Патент USA US2380869

July 31, 1945.
J. P. QUAM
2,380,869
LOUD SPEAKER
Filed March 10, 1941
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Patented July 31, 1945
2.380.869
UNITED STATES PATENT orrlcs
2,380,889
MUD-SPEAKER
James P. Qusm, Chicago, 11]., assignor to Quain
Nichols Company, Chicago, lll., a corporation
of Missouri
'
Application-March 10, 1941, Serial No. 382,598
13 Claims. (01. 179-119)
This invention relates in general to loud speak
date the maximum possible magnetic forces
ers, and in particular to- a ‘magnetic-lune such
which might be applied to the magnetic-type of
as is disclomd in my Patent No. 2,124,338, issued
motor for speakers.
July 19, 1938.
Another di?lculty in the prior art magnetic
type speakers, whose motors, after all, have quite
Although the magnetic-type
speaker of my Patent No. 2,124,338 operated
'
satisfactorily, it had certain limitations peculiar
a number of parts, has been to provide a com
to ‘it, and included certain limitations peculiar
pact,‘ sturdy motor. and yet one in which the
to prior art speakers in general, which have all
several parts are readily accessible for inspection
been overcome in the present improved construc
and handling. if required. This iaparticulsrly
tion.
10 true of those motors in which aniarmature oscil
In composition paper diaphragm for mag
lates or vibrates about an axis centrally of the
netic-type loud speakers of the prior art, there
armature. In many instances, the frame and
has been a noticeable lack of uniformity in com
magnet structure has- served practicalbz as a
position over the entire body of the diaphragm
housing for the motor unit, and has substantially
which has resulted in surface and body varia
covered up the other parts.‘
.
tions so that there is not a perfectly uniform
_ In the prior art magnetic-type speakers there
movement of all parts of the diaphragm in a
has been-a further di?iculty m an undesired
normal vibratory operation. .Diaphragms of the
emphasis on the high frequencies in a particular
cone type are normally well anchored in a dia
range of operating freque cies, with actual dis;
tortion sometimes taking lace at the high fre
phragm frame and of considerable size so that,
they represent quite a body to be moved by the
quencles. Furthermore, there are many varied
likes and dislikes as to the cut-oi! frequency at
armature of the vibratory motor for the speaker.
The lack of uniformity distorts or twists the dia
the upper end of the frequency range among
Dhragm out of its usual operating path, and in
purchasers of speakers and much expense and
turn may move or force the armature of the
effort has been expended in providing a line of
vibratory unit out of its normal path oi move
speakers to match the particular tone require“
ment so that the armature contacts one or the
other pole face, and creates an undesirable me
ments of a purchaser. The usual method for
taking care of this situation has been to try one
tallic sound. Furthermore, the possible distor
diaphragm after anotherfor' the speaker until
tion of the cone diaphragm, and the armature, 30 a sample is obtained with the required matching
characteristics. This has been a "cut and try”
or at least one of the two, introduces the possi
bility of losses in the diaphragm driving energy
method requiring a very large supply of compo
sition paper diaphragms of various types and
over the entire operating system of the speaker.
composition. Relying upon this method caused
There has been a further diihculty in the prior
di?iculties when the diaphragm composition
devices of the type discussed in providing an
changed after the speaker left the manufacturer
armature mounting and assembly which was
rugged enough to withstand a large driving force
due to the absorption of moisture ‘or .the like.
A still further di?iculty has been encountered
‘on the armature to be transmitted to the dia
in magnetic-type speakers where metallic sounds
phragm so as to produce a sound output com
parable to the dynamic-type speaker, which is
generally recognized as more powerful. In the
dynamic-type speaker, the voice coil or movable
element, which, in some respects, is comparable
to the armature of the magnetic-type motor, has
a substantially unlimited path for movement-in
a linear direction as contrasted to the air gap
40
resulted from the usual metallic washer and
stylus connection at the apex of the diaphragm:
cone. Dimculties in this regard have oiitenv be;
come apparent after the speaker has
for some time.
in‘
, ..
v
improved
It is an loud
object
speaker
of thisofinvention
the magnetic
to’ provide
type. - ' .
which limits the vibratory path of movement of
_ A further object of this inventionis to provide
a rugged, magnetic-etype speaker capable ‘of pro
.a magnetic-type Speaker
Furthermore, the
mounting for a voice coil in the dynamic-type
ducing a strong magnetic ?eld, and accommo
speaker is of such construction that almost un 50 dating in all'of the operating parts large vlbra;
tory forces generated in the moving armature
limited movement can be applied thereto with
for the unit as a result of the large magnetic
out weakening such mounting. However, the
forces applied.
l
prior art generally has been unsuccessful in pro
viding an energy output at the armature and a
A still further object of this invention is to pro
mounting therefor rugged enough to accommo 55 vide a magnetic-type loud-speaker liberating with
2
a,sso,aoo A
which can beassembled accurateiyandatlow
high ?delity in a pleasing frequency range, and
without undesirable metallic noises, regardless of
structural variations in the composition paper
cost. A short-circuited coil is provided around
the stationary voice coil of the motor unit to serve
optionally, or simultaneously, as a part-of a tone
cone diaphragm of the speaker.
control system for the speaker, and a corrective
Another object of this invention is to provide
network for the speaker circuit and output circuit
a vibratory motor comprised of relatively few
of the radio receiver ?ierewith to prevent distor
parts easily assembled into an open assembly read
tion at the high frequency end of the operating
ily accessible for inspection and handling, and yet
range. A ‘driving mechanism yieldahle in sub
provide a motor and loud speaker comparable in
?delity of reproduction with large expensive 10 stantially all directions radially of the apex of
the diaphragm cone. acts to absorb possible dis
mechanisms with precision parts.
tortion in the movement of the diaphragm, and
One of the features of this invention is the
yet at the same time accurately transmits the
provision of an improved powerful magnetic cir
driving movement of the armature from the motor
cuit for the vibratory unit of the speaker with a
large vibratory energy output, which unit is 15 to the diaphragm. The entire driving mechanism
and the remainder of the motor structure is gen
capable of fully utilizing this output in providing
erally readily accessible from all four sides of the
a greater volume and ?delity of reproduction in
substantially open frame for the motor.
the speaker.
Referring now to the drawing, the complete
Another feature of this invention is the provi
sion of means for varying the tone of reproduc 20 speaker is shown in Pig. 1 with the usual cone
shaped composition paper diapbrlkm I suitably
tion, and providing a cut-‘oi! for frequencies at the
supported on basket-like frame means l h'aving
high frequency end of the operating range to
afiatportion ‘Irearwardlythereoftomounta
minimize undesirable distortions in the repro
duction.
,
vibratorymotorl. 'rhevibratornmmormotor.‘
-
A further feature is the provision of yieldable. 25 includes a pair of spaced frame members 8 and
ILWiththememberHbeingsuitabIysecuredin
diaphragm driving mechanism in the speaker of
arigidfasteningtotheportion‘lofthediapnrsgm
my invention which mechanism will take up and
frame. Apermanentmagnetllinbiockshape
absorbany undesirable tenseness in the moving
parts of the speaker to thus avoid undesirable dis
composedofamaterialhavinghighmagnetiere-v
30 tentivity characteristics, such as various‘matal
tortion. noise, and loss of operating emciency.
alloys available commercially,- is positioned with Further objects, features, and advantages of
twoopposite facesres?ngagainsttheframemsm-.
this invention will become apparent from the fol
bersiandllwhich'arepartofthemmdr
lowing description when taken in connection with
the accompanying drawings,inwhich:
cult through such permanent magnet is and
1'
Fig. 1 is a side elevation of the compietely.'as
35
throughtheremainderofthemagne?cstructure
ofthemotor,aswillbeexplained.
'rhearmatureandpolepieceassemblyforthe
sembled loud speaker with the diaphragm and
diztphragmi supporting frame assembly shown in
motor includes a pair of substantially U-sh'aped
on;
pole pieces I‘ and I! oppositely disposed, as
Fig. 2 is an enlarged fragmentary sectional view
40 shown in Fig. 1, both of laminated construction.
taken along the line 2-2 mm. 1:
avoioe coilvsubstantialiyovalinshape ?tting
Fig. 2A is a fragmentary sectional view along
the line 2A-2A of Fig. 2 to illustrate primarily the _ snugly withinthe channels of the pole'pieces, and
air gaps between the armature and active faces of
alaminatedarmature II 'withassociatedmount
the pole pieces, with a mounting in the back
ingmcans. 'l‘hearmature i1,intheillustrated
45 embodiment, includes a pair of relatively heavy
ground intermediate such faces;
Fig. 3 is an exploded fragmentary view of the
laminations ll. outwardly to each side of said
armature unit for the speaker motor at a step in
heavy laminations are thinner laminations ll of
the process of assembly of the motor prior to its
thesamearea. Adiaphragm'drivingarmor
portion 2. has a body portion integral therewith
?nal assembled form;
“
Fig. 4 is a circuit diagram of the output circuit
ofthesamesizeasthearmaturelaminations.
of a receiver system utilizing the loud speaker,
and the body portion is positioned intermediate
and the electrical circuit of the loud speaker; and -.theheavylaminationsllasisshowninl1g.2.
Figs. 5, 6,- and '1 are diagrams of modi?cations of
The laminations II and the intermediate mem
se
ber 20 haveacentralapertureineachofsub
theshort-circuited coil portion of the electrical
system shown in Fig. 4.
.
55
In practicing the invention I provide a mag
netic-type speaker having a cone-shaped dia
phragm with a wooden plug at the apex thereof
driven by a vibratory motor including a pair of
frame members supported on the diaphragm sup
porting frame as well as adJustably serving-as a
part ‘of the magnetic circuit of the motor}- and
clamping means to maintain the separable parts
stantiallythesamesizeasanarmaturemolmting
or torsion spring 2| rectangular in crom-section
and extending through the apertures in a press
lit. The laminations ll have a larger central
aperture which together form a bore 22 oneach
side of the laminations It. To rigidly secure the
central portion of the spring 2| within the ‘lami
nated armature II, the spring is driven into the
apertures in the laminations II and the member
of the motor in assembled condition. The motor
2| with a drivingv or press ?t. This is accom
unit includes an armature positioned between a 65 plished with a press. Punches driven in from
pair of pole pieces, and mounted for vibratory
each side of the armature through the bores 22
movement on mounting blocks at the ends of the
then stake the spring and these members to
armature supported directly upon the active pole
gether to make the connection even more rigid
faces of'the pole pieces, The blocks also act to
and secure. Rivets ll extend lengthwise through
space the pole faces apart to form with‘ said arma- ' 70
ture, air gaps between the armature andpole
faces. I The armature is operatively connected
with the mounting blocks in a manner to accom
thepartsofthearmaturetosecm'esuchparts
rigidly together; 'nie completely assembled ar
matureisdippedinhotsolderandthenshahsn.
Bolderwilladheretothelamina'tions "and,
modate very heavy operating forces developed in
springil attheirconnectiombutwillbelhaken.
the- armature, and yet provide a comstmction 76 freeofthelaminationssndspringinthsbmu
3
2,880,869
22 so that the spring will be free of the armature
over the length outwardly from laminations l8 to
the stationary ends, as will be described. In the
illustrated embodiment the free portions of the
spring are each 5'‘, inch in length. This length
sembly of the armature II, a paper disc or ele
ment 28 with a central aperture is placed over
each spring extension with the edge of the aper
ture hugging the spring so that no solder will
subsequently ?ow from the outer end of the
must be great enough to provide a wide am
spring onto the movable portion outside the end
plitude of vibration for the armature, but short
of the armature and extending into the bore 22
enough so that the armature will be snubbed or
of the armature. This assembly is then placed
stopped quickly and decisively for the reverse
in a ?xture and the discs 21 are driven or pressed
movement in a complete cycle. At ordinary op 10 thereon, as previously described, being spaced 9.
erating frequencies the armature vibrates at
distance of 31; inch away from the corresponding
great speeds, and with great power, as can be
end face of the armature. In the embodiment of
readily understood. with the present magnetic
the invention illustrated herein, the armature
from end face to end face is {1; inch wide, and
circuit,
The torsion spring 2| has an extension at eac
with the spacing of 3‘; inch between each disc
end beyond the outer armature ends as shown in
21_and the corresponding armature end, the in
Figs. 2 and 3 which is yieldable over at least a
side faces of the discs themselves are spaced 1/2
portion thereof in accordance with the vibratory
inch apart. After this operation, the armature
movement of the armature 11 as has been ex
and assembled elements are mounted on the blocks
plained. The outer ends of the extensions, how 20 24 with the discs 21 ?tting loosely within the
ever, are rigidly supported, as will be described.
aperture 29 in each mounting block. The aper
The spring must be of such material as to pro
ture 29 has an inside diameter greater than the
vide the necessary flexibility and yet not permit
outside diameter of the discs so that there will
the armature to vibrate through so great an am
be relative play therebetween in the original as
plitude of vibration that it will strike the adja
sembly. These parts are then properly positioned
cent pole faces of the pole pieces ill and It. The
in two pole pieces in the manner shown in Fig.
entire driving force of the armature is applied
1, and with these parts assembled in a jig, the
to the torsion spring between the laminations l8
armature is shimmed on each side to provide
and the stationary ends, and concentrated at its
the desired airgap intermediate the armature
maximum at the axial center line of the spring.
and active pole faces A, the discs 21 meanwhile
With the strong magnetic ?eld developed in the
moving within the aperture 29 of each stationary
magnetic circuit of the present invention and
block 24 until the armature is centered as de
the high eiiiciency in the utilization of the mag
sired.
netic forces in the motor, a considerable twisting
With the inside dimension of the aperture 29
or torsional de?ection is applied at the axial
being greater than the perimeter of the disc 21,
center of the stationary ends.
any misalignment between the discs and the
The armature 'I1 is supported through the ex
spring 2| which might have occurred from shear
- tending ends of the torsion spring 2i in mounting
or torsion blocks 24 of a non-magnetic metal,
ing one side or the other in the pressing oper
with one of each of said blocks at each spring
extension. Slight projections 26 on each of the
two opposite sides of the mounting blocks ?t be
ation, is accommodated and the axial center of
the armature can be centered in the air gap.
Furthermore, inequalities in the disc and mount
ing blocks can be accommodated, and rather wide
tween the corresponding legs of the oppositely
disposed pole pieces l4 and It to center the blocks
manufacturing tolerances permitted for the
discs 21, and the apertures 29 in the mounting
with reference to the active pole faces A of the " blocks.
pole pieces, and the‘adjacent edges 25 of each
block rest directly against such active pole faces,
as shown in Fig. 1. Thus, the mounting blocks
support the armature and at the same time de
termine the spacing between the active pole faces
A of the pole pieces I4 and IS. The faces A with
the adjacent faces of the armature, form an air
gap, or air gaps between the armature and pole
pieces, as shown in Fig. 2A. The width of such
air gap or gaps, determines the limits of the am- '
plitude of vibration of the armature about its
axial center without it actually striking the pole
faces so as to cause an undesirable metallic sound
in the speaker.
To accommodate the considerable forces de
veloped upon movement of the armature and
transmitted through the torsion spring to the
This makes possible a fast and inexpen
sive assembly, and also permits greater tolerances
in the parts themselves which speeds up manu
facturing and reduces costs without in any way
sacri?cing precision of operation in the ?nally
assembled unit. When the armature is properly
positioned‘ with reference to the pole faces A,
solder is ?owed onto the mounting blocks to
completely solder the gap between the edge of
the discs and the inside edge of the apertures 29.
At the same time the ends of the spring exten
sions in the apertures 21' of the discs are soldered
to the discs. As mentioned, the paper blocks 28
prevent any of this solder from ?owing on to
the free portion of the spring where it might
change the twisting action of the spring. The
papers can be quickly torn from the armature
assembly afterv the soldering operation.
mounting. blocks without any danger of loosening
between‘the spring 2| and its entire support, this
After this assembly operation, a voice coil V
including a wire coil 3| is inserted in the op
force is dissipated substantiallyjthrough a rel
positely disposed channels of the pole pieces, the
corresponding armature assembly is inserted into
the center opening in the voice coil, and the
active pole faces of the pole pieces l4 and iii
atively integral metal portion at each.‘ stationary
end of the spring, and is materially lessened .
when it reaches the ?rst soldered connection in
are pressed against the edges 25 of the mounting
the mounting structure, as will be described. This
is accomplished by metal discs 21 which are Ti) blocks, as previously described. The armature
will take the same position with reference to the
pressed on to corresponding ends of the torsion
pole faces as it did in the original assemblv
spring 2| in a driving ?t. The aperture 21’ in
which included the soldering of the discs 21 and
each disc 21 corresponds as precisely as possible
mounting blocks 2i.
to the cross-sectional area of the torsion spring
LI
The pole-piece-armature assembly is positioned
2| at each extension. After the complete as
4
2,880,889
intermediate the frame members 8 and H at
the end of the frame opposite that in which the
magnet I2 is supported. The attraction between
the frame members, in the magnetic circuit of
the permanent magnet is such that the pole
accurately transmits the movement of the driv
ing arm 20in the desired step-up ratio. The
step-up arm 38 is connected to the driving arm
20 by a connecting member 42 of substantially
the same thickness as the stylus 34 and of the
same material. Connecting member 42 is rec
tionary, but in addition a pair of‘ bolts or screws
tangular in cross-section and yieldable in the same
32 extend through the two frame members to
lateral directions as the stylus 34 if strains are
maintain a clamping tension on the motor to
applied to the driving mechanism to move it
10
supplement the normal magnetic holding force,
slightly out of a normal substantially straight
as described. The difference in length between
line movement for its individual parts.
piece and armature assembly is maintained sta
the magnet l2 and the pole-piece-armature as
The yieldability of the driving mechanism in
sembly is accommodated by bending the frame
at least four directions in addition to absorbing
member ll inwardly toward the diaphragm frame
unequal‘ stresses and strains in the diaphragm 5
at the outer end of the motor as shown in Fig. 1. 15 also prevents undesirable strains which have here
The diaphragm driving portion 20 extending
tofore been applied to the diaphragm by the driv
from the armature is ?at in form and provided in
ing mechanism of the magnetic-type speakers of
a relatively rigid material. The member 20 is op
the prior art. As will be noted from Fig. 1, the
eratively connected with vthe diaphragm by means
upper end 33 of the driving arm 20, by virtue of
of driving mechanism including elements consti 20 the length of such driving arm, moves through
tuting a step-up transformer for the vibratory
an arcuate path of appreciable length. The move
ment of the end 33 is stepped-up in the driving
motion of the armature. The mechanism is yield
able in at least four directions extending radially
mechanism, and there is appreciable movement of
outwardly from the apex of the diaphragm cone
the members 38 and 34, with the end of the mem
5. The yieldability of the driving mechanism 25 ber 38 moving in the same general arcuate path.
With the normally rigid parts of the prior art
absorbs strains and stresses which might develop
in the cone 5 in its normal vibratory motion as a
driving mechanism it is readily understood that
result of a lack of uniformity in composition over
an element comparable to the stylus member 34
would act to pull the diaphragm out of a straight
its entire body and surface. It has been substan
tially impossible to provide entirely uniform cone 30 line movement axially of the axis of the cone.
diaphragms of composition paper material so
The members of the present driving mechanism
that each part of the diaphragm will move uni
yield so that the diaphragm moves in the desired
formly in a straight-line direction axially of the
straight-line path, rather than beingfor'ced, due
axis of the cone. In magnetic-type speakers of
to a rigid stylus and associated elements, to follow
the ‘prior art this condition of the cone dia 35
the stylus.
phragms resulted many times in distorting the
As previously mentioned, if the diaphragm, on
the other hand, would tend to move irregularly
due to any inequalities in its composition this
armature out of its normal path of movement so
that it was forced into contact with one or the
'
other, or both, of the, pole faces A causing unde
is absorbed in the driving mechanism and the
sirable noises to be reproduced in the speaker. 40 armature is not disturbed in its normal-vibratory
path. The yieldability of the entire driving mech
This di?iculty has been overcome, however, by the
driving mechanism including a stylus member 34
anism connected to the arm 20 is improved by
virtue of the rubber mounting 38 for the step-up
rigidly secured at one end in a wooden plug 36,
which in turn is cemented to a flange F at the
arm, and the entire mechanism has a desired de
apex of the diaphragmuilsAbore, or recess R, is 45 gree of ?exibility without in any way impairing
provided centrally of the plug at the rear face
an efficient transmission of force from the arm 20
to the diaphragm 5.
»
thereof, and a hooked end 35 of the stylus mem
The accepted method of connecting a stylus
ber 34 is secured in the recess R by a suitable ce
and paper cone diaphragm in the prior art mag
mentious material.
The stylus 34 is preferably provided in a phos 60 netic-type speakers has been a metal washer as
_ phor-bronze alloy material, of ?at form, and
sembly at the apex of the cone to which the sty
' about .007 of an inch in thickness. ‘This thick
lus is soldered or otherwise secured. This has
ness provides su?icient rigidity so as to faithfully
resulted in undesirable metallic sound being re
transmit the movement of the driving mechanism
produced in such speakers, and at times di?icul
to the diaphragm in a direction substantially lon 55 ties have arisen as a result of the metal washer
gitudinally of the stylus, and yet the thickness
unit becoming loose on the cone. These difficul
and ?at form permits the stylus to yield or bend
ties have been- overcome, and a more mellow,
slightly when necessary in two opposite lateral
pleasing tone obtained from the speaker by use '
directions extending from the opposite flat faces
of the wooden plug 36 cemented to the cone 5 at
of the stylus. The projecting end 31 of the stylus 60 its apex and carrying the stylus 34, as previously
is rigidly secured to the outer end of a step-up
described. In the preferred embodiment of the
arm 38, which is yieldably supported at its inner
invention a plug of white birch has been em
end on a rubber mounting or grommet 39. The
ployed. There is a desired porosity in this wood,
mounting 38, in turn, is supported on the frame
although somewhat limited, and a hardness such
member II, by a screw or similar supporting 65 that sound is faithfully reproduced by the speaker.
means 4|. The step-up arm 38 likewise is pref
A soft wood is undesirable because it will not
erably provided in a phosphor-bronze alloy ma
faithfully reproduce sounds, and yet the plug
terial, ?at in form, and approximately .020 of an
material must not be so hard that a. shrillness
inch in thickness. Although the step-up arm 38
results.
'
is thicker in cross-section than stylus 34, it is 70
In loud speakers of the prior art, particularly
still yieldable in two opposite lateral directions
of the magnetic type there have been at least two
which are at right angles to the direction of lat
problems of a serious nature with reference to
eral movement of the stylus 34 as can be under
the frequency of reproduction in the speaker sys
stood from the consideration of Fig. 1. However,
tem. The normal extremes of frequencies in the
the step-up arm 38 is su?iciently rigid so that it 75 operating range are 100 cycles and 5000 cycles.
2,380,869
Various radio receiver manufacturers desire dif
5
factors can be changed to affect the optimum load
resistance on the output tube 44, as well as change
the frequency cut-off point to obtain the tone
ferent cut-oi! frequencies in' the loud speakers
for their receivers, so that the ?nal result seems
to be an emphasis on one range of frequencies
or another rather than the maximum ?delity over
desired by a particular purchaser. After the par
ticular result is obtained the coil 43 can be du
the entire range. The accepted method in the
prior art of satisfying these requirements has
plicated ‘for all future speakers to provide the
been to shift from one paper composition cone di
speaker characteristics.
However, since the coupling, and the num
same coil factors, and consequently the same
aphragm to another until the desired reproduc
tion is obtained. This has necessitated carrying 10 ber of turns in the coil 43 can be designed to be
a large number of cone diaphragms in stock.
constant for a rather wide variety of conditions,
light, heavy, and intermediate, in composition.
control over the operating range of the speaker
Merely by "cut and try" the desired result was
can be obtained by inserting variable means in
?nally obtained. Such efforts in this respect were
the supplementary coil circuit. In Fig. 5 the
sometimes wasted, however, when diaphragm
coil 43 is illustrated in a circuit with a variable
characteristics changed as a result of absorbing
moisture or the like after the speaker was man
resistor 46 which can be installed so that it is
available at the front of the radio receiver cab
inet in which the speaker is installed, and hence
ufactured.
serve as a tone control for the speaker. Like
The second di?iculty considered above has-been that of providing a corrective network for mag 20 wise, as can be understood, such a circuit can
netic-type speakers, in particular, to compensate
be used to advantage by a manufacturer in de
for a normal impedance increase with an in
termining the speaker characteristics he desires.
crease in frequency in the output tube and
The resistor can be varied until the desired fre
speaker circuit. Normally, as the impedance rises
quency cut-off is obtained and the circuit of coil
in the vibratory motor circuit beyond an opti
43 can then be duplicated in a coil to be wound
upon the voice coil 3|, as previously described.
mum resistance, or load, to be applied to the out
Another variable circuit is illustrated in Fig. 6
put tube in the circuit of the receiver, harmonics
with the short-circuited coil circuit including a
are generated and they introduce distortion in
the speaker system.
?xed resistor 41, and a switch in which an arm
Both of these difficulties have been overcome 30 48 can be moved to various terminals to vary the
resistance in the complete circuit.
by the use of a supplementary short-circuited coil
Fig. 7 illustrates a coil 43' normally of a num
43 wound around the insulation on the wire 3|
of the voice coil and inductively coupled to such
ber of turns to take care of the maximum con
voice coil. The voice coil has a certain self-in
ditions, and a switch with terminals 49 connected
duction, and with the coil 43 wound upon the 35 to various parts of the coil 43'. A switch arm 5!
is movable over the terminals to vary the ef
voice coil so that the coupling, or mutual induct
fective coil portion in the circuit. The circuits
ance between the coils is not zero, the effective
and structures of Fig. 6 and Fig. 7 can be. em
_ inductance of the voice coil 3| is reduced. The
ployed as tone controls in the same manner as
voice coil becomes, in one sense, a primary and
the coil 43, a short-circuited secondary thereon.
40
The amount of reduction in the effective induct
ance of the voice coil depends upon the degree of
coupling between the two coils, upon the fre
quency in the voice coil, and upon the resistance
of the circuit of the supplementary coil 43.
Furthermore, the coil 43 not only produces a re_
duction in the effective inductance of the voice
coil, as the frequency increases in the coil cir
cuit, but the coil 43 also increases the resistive
component of the voice coil. Therefore, as the 50
frequency in the circuit of the output tube 44,
and hence in the voice coil, increases, the amount
of current induced in the coil 43 is increased and
a greater proportion of the energy available from
the tube 44 is consumed by the coil 43. This
tends to maintain the optimum resistance or load
on the tube 44 constant throughout the fre
quency range to be produced, and to prevent gen
eration of harmonics at the high frequencies
which would result in undesirable distortion in (it
the sound reproduced in the speaker.
_
described for the circuit of Fig. 5.
The invention thus provides a magnetic-type
loud speaker with a powerful magnetic circuit,
and a ruggedness of mechanical design to accom
modate the large power output of the vibratory
motor. The vibratory motor and associated ele
ments are simple in design, and readily adapted
for inexpensive and yet accurate manufacture,
and with all of the parts easily accessible in the
motor frame both during manufacturing assem
bly, and service work. The entire unit is provided
in a construction and with an electrical circuit
(including the magnetic circuit), such that a
pleasing reproduction is obtained with remark
ably high ?delity. The same vibratory unit em
bodying the present invention has been used in
a single size, except possibly a slight change in the
size of the permanent magnet, to drive cone dia
phragms ranging all the way from three to eight
inches in diameter, and provide the same desir
able operating characteristics for the speakers in
all of these sizes.
The amount of decrease of the impedance of
It is to be understood that only the preferred
embodiment of the present invention has been
the voice coil depends upon various factors in
the supplementary coil 43, and in the relation
illustrated and described herein, and that altera
between the two coils. The action of the coil 43 65 tions thereof can be made which are within the
depends upon the degree of coupling between it
‘scope of the invention as defined by the appended
claims. It is understood that these dimensions
and the voice coil, upon the number of turns of
wire in the supplementary coil, and upon the re
are merely illustrative and not limiting as to em
bodiments of the invention.
sistance in the supplementary coil circuit. These
I claim:
factors can be changed in a single coil by varying 70
the spacing between the coils 3| and 43, by vary
1. A magnetic type motor including a pair of
spaced apart pole faces, an armature positioned
ing the number of turns in the coil 43, and chang
between said pole faces having an axially extend
ing the resistance in the coil 43 circuit, by the
ing mounting portion on each side, a mounting
means, for instance, of changing the wire to one
block for each mounting portion positioned be
of a different resistance. Some one or all of these
6
2,880,869
tween the pole faces and axially of the corre
spending end of the armature, with each mount
ing block having an .aperture centrally thereof,
means for operatively connecting each mounting
portion and its corresponding mounting block in
cluding a disc with an outside perimeter smaller
., than the inside dimensions of the mounting block
aperture, whereby the armature may be centered
with reference to the pole faces during the assem
bly of the parts, and means rigidly mounting
each of said discs in its corresponding aperture
against relative movement after the ?nal posi
tioning thereof.
,
'
'
'2. In a vibratory unit for a loud speaker having
a diaphragm, an armature unit including an
armature member having an axially extending
supporting spring, a disc element rigidly mounted
at each end of said spring, a pair of spaced non
magnetic supporting members for said spring,
each of said non-magnetic members having an
opening therein adapted to loosely receive a cor
responding one of said disc elements, and a pair
of oppositely arranged magnetic pole faces op
eratively associated with said armature member,
said two disc elements being of lesser dimensions
magnet in block shape resting on said frame
member at one end thereof, a pair of pole pieces
having an armature and a voice coil vtherebe
tween supported as an assembly on said frame
Cl
member at the other end thereof with the outside '
of said assembly exposed and readily accessible
at the end of the frame member, said armature
having a driving portion thereon extending to
ward said one end, a second frame member sub
stantially parallel to said ?rst frame member en
gaging said magnet on a side thereof opposite
said ?rst frame member and engaging the pole
piece assembly on a side thereof opposite the ?rst
frame member, with said frame members being
maintained in position generally by the magnetic
attraction in the magnet block and pole pieces,
means operatively connected to said driving por
tion and extending therefrom for connection with
a loud speaker diaphragm, and supplementary
frame assemblylng means consisting of a pair of
bolts extending between said frame members,
with said driving portion and said operatively con
necting means being exposed and readily acces
sible at the ends of the frame members adjacent
the permanent magnet.
,
than the openings in said non-magnetic mem
6. A motor for driving a loud speaker dia
bers to provide for a predetermined spaced rela
phragm including frame means, an armature unit
tion of said armature member with said pole
having a diaphragm driving portion, and means
faces, and means rigidly securing said disc ele
operatively connected with said driving portion
ments to said non-magnetic members to retain 30 for connection to a diaphragm including a stylus
, said predetermined spaced relation.
member having a projecting end, with said stylus
3. In a motor for a magnetic type loud speaker
member being rectangular in cross-section and
having spaced pole means de?ning a gap there
yieldable laterally in only two opposite directions,
between, the combination of an armature posi
a step-up arm rigidly secured at one end to the
tioned in said gap adapted to oscillate about an 3._ projecting end of said stylus member, being rec
axial center therein and apertured mounting
means on each of two sides of the armature for
mounting the armature in said gap, with said
tangular in cross-section and yieldable only in
two opposite directions, said directions being sub
stantially at right angles to the direction of lat- -
armature and the two mounting means being op
eral movement of the stylus member, said step-up
eratively connected at one portion on each 40 arm being supported at its other end on said
mounting means in a fused metal connection, said
frame. means, and means connecting said step-up
armature having an extension to each side there
arm with said diaphragm driving portion being
of including the axial center for the armature,
rectangular in cross-section and yieldable later
and means for displacing said fused metal con
ally in the same directions as the stylus member,
nection radially from the axial center of the ex 45 said yieldability of the stylus member, said step
tension at each mounting means including a disc
up arm, and said connecting means being such as
on each extension and rigidlysecured thereon
to accurately transmit the driving motion of said
and ?tting within the aperture in the correspond
driving portion to a diaphragm while permitting
ing mounting means, with the perimeter of each
a substantially free movement of such diaphragm
disc displaced radially from said axial center, and 50 in a direction other than a straight-line direction
said fused metal connection being between said
longitudinally of the stylus member.
disc and said mounting means at said perimeter
7. A vibratory unit for a loud speaker dia
and said aperture.
phragm including frame means, an armature unit
4. In‘ a motor of the magnetic type having
having a diaphragm driving portion, a step-up
spaced pole faces with a gap therebetween, the
arm of ?at form laterally ?exible in two direc
combination of a vibratory armature positioned
tions, means supporting one end of said step-up
in the gap between said pole faces having an axial
arm on said frame means, with its other end be
portion extending to each of two opposite sides
ing rigidly secured to the projecting end of a
beyond the corresponding side faces of the arma
stylus element for a diaphragm, a stylus element
ture, said axial portion being stationary at its 60 of flat form laterally ?exible in two directions
outer ends outside of the corresponding sides of
which are substantially at right angles to the
said armature and being movable with said arma
directions of lateral movement of said step-up
ture inwardly of said ends, an apertured stationary
arm, and a connecting portion rigidly secured at
mounting block for each stationary end, and
one end to said step-up arm at a point interme
means for anchoring the outer ends of said axial 65 diate said supported end and stylus element and
portion within the apertures of said mounting
rigidly secured at its opposite end to said dia
blocks, said anchoring means comprising ?at
metal parts rigidly mounted upon the ends of said
phragm driving portion, said connecting portion
being of ?at form and laterally ?exible in the two
axial portion and having edges which loosely ?t
lateral directions of said stylus member, with the
within said apertures, and a fused metal connec 70 ?exibility and relative arrangement of said stylus
tion between the outer edge surface of each of
member, step-up arm, and connecting portion
said metal parts and the adjacent inner edge sur
providing for a free vibrational movement of a
face of its associated mounting block.
diaphragm in response to the movement of said
5. A motor for driving a loud speaker dia
armature and diaphragm driving portion.
phragm including a frame member, a permanent 75 8. A vibratory unit for a loud speaker dia
7
phragm including frame means, an armature
unit having a diaphragm driving portion, said
diaphragm driving portion being of relatively
rigid construction and straight over its longitu
dinal length, a stylus member rigidly secured at
one end to said diaphragm and having a portion
projecting therefrom, said stylus member being
in one of said openings, said mounting elements
being of lesser dimensions than said openings
but of substantially greater dimensions than the
cross-sectional dimensions of said spring bar,
fused metal connections between the adjacent
surfaces of said ‘mounting elements and said
supporting members, and an armature rigidly
mounted upon said spring bar between said sup
adapted for yielding in a plane which is at sub
stantially right angles to the plane in which said
porting members.
driving portion normally moves, a step-up arm 10
12. in a unit for vibrating a loud speaker dia
phragm, a pair of spaced-apart assembly mem
rigidly secured at one end to the projecting por
tion of said stylus member, means including
bers, a ?eld structure including said members
yieldable means for directly supporting said step
and a pair of magnetic ?eld pieces having op
positely disposed pole faces, spaced-apart non
up arm at its opposite end on said frame means,
said step-up arm extending longitudinally sub 15 magnetic mounting platesv interposed between
stantially in the direction of said driving portion
said neld pieces and having edge portions bear
but spaced therefrom and being yieldable in lat
ing against said pole faces to maintain said ?eld
eral directions opposite to the directions of lat
pieces spaced apart, means extending between
eral yielding of said stylus'member, and a mem
said assembly members for clamping the named
ber connecting said driving portion with said
parts together to Provide a rigid assembly, an
step-up arm and yieldable laterally in the same 20 elongated armature driving element ?exibly an
directions as said stylus member, with said con
chored at one end on one of said assembly mem
necting member extending in a plane substan
bers, a second elongated driving element con- tially parallel to the plane of said stylus member,
nected at one of its ends to an intermediate por
said stylus member, said connecting member, said 25 tion of said armature driving element and ex
step-up arm, and said yieldable supporting
tending substantially normal thereto, an arma
means cooperating on movement of said driving
portion to absorb any strains which might de
velop in a diaphragm and thereby provide for a
substantially free vibratory movement of such a
diaphragm.
' 9. In driving means for a loud speaker dia
phragm a vibratory armature with a diaphragm
- driving portion, the means connected to said dia
phragm driving portion for operatively connect
ing said portion to a diaphragm and absorbing in
said means strains-which might develop in said
ture interposed between said pole faces and
provided with a driving arm connected to the
opposite end of said second driving element, said
mounting plates each being, provided with an
therethrough, an elongated torsion
spring rigidly supporting said armature between
said pole faces and provided with ends extending
within said openings, mounting elements rigidly
30 opening
' mounted upon the ends of said torsion spring
and loosely ?tting within said openings, and
fused metal connections between the adjacent
armature or such a diaphragm to be driven
edge surfaces of said mounting elements and
thereby tending to disrupt the free movement of
said plates.
either, said means including a plurality of con
13. In a unit for vibrating a loud speaker dia
nected driving members, at least two of which 40 phragm, a pair of spaced-apart assembly mem
driving members are rectangular in cross-section
bers, a field structure including said members
and substantially non-yieldable in either of two
and a pair of magnetic ?eld pieces having op
lateral directions ther from, and yieldable in two
positely disposed pole faces, spaced-apart non- ,
oppositely disposed la eral directions substan
magnetic mounting plates interposed between
tially at right angles to said ?rst two mentioned 45 said ?eld pieces and having edge portions bear
lateral directions.
ing against said pole faces to maintain said ?eld
10. In a vibratory motor having an air gap,
pieces spaced apart, means extending between
and a movable driving member therein having
said assembly members for clamping the named
axial extensions extending outwardly in two op
parts together to provide a rigid assembly, an
posite directions therefrom, apertured mount 50 elongated armature driving element ?exibly an
ing means for each axial extension, and means for
securing ,each axial extension in a corresponding
aperture with said driving member occupying a
predetermined position in said air gap, includ
ing a. soldered connection displaced from the
chored at one end on one of said assembly mem
bers, a second elongated driving element con
nected at one of its ends to an intermediate
portion of said armature driving element and
extending substantially normal thereto, said two
axial center of the driving member so that the
driving members being rectangular in cross sec
forces generated upon movement of said driv
tion and being arranged with their ?at surfaces
ing member are transmitted to said mounting
disposed in planes which are substantially nor
means through substantial segments of the sol
mal to each other, an armature interposed be
dered connections, and including a disc rigidly 60 tween said pole faces and provided with a driv
secured on each axial extension with the perim
ing arm connected to the opposite end of said
eter of the disc smaller than the inside edge of
second driving element, said mounting plates
the aperture of the corresponding mounting
each being provided with an opening there
means into which it is positioned, and with said
through, an elongated torsion spring rigidly sup
soldered connection being applied between the
porting said armature between said pole faces
disc and the mounting means at such aperture.
and provided with ends extending within said
11. In a unit for vibrating a loud speaker dia
openings, mounting elements rigidly mounted
phragm, a pair of spaced-apart metal support
upon the ends of said torsion spring and loosely
ing members each provided with an opening
?tting within said openings, and fused metal
therein, a spring bar having ends positioned 70 connections between the adjacent edge surfaces
within said openings, a mounting element rigidly
of said mounting elements and said plates.
mounted upon each end of said spring bar with
JAMES P. QUAM.