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Патент USA US2145318

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Jan. 3l, 1939.-
w. scHENK‘E-r A1.`
„ 2,145,318 ‘
med July 1o, 1937
-"Patented Jan. 31, 1939
Walter Schenk and Waldemar Marthiens, Berlin,
Germany, assignors to Telefunken Gesellschaft
für Drahtlose Telegraphie m. b. H., Berlin, Ger
many, a corporation of Germany
_ Application July 10, V1937, Serial No. 152,916
In Germany July 14, 1936
(Cl. 179-1)
3 Claims.
ums, on station platforms, in long halls, etc., in '
The invention relates to a loudspeaker arrange
ment in which the individual loudspeakers are order to avoid lateral echo andecho-phenomena.
equipped with sound conducting surfaces. With ’ In many cases it may be'necessary to avoid
the arrangement there is obtained a preferably pronounced silent Zones at right angle to the_
5 longitudinally extended characteristic of the main radiation. In accordance with a further E
sound distribution in the direction of the axis of development of the loudspeaker arrangement ac
cording to the invention, measures are taken
the loudspeakers, while approximately at right
whereby the air enclosed in the housing of the
angle to the main axis of the loudspeakers sound
should pass at a possibly low degree.
It is known to impart to loudspeakers having
large surface diaphragms a certain directive ef
loudspeaker arrangement can communicate with `
fect by attaching to the loudspeakers cone-shaped
sound guides.` If the sound should be radiated
preferably only in two directions for instance in
15 the same axis, two loudspeakers are set up of
which the one radiates towards the one direction
and the-other loudspeaker towards the other
the outer air. It is advisable to provide openings w
in the walls of the housing whereby the sizeof
said openings is possibly controllable, or else,
shutter-like arrangements are built into the walls
so as `to obtain a greater or lesser couplingv of the
interior space with the outer air. Eventually, w
the walls not having loudspeakers fastened there
to may also additionally be adapted to open up
or may open up as such.
Now it was found in such arrangements that,
[email protected] especially when transmitting orders or commands,
the low frequencies propagating spherically are
noticed also outside the main direction of radi
ation of the loudspeaker, so that desirable silent
zones cannot be established, for instance when
my, speaking in long halls, on station platforms, etc.
In accordance with the invention a more favor
With these arrangements the characteristic of
the loudspeaker will be modified such that the @il
8-like shape will be widened out in the center so «
that an elongated characteristic will be obtained.
This entails the advantage that the transmission
can be properly heard directly underneath the
loudspeaker and in its vicinity. These control g5
arrangements at the housing have the further
advantage that the range of the sound waves can
loudspeakers equipped with sound guide, for in- » be influenced.
The loudspeaker arrangement can be so oper
stance in the form of a cone and radiating in
able reproduction with large surface diaphragm
9,@ opposite directions, is obtained in-that the two
systems are accommodated within a common
The air space enclosed in the housing causes
ated that when using for instance two loud- ao
speakers the diaphragms of the loudspeakers move
both simultaneously outwards with respect to the
In order to obtain especially sharp ex
a damping of the large amplitudes of _the dia
m phragm and therefore predominantly a damping
of the low frequencies.
In this way the propagation of the low frequen
cies particularly in the directions at right angle
to the main direction of radiation will be reduced.
tinction zones, the loudspeakers can be so con
¿m Laterally to the main direction, silent zones are
obtained in which the sound is greatly reduced
so that disturbances cannot occur.
can be iniiuenced in wide limits.
The directional characteristic of the loudspeak
ers has the shape of an 8 in this arrangement.
,w The constricted part of the directional character
istic lies practically on the center line between
both loudspeakers. With such a characteristic of
the loudspeaker arrangement it is now possible to
set up a microphone in the direct vicinity of the
5U loudspeakers in the direction at right angle to the
main direction of radiation without acoustic feed
back taking place between the microphone and
the loudspeakers.
The elongated characteristic is of particular
importance to the transmission of orders in stadi
nected that one of the loudspeaker diaphragms gg
moves inwards while at the same moment the
other loudspeaker diaphragm moves outwards.
With these different types of operation the range
and the sound distribution of the sound waves
In placevof a single loudspeaker, several loud
speakers may operate on one or several cone
shaped sound guide surfaces in the same direc
The figures show an example of construction of dt
the loudspeaker arrangement in accordance with
the invention.
Figures 1, 2 and 3 show bottom, side (partly
in section) and end (partly in section) views,
respectively, of an embodiment according to the ao _
Figure 4 represents directional char
acteristics of the loudspeaker arrangement ac
cording to the invention, and Figure 5 represents
one of the possibilities of applying the loudspeaker
arrangement according to the invention.
In a housing I (Figures 1 to 3) the loudspeakers
5 and 6 are arranged in the obliquely disposed
walls 3 and 4. Cone-shaped sound guides ‘I and
8 are disposed in front of these loudspeakers
loudspeakers set up in the adjacent field. The
lines I9 and 20 show, for instance, the radiation
cone at right angle to the direction of the axis
of the loudspeaker belonging to the loudspeaker
having large surface diaphragms. The length o!
the sound guides corresponds approximately to
the length of the ordinary sound Walls. The
In the example of construction the walls I2 and
I3 are opened up at different degrees.
sound guides 'I and 8 are likewise disposed ob
liquely downwards. The loudspeaker and even
10 tually the sound guides may however also be ar
ranged in the same axis.
In the bottom 9 of the housing I one or more
slots I IJ are provided which can be covered up
to a greater' or lesser degree by movable plates or
15 bars II.~ In place of the slots to be covered also
other means may be used, for instance, displace
able shutters, slides, or the like. Furthermore,
also the side walls I2 and I3 may beopened up t0
a greater or lesser degree independently of each
20 other. At the top of the housing a hook I4 is ar
ranged from which the loudspeaker arrangementv
con be suspended, or a hole may be provided in
the bottom 9 of the housing I through which a
mast may be inserted so that the loudspeaker can
25 be supported from the ground.
Figure 4 shows directional characteristics of a
loudspeaker arrangement according to the inven
tion. The curve I6 at the loudspeaker arrange
ment I5 shows schematically the characteristic
30 for an entirely closing housing. At the con
stricted place of the characteristic IS a micro
phone may be set up for instance at the place I'I.
When opening the slots I0, or the side walls I2
and I3 the characteristic can be varied to such
35 an extent that for instance the characteristic I8
is obtained.
Figure 5 shows the use oi the loudspeaker ac
cording to the invention, for instance over oblique
terrain such as found in open air stages or other
arrangement when set up on an oblique line 2|. CII
What we claim is:
l. A loudspeaker system for controlling the di
rectional radiation characteristic thereof, com 10
prising an enclosure provided with upper and
lower walls, a pair of oppositely disposed side
walls which are inclined downwardly and which
have each a central aperture therein, and a sec
ond pair of oppositely disposed side walls which
are hinged at their upper edges, a pair of loud
speakers arranged within the enclosure with each
loudspeaker diaphragm mounted on its respective
apertured side wall to permit the sound therefrom
to radiate in substantially opposite directions, 20
and a horn member mounted on each apertured
side wall external of the enclosure, the hinged
side walls adapted to be separately adjustable
whereby the space within the enclosure may be
made to communicate with the outside air to a
greater or less degree.
2. A loudspeaker system for controlling the di
rectional radiation characteristic thereof, com
prising a pair of loudspeakers disposed to radiatein- substantially opposite directions, a common 30
enclosure for said loudspeakers, a cone-shaped
sound guide associated with each of said speak
ers,l and adjustable apertures provided in the
common enclosure, the extent to which the aper
tures are opened determining the amount of 35
radiation in a direction at right angles to the
main direction of radiation.
3. A loudspeaker system according to claim 2,
wherein the common enclosure is provided with
arrangements. By opening up the side walls I2
adjustable side walls whereby the space within
and I3 the radiation cone of the loudspeaker ar
» rangement can be influenced, and it is possible in
this manner so to adjust the sound energies
the enclosure may be made to communicate with
the outside air to a greater or less degree.
radiated by the loudspeaker that the field covered
by this loudspeaker will not be disturbed by other
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