CA1276285C - Multidriver loudspeaker - Google Patents
Multidriver loudspeakerInfo
- Publication number
- CA1276285C CA1276285C CA000500840A CA500840A CA1276285C CA 1276285 C CA1276285 C CA 1276285C CA 000500840 A CA000500840 A CA 000500840A CA 500840 A CA500840 A CA 500840A CA 1276285 C CA1276285 C CA 1276285C
- Authority
- CA
- Canada
- Prior art keywords
- voice coil
- frequency driver
- coil former
- low frequency
- high frequency
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Abstract
IMPROVED MULTIDRIVER LOUDSPEAKER
ABSTRACT
A multidriver loudspeaker includes a low frequency driver formed with an elongated voice coil former terminating in an inverted speaker cone. A high frequency driver is located along the voice coil former, which is formed so as to move the apparent acoustical source of the low frequency driver along the voice coil former to a location substantially coincident with the apparent acoustical source of the high frequency driver.
ABSTRACT
A multidriver loudspeaker includes a low frequency driver formed with an elongated voice coil former terminating in an inverted speaker cone. A high frequency driver is located along the voice coil former, which is formed so as to move the apparent acoustical source of the low frequency driver along the voice coil former to a location substantially coincident with the apparent acoustical source of the high frequency driver.
Description
i27628~
Description of the Invention The invention relates generally to loudspeakers and particularly to an improved multidriver loudspeaker.
Ideally, a loudspeaker-driver should be capable of reproducing all frequencies so that the source of, for example, the high and low frequency sound waves is a single location. This would result in the time and phase coherence of all sound waves, thereby producing undistorted natural sound. It is difficult, however, to build a conventional driver that is both big enough to reproduce the low frequencies and light enough to reproduce the high frequencies. Therefore, most loudspeaker systems utiIize two or rnore drivers and are terrned multidriver loudspeakers. Several major problems arise when multiple drivers are used in a single loudspeaker. Specifically, at some frequencies several drivers are functioning and the actual location of the sound is not fixed for the listener. In addition, as tne listener moves around the listening area, the distance fro~n each driver to the listener changes in a non-uniform manner, such that at one location the listener is closer to the low frequency driver and at the second location the listener is closer to the high frequency driver. This results in the non-synchronization of the wave fronts reaching the listener at all frequencies. Finally, at the crossover point, where both drivers are producing the same ~, amount of output, phase shifts will exist between the sound waves emanating from the two drivers caused by the difference in path lengths from the drivers to the listener. To a great extent, these problems are inherent in any multidriver loudspeaker system and are caused by the fact that the apparent acoustical source of the drivers are not all at the same location. The apparent acoustical source of a driver is the point in space where the sound wave front from the driver appears to a listener to originate at the time the input is applied to the driver. Typically, in view of the inertial characteristics of the driver, the apparent acoustical source of a driver is behind the voice coil - cone junction and within the magnetic structure of the driver.
15 Obviously, if the apparent acoustical time source for all of the drivers were the same point in space many of the problems described above would be solved. In fact, several complex mechanical structures have been developed in an attempt to achieve this, resulting in the embedding of the high frequency driver inside the magnetic structure of the low frequency driver. Practically, these speakers are too expensive to manufacture and as such, are not manufactured. ~urther, even if speakers of this type could be manufactured at a reasonable cost, they incorporate other disadvantages since the sides of a low frequency driver tend to act somewhat like a horn with respect to the sound emanating from the low frequency driver (horn loading) thereby dis~orting the sound produced thereby.
Other at~empts ~o solve the problems inheren~ in multidriver loudspeakers include positioning the high frequency driver in front of ~he low frequency driver.
This solu~ion is unsatisfactory as i~ creates a constant time delay in ~he sound waves emana~ing from the low frequency driver which becomes acu~e a~ the crossover of the two drivers. Further, the high frequency driver in such an arrangement serves as a diffrac~ing object and interferes with the sound produced by ~he low frequency driver.
It is ~herefore an object of ~he presen~
invention to provide an improved mul~idriver loudspeaker which overcomes the problems inherent in mul~idriver loudspeakers of the prior art.
Ano~her object of ~he presen~ inven~ion is to provide an improved mul~idriver loudspeaker in which the apparent acoustical source of both ~he high and low frequency drivers appear to a listener to be at a single location.
Still ano~her objec~ of ~he presen~ invention is to provide an improved mul~idriver loudspeaker in which the wave fron~s from the high and low frequency drivers are synchronized wi~h respec~ to time, phase and response.
A fur~her objec~ of the present invention is to provide an ~mproved multidriver loudspeaker which is simple in cons~ruc~ion and inexpensive to manufacture.
~276Z85 In accordance with ~he presen~ inven~ion an improved mul~idriver loudspeaker includes a low frequency driver having an elongated voice coil former ~ermina~ing in an inverted speaker cone and a high frequency driver S located along the voice coil former. The voice coiL
former is formed so as ~o move ~he apparent acous~ical source of ehe low freqnency driver along the voice coil former tO a loca~ion substan~ially coincident wilh the apparen~ acoustical source of the high frequency driver.
The above brief description as well as further objects, features and advantages of the present inven~ion will be more fully unders~ood by reference ~o ~he following de~ailed descrip~ion of the presently preferred bu~ none~heless illus~ra~ive embodimen~s in accordance wi~h ~he presen~ inven~ion, when ~aken in conjunc~ion wi~h tl-e accompanying drawing, wherein:
FIG. 1 is a fron~ eleva~ional view of ~he multidriver loudspeaker of ~he presen~ inven~ion;
FIC. 2 is a righ~ side elevational sec~ional view of ehe multidriver loudspeaker ~aken subs~an~ially along the line 2-2 of FIG. l and looking in ~he direc~ion of ~he arrows;
FIG. 3 is a fron~ eleva~ional view of an aL~erna~e embodimen~ of ~he mul~idriver loudspeaker of the presen~ inven~ion; and FIG. 4 is a righ~ side eleva~ional sec~ional view of ~he mul~idriver loudspeaker ~aken subs~antially along the line 4-4 of FIG. 3 and looking in the direc~ion ~Z76285 of the arrows.
Referring first ~o FI~S~ 1 and 2 a mul~idriver loudspeaker, indicated generally by ~he reference numeral 10, includes both a high frequency driver and a low frequency driver and is formed from a base 7 2 adapted ~o support a steel basket enclosure 14 and a magne~ assembly 16 for the low frequency driver. Disposed within ~he basket 14 is an inverted conical diaphragm or cone 18 which is a thin, curved sheet, ~he surface of which is of a shape such as would be genera~ed by ~he rota~ion of a straigh~ or, alternatively, a curved line about an axis.
Such a surface, generated by a curved line, is no~ a ~rue cone, but is generally referred ~o as such in ~he industry and is included wi~hin ~he ~erm "cone" as used herein.
The cone 18 may be made of a stiff material, such as felted fiber, paper, a fel~ed fiber and paper composition, or plastic.
The cone 18 is associa~ed wi~h ~he low frequency driver and includes an inner concave sound radiating surface 18a and an outer convex sounà radiating surface 18b. The cone 18 also includes ~wo coaxial ends; the upper, smaller end of ~he cone 18 is referred ~o as the driving circle 20 and ~he larger end of ~he cone 1~ is referred to as ~he surround 22- The angle ~' of the cone 18 refers ~o ~he angle formed be~ween a line perpendicular ~o ~he base 12 and ~he inner surface 18a a~ ~he surround 22. Tlle angle X in ~his par~icular embodiment approxima~es 60 degrees. A damping ring 24 secures the ~2~7628~;
surround 22 of cone 1~ ~o the bas~e~ 14. ~lle driving circle 20 is secured to one end of an elongated voice coil former 26, the opposi~e end of which is cen~ered in ~he annular gap between ~he pole pieces of ~he magne~ assembly 16 and includes a voice coil 18. A damping ring 30 secures the end of the voice coil former 26 proximate eo the voice coil 2~, to ~he basked 14. The damping rings 24 and 30 serve ~o cen~er ~he voice coil former 26 and the cone 18 within ~he basket 14 bu~ permi~ ~he cone and former freedom ~o move axially.
The voice coil 23 is glued tO ~he former 26 and positioned in ~he air gap of ~he magne~ assembly 14, which together wi~h coil 2~3 forms a conven~ional loudspea~er motor. Varyin~ curren~s proportional ~o audio frequencies genera~ed by a sound source such as a record or ~ape are suitably amplified and are applied ~o conven~ional input terminals (not shown) of ~he voice coil 2~ which ~hen in~erracts with the magne~ic field in ~he ~ap ~o cause the coil to undergo mechanical longi~udinal ~ran51ational movements a~ 2 ra~e which is proportional ~o the audio frequencies. I~hen ~he voice coil 2~ undergoes i~s longi~udinal ~ransla~ional mo~ion, ~hat mo~ion is imparted ~hrough the former 26 ~o ~he cone 1i3 and audible sound (in ~he low frequency range) is produced in ~he air.
~ conven~ional high frequency driver 32 is loca~ed wi~hin ~he former 26 a~ ~he end proxima~e ~o ~he driving circle 20 and is supporced by a pin 34 and a housing 36 ex~ending alonq ~he leng~h of ~he former 26.
~27~2~5 As such, the high frequency driver is coaxial with ~he low frequency driver.
The multidriver loudspeaker described ~hus far shows the coaxial arrangemen~ of both ~he low frequency and high frequency drivers. I~owever, in this arrangemen~, the apparent acous~ical source of ~he low frequency driver is not the same as ~he apparen~ acous~ical source of ~he high frequency driver. Specifically, the apparent acoustical sources of both ~he high frequency driver and low frequency driver are located just in fron~ of their respective magnet assemblies. Different apparent acoustical sourccs for ~he low frequency and high frequency drivers crea~es a ~ime delay dis~or~ion in which tthe re~roduced sounds are vaguely unnatural. This dis~ortion is due ~o ~he fac~ ~ha~ ~he reproduced sounds from the high frequency driver and ~he low frequency driver do not simul~aneously arrive a~ ~he lis~ener's ear.
The ins~ant invention minimizes ~his problem by moving the apparent acoustical source of ~he low frequency driver to a point substantially coincident with the location of ~he apparent acous~ical source of ~he high frequency driver. This is accomplisiled by manipulating ~he ~ime delay of the low frequency driver in a manner co be more fully described hereinbelow.
Specifically, ~he cone 18 will ~ove similarly to the voice coil 28 but delayed by the time i~ ~a~es for ~he sound ~o ~ravel ~he length of ~he voice coil former 2~.
This time delay is represen~ed by ~he follcwing equation:
1Z76Z~3~
Time Delay = Lena~h of Former ., Soeed of sound ln Former as a mul~iple of ~he speed of Sound in Air Typically, drivers are formed wi~h as shor~ a voice coil former as possible so as to minimize this time delay.
However, ~he creation of an appropriate ~ime delay serves to move the apparen~ acous~ical source of ~he low frequency driver out of ~he magnet assembly 16 and forward along the voice coil former 26. Placing ~he high frequency driver 32 wi~hin ~he former 26 and crea~ing a time delay which moves the apparent acous~ical source of the low frequency driver to approxima~ely ~he same location as the high frequency driver 3 resul~s in ~he in-phase ou~pu~ of both ~he lligil and low frequency drivers. ~s such, bo~h drivers, while no~ a~ ~he same physical loca~ion, are perceived ~o have ~he same acoustical source in view of ~he synchronized wave fronts emanating from both ~he low and high frequency drivers.
The appropria~e ~ime delay may be accomplished by ex~ending ~he leng~h of ~he voice coil former 26, which is made of a ma~erial which ~ransmi~s sound a~ a speed grea~er ~han ~he speed of sound in air. For example, if the former is 5 inches long and has a speed of sound ~ransmission ~en ~imes ~hat of air, the acoustical apparent leng~h of ~he former would only be .5 inches. By placing ~he high frequenc'~ driver .5 inclles into ~he end of ~he former 26, oroximate to ~he driving circle 20, the ~276285 apparen~ acoustical source of bo~h the high and low frequency drivers would be at approxima~ely the same location. The specific length of the voice coil former 26 and the material chosen for its construction may be varied to suit the particular application. For example, voice coil formers made from metal instead of paper are contemplated. Specifically, a longer former will result in a longer time delay while a shorter former will usually result in a shorter time delay, with the increasing speed of sound transmission of the ma~erial serving ~o shorten the time delay.
Ic is no~ necessary to achieve the exact coincidence of the apparenc acoustical sources of the ~wo drivers. A lis~ener hearing cwo sources of sound that are within one-six~h of a waveleng~h of each other will not be able tO perceive the ~wo sources separacely and ins~ead perceives the sound waves coming from ~he cto sources as if they were coming from a single source. As such, it iS
only necessary ~o posi~ion ~he cwo apparen~ acous~ical sources such ~hac the sound waves emanacing cherefrom are wichin one-six~h of a waveleng~h of each o~her. The lis~ener will perceive ~he ~wo sources as being only one.
Referring now ~o FIGS. 3 and 4 an al~erna~e embodimen~ of che mul~idriver loudspeaker of che present inven~ion is indicated generally by che reference numeral 40 and includes bo~h a hic3h frequency driver and a low frequency driver. A base 42 is adap~ed to support a steel baske~ enclosure 44 and a magnet assembly a6 for the low i276Z85 frequency speaker.
Disposed within ~he basket 44 is an inverted conical diaphragm or cone 48 which is associated with ~he low frequency driver and incLudes an inner concave sour.d radiating surface 4~a and an outer convex sound radia~ing surface 48b. The cone 48 also inclucles ~wo coaxial ends;
the upper, smaller end of the cone 48 is referred ~o as the driving circle 50 and the larger end of ~he cone 48 is referred to as the surround 52. A damping ring 54 secures the surround 52 of cone 48 ~o che '~aske~ 44. The driving circle 50 is secured ~o one end of an elonga~ed voice coil former 26, ~he opposi~e end of which is centered in ~he annular gap becween ~he pole pieces of ~he magne~ assembLy 46 and includes a voice coil 58. A damping ring 60 1~ secures the end of the voice coil former 56 proximate tO
~he voice coil 28 to the basket 44. The damping rings 54 and 60 serve to center ~he voice coil former 56 and the cone 48 within the basket 44 but permit the cone and former to move axially.
The voice coil 58 is glued or otherwise permanently affixed to the former 56 and posi~ioned in the air gap of the magne~ assembly 44, whic'l ~ogether ~ith coil 53 forms a conven~ional loudspeaker motor for ~he Low frequency driver.
A conventional hi~h frequency driver S2 is located along and partially within ~he former 56 a~ ~he end proxima~e ~o the drivin~ circle 50. E~igh frequency driver 62 is secured to an L-shaped moun~ing bracket 64 12~6Z~S
which is supported by a pin 66 and a housing 68 extendins along ~he leng~h of ~he former 56. The high frequency driver 62 is can~ed wi~h respec~ ~o a plane perpendicular to the axis of ~he low frequency driver and formed at ~he driving circle 20, at an angle Y. The angle Y in ~his particular embodiment approximates 105 degrees.
The voice coil former 56 is formulated in accordance with the principles ou~lined above tO create an appropriate time delay in low frequency driver by moving the apparent acoustical source of the low frequency driver out of the magnet assembly 46 and forward along the voice coil former 56 to approximaeely ~he same location as the apparent acoustical source of ~he high frequency driver 62. In ~his particular embodiment the voice coil former is cons~ructed so as ~o move the apparent acoustical source of ~he low frequency driver as close as possible to ~he end of the voice coil former 56 proximate the driving circle 50. ~ ~his loca~ion, ~he sound waves emana~ing from the low and high frequency drivers are within one sixlh of a wavelength of each o~her, and a listener will perceive ~he ~wo sources as being only one.
This embodimen~ is par~icularly adap~ed for use as an au~omobile loudspeaker. The use of ~he can~ed high frequency driver 62 is well sui~ed for ~he placemen~
loca~ions available for loudspeakers in automobiles.
Typically, these locations include ~he package shelf (si~ua~ed behind ~he rear seats), ~he dash board and ~he lower portions of ~he car doors. The limited number of 1Z76Z8~i possible loudspeaker locations coupled wi~h the fact tha~
the position of ~he lis~eners in automobiles is generaLly stationary wi~h respect to the loudspeakers, permi~s the use of the can~ed high frequency driver 62 arrangement ~o direct the sound emana~ing from ~his smaller, lower power driver directly a~ the lis~eners. As a result, ~he sound emanating from the high frequency driver 62 is not directed against ~he rear window, windshield or into the footwells of the au~omobile. This is accomplished without the problems normally encountered when ~he high frequency driver is placed in fron~ of ~he low frequency driver in a mul~idriver loudspeaker. Fur~her, ~he listeners will perceive the separa~e sound waves emana~ing from the high and low frequency drivers as origina~ing from a single loca~ion.
As will be readily apparen~ ~o ~hose skilled in ~he ar~, ~he inven~ion may be used in o~her specific forms or for o~her purposes withou~ depar~ing from i~s spirit or central characteristics. The presen~ embodiment is ~herefore ~o be considered as illus~ra~ive and no~
res~ric~ive, the scope of ~he inven~ion being indicated by ~he claims ra~her ~han bv ~he fore50ing descrip~ion, and all embodimen~s which come within ~he range of equivalence of ~he claims are in~ended to be embraced.
Description of the Invention The invention relates generally to loudspeakers and particularly to an improved multidriver loudspeaker.
Ideally, a loudspeaker-driver should be capable of reproducing all frequencies so that the source of, for example, the high and low frequency sound waves is a single location. This would result in the time and phase coherence of all sound waves, thereby producing undistorted natural sound. It is difficult, however, to build a conventional driver that is both big enough to reproduce the low frequencies and light enough to reproduce the high frequencies. Therefore, most loudspeaker systems utiIize two or rnore drivers and are terrned multidriver loudspeakers. Several major problems arise when multiple drivers are used in a single loudspeaker. Specifically, at some frequencies several drivers are functioning and the actual location of the sound is not fixed for the listener. In addition, as tne listener moves around the listening area, the distance fro~n each driver to the listener changes in a non-uniform manner, such that at one location the listener is closer to the low frequency driver and at the second location the listener is closer to the high frequency driver. This results in the non-synchronization of the wave fronts reaching the listener at all frequencies. Finally, at the crossover point, where both drivers are producing the same ~, amount of output, phase shifts will exist between the sound waves emanating from the two drivers caused by the difference in path lengths from the drivers to the listener. To a great extent, these problems are inherent in any multidriver loudspeaker system and are caused by the fact that the apparent acoustical source of the drivers are not all at the same location. The apparent acoustical source of a driver is the point in space where the sound wave front from the driver appears to a listener to originate at the time the input is applied to the driver. Typically, in view of the inertial characteristics of the driver, the apparent acoustical source of a driver is behind the voice coil - cone junction and within the magnetic structure of the driver.
15 Obviously, if the apparent acoustical time source for all of the drivers were the same point in space many of the problems described above would be solved. In fact, several complex mechanical structures have been developed in an attempt to achieve this, resulting in the embedding of the high frequency driver inside the magnetic structure of the low frequency driver. Practically, these speakers are too expensive to manufacture and as such, are not manufactured. ~urther, even if speakers of this type could be manufactured at a reasonable cost, they incorporate other disadvantages since the sides of a low frequency driver tend to act somewhat like a horn with respect to the sound emanating from the low frequency driver (horn loading) thereby dis~orting the sound produced thereby.
Other at~empts ~o solve the problems inheren~ in multidriver loudspeakers include positioning the high frequency driver in front of ~he low frequency driver.
This solu~ion is unsatisfactory as i~ creates a constant time delay in ~he sound waves emana~ing from the low frequency driver which becomes acu~e a~ the crossover of the two drivers. Further, the high frequency driver in such an arrangement serves as a diffrac~ing object and interferes with the sound produced by ~he low frequency driver.
It is ~herefore an object of ~he presen~
invention to provide an improved mul~idriver loudspeaker which overcomes the problems inherent in mul~idriver loudspeakers of the prior art.
Ano~her object of ~he presen~ inven~ion is to provide an improved mul~idriver loudspeaker in which the apparent acoustical source of both ~he high and low frequency drivers appear to a listener to be at a single location.
Still ano~her objec~ of ~he presen~ invention is to provide an improved mul~idriver loudspeaker in which the wave fron~s from the high and low frequency drivers are synchronized wi~h respec~ to time, phase and response.
A fur~her objec~ of the present invention is to provide an ~mproved multidriver loudspeaker which is simple in cons~ruc~ion and inexpensive to manufacture.
~276Z85 In accordance with ~he presen~ inven~ion an improved mul~idriver loudspeaker includes a low frequency driver having an elongated voice coil former ~ermina~ing in an inverted speaker cone and a high frequency driver S located along the voice coil former. The voice coiL
former is formed so as ~o move ~he apparent acous~ical source of ehe low freqnency driver along the voice coil former tO a loca~ion substan~ially coincident wilh the apparen~ acoustical source of the high frequency driver.
The above brief description as well as further objects, features and advantages of the present inven~ion will be more fully unders~ood by reference ~o ~he following de~ailed descrip~ion of the presently preferred bu~ none~heless illus~ra~ive embodimen~s in accordance wi~h ~he presen~ inven~ion, when ~aken in conjunc~ion wi~h tl-e accompanying drawing, wherein:
FIG. 1 is a fron~ eleva~ional view of ~he multidriver loudspeaker of ~he presen~ inven~ion;
FIC. 2 is a righ~ side elevational sec~ional view of ehe multidriver loudspeaker ~aken subs~an~ially along the line 2-2 of FIG. l and looking in ~he direc~ion of ~he arrows;
FIG. 3 is a fron~ eleva~ional view of an aL~erna~e embodimen~ of ~he mul~idriver loudspeaker of the presen~ inven~ion; and FIG. 4 is a righ~ side eleva~ional sec~ional view of ~he mul~idriver loudspeaker ~aken subs~antially along the line 4-4 of FIG. 3 and looking in the direc~ion ~Z76285 of the arrows.
Referring first ~o FI~S~ 1 and 2 a mul~idriver loudspeaker, indicated generally by ~he reference numeral 10, includes both a high frequency driver and a low frequency driver and is formed from a base 7 2 adapted ~o support a steel basket enclosure 14 and a magne~ assembly 16 for the low frequency driver. Disposed within ~he basket 14 is an inverted conical diaphragm or cone 18 which is a thin, curved sheet, ~he surface of which is of a shape such as would be genera~ed by ~he rota~ion of a straigh~ or, alternatively, a curved line about an axis.
Such a surface, generated by a curved line, is no~ a ~rue cone, but is generally referred ~o as such in ~he industry and is included wi~hin ~he ~erm "cone" as used herein.
The cone 18 may be made of a stiff material, such as felted fiber, paper, a fel~ed fiber and paper composition, or plastic.
The cone 18 is associa~ed wi~h ~he low frequency driver and includes an inner concave sound radiating surface 18a and an outer convex sounà radiating surface 18b. The cone 18 also includes ~wo coaxial ends; the upper, smaller end of ~he cone 18 is referred ~o as the driving circle 20 and ~he larger end of ~he cone 1~ is referred to as ~he surround 22- The angle ~' of the cone 18 refers ~o ~he angle formed be~ween a line perpendicular ~o ~he base 12 and ~he inner surface 18a a~ ~he surround 22. Tlle angle X in ~his par~icular embodiment approxima~es 60 degrees. A damping ring 24 secures the ~2~7628~;
surround 22 of cone 1~ ~o the bas~e~ 14. ~lle driving circle 20 is secured to one end of an elongated voice coil former 26, the opposi~e end of which is cen~ered in ~he annular gap between ~he pole pieces of ~he magne~ assembly 16 and includes a voice coil 18. A damping ring 30 secures the end of the voice coil former 26 proximate eo the voice coil 2~, to ~he basked 14. The damping rings 24 and 30 serve ~o cen~er ~he voice coil former 26 and the cone 18 within ~he basket 14 bu~ permi~ ~he cone and former freedom ~o move axially.
The voice coil 23 is glued tO ~he former 26 and positioned in ~he air gap of ~he magne~ assembly 14, which together wi~h coil 2~3 forms a conven~ional loudspea~er motor. Varyin~ curren~s proportional ~o audio frequencies genera~ed by a sound source such as a record or ~ape are suitably amplified and are applied ~o conven~ional input terminals (not shown) of ~he voice coil 2~ which ~hen in~erracts with the magne~ic field in ~he ~ap ~o cause the coil to undergo mechanical longi~udinal ~ran51ational movements a~ 2 ra~e which is proportional ~o the audio frequencies. I~hen ~he voice coil 2~ undergoes i~s longi~udinal ~ransla~ional mo~ion, ~hat mo~ion is imparted ~hrough the former 26 ~o ~he cone 1i3 and audible sound (in ~he low frequency range) is produced in ~he air.
~ conven~ional high frequency driver 32 is loca~ed wi~hin ~he former 26 a~ ~he end proxima~e ~o ~he driving circle 20 and is supporced by a pin 34 and a housing 36 ex~ending alonq ~he leng~h of ~he former 26.
~27~2~5 As such, the high frequency driver is coaxial with ~he low frequency driver.
The multidriver loudspeaker described ~hus far shows the coaxial arrangemen~ of both ~he low frequency and high frequency drivers. I~owever, in this arrangemen~, the apparent acous~ical source of ~he low frequency driver is not the same as ~he apparen~ acous~ical source of ~he high frequency driver. Specifically, the apparent acoustical sources of both ~he high frequency driver and low frequency driver are located just in fron~ of their respective magnet assemblies. Different apparent acoustical sourccs for ~he low frequency and high frequency drivers crea~es a ~ime delay dis~or~ion in which tthe re~roduced sounds are vaguely unnatural. This dis~ortion is due ~o ~he fac~ ~ha~ ~he reproduced sounds from the high frequency driver and ~he low frequency driver do not simul~aneously arrive a~ ~he lis~ener's ear.
The ins~ant invention minimizes ~his problem by moving the apparent acoustical source of ~he low frequency driver to a point substantially coincident with the location of ~he apparent acous~ical source of ~he high frequency driver. This is accomplisiled by manipulating ~he ~ime delay of the low frequency driver in a manner co be more fully described hereinbelow.
Specifically, ~he cone 18 will ~ove similarly to the voice coil 28 but delayed by the time i~ ~a~es for ~he sound ~o ~ravel ~he length of ~he voice coil former 2~.
This time delay is represen~ed by ~he follcwing equation:
1Z76Z~3~
Time Delay = Lena~h of Former ., Soeed of sound ln Former as a mul~iple of ~he speed of Sound in Air Typically, drivers are formed wi~h as shor~ a voice coil former as possible so as to minimize this time delay.
However, ~he creation of an appropriate ~ime delay serves to move the apparen~ acous~ical source of ~he low frequency driver out of ~he magnet assembly 16 and forward along the voice coil former 26. Placing ~he high frequency driver 32 wi~hin ~he former 26 and crea~ing a time delay which moves the apparent acous~ical source of the low frequency driver to approxima~ely ~he same location as the high frequency driver 3 resul~s in ~he in-phase ou~pu~ of both ~he lligil and low frequency drivers. ~s such, bo~h drivers, while no~ a~ ~he same physical loca~ion, are perceived ~o have ~he same acoustical source in view of ~he synchronized wave fronts emanating from both ~he low and high frequency drivers.
The appropria~e ~ime delay may be accomplished by ex~ending ~he leng~h of ~he voice coil former 26, which is made of a ma~erial which ~ransmi~s sound a~ a speed grea~er ~han ~he speed of sound in air. For example, if the former is 5 inches long and has a speed of sound ~ransmission ~en ~imes ~hat of air, the acoustical apparent leng~h of ~he former would only be .5 inches. By placing ~he high frequenc'~ driver .5 inclles into ~he end of ~he former 26, oroximate to ~he driving circle 20, the ~276285 apparen~ acoustical source of bo~h the high and low frequency drivers would be at approxima~ely the same location. The specific length of the voice coil former 26 and the material chosen for its construction may be varied to suit the particular application. For example, voice coil formers made from metal instead of paper are contemplated. Specifically, a longer former will result in a longer time delay while a shorter former will usually result in a shorter time delay, with the increasing speed of sound transmission of the ma~erial serving ~o shorten the time delay.
Ic is no~ necessary to achieve the exact coincidence of the apparenc acoustical sources of the ~wo drivers. A lis~ener hearing cwo sources of sound that are within one-six~h of a waveleng~h of each other will not be able tO perceive the ~wo sources separacely and ins~ead perceives the sound waves coming from ~he cto sources as if they were coming from a single source. As such, it iS
only necessary ~o posi~ion ~he cwo apparen~ acous~ical sources such ~hac the sound waves emanacing cherefrom are wichin one-six~h of a waveleng~h of each o~her. The lis~ener will perceive ~he ~wo sources as being only one.
Referring now ~o FIGS. 3 and 4 an al~erna~e embodimen~ of che mul~idriver loudspeaker of che present inven~ion is indicated generally by che reference numeral 40 and includes bo~h a hic3h frequency driver and a low frequency driver. A base 42 is adap~ed to support a steel baske~ enclosure 44 and a magnet assembly a6 for the low i276Z85 frequency speaker.
Disposed within ~he basket 44 is an inverted conical diaphragm or cone 48 which is associated with ~he low frequency driver and incLudes an inner concave sour.d radiating surface 4~a and an outer convex sound radia~ing surface 48b. The cone 48 also inclucles ~wo coaxial ends;
the upper, smaller end of the cone 48 is referred ~o as the driving circle 50 and the larger end of ~he cone 48 is referred to as the surround 52. A damping ring 54 secures the surround 52 of cone 48 ~o che '~aske~ 44. The driving circle 50 is secured ~o one end of an elonga~ed voice coil former 26, ~he opposi~e end of which is centered in ~he annular gap becween ~he pole pieces of ~he magne~ assembLy 46 and includes a voice coil 58. A damping ring 60 1~ secures the end of the voice coil former 56 proximate tO
~he voice coil 28 to the basket 44. The damping rings 54 and 60 serve to center ~he voice coil former 56 and the cone 48 within the basket 44 but permit the cone and former to move axially.
The voice coil 58 is glued or otherwise permanently affixed to the former 56 and posi~ioned in the air gap of the magne~ assembly 44, whic'l ~ogether ~ith coil 53 forms a conven~ional loudspeaker motor for ~he Low frequency driver.
A conventional hi~h frequency driver S2 is located along and partially within ~he former 56 a~ ~he end proxima~e ~o the drivin~ circle 50. E~igh frequency driver 62 is secured to an L-shaped moun~ing bracket 64 12~6Z~S
which is supported by a pin 66 and a housing 68 extendins along ~he leng~h of ~he former 56. The high frequency driver 62 is can~ed wi~h respec~ ~o a plane perpendicular to the axis of ~he low frequency driver and formed at ~he driving circle 20, at an angle Y. The angle Y in ~his particular embodiment approximates 105 degrees.
The voice coil former 56 is formulated in accordance with the principles ou~lined above tO create an appropriate time delay in low frequency driver by moving the apparent acoustical source of the low frequency driver out of the magnet assembly 46 and forward along the voice coil former 56 to approximaeely ~he same location as the apparent acoustical source of ~he high frequency driver 62. In ~his particular embodiment the voice coil former is cons~ructed so as ~o move the apparent acoustical source of ~he low frequency driver as close as possible to ~he end of the voice coil former 56 proximate the driving circle 50. ~ ~his loca~ion, ~he sound waves emana~ing from the low and high frequency drivers are within one sixlh of a wavelength of each o~her, and a listener will perceive ~he ~wo sources as being only one.
This embodimen~ is par~icularly adap~ed for use as an au~omobile loudspeaker. The use of ~he can~ed high frequency driver 62 is well sui~ed for ~he placemen~
loca~ions available for loudspeakers in automobiles.
Typically, these locations include ~he package shelf (si~ua~ed behind ~he rear seats), ~he dash board and ~he lower portions of ~he car doors. The limited number of 1Z76Z8~i possible loudspeaker locations coupled wi~h the fact tha~
the position of ~he lis~eners in automobiles is generaLly stationary wi~h respect to the loudspeakers, permi~s the use of the can~ed high frequency driver 62 arrangement ~o direct the sound emana~ing from ~his smaller, lower power driver directly a~ the lis~eners. As a result, ~he sound emanating from the high frequency driver 62 is not directed against ~he rear window, windshield or into the footwells of the au~omobile. This is accomplished without the problems normally encountered when ~he high frequency driver is placed in fron~ of ~he low frequency driver in a mul~idriver loudspeaker. Fur~her, ~he listeners will perceive the separa~e sound waves emana~ing from the high and low frequency drivers as origina~ing from a single loca~ion.
As will be readily apparen~ ~o ~hose skilled in ~he ar~, ~he inven~ion may be used in o~her specific forms or for o~her purposes withou~ depar~ing from i~s spirit or central characteristics. The presen~ embodiment is ~herefore ~o be considered as illus~ra~ive and no~
res~ric~ive, the scope of ~he inven~ion being indicated by ~he claims ra~her ~han bv ~he fore50ing descrip~ion, and all embodimen~s which come within ~he range of equivalence of ~he claims are in~ended to be embraced.
Claims (9)
1. A multidriver loudspeaker comprising a low frequency driver having an inverted speaker cone and an elongated voice coil former secured at one end to said inverted speaker cone, a high frequency driver located proximate to the end of said voice coil former secured to said inverted speaker cone, said voice coil former formed so as to locate the apparent acoustical source of said low frequency driver at a point substantially coincident with the apparent acoustical source of said high frequency driver.
2. Apparatus as in Claim 1 in which the apparent acoustical source of the low frequency driver is dependent upon the length of the voice coil former and the speed of sound transmission of the material from which the voice coil former is made, such that the voice coil former is formed to locate the apparent acoustical source of the low frequency driver at a point substantially coincident with the apparent acoustical source of the high frequency driver by so choosing the length of the voice coil former and the material from which the voice coil former is made,
3. A multidriver loudspeaker comprising a base, a magnet assembly secured to said base, a voice coil positioned in communication with said magnet assembly, an elongated voice coil former adapted at one end to support said voice coil, an inverted speaker cone secured to the opposite end of said voice coil former, said magnet assembly voice coil, voice coil former and speaker cone forming a low frequency driver, said elongated voice coil former formed so as to locate the apparent acoustical source of said low frequency driver at a point along said voice coil former remote from said magnet assembly, a high frequency driver, means including said base for locating said high frequency driver at a point along said voice coil former such that the apparent acoustical source of said high frequency driver is substantially coincident with the apparent acoustical source of said low frequency driver.
4. Apparatus as in Claim 3 in which said high frequency driver and the apparent acoustical source of said low frequency driver are located along the voice coil former at a point promimate to the end of the voice coil former secured to said inverted speaker cone.
5. Apparatus as in Claim 3 in which the apparent acoustical source of the low frequency driver is dependent upon the length of the voice coil former and the speed of sound transmission of the material from which the voice coil former is made, such that the voice coil former is formed to locate the apparent acoustical source of the low frequency driver at a point substantially coincident with the apparent acoustical source of the nigh frequency driver by so choosing the length of the voice coil former and the material from which the voice coil former is made.
6. A multidriver loudspeaker comprising a base, a magnet assembly secured to said base, a voice coil positioned in communication with said magnet assembly, an elongated voice coil former adapted at one end to support said voice coil, an inverted speaker cone secured to the opposite end of said voice coil former, said magnet assembly, voice coil, voice coil former and speaker cone forming a low frequency driver, said elongated voice coil former formed so as to locate the apparent acoustical source at a point proximate to the end of the voice coil former secured to said inverted speaker cone, a high frequency driver, means including said base for locating said high frequency driver at a point proximate to the end of the voice coil former secured to said inverted speaker cone such that the apparent acoustical source of said high frequency driver is substantially coincident with the apparent acoustical source of said low frequency driver.
7. Apparatus as in Claim 6 in which the apparent acoustical source of the low frequency driver is dependent upon the length of the voice coil former and the speed of sound transmission of the material from which the voice coil former is made, such that the voice coil former is formed to locate the apparent acoustical source of the low frequency driver at a point substantially coincident with the apparent acoustical source of the high frequency driver by so choosing the length of the voice coil former and the material from which the voice coil former is made.
8. Apparatus as in Claim 7 in which said high frequency driver extends outwardly from said voice coil former.
9. Apparatus as in Claim 8 in which said high frequency driver is canted with respect to a plane perpendicular to the axis of the low frequency driver and formed at the end of the voice coil former secured to said inverted speaker cone.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000500840A CA1276285C (en) | 1986-01-31 | 1986-01-31 | Multidriver loudspeaker |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000500840A CA1276285C (en) | 1986-01-31 | 1986-01-31 | Multidriver loudspeaker |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1276285C true CA1276285C (en) | 1990-11-13 |
Family
ID=4132394
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000500840A Expired - Lifetime CA1276285C (en) | 1986-01-31 | 1986-01-31 | Multidriver loudspeaker |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1276285C (en) |
-
1986
- 1986-01-31 CA CA000500840A patent/CA1276285C/en not_active Expired - Lifetime
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed | ||
| MKLA | Lapsed |
Effective date: 19950513 |