group consisting of acrylic, styrene, PVC, and polycarbonate / polypropylene-based broadband acoustic wave shaping and control system.