US 3111189 A
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Nov. 19, 1963 T. R. SCHOLL ELECTRODYNAMIC LOUDSPEAKER 2 Sheets-Sheet 1 Filed Jan. 12, 1962 7050001?! A. JLI/Ull Nov. 19, 1963 T. R. scHoLL ELECTRODYNAMIC LOUDSPEAKER 2 Sheets-Sheet 2 Filed Jan. 12, 1962 1N VENTOR.
7/11? 000! A. SCI/01 l wmwm floil ATTORNEYS United States Patent 3,111,189 ELECTRODYNAMHC LGUDSPEAKER Theodore R. Scholl, 5007 47th NE., Seattle, Wash. Filed Jan. 12, 1962, Ser. No. 165,741 21 Claims. (Cl. 181-32) The present invention relates to electroacoustic devices, and more particularly to dynamic loudspeakers of the socalled single diaphragm type.
According to the present invention, a loudspeaker diaphragm is configured to be elongated in one face dimension and laterally inset at generally intermediate but somewhat off-center side portions so as to provide a unique viol shaped diaphragm edge configuration providing an effective piston area wherein the end areas are geometrically similar with one somewhat larger than the other, the larger end area constituting a woofer zone, while the somewhat smaller end area constitutes a mid-range zone, and the relatively narrow or necked connecting area therebetween constitutes a tweeter zone, the configuration and construction of the tweeter zone accomplishing what may be termed dynamic decoupling between the woofer zone and mid-range zone so that the speaker is essentially dynamically balanced even though somewhat nonsymmetrical constructionally.
As a direct consequence and primary advantage of the loudspeaker diaphragm configuration here presented, with varying radial dimensions in the various woofer, midrange, and tweeter zones of the diaphragm piston area, a wide and continuous range and spectrum of natural frequency modes are available, the lowest natural frequency mode of the diaphragm piston area being determined by the largest radial dimension thereof in the woofer zone and the highest natural frequency mode of the diaphragm piston area being determined by the smallest radial dimension of the tweeter zone piston area. To augment the dynamic separation of the woofer and mid-range zones, the wall of the tweeter zone is relatively stiff, and the walls of the mid-range and woofer Zones are each relatively less stifi". Thus, the relatively stiff tweeter zone surrounding the diaphragm driving element serves to balance the vibration excursions of the diaphragm, since the primary ordominant impedance of the diaphragm as seen by the motor element is that of the tweeter zone, so that whatever impedance unbalance arises from the relative difference in geometry of the woofer and mid-range zones does not materially unbalance the vibration excursions of the diaphragm.
It is also an important feature and characteristic of the unique speaker diaphragm configuration of the pres .ent invention that the viol shape edge configuration thereof is substantially the same shape as many instruments creating music reproduced by the speaker, and therefore has a greater capability of achieving similar natural resonance characteristics.
Any imperfection in loudspeaker fidelity is most discernible when the sound being reproduced comprises music played by stringed musical instruments. Violin music is commonly and particularly notable in this respect in that its true tonal qualities are notoriously diiiicult to reproduce. The Viol-shaped speaker diaphragm here presented has a periphery with a geometry quite similar to the resonance boxes of stringed instruments of the viol family, and'therefore has a range and spectrum of nat ural resonance frequency modes functionally compara ble to that of the instruments themselves. The speaker of the present invention is thus ideally and uniquely configured for accurate electroacoustic reproduction of music played by stringed instruments. It is physically shaped like, and therefore geometrically tuned to such instruments, and the performance of the speaker in this respect is demonstrably superior to conventional round or oval loudspeakers of comparable quality of construction.
Other objects, advantages and characteristics of the present invention include; the provision in an electrodynamic loudspeaker of the single diaphragm type of optional means to accentuate high frequencies by surface coatings on all or part of the diaphragm piston area, such a surface coating preferably having particulate, crystalline material therein over certain portions of such diaphragm piston area; the provision of optional diaphragm housing arrangements, certain of which provide a degree of control of rear air impedance so as to augment the high frequency performance characteristics of the tweeter zone portion of the diaphragm; provision of a single diaphragm loudspeaker design having essentially the frequency re sponse characteristics of multiple-speaker systems without the cost or complexity thereof; and provision of extended range single diaphragm loudspeakers which can be fabricated essentially as simply as and at essentially the same cost as conventional round or oval single diaphragm speakers of comparable size.
These and other inherent objects, features, advantages and characteristics of the present invention will be apparent from the following discussion of certain typical and therefore non-limitative embodiments thereof, taken together with the accompanying drawings, wherein like letters and numerals refer to like parts, and wherein:
FIG. 1 is a front face view of a loudspeaker according to the present invention;
FIG. 2 is a rear view of the speaker shown at FIG. 1;
FIG. 3 is a side view of the speaker shown at FIGS. 1 and 2;
FIG. 4 is a top view of the speaker shown at FIGS. 1-3;
FIG. 5 is a view in longitudinal cross section of the speaker shown at FIGS. 1-4, taken substantially along line 5-5 of FIG. 1;
FIG. 6 is a cross sectional view of the speaker shown at FIGS. 15 taken substantially along line 6-6 of FIG. 1; and
FIG. 7 is a front face view of a somewhat modified form of loudspeaker according to the present invention, utilizing a non-symmetrical surface coating in predominantly the mid-range and tweeter zones of the diaphragm piston area, and further incorporating a tweeter zone radiator at the diaphragm apex.
The permanent magnet type electrodynamic loudspeaker shown in FIGS. 1-6 comprises a concave openfaced diaphragm collectively designated DW, DT, DM and a motor or driver element generally designated M, the diaphragm edge and motor M being structurally attached to a rear housing or frame H. The piston area of the diaphragm, collectively designated 10W, 10T, 10M, includes a series of compliance or stiffening ribs 11 and is joined by a flexible annulus 12 to a rigid housing edge 14 extending along the periphery of the diaphragm, and a cushioning ring 16 is in turn attached to the housing edge 14. Mounting holes, certain of which are indicated at 18, are provided for mounting of the speaker in an enclosure or the like in the usual manner.
Any desired number of compliance rings 11 and flexible annuli 12 can be provided, the basic purpose of the latter being simply that of providing a relatively flexible decoupling between the piston area 10W, 10T, 10M and the retained diaphragm peripheral edge. It is important, however, that the diaphragm wall be relatively more flexible inthe portions thereof more remote from the diaphragm apex and be relatively stiff in the portions thereof immediately around the diaphragm apex, i.e. in the portions thereof within the central diaphragm area DT, in order to enhance the dynamic decoupling of the diaphragm areas DW, DM, as hereinafter more fully discussed.
Diaphragm DW, DT, DM is suitably constituted of pressed paper stock or like pliant material which without surface finish or stiffening coating is relatively soft, and in the embodiment of the invention shown at FIGS. 16 the major portion of the diaphragm piston area 10W, 10T, 10M out to the first compliance ring 11 is coated with a stiffening agent such as shellac, starch or the like, as. shown in FIG. 1 by light stippling. Preferably, also, the immediate area surrounding the diaphragm apex, i.e. piston area portion 10T is more heavily coated with the stiffening agent, as shown in FIG. 1 by heavy stippling, to augment high frequency response and relatively increase the impedance of the central diaphragm area DT. In addition, it has been found advantageous from the point of view of increasing high frequency response to include in the stiffening coatings a particulate crystalline material such as burnt amber crystals.
As will be evident, a considerable latitude is available as to the arrangement of a stiffening coating in the various piston area portions 10W, ltiT, 10M (noting FIG. 7 and the discussion thereof below, for example) and it is a practical feature of the loudspeaker diaphragm configurations of the present invention that if in production a given speaker or speaker design evidences some dynamic unbalance or undesired frequency response pattern, such can be compensated for to a considerable degree simply by appropriate non-symmetrical application of a stiffeningcoating to more nearly equalize the impedance of the piston area end portions 10W, 10M.
The construction and fabrication of the rear housing H can be accomplished in any desired manner known per se, so long as at least the major diaphragm piston area is suitably vented to reduce rear air impedance, as by cutouts, open framing or vent holes of any desired size, such as the various vent holes provided in rear housing H and indicated in certain instances at 20. It has been found preferable, however, to provide a solid wall structure in the areas of housing H directly to the rear of the central diaphragm area DT, to improve the impedance and high frequency response thereof.
The speaker drive mechanism or motor M can suitably be a type conventional per se, For example, as shown at FIG. 6, the motor M can be of the permanent magnet type, presenting a pole piece 22 to a so-called moving coil or voice coil 24 wound on a short sleeve 26 attached to the apex hole of the diaphragm, the vibration excursions of moving coil 24 being transmitted through sleeve 26 to the diaphragm. A flexible annular spider 28 seals the motor M in the conventional manner. Also in a manner conventional per se, a dome 30 caps the diaphragm opening around the moving coil 24 and pole piece 22. As will be understood, vibration excursions of sleeve 26 occur perpendicularly of the face plane of the speaker (coincident with ring 14), in the same manner as characteristic of conventional electrodynamic loudspeakers.
Turning to a more specific consideration of the characteristic configurations of diaphragm DW, DT, DM and piston area 10W, 10T, 10M, it will be seen from the accompanying illustrations the face configuration is characterized by: a lower (as shown), relatively wide, relatively large end area DW (with piston area 10W), constituting a woofer zone; an upper (as shown), somewhat less wide and somewhat lesser area end portion DM (with piston area 10M) constituting a mid-range zone; and a narrow, smaller area throat or necked portion DT (with piston area 10T), constituting a tweeter zone.
characteristically, also, the diaphragm and piston area configurations are symmetrical laterally of the major axis of the speaker and somewhat non-symmetrical along such major axis. This diaphragm configuration is describable simply as an elongated, centrally constricted sloped-wall diaphragm, with a major end lobe (DW) and a minor end lobe (DM) having a relatively constricted connecting portion (DT) therebetween, the major axis of the diaphragm face (section line 5') bisecting said lobes and the diaphragm apex (with the motor element or moving coil 24) of the speaker being situated so that the axis of movement thereof is substantially perpendicular to and coincident with said major axis substantially at the relatively constricted connecting portion between the end lobes.
Considering the diaphragm configuration of the speaker shown at FIGS. l6 in yet another aspect, the wall of the piston area 10W, 10M, NT is seen to variously presentrelatively small acute angles with reference to the fiat face plane of the speaker where the radii of such piston area are relatively long (10W, 10M) and present relatively large acute angles thereto where the radii of such piston areas are relatively short (10T), with progressive and continuous intermediate variations in wall angles and length of radii. Consequently a wide range and good spectrum of natural frequency modes are avail able, the shortest, lateral radii in the piston area 101 of the tweeter zone being only about one-fifth (for example) the length of the effective radii of the piston area ltiM of the mid-range zone, which are in turn about four-fifths (for example) the radial length of the opposite radii in the piston area 10W of the woofer zone.
The relatively abrupt wall angles at the sides of the tweeter zone also serve the advantageous purpose of providing good lateral dispersal of high frequencies.
The dominant impedance presented to the vibration excursions generated by movement of moving coil 24 is that impedance generated by the structural characteristics of the tweeter zone DT. As a consequence of this, the relatively lesser impedances characteristic of the midrange piston area 10M and the woofer piston area 10W do not materially manifest any dynamic unbalance to the diaphragm as a whole even though they may be somewhat unlike in impedance because of the non-symmetry of the speaker configuration along its major axis. The structural non-symmetry of the woofer and mid-range zones can thus be said to be essentially dynamically decoupled by the laterally narrow and relatively stiff tweeter zone therebetween.
The open-faced diaphragm edge configuration here presented is for simplicity also describable as of vio shape, employing the term viol by analogy to the usage thereof in the field of stringed instruments, wherein it denotes a type of instrument having a hollow resonance box or enclosure with a constricted or necked region separating two relatively large end regions which are geometrically similar, with one slightly larger than the other.
FIG. 7 shows a somewhat modified form of speaker also characteristic of the invention, constructed and configured like that shown in FIGS. 1-6 except that the piston area 10W, 10T, 10M has (as shown by stippling) a stiffening coating applied thereto which extends over most of the mid-range piston area 10M out to the first compliance ring 11 and over all of the tweeter piston area WT but not over the woofer piston area 10W. Also, in a manner conventional per se, a conical dispersal cone or radiator 32 stands outwardly from the diaphragm apex, as by being cemented to the edge of dome 30, to augment the relatively abrupt sides of the tweeter zone in providing a good highs dispersion pattern. As earlier discussed, the non-symmetrical stiffening coating, applied as shown in FIG. 7 to the tweeter zone and but one lobe of the diaphragm, increases the effective impedance of that lobe, while the non-stiffened larger lobe provides maximum lows response and the radiator 32 further extends the highs response.
To illustrate a typical dimensional pattern for a speaker according to the present invention, the speaker shown at FIGS. 1-6 can have an overall diaphragm area the same as a round conical speaker 15 in overall diameter, the specific dimensions thereof measured edge to edge of the housing frame being 19" along the major axis, 12" at the widest lateral dimension in the major lobe, 9" in the widest lateral dimension in the minor lobe, and 6.
across at the narrowmost lateral dimension, the cone depth from face plane to apex being 1%, and the motor having a 2" voice coil and a 1-3 lb. permanent magnet. The relatively quite shallow depth (1%") of the cone, along with commercially available shallow or inverted motor units, makes practicable the use of the speaker with quite thin enclosures, or as a built-in installation in a wall, for example. It will be of course understood that the speaker can be any desired size so long as the essential viol shape edge configuration is preserved. As will also be apparent, any suitable type of motor or equivalent driver can be used. It is also possible to adapt the basic diaphragm configuration to exponential horn applications. Usage of various size speakers in concert, all with a viol-shaped edge configuration, or with only a part of the speakers with a Viol-shaped edge configuration, are of course also readily possible.
From the foregoing, further diaphragm geometry and pattern variations, as well as various other constructional modes characteristic of the present invention will be apparent to those skilled in the art to which the invention is addressed, within the scope of the following claims.
What is claimed is:
1. An electrodynamic loudspeaker having an open diaphragm face sloping from a single apex to a planar edge of substantially viol shape.
2. An electrodynamic loudspeaker comprising an openfaced diaphragm with a. planar edge of essentially viol shape, the diaphragm apex area being substantially between the laterally narrowmost edge portions of the diaphragm, and the said loudspeaker further comprising motor means in driving relation to said diaphragm apex area.
3. An extended range dynamic loudspeakercompr-ising a sloped-faced diaphragm with a single diaphragm apex, a motor element coupled to the diaphragm apex, a rigid frame mounting said motor element and rigidly retaining the edge of said diaphragm, the sloped-face configuration of said diaphragm being characterized by a planar edge and by a wide, relatively large lower piston area and a somewhat less wide upper piston area with a smaller, relatively narrow intermediate piston area therebetween, the diaphragm apex being in said intermediate piston area and the said motor element being situated to directly drive said narrow intermediate piston area.
4. An extended range dynamic loudspeaker comprising an open-faced diaphragm radiating from an apex occupied by a single motor element and having at least one compliance ring situated near the edge thereof, which edge is in turn affixed to a rigid frame through a flexible annulus, the face configuration of the diaphragm being that of a large area major lobe and a somewhat lesser area minor lobe with a relatively constricted lobe connecting area therebetween, the major axis of the diaphragm face bisecting said lobes, and the diaphragm apex being situated in said relatively constricted lobe connecting area.
5. An extended range dynamic loudspeaker comprising an open-faced diaphragm with a motor element positioned at the diaphragm apex, said diaphragm being flexibly joined at its edge to a rigid frame extend-ing peripherally of the diaphragm, the face configuration of the diaphragm and frame being characterized by a wide, relatively large lower area and a somewhat less wide upper area with a relatively small and narrow intermediate area therebetween, the radial angles of the diaphragm wall with respect to its face plane being substantially inversely related to the corresponding radial dimensions thereof.
6. An electrodynamic loudspeaker having a sloped- Wall, open-faced diaphragm of elongated and necked edge configuration, the necked portion of the diaphragm edge being situated somewhat non-symmetrically of the ends thereof, with one end area of said diaphragm being slightly larger than the other end area so that the larger 6 end area essentially provides a woofer zone, the smaller end area essentially provides a mid-range zone, and the necked diaphragm area therebetween essentially provides a tweeter zone, all driven by a motor element situated in said tweeter zone.
7. A loudspeaker according to claim 6, comprising a dispersal cone situated in said tweeter zone.
8. An extended range dynamic loudspeaker comprising a motor element and an open-faced sloped-wall diaphragm emanating therefrom to flexible annulus means in turn attached to a rigid frame of essentially Viol-shape, with the motor element situated at the laterally narrowmost portion of the diaphragm face, the piston area of the diaphragm presenting relatively shallow angles with reference to the face plane of the loudspeaker where the radii of such piston area are relatively long and presenting relatively abrupt angles thereof where the radii of such piston area are relatively short.
9. A loudspeaker according to claim 8, wherein the piston area of said diaphragm is relatively flexible along the relatively large radii thereof, and relatively stiff along the relatively short radii thereof, so that the acoustic impedance of said piston area as seen by said motor element is relatively high in the laterally narrowmost portion of the diaphragm face.
10. A loudspeaker according to claim 8, wherein said rigid frame is the edge of a diaphragm rear housing presenting an essentially solid form rearwardly of the relatively short radii portions of the diaphragm to maintain the rear air impedance thereof relatively high, and presenting housing openings rearwardly of the relatively long rad-ii portions of the diaphragm to maintain the rear air impedance thereof relatively low.
11. An extended range dynamic loudspeaker having a single motor element and an elongated, shallowly openfaced, sloped-walled diaphragm radiating therefrom, the face configuration of said diaphragm being with relatively large area laterally wide end portions and a relatively small area necked portion therebetween, one of said end portions being relatively larger than the other and constituting a woofer zone, the other said end area constituting a mid-range zone, and the necked, intermediate area therebetween constituting a tweeter zone, the said motor element being situated to directly drive said tweeter zone, the acoustic impedance presented to said motor element being predominantly that of the necked portion of the diaphragm so that the loudspeaker is essentially dynamically balanced even though the end areas thereof are relatively non-symmetrical.
12. A loudspeaker according to claim 11, wherein the piston area of said tweeter zone is relatively stiff and the piston areas of said woofer and mid-range zones are each relatively less stiff so that high frequency excursions of the diaphragm are primarily confined to said tweeter area and the mid-frequency and low frequency excursions thereof are primarily developed in the mid-range and woofer piston areas, with a wide range and good spectrum of natural frequency modes, the lowest natural frequency mode of the diaphragm being determined by the largest radial dimension of the woofer zone piston area, and the highest naturalfrequency mode of the diaphragm being determined by the smallest radial dimension of the tweeter zone piston area.
13. A loudspeaker according to claim 12, wherein the ratio of the shortest tweeter zone radius to the longest mid-range zone radius is about 1:5 and the ratio of the longest mid-range zone radius to the longest woofer zone radius is about 4:5.
14. A single cone, single motor element loudspeaker providing combined woofer, mid-range and tweeter response; said loudspeaker having an open-faced, slopedwall type diaphragm with a face configuration involving wide, large area ends with a narrow, small area throat portion therebetween, and a magnetic type motor means comprising a voice coil element situated in said throat portion, such throat portion being of relatively stiff-wall construction and providing a tweeter zone, one of the end areas being somewhat-larger than the other and providing a woofer zone, and the smaller of the end areas providing a mid-range zone, the stiff-walled tweeter zone construction establishing the dominant impedance presented to the motor element so that, the diaphragm is essentially dynamically balanced even though of somewhat non-symmetrical configuration.
15. An electrodynamic loudspeaker having an openfaced. sloped-wall diaphragm of elongated and necked edge configuration bounded by a planar rigid frame and driven by a motor element situated at the diaphragm apex, the necked portion of the diaphragm being situated somewhat non-symmetrically of the ends thereof along a major axis with one end area being slightly larger than the other end area sov that the larger end area provides a woofer zone, the smaller end area provides a mid-range zone, and the necked diaphragm area therebetween provides a tweeter zone, with said diaphragm apex being situated in said tweeter zone; the said loudspeaker having substantially the following relative dimensions:
Dimension Dimensional units Major axis 19 Widest lateral dimension at woofer zone l2 Widest lateral dimension at mid-range zone 9 Narrowest lateral dimension at tweeter zone 6 16. A loudspeaker according to claim 15, wherein the depth of the diaphragm from the face plane thereof to the diaphragm apex is about 1% dimensional units.
17. An electrodynamic loudspeaker of extended frequency response and a, wide range of natural frequency modes, comprising an open-faced, sloped-wall type diaphragm of pressed paper construction, driven by a motor means and, having a piston area configuration involving a large woofer lobe and a somewhat smaller mid-range lobe, and with a necked tweeter portion therebetween, the
' said motor means being connected to said diaphragm in said tweeter portion, and the said piston area having a stiffening coating on the central portion thereof, applied most heavily in said tweeter portion.
18. A loudspeaker according to claim 17, wherein said stiffening coating incorporates crystalline particulate material to augment high frequency response of the speaker.
19. A loudspeaker according to claim 18, wherein the crystalline particulate material comprises burnt amber.
20. A loudspeaker according to claim 17, wherein said stiffening coating is applied entirely over the said tweeter portion, and partly over said mid-range portion, but not over said woofer portion of the diaphragm piston area.
21. An electrodynamic loudspeaker comprising a motor element, a rigid frame, and a pliant, concavely open-faced diaphragm magnetically driven by said motor element and edge joined to said frame along a fiat face plane, the edge configuration of said diaphragm at its planar juncture with said frame being of substantially viol shape, with the concave face of said diaphragm being deepest substantially in the laterally narrowmost portion thereof, and with the said motor element being coupled to said diaphragm at its deepest face portion.
References Citetl in the file of this patent UNITED STATES PATENTS 1,689,136 Hastings Oct. 23, 1928 2,146,975 Nagelvoort Feb. 14, 1939 2,549,091 Hopkins Apr. 17, 1951 2,717,047 Buchmann Sept. 6, 1955 3,026,958 Haerther Mar, 27, 1962 FOREIGN PATENTS 176,098 Great Britain Feb. 27, 1922