Improvements in Sound Transmitting. Recording, and Reproducing Apparatus, applicable to Telephones, Gramophones, and the like.
Year: 1898

page_text: Date of Application, 9th Aug., 1898-Accepted, 1st Oct., 1898
Improvements in Sound Transmitting. Recording, and Reproducing
Apparatus, applicable to Telephones, Gramophones, and the like.
A communication by EMILE BERLINER and JOSEPH SANDERS, of McGill Building,
Washington, D.C., United States of America, Electricians.
I, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of the Agency for Foreign
Patent Solicitors, G, Lord Street, Liverpool, and 6, Bank Street, Manchester, both
in the County of Lancaster, 118, New Street, Birmingham, in the County of
Warwick, and 322, High Holborn, in the County of Middlesex, Civil Engineer, do
hereby declare the nature of this invention and in what manner the same is to bo
performed, to be particularly described and ascertained in and by the following
statement:-
This invention has reference to improvements in sound transmitting, recording
and reproducing apparatus, and is particularly applicable to telephones and
gramophones of all descriptions. In all sound transmitting reproducing or record-
ing apparatus, there is used a diaphragm which either vibrates under the impact
of sound waves, or in response to other periodic mechanical or magnetic forces;
and in all such cases it is essential that the diaphragm be particularly responsive
to the forces acting upon it and have as little tendency as possible to vibrate at
other rates than those of the periodic forces. Another requirement of such
diaphragm is that it vibrate with considerable amplitude in response to faint
impulses received; and it has been found that these two requirements are, in the
ordinary diaphragms; exclusive of each other. That is to say, a diaphragm which
vibrates with considerable amplitude under the impact of sound waves, or, under
the action of other periodic forces, displays a tendency to vibrate at the same time,
and persistently, at other rates than those imposed upon it. The meaning of this
general statement will become clear by the following considerations.
It is well known that a thin and large diaphragm will vibrate with considerable
amplitude under the impact of even faint sound waves, and this is a characteristic
which is highly desirable both in a gramophone or telephone; but it is found that
a diaphragm of this description has a fundamental note of its own which is
ordinarily of a far lower pitch than the sounds to be transmitted recorded or repro-
duced. In consequence thereof the rate and form of vibration of such diaphragm
does not exactly correspond to the rate and form of vibrations which it would
have if it faithfully obeyed the impulses which it receives. Whether such
diaphragm be used for the production or for the reproduction of a sound record,
or for telephonic transmission or reception, it will always superimpose upon the
vibrations which it receives by the periodic impulses which act upon the same, the
vibrations due to its own deep fundamental pitch; so that the sounds which it
should record or reproduce or transmit will be accompanied by the deep hum or
roar of its own fundamental note.
When the diaphragm is comparatively thick and small, its own fundamental
pitch is ordinarily higher than that of the sounds which directly or indirectly act
upon it, and while, theoretically, this fundamental pitch is still superimposed upon
the sounds received or conveyed by such diaphragm; such superposition ceases

page_text: to be practically effective, and the reproduction of recorded sounds, or the record
of sounds produced, or the transmission and reception of sounds obtained from
such diaphragm, is of particular purity, and highly desirable.
As above stated, however, the amplitude of vibration of such diaphragms are
very small, so that the sounds transmitted, reproduced or recorded, are faint.
It is the object of this invention to so construct a diaphragm and its appur-
tenances that it will have the sensitiveness of a large and thin diaphragm and
the purity of action of a small and comparatively thick one. This result we obtain
by connecting with a large and thin diaphragm an elastic resonant body of high
fundamental pitch, but which is so flexible that it does not reduce the amplitude
of vibration of the diaphragm to any considerable extent. Practically this is done
by connecting with the diaphragm, and preferably at its center, a short but thin
spring, which normally does not bear upon the diaphragm; that is to say that in
the position of rest of the diaphragm, neither the diaphragm nor the spring are
under strain, while when the diaphragm vibrates in either direction, it is forced
to bend, compress or expand the spring, so that both vibrate together as a com-
pound resonant system, each modifying the natural rate of vibration of the other.
A sonorous structure is thus obtained composed of one low pitched and one high
pitched element.
My correspondents have found that such sonorous structure combines the advan-
tage of a large and a thin diaphragm with the advantages of a small and thick
diaphragm, and is free of the disadvantages of both.
All this will more fully appear from the following detailed description; with
reference to the accompanying drawing, in which:
Figure 1 is an axial section of a sound box provided with our improved
resonant structure;
Figure 2 is an axial section of a sound box for a gramophone, embodying our
invention;
Figure 3 represents a section of the pivot and its bearings, of a gramophone sound
box, showing the latter in elevation, and
Figure 4 represents a like section of a gramophone sound box, with a modifica-
tion of our improved resonant structure.
Like numerals of reference indicate like parts all throughout the drawing.
Referring now particularly to Fig. 1, there is shown a diaphragm 1, mounted
in a casing 2, in any usual or preferred manner; and this diaphragm is by prefer-
ence made large and thin, so as to respond with great amplitude to periodic impulses
conveyed to the same, either by sound waves, or inagnetic pulls, or by a gramophone
or phonograph record. A diaphragm of this character has, as hereinbefore
explained, a low fundamental pitch of its own, which, whether the diaphragm be
used for recording or transmitting or reproducing sounds, superposes itself, and
thereby modifies in a disturbing manner the sounds which it is designed to record,
transmit or reproduce. In order to overcome this tendency a short and rather
thin spring 3 is employed which in this instance is shown as a leaf spring, fast
to any portion of the diaphragm support. In the present case this spring is shown
as secured to the underside of the face plate 4, of the sound box, and extends from
the same towards the middle of the diaphragm, with its free end either barely
or not at all touching the latter, so that neither the diaphragm nor the spring 3,
is under strain so long as the diaphragm is in its normal position. The free end
of the spring is secured to the diaphragm either by a drop of bees wax or solder,
or by any other means that excludes the possibility of putting strain upon either
the diaphragm or the spring. This mode of fastening the spring to the diaphragm
is indicated in the drawing by the numeral 5, and it has been found that some such
soft material as bees wax is eminently adapted for this purpose.
The leaf spring 3, being very short, has a high fundamental pitch of its own,
and the length and thickness of the spring should be so chosen that its fundamental
pitch is considerably higher than the pitch of any sound that is to be produced by,
or that controls the diaphragm.

page_text: The resonant compound structure of diaphragm and spring thus obtained, has
the characteristics hereinbefore indicated, that is to say, the diaphragm will now
vibrate with considerable amplitude and great purity in response to faint sounds
or other periodic impulses, without perceptible or obtrusive assertion of its own
fundamental pitch.
This characteristic of a diaphragm is particularly useful in connection with
sound recording and sound reproducing apparatus, and in Figure 2
one mode of applying this invention to gramophone recorders or repro-
ducers is illustrated. Here the diaphragm is mounted in the sound
box 2, in the usual manner, as indicated, and the corrective spring 3,
is fast to the underside of the face plate 4, and extends toward the middle of the
diaphragm, where it is bent up at right angles to the face of the diaphragm, with
its free end 6, fastened to one end of the stylus lever 7, At the bend, the spring
barely, or not at all, touches the diaphragm, and is secured to the same by a drop
of bees wax 5, or some other like material. The stylus lever passes between and
is pivoted in the legs 8, 8, of the forked standard 9, which is mounted upon the
sound box, as shown. A pivot pin 101, passing loosely through the stylus lever,
is screwthreaded and is securely fastened to the lever by the nuts 11, 11, one on each
side of the lever, and the lateral projecting ends of the pin 10' are conical and
engage the bearings 12, in the legs of the standard 9, as shown particularly in
Figure 3. By preference the bearings are also conical, but reversed with respect
to the conical ends of the journal pin, whereby the bearing surface at each end
is practically reduced to a line. The legs of the standard are so constructed so
as to normally spread apart, and they are adjusted for engagement of their bear-
ings with the pivot pin 10!, by a screw 10, which passes loosely through the two
legs, and by the nuts 14, 15, in a manner well understood. This affords a very
delicate means of adjustment of the bearings with respect to the pivot pin, so
that the minimum friction can be secured, and at the same time all wabbling or
lost motion may be avoided. Instead of making the forks of the standard so as
to normally spread outwardly, they may be made so as to normally spring inwardly;
in either case the adjustment of the bearings for minimum friction without lost
motion is readily obtained.
The outer end of the stylus lever is provided with a socket 16, for the reception.
of the stylus 17, which is clamped by the screw 18.
A device thus constructed, when used as a gramophone recorder, makes a record
of great amplitude and purity, and when used as a gramophone reproducer it
emits the recorded sounds loudly, faithfully and without the admixture of the
deep fundamental note of the diaphragm proper.
In Figure 4, a modified form of gramophone recorder or reproducer is shown.
In this case an arched stiff bridge piece 19, is secured to the face plate 4 of the
sound box; and from the center of this bridge extends a coiled spring 31, which
here takes the place of the leaf spring 3, shown in Figure 2. At the free end of
the helical spring 3' is secured a small rod 20, which extends to the middle of the
diaphragm, without touching it, and is connected with the diaphragm by a drop
of bees wax, so that in their normal condition neither the spring nor the diaphragm
is under tension. But when the diaphragm vibrates outwardly it compresses the
spring, and when it vibrates inwardly it stretches the spring; so that here again
we have a complex resonant structure, composed of a diaphragm of low fundamental
pitch and a spring of high fundamental pitch, the same as in the case of the con-
struction shown in Figures 1 and 2.
It will be readily understood that the combination of the low pitched diaphragm
and high pitched spring, into one resonant structure, may be effected in many
different ways, and we are therefore not confined to the identical structures herein-
before described.
It will also be understood that, while this improved resonant structure, combin-
ing the advantages of a large and thin diaphragm with those of a small and thick
diaphragm, and avoiding the disadvantages of both; is particularly useful in

page_text: telephones, gramophones or phonographs, it may be used for other purposes and
wherever vibrations that are strictly in accordance with impressed periodic
impulses, are required.
Having now particularly described and ascertained the nature of this said inven-
tion and in what manner the same is to be performed, as communicated to me by
my foreign correspondents, I declare that what I claim is;-
1. A resonator consisting of a resonant element having a low fundamental
pitch and a resonant element having a high fundamental pitch, joined and sup-
ported for simultaneous vibration without strain on either element in the normal
position of rest, substantially as described.
2. A resonator consisting of a diaphragm having a low fundamental pitch and
a resonant body having a high fundamental pitch, the two being joined and sup
ported for simultaneous vibration without strain on either in the normal position
of rest, substantially as described.
3. A resonator consisting of a large and thin diaphragm having a low funda-
mental pitch and a spring having a high fundamental pitch connected with the
diaphragm for vibration therewith and without mutual reaction in the normal
position of rest of the diaphragm, substantially as described.
4. A sound box consisting of a casing, a diaphragm having a low fundamental
pitch mounted therein, and a spring having a high fundamental pitch secured at
one end to the casing or its appurtenances, extending to the middle of the
diaphragm and secured thereto without strain of either, substantially as described.
5. A gramophone recorder or reproducer, consisting of a mounted diaphragm,
a spring connected therewith without strain between the two in the normal position
of rest of the diaphragm, and a stylus in operative relation to the diaphragin, sub-
stantially as described.
6. A gramophone recorder or reproducer, consisting of a mounted diaphragm,
a leaf-spring fixed at one end and extending over the face of the diaphragm to
the center thereof, and connected with the same by bees wax or similar material
without strain upon diaphragm and spring, and a pivoted stylus in operative
relation to the diaphragm, substantially as described.
7. An adjustable pivot support for a gramophone stylus-lever, consisting of a
forked standard provided with thrust bearings for the pivot of the stylus lever,
the legs of the standard normally tending toward or from each other, and means
for adjusting the legs against their tendency to the desired position, substantially
as described.
8. An adjustable pivot support for a gramophone stylus lever consisting of a
forked standard pro. ided with thrust bearings for the pivot of the stylus lever,
and means for adjusting the legs of the standard comprising a threaded rod passing
through them and provided with nuts arranged to engage and hold the legs in
the desired position, substantially as described.
Dated this 8th day of August 1898
WM. P. THOMPSON & Co.,
Agents.