Omni-directional Globular Speaker System

Abstract

An omni-directional globular speaker system employs a substantially globular speaker baffle, a plurality of speakers attached to an entire peripheral surface of the speaker baffle, and means for variably adjusting the audio output of a preferred speaker out of a plurality of speakers. The directivity characteristic of the globular speaker system is omni-directional and of a spherical form when the adjusting means is not yet variably adjusted. The variable adjusting means adjusts the directivity characteristic so that the speaker system will have a specified directivity characteristic of a non-spherical form.

Description

BACKGROUND OF THE INVENTION

This invention relates to an omni-directional globular speaker system and more particularly to a system having omni-directivity and performing similar to a pulsating sphere by using of a globular speaker baffle.

DESCRIPTION OF PRIOR ART

It has hitherto been proposed to provide a pulsating sphere as an ideal type of perfect omni-directional sound radiation system. This pulsating sphere is a sound radiation device which comprises a spherical vibrating diaphragm to expand and contract for radiating sound at the same time having its shape retained in a perfect sphere. The directivity of sound radiation of such a prior art pulsating sphere is perfectly omni-directional and it provides spherical expansion irrespective of its frequencies. As compared with a piston type vibrating sound radiation device having an infinite baffle and using the vibrating surface of a disk of diameter equal to the diameter of the pulsating sphere, the pulsating sphere can achieve, as regards sound radiation, nearly double the output for unit area in a lower audio frequency range where the radiation resistance of air impedance is small.

Thus, a spherical vibrator is more advantageous than a plane vibrator in the respect that it has the desired omni-directivity and a large sound output in the lower frequency range. Therefore, a speaker system using a pulsating sphere is considered most desirable.

It has been theoretically conceivable but practically impossible to obtain a spherical vibrating diaphragm, which radiates sound by expansion and contraction keeping a full spherical form. According to this invention, a sound radiation body similar to the above ideal pulsating sphere is obtained by providing a number of speakers in a spherical enclosure of a globular speaker baffle.

A speaker system is generally required to have omni-directivity but in certain cases it may be required to have a certain directional bias depending on the place of installation, object of use, and program of reproduction of the speaker system. Adjustment of the directivity in such cases however, is not possible with the pulsating sphere system described. Thus, the invention, as described below, provides a number of speakers respectively controlled or controlled in each group as to their directivity so adjust the resultant directivity of the entire speaker system.

SUMMARY OF THE INVENTION

It is a general object of the present invention, therefore, to provide a novel and useful speaker system of the omni-directional globular type which is particularly adapted for practical production.

Another object of the invention is to provide a globular speaker system which is normally omni-directional but can easily and desirably adjusted as to its directivity.

A further object of the invention is to provide a globular speaker system of the omni-directivity type, which has relatively few adjusting means such as attenuators but permits efficient adjustment of the directivity.

These and other objects and advantages of the invention will become apparent from the description set forth hereafter when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is an exploded perspective view for explaining an assemblage of an embodiment of a globular speaker system according to the invention;

FIG. 2 is a vertical sectional view of the globular speaker system shown in FIG. 1 after assembling, with the speaker being taken away;

FIG. 3 is an enlarged view of a joint part of semi-globular shells of the baffle shown in FIG. 2;

FIGS. 4 to 6 are respectively a front view, a back view and a plan view of the globular speaker system after assembling;

FIGS. 7A and 7B are respectively circuit diagrams of a first embodiment of a directivity adjusting circuit of a globular speaker system according to the invention;

FIG. 8 is a directivity characteristic of a globular speaker system in an omni-directional state;

FIG. 9 is a directivity characteristic of a globular speaker system in an adjusted state of directivity;

FIGS. 10a and 10b are respectively circuit diagrams of a second embodiment of the directivity adjusting circuit;

FIG. 11 is a vertical sectional view of another embodiment of the globular speaker system according to the invention;

FIG. 12 is a directivity characteristic in the globular speaker system shown in FIG. 11; and

FIG. 13 is a sound pressure frequency characteristic of the globular speaker system shown in FIGS. 1 to 6.

Now, referring to FIGS. 1 to 3, a globular baffle of one embodiment of an omni-directional globular speaker system according to the invention will be described. Semi-globular baffle shells 11a and 11b are respectively formed in the semi-spherical shape and made by injection-molding a polystyrene resin of low foaming such as,for example, acrylonitrile butadiene styrene (ABS) resin. The ABS resin is molded by foaming at a forming rate of 0.7-0.8 to have sound characteristics like those of wood. The semi-globular shells 11a and 11b are respectively provided with speaker openings 12a-12d of relatively large diameter and speaker openings 13a-13d of relatively small diameter in an arrangement as later described. The semi-globular shells 11a and 11b have respectively folded flanges 14a and 14b at their ends. Tops of the semi-globular shells 11a and 11b are respectively provided with apertures 15a and 15b. The speaker openings 12a-12d and 13a-13d of the semi-globular shells 11a and 11b are respectively provided with woofers and tweeters mounted therein as described later.

In assembling a globular speaker system, semi-spherical metal covers 17a and 17b having a number of apertures for sound radiation punched therethrough are respectively applied over the shells 11a and 11b. Edges of the metal covers 17a and 17b are curved as shown in FIG. 3. These curved portions are inserted into grooves 18a and 18b formed between the flanges 14a and 14b and the semi-globular shells 11a and 11b. Tops of the metal covers 17a and 17 b are also provided with apertures.

A flanged cap nut 19 is inserted into the top aperture 15 b of the semi-globular shell 11b. One end of a connecting rod 20 having screw portions at both ends is screwed with the cap nut 19. The other end of the connecting rod 20 is screwed with a joint 21. The joint 21 is provided with a passage 22 to draw out wires from speakers.

The semi-globular shells 11a and 11b contain speakers therein and are filled with acetate wool, cotton or similar sound absorbing material. The filling material serves for preventing generation of inner standing waves in the globular shell, moderating the characteristics in the higher frequency range, and reducing the cut-off frequency. The top aperture 15a of the semi-globular shell 11a is passed through with the joint member 21. Edges of the semi-globular shells 11a and 11b are attached to each other using a spacer 16 of felt therebetween so as to form a baffle of a globular shape. In this instance, projections and holes (not shown) provided on the joint surfaces of the semi-globular shells 11a and 11b regulate the relative positions of both shells.

A name plate 23 with a mark indicating a front side of the globular baffle is fitted to a joint 21 projecting on the shell 11a and metal cover 17a and thereafter the joint 21 is screwed with a nut 24. As the nut 24 is fastened with the joint 21, the semi-globular shells 11a and 11b are tightly secured to each other through the spacer 16. Therefore, there is obtained a globular baffle 10 of high airtightness. Finally, a rubber belt 25 is applied on the outer periphery of the flange.

The globular speaker baffle 10 of the invention may be readily disassembled in a manner inverse to the above described manner of assembling. The assembling and disassembling operations are made with considerable ease.

In practical use of the globular baffle 10 assembled as above described, a suspension means is attached to the joint 21. The baffle 10 may be suspended from the ceiling of a room. Alternatively, the suspension means with joint 21 may be turned upside down and supported on a floor stand for practical use.

The front view, back view and plan view of the globular baffle 10 are respectively shown in FIGS. 4 to 6. The speaker openings 12a-12d of the semi-globular shells 11a and 11b are respectively provided with, for example, low and medium sound speakers of a diameter 13cm as woofers 30a-30d and, the speaker openings 13a-13d are respectively provided with, for example, high sound horn speakers of a diameter 5cm as tweeters 31a-31d. Here, in the semi-globular shell 11a, the woofers 30a and 30b and the tweeters 31a and 31b are alternately disposed. In the semi-globular shell 11b, the woofers 30c and 30d and the tweeters 31c and 31d are alternately disposed. Furthermore, between the semi-globular shells 11a and 11b, the woofers 30a-30d and the tweeters 31a-31d are provided adjacent to each other in the vertical direction. Thus, the woofers or tweeters each are not positioned at closest intervals between themselves.

The globular speaker system of the above construction has directivity characteristics similar to that of the pulsating sphere. As measured from whatever angle on the peripheral part of the sphere, the same frequency characteristics of sound pressure can be obtained as shown in FIG. 13. The figure shows the result of measurement obtained at a position 50cm apart from the globular baffle surface with a constant input of 2.8 volt. In the figure, Curve I shows an output sound pressure level, Curve II an impedance characteristic, Curve III the second harmonics, and Curve IV the third harmonics, respectively. The characteristics of directivity represented by the output sound pressure levels are illustrated in FIG. 8. As will be apparent from FIG. 8, the characteristic of the spherical omni-directivity is nearly perfect.

Now, a first embodiment of the directivity adjusting circuit of the globular speaker system is described. In FIG. 7A, a signal to be sounded is applied between input terminals 32a and 32b. The terminals 32a and 32b are respectively connected to pin terminals 34a and 34b of a 4-pin plug 33. A pin terminal 34c of the plug 33 is connected to a slider 35a of an attenuator 35. An end of one resistor 35b of the attenuator 35 is connected to the terminal 32a and an end of the other resistor 35c is connected to the terminal 32b.

In FIG. 7B, a socket 36 has perforated terminals 37a-37c, which are respectively inserted with pin terminals 34a-34c of the plug 33. The woofers 30a and 30c in series connection and tweeters 31a and 31c in series connection are connected in parallel between terminals 37a and 37b. Also, the woofers 30b and 30d in series connection and tweeters 31a and 31c in series connection are connected in parallel between terminals 37a and 37c. In the figure, the capacitance of capacitors 38a and 38b are respectively 1 .mu.F and, inductance of coils 39a and 39b are respectively 0.77 mH.

For adjustment of the directivity characteristics, the slider 35a of the attenuator 35 is slidably moved. The woofers 30a and 30c and the tweeters 31a and 31c disposed in the front part of the globular baffle 10 are directly connected through terminals 37a, 37b and 34a, 34b to the input terminals 32a and 32b. Therefore, the woofers 30a and 30c and the tweeters 31a and 31c are not affected by adjustment of the attenuator 35. The globular speaker system has thus constant directivity always in front of the globular speaker system. When the slider 35a is in a position of maximum resistance on the resistor 35b (in a position of zero resistance on the resistor 35c), the woofers 30b and 30d and the tweeters 31b and 31d on the rear side of the globular baffle 10 radiate sound in the same way as the above-mentioned front speakers. Then, the total directivity characteristic of the globular speaker shows omni-directional characteristics with spherical expansion.

When the slider 35a is slidably moved in the direction in which the resistance of the resistor 35b becomes small(namely in the direction in which the resistance of the resistor 35c becomes large), the rear surfaces speakers 30b, 30d, 31b and 31 d are affected by attenuation and their sound volume decreases. If the slider 35a is moved to a position in which the resistance of the resistor 35b becomes zero (namely in the direction in which the resistance of the resistor 35c reaches its maximum), the direct sound volume from the rear surface speakers turns substantially to zero. FIG. 9 shows the directivity characteristics in case only the front speakers radiate sounds and the rear speakers do not radiate sound. If the slider 35a is continuously moved, the directivity characteristics of the globular speaker system can be changed from the omni-directivity as shown in FIG. 8 to the state of large directivity continuously in a specified direction as shown in FIG. 9.

A second embodiment of the directivity adjusting circuit is illustrated with reference to FIGS. 10A and 10B. As shown in FIG. 10A, input signals are applied respectively between the input terminals 40a and 40b, between terminals 40c and 40d, between terminals 40e and 40f, and between terminals 40g and 40h. The terminals 40a, 40c, 40e and 40g are respectively connected through attenuators 41, 42, 43 and 44 to pin terminals 46a, 46b, 46c and 46d of a 5-pin plug 45. Also, the terminals 40b, 40d, 40f and 40h are respectively connected to a pin terminal 46e.

As shown in FIG. 10B, a socket 47 has hole terminals 48a-48e into which the pin terminals 46a-46e of the plug 45 are respectively inserted. On the globular baffle 10, the woofer 30a and tweeter 31a located in the front and upper quarter part of the globular baffle 10 are connected in parallel between terminals 48a and 48e; woofer 30b and tweeter 31b located in the rear and upper quarter part in parallel between terminals 48b and 48e; woofer 30c and tweeter 31c located in the front and lower quarter part in parallel between terminals 48c and 48e; and woofer 30d and tweeter 31d located in the rear and lower quarter part in parallel between terminals 48d and 48e, respectively. Capacitors 49a-49d are respectively connected in series with tweeters 31a-31d and coils 51a-51d are respectively connected in parallel therewith.

Here, for adjustment of the directivity characteristics, the attenuators 41-44 are respectively and individually adjusted for the objective. Thereby, the sound volume is separately adjusted for each speaker group in the front and upper quarter part, rear and upper quarter part, front and lower quarter part, and rear and lower quarter part of the globular baffle. By adjustment of sound volume with respect to these four directions, the overall directivity can be desirably adjusted adequately for the non-globular surface. According to the present embodiment, more varied adjustment can be made in the directivity characteristics than in the previous embodiment.

FIG. 11 is a vertical cross section of a further embodiment of the globular speaker system according to the invention.

Formed similarly as in the above embodiment, a globular speaker baffle 60 is provided with a plurality of speakers 61a, 61b - - - - - . Voice coils 62a, 62b - - - of speakers 61a, 61b - - - - - are respectively connected in series with variable resistors 63a, 63b - - - - - of constant impedance type. The voice coils 62a, 62b - - - - - are interconnected in parallel and further connected to a terminal 64 provided on the baffle 60.

Here, if the resistance value of each variable resistor 63a, 63b - - - - - is adjusted all to zero or the same value, the directivity characteristic of a globular speaker system 65 of the above construction turns to omni-directional in a globular direction. The characteristics in this instance are diagrammatically shown by the broken line A in FIG. 12. For example, if the resistance values of the variable resistors connected to the speakers at the upper part of FIG. 11 are increased and the sound outputs of the speakers are decreased, with the speakers at the lower part unchanged in the sound outputs, the directivity characteristic of the globular speaker system 65 turns to the directivity characteristic of a nearly heart shape as shown by curve B in FIG. 12. Furthermore, as shown in FIG. 11, the resistance value of the variable resistor connected to the speakers on the right and left sides will increase and the speakers on the upper and lower sides may not be changed. Then, the directivity characteristic of the globular speaker system 65 turns to bi-directional as shown by curve C in FIG. 12. In another case, each variable resistor 63a, 63b - - - - - may be properly adjusted so as to obtain desired directivity characteristics. In such a case, all speakers can be respectively adjusted for the best sound output. According to the present embodiment, the directivity characteristic can be precisely adjusted and desired directivity characteristic can be obtained.

Claims

What we claim is:

1. An omni-directional globular speaker system comprising: two semi-globular complementary baffel shells, each of said semi-globular shells having a folded flange formed at a peripheral edge thereof and provided with a plurality of apertures for sound speakers which open to the peripheral surface of each said semi-globular baffle shells, said two semi-globular baffel shells abutting at said peripheral edges thereof and forming a compete globular baffle assembly, said peripheral edges of the semi-globular baffle shells being provided with projections and mating recesses so that the projections and recesses of one of the semi-globular baffle shells complementarily fit into respective recesses and projections of the other semi-globular baffle shells; two semi-globular cover members perforated with apertures for sound transmission and respectively disposed substantially concentrically covering said semi-globular baffle shells, each said semi-globular cover having a curved edge which is inserted into a groove formed between the folded flange and the semi-globular baffle shells; and jointing means passing through the top of said semi-globular baffle shells and said semi-globular cover members, said joining means including a connecting rod extending within the globular baffle assembly and having grooved portions at ends thereof, a cap nut being screwed with one of the screwed end portions of the connecting rod through the top of one of the semi-globular baffle shells and one of the semi-globular covers, a joint member screwed with the other screwed end portion of the connecting rod through the tops of the other semi-globular baffle shells and the other semi-globular cover, and a nut screwed with the joint member for fastening the globular baffle assembly.

2. The omni-directional globular speaker system as claimed in claim 1, wherein said joint member is provided with an opening in the form of a passage to draw out wires from the speakers.

3. The omni-directional globular speaker system as claimed in claim 1 wherein said plurality of speakers comprises a plurality of woofers and a plurality of tweeters, said plurality of woofers and tweeters being respectively disposed on said globular baffle assembly in such locations that each woofer and each tweeter is disposed adjoining each other at smaller interval than intervals between adjacent woofers and intervals between adjacent tweeters.

4. The omni-directional globular speaker system as claimed in claim 3 wherein each of said woofers and its adjoining tweeters are grouped in a group, and said woofers and tweeters form a plurality of such groups, the woofer and tweeter in each group being connected in parallel, the speaker system further comprising as many variable resistors as there are said groups, said variable resistors being respectively connected in series to the parallel combinations of the woofer and the tweeters for adjusting the sound output of the woofer and the tweeter in each group.