JPS6150559B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to loudspeaker systems, and more particularly to systems capable of reproducing sound with a high degree of accuracy and without distortion.

Conventionally, most high-volume, low-distortion loudspeakers capable of reproducing sound in the 35 to 40 cycles/second range have a low frequency speaker (hereinafter referred to as a woofer) facing the listener. The cone diameter of this woofer is at least 25.4cm to 30.5cm
(10 to 12 inches), and the innermost 7.6 cm or 10.2 cm (3 or 4 inches) of this cone is structural due to the stress created in the cone by the heavy forces from the woofer's voice coil. subject to distortion. This structural distortion causes a disturbing amount of distortion in the reproduced audio. Although this distortion is slight, it occurs in the frequency range of 500 to 1500 cps, which is the lowest part of the lowest frequency range accessible to the human ear, when measured relative to the full output of the speaker system. This distortion (hereinafter referred to as central cone distortion)
It produces an intermittent screeching sound that is particularly pervasive in the mid-range frequencies of instruments such as pipe organs and violins.

Traditionally, to eliminate this center cone distortion, frequencies above 500 cps from the woofer are canceled. Various proposals were made, including the installation of an electrical crossover network and the installation of large mid-range speakers capable of reproducing sound below 500 cps. However, even with such a method, a significant ghost of central cone distortion appears in the woofer, and its own central cone distortion appears at the upper end of the frequency band to which the human ear is most sensitive (typically expensive occurs from ). 4000 to 6000 cps or if possible, depending on the specific design of the large midrange speaker
Central cone strains in the low range of around 2500 cps are expected to occur. Attempts have been made to eliminate center cone distortion from speaker systems by installing damper members in the center region of the woofer cone. Adding a damper member to the woofer cone violates the basic principle of low strain woofers, which is to keep the inertia of the cone mechanism as low as possible. Therefore, the added components had the disadvantage of significantly distorting the woofer at significantly lower frequencies.

Another problem with traditional loudspeaker systems is that high frequencies have a more linear transition and need to be reflected to turn corners.
The problem is that the distribution of sound at the upper end of the frequency range covered by the woofer is poor. This effect becomes a significant factor above about 500 cps. Conventionally,
Various loudspeaker systems used woofers designed to cut off at 1000 to 1500 cps. The linearity of the propagation of the frequencies these woofers emit at 500 to 1500 cps means that these frequencies form a narrow band along the axis of the speaker. These frequencies have a poor distribution, while frequencies below 500 cps have a good distribution due to their non-linearity.

Another problem with conventional loudspeaker systems concerns the shape of the woofer response curve. Ideally, the highest volume of playback should be generated at the lowest audible frequency. However, in reality, most good quality woofers have a peak or "knee" in their response curve at the highest volume of audio, which occurs at about 1000 cps, due to distortion in the center of the cone. This peak or protrusion appears just below the crossover point between the woofer and the midrange speaker and produces a metallic sound that is rarely resolved in the electrical crossover network described above. The frequency range that is most sensitive to the human ear is 1000 and
Since the frequency is between 3000cps, the woofer is approximately
It is cut off at 1000cps, and the midrange speaker is approximately
Preferably, the cone can take over 1000 cps or more, has a small, low-inertia cone that reproduces the loudest frequencies, and has as little distortion as possible.

To solve the problem of central cone distortion, it has been proposed to use a cone with a non-metallic layer sandwiched between the inner and outer metal members to improve the strength of the cone and eliminate the above-mentioned distortions. Ta. Hitachi's metal cone loudspeaker (1977)
Published in October, Stereo Review Magazine No. 12
) are such types of speakers. Tanoy speakers (published June 1977, stereo
Review (described on page 107) is a speaker cone that uses rib members to prevent damage or distortion of the cone due to stress.

Another attempt to avoid central cone distortion is
The idea was to use strong carbon fiber in the paper cone.

From the outer edge of the cone to the voice coil in the center of the cone, there are at least three factors that increase stress in the loudspeaker cone:

(1) The area of the cone is increased by the second power of the diagonal height of the cone. Therefore, the air resistance to cone movement is increased by the second power of the cone's diagonal height.

(2) The outer part of the cone is constructed by simultaneously generating half waves of sound waves so that the inner part of the cone can withstand not only the pressing force of the air but also the force from the outer part. Since a compressive or tensile force is applied along the diagonal height, it is necessary to add another first power.

(3) Since the cross-section of the paper cone that needs to transmit force to the voice coil reduces the diagonal height, the stress of this mechanism is the first power that is directed toward the voice coil along the diagonal height of the cone. increases as

As mentioned above, the stress along the diagonal height of the cone increases as at least the fourth power is directed from the outside of the cone to the voice coil. Approximately 0.25
The total combined compressive force in a paper cone that is approximately 0.01 inch thick is greater than 1 pound near the center of the cone. This produces a unit stress on the order of about 10 kg (20 pounds) per inch square. Although this is considered a significantly small unit stress, it is sufficient to compress the internal 1 inch slope distance by about 0.0064 mm. However, there is a fourth power that creates a stress that greatly reduces the distance away from the voice coil, so that the portion of the cone 2.54 cm (1 inch) outward from the voice coil under the same conditions is 0.0004
compressed by mm. As you can see from this,
A cone with an internal diameter of 9.1 cm (3 1/2 inches)
About 16 times more strain than the paper cone sections in the 8.9 cm (3.5 inches) and 14.0 cm (5.5 inches) range.

It is understood that the distortion in question here is caused by a compressive or tensile force so weak that it is impossible to measure, and at a volume loud enough to be heard by the human ear.

US Pat. No. 1,786,279 (Wolf) and US Pat. No. 2,643,727 (Leon) disclose reflective mechanisms for speaker systems. However, these patents show a reflective mechanism that extends across the center of the speaker, so that the reflective mechanism reflects almost all of the sound output from the speaker. Therefore, it has been impossible for such a reflection mechanism to discriminate the sound emitted from the speaker. U.S. Patent No. 2037185 (Saras) and U.S. Patent No. 27170.47 (Butukuman)
Both patents disclose loudspeaker systems having a damper-like member mounted near the center of the speaker cone; There is no disclosure of using a damper member combined with a reflecting mechanism and placed in place to reflect only the reflected light.

The present invention provides: (a) an outer box forming a sound chamber having a front wall with an opening from which sound is emitted; and (b) an outer box attached to the outer box adjacent to the sound emitting opening. a loudspeaker cone flared forward in the orientation, the loudspeaker having a central portion that produces a distorted sound during operation, an outer portion that produces a substantially non-distorted sound during operation, and at least one a reflecting mechanism is mounted outside the outer box and in front of the external portion of the loudspeaker cone, and the undistorted sound reflected from the reflecting mechanism extends forward along the axis of the loudspeaker cone. A loudspeaker system of the type configured to reflect only said undistorted sound from an external portion of a loudspeaker cone so as to be directed outwardly of said outer box at an angle of at least 90° from a line. When using this loudspeaker system, make sure that the distorted sound coming from the middle part is not directed directly towards the listener.
The cone is placed 90° away from the listener. At least one reflection mechanism is placed to reflect only undistorted sound from the outer portion of the speaker cone toward the listener, and to distribute this sound over a wide area on the listener's side. Preferably, a damper pad is placed along the cone axis of the woofer to interrupt and eliminate distortion in the central cone. Proper placement of these components produces virtually distortion-free sound, with good distribution at the upper end of the woofer's frequency range, close to the ideal response curve, and provides inexpensive and simple amplification. A container system may be provided.

Next, one embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to this embodiment.

In FIG. 1, which is shown in detail to provide a better understanding of the invention, the outer box 10 is formed of wood or other suitable material. A low frequency speaker or woofer 11, an intermediate frequency or midrange speaker 12, and a high frequency speaker or tweeter 13 are placed in this outer box.

The woofer 11 has a paper cone 14 that vibrates due to the current induced in the voice coil 16 under the influence of the magnetic field in the magnet 17. This voice coil 1
6 generates a fairly heavy force on a relatively weak paper cone, and at the same time the cone 14 is required to be lightweight and is therefore made thin to minimize inertial forces.

Because the force applied to cone 14 is high and the strength of the cone is low, cone 14 will undergo some deformation or strain due to the stress created by voice coil 16. When the central portion of the cone 14 is deformed, a distorted sound is produced from the central portion of the cone in the area indicated by "X" in FIG. Since the damper pad 18 is fixedly supported by the bracket 19, it absorbs most of the distortion sound coming from the central cone. Spreads through the pads. No matter how weak the distortion sound,
Because it propagates in a straight line, most of it is wasted and radiated away from the listener.

A reflection mechanism 2 fixedly supported in front of and near the speaker cone 14 by a stud 22.
1 is attached. This reflection mechanism 21 is
It is positioned and shaped to reflect only sound from the outer, non-distorted portion of the woofer cone 14, indicated by "Y". In a most preferred embodiment, the reflective mechanism 21 is a tissue surface 2 of a thin sheet of fibers or other sound absorbing material.
By optimizing the sound reflection at the upper end of the woofer response curve for having a reduced ideal response curve. By using an appropriately shaped reflection mechanism, preferably a parabolic reflection mechanism, the approximate linear audio frequency can be
It can be radiated in a wide band designated "Z". Because most midrange speakers produce good sound, there is usually less radiation at the upper end of the woofer frequency.

Although a modified parabolic reflection mechanism as shown at 21 in FIG. 1 is preferred, it should be understood that good results may be obtained using reflection mechanisms having various other shapes. For example, FIG. 2 shows a V-shaped reflection mechanism 21a, which can be used to obtain favorable results.

The reflector may take the form of two separate surfaces adapted to cooperate with each other to act as a concave reflector. An example of this type of composite reflection mechanism is shown in FIG. 3, in which the support bracket 20 is positioned so that the two planar reflection mechanisms 21b cooperate to form a concave reflection mechanism.
It is maintained by FIG. 4 shows another embodiment of the composite reflection mechanism, in which the bracket 24
By fixing and holding the two curved reflecting members 21c, these members cooperate to provide the function of a concave reflecting mechanism.

In some cases, it may be desirable to use more than one woofer 11. The advantages of the invention are equally applicable to speaker systems having one or more woofers, as shown in FIG. Although the embodiment shown in FIG. 5 uses two reflection mechanisms, it can provide an excellent frequency distribution at the upper end of the woofer response curve.

By using one or more reflection mechanisms 21, it is not necessary to provide one or more woofers in order to obtain excellent low-frequency and mid-range distribution characteristics. FIG. 6 shows that one reflection mechanism 21 is placed on each side of the woofer 11. In Figure 6, bracket 2
6 straddles between the reflection mechanisms 21 and holds the damper pad 18 in an appropriate position.

In the graph of FIG. 7, the approximate response curve for a 10-inch acoustic suspension speaker facing the listener is shown by the solid line 27, and the approximate response curve for the same speaker rotated relative to the listener is shown by the solid line 27. The response curve is shown by dotted line 28. Most conventional woofers have distortion in the central cone, so the highest volume of the reproduced sound cannot be obtained at the lowest audible frequency, and as shown by solid line 27, there is a peak in the response curve at the highest volume sound, which occurs at about 1000 cps. or have sharp protrusions. This peak or bulge in the woofer response curve occurs just below the intersection between the woofer response curve 27 and the midrange speaker response curve 29, and is a high-frequency component that can hardly be removed by electrical crossover networks. will occur. The response curve of a high frequency speaker or tweeter is shown at 31. The smooth, non-sharp response curve obtained with the loudspeaker according to the invention is indicated by the dotted line 32.

As mentioned above, the loudspeaker according to the invention is capable of reproducing sound without distortion, and by keeping the mass of the speaker cone sufficiently low, distortion can be prevented from occurring to a disturbing extent. Furthermore, the loudspeaker system according to the present invention has a simple configuration, can be manufactured at low cost, and can save assembly time and labor.

Although the present invention has been described with respect to one embodiment thereof, it will be apparent that various modifications and variations may be made by those skilled in the art in accordance with this disclosure.

[Brief explanation of the drawing]

1 is a longitudinal sectional view showing an embodiment of a loudspeaker system according to the invention having a woofer that does not face the listener, a reflection mechanism fixed thereto and a damper pad; FIGS. 2, 3 and 4; FIG. 5 is a partial sectional view showing another embodiment of the reflection mechanism; FIG. 5 is a longitudinal sectional view showing an embodiment of the loudspeaker system according to the invention having two woofers to which a reflection mechanism and a damper pad are fixed;
FIG. 6 is a longitudinal cross-sectional view of an embodiment of a loudspeaker system according to the invention having two reflection mechanisms mounted on a single woofer to improve the midrange frequency distribution; FIG. 2 is a graph showing approximate response curves for a 10-inch acoustic suspension loudspeaker and its associated improved reflection mechanism when oriented toward the listener and toward a non-listener. 10...Outer box, 11...Low frequency speaker or woofer, 12...Middle range speaker, 13
...High frequency speaker or tweeter, 14...
... Cone, 16 ... Voice coil, 18 ... Damper pad, 21 ... Reflection mechanism.

Claims (1)

[Scope of Claims] 1. (a) an outer box forming a sound chamber having a front wall with a sound emitting opening; (b) an outer box adjacent to the sound emitting opening; A loudspeaker consisting of a mounted outward-facing, forward-expanding loudspeaker cone, the innermost part of which produces the most distorted sound, and the outermost part of which produces the least distorted sound. In the system, at least one reflection mechanism 21 is provided outside the outer box 10 and in front of the loudspeaker cone 14, and the sound reflected by this reflection mechanism is directed forward along the axis of the loudspeaker cone 14. The outermost edge of the reflection mechanism is directed outward of the outer edge of the loudspeaker cone and forward of the axis of the loudspeaker cone, such that it is guided toward the outside of the outer box at an angle of at least 90° from the extended line. A loudspeaker system characterized in that the loudspeaker system is positioned radially outside the outer box with respect to a line extending from the outside. 2. The loudspeaker system according to claim 1, wherein the reflection mechanism 21 is made of a material having a tissue surface that directly directs the higher frequency reflected from the external portion of the loudspeaker cone to the outside. . 3 a plurality of reflection mechanisms 21 are connected to the loudspeaker cone 14;
3. A loudspeaker system as claimed in claim 1, wherein the loudspeaker system is placed at a remote angle in front of the external part of the loudspeaker system. 4. Claims 1 to 3, wherein the reflection mechanism 21 is formed to have a concave cross section.
Loudspeaker system according to any of paragraphs. 5. The loudspeaker system according to any one of claims 1 to 3, wherein the reflection mechanism 21 is formed to have a parabolic cross section.