U.S. patent number 3,767,005 [Application Number 05/259,379] was granted by the patent office on 1973-10-23 for flat loudspeaker with enhanced low frequency.
Invention is credited to Jose Juan Bertagni.
United States Patent |
3,767,005 |
Bertagni |
October 23, 1973 |
FLAT LOUDSPEAKER WITH ENHANCED LOW FREQUENCY
Abstract
Flat loudspeaker diaphragm with means for enhancing the low
frequencies, wherein the diaphragm has a marginal vibration damping
portion surrounding a sound producing figure portion and at least a
portion of said marginal vibration damping portion is connected to
a plate-like member adapted to vibrate only in the low frequency
range.
Inventors: |
Bertagni; Jose Juan (Buenos
Aires, AR) |
Family
ID: |
3462013 |
Appl.
No.: |
05/259,379 |
Filed: |
June 5, 1972 |
Foreign Application Priority Data
Current U.S.
Class: |
181/160; 181/166;
181/174 |
Current CPC
Class: |
H04R
7/04 (20130101) |
Current International
Class: |
H04R
7/00 (20060101); H04R 7/04 (20060101); G10k
013/00 (); H04r 007/00 () |
Field of
Search: |
;181/32R,32A,31R,31B,DIG.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tomsky; Stephen J.
Claims
I claim:
1. In a diaphragm for flat loudspeakers, means to emphasize the low
frequencies and to change the shade and colour of the sound,
comprising a first plate-like member having a substantially flat
front face and a rear face defining a figure portion and a first
marginal vibration damping portion which substantially
circumscribes said figure portion, said figure portion being of
non-uniform thickness and having a zone of maximum thickness for
receiving vibrations from a driving unit, at least one part of said
rear face, in the zone corresponding to said first marginal
vibration damping portion, being connected to a second plate-like
member at least a portion of which projects beyond said first
marginal vibration damping portion, said second plate-like member
being capable of collecting low frequency vibrations which are
capable of entering said first marginal vibration damping
portion.
2. The diaphragm of claim 1, wherein said second plate-like member
covers and is connected to the entire zone of said first marginal
vibration damping portion and projects beyond the periphery of said
first plate-like member.
3. The diaphragm of claim 2, wherein said second plate-like member
has a cut-out central portion, defining an endless lateral wall,
the periphery of said figure portion defining an endless side wall,
and said side wall and lateral wall are coplanar.
4. The diaphragm of claim 3, wherein said second plate-like member
is of conglomerated wood and its endless lateral wall as well as
its periphery are sealed.
5. The diaphragm of claim 1, wherein said first plate-like member
is integral with an additional portion of smaller size, which
includes a further figure portion surrounded by a further pertinent
marginal vibration damping portion, said further pertinent marginal
vibration damping portion is acoustically isolated from said first
marginal vibration damping portion by means of a channel member
filled with a resilient material.
6. The diaphragm of claim 1, wherein said first plate-like member
is made of a foamed plastic.
7. The diaphragm of claim 1, wherein said second plate-like member
forms part of a resonance box comprising a first plate member
connected to one part of said rear face in the zone corresponding
to said first marginal vibration damping portion and projecting
beyond said first plate-like member, said first plate member having
a peripheral portion, a perimetrical cross band member connected to
said peripheral portion and a second plate member connected to said
perimetrical cross band member; each of said first and second plate
members having a cutout portion, said cutout portions being
substantially aligned; the cutout portion of said second plate
member being of smaller area than said cutout portion of said first
plate member; said first plate member, perimetrical cross band
member, and second plate member defining said resonance box; said
second plate member having an internal free edge portion
overhanging said figure portion of said plate-like member.
8. The diaphragm of claim 7, wherein said second plate member
includes holes connecting the inside of said resonance box with the
outside.
9. The diaphragm of claim 7, wherein said perimetrical cross band
member includes holes connecting the inside of said resonance box
with the outside.
10. The diaphragm of claim 7, wherein said free edge portion
overhangs the entire periphery of said figure portion.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a diaphragm for flat loudspeakers,
where the low frequencies are enhanced to change the shade and
colour of the sound.
The tastes in relationship to musical reproductions are not equal
throughout the world; thus some people prefer that in a musical
song the human voice be clearly distinguishable from the musical
background, while others prefer that the human voice merge into the
music.
In this latter case it is advisable to increase the low frequencies
of the sound reproduction; such an emphasis may be obtained by
providing suitable means which increase the range of the low
frequency vibrations.
2. Description of the Prior Art
In conventional loudspeakers, this effect is achieved by housing
the loudspeakers in large wood casings which act as resonance boxes
or baffles. In many cases these casings are several times larger in
surface and volume than that actually required for the installation
of the loudspeakers and in a good number of embodiments it is
necessary to provide these casings with heavy weights to avoid that
due to the low frequencies the casings start to move along the
floor. From the foregoing it is apparent that the known embodiments
are large in volume and rather expensive.
As to the resulting sound, its colour and shade, this depends on
the type of material (usually wood) used for manufacturing the
casing.
SUMMARY OF THE INVENTION
Bearing in mind the foregoing, a diaphragm has been conceived for
loudspeakers which enables to emphazing the low frequencies and
changing the colour and shade of the sound without requiring
excessively large surfaces or volumes and without requiring special
weights to immobilize the assembly. At the same time, such
diaphragms are extremely simple to manufacture and of much lower
cost than those of the known systems. The present invention is
applied to the so called "flat loudspeakers" which have generally a
flat front face and a rear face to which is connected a driving
unit, that is, electromagnetic assembly, which includes a vibratory
coil. All these flat loudspeakers have a zone to vibrate and this
zone is surrounded by a vibration damping marginal portion. As a
typical example the diaphragm described in my U.S. Pat. No.
3,596,733 may be cited, as well as the earlier known flat
diaphragms some of which are described in the introductory portion
of said patent.
The present invention consists in connecting to said marginal
vibration damping portion a plate adapted to vibrate in the low
frequency range, to emphasize said frequencies. Said plate may
project beyond the member defining the diaphragm and which is
preferably made of a foamed plastic. More particularly, the present
invention refers to a diaphragm for flat loudspeakers which
emphasize the low frequencies and changes the shade and colour of
the sound and which comprises a first plate-like member preferably
made of foamed plastics and which has a substantially flat front
face and a rear face defining a marginal vibration damping portion
which substantially circumscribes a figure portion including a zone
for collecting vibrations arranged out of the geometric center of
said figure portion and wherein at least one part of the rear face,
in the zone corresponding to the marginal vibration damping
portion, is connected to a second plate like member, which projects
beyond said marginal vibration damping portion, said second
plate-like member being capable of collecting low frequency
vibrations which are capable of entering in said marginal vibration
damping portion.
It may be stated that within the concept of the present invention
it is also conceivable to arrange, within said marginal damping
vibration portion a tweeter for reproducing high frequency
vibrations or the first plate-like member may include an additional
portion defining a second loudspeaker for reproducing high
frequencies and in this event the second-plate like member projects
beyond the first plate-like member corresponding to the first
loudspeaker and may cover the zone corresponding to the second
loudspeaker intended for reproducing high frequency vibrations,
without changing the behaviour of the second plate-like member and
thus it is not necessary that the second plate-like member projects
beyond the second loudspeaker since the behaviour of one does not
interfere with the other. In this latter embodiment it is advisable
that the first plate-like member has a dividing zone formed by
means of a channelled portion in said first plate-like member which
separates the two loudspeakers. Conveniently this channelled member
is filled with a resilient material, such as a silicone rubber,
which is capable of maintaining its resiliency and will not attack
the material from which the first plate-like member is
manufactured, when the latter is made of foamed plastics, such as
polystyrene or polyurethane.
Another concept which falls within the scope of the present
invention is that the second plate-like member, to collect the
sounds corresponding to the low frequencies, is replaced by a
resonance casing (of the type of a violin casing) the shape of
which may vary so that it may be adjusted to define any particular
shade and colour of tone.
BRIEF DESCRIPTION OF THE DRAWINGS
In order to facilitate the comprehension of the present invention
reference will now be made to the drawings wherein, by way of
example, three structural embodiments are shown, in which:
FIG. 1 is a perspective view of the front portion of the diaphragm
of the present invention.
FIG. 2 is a perspective view of the rear portion of the diaphragm
shown in FIG. 1.
FIG. 3 is a longitudinal section through a diaphragm which is to
form part of two loudspeakers of which the portion corresponding to
the smaller loudspeaker is to act as a tweeter.
FIG. 4 is a longitudinal section through an arrangement of a
diaphragm including a resonance casing to emphasize the low
frequencies.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As may be appreciated from FIG. 1, the diaphragm of the present
invention consists of a first plate-like member 1, preferably
manufactured of foamed plastics, such as polystyrene or
polyurethane. The plate-like member 1 has a substantially flat
front face 2 and side faces 3 which link the front face 2 to a rear
face 4 (FIG. 2). To this rear face 4, as will be later explained, a
second plate-like member 5 is connected in a particular manner and
which projects beyond the first plate-like member 1, (with regard
to the side faces 3). The second plate-like member 5 may be
manufactured of any suitable material which is capable of vibrating
in the low frequency range. A material which has proven excellent
for the purpose above specified is conglomerated or compensated
wood which exists on the markets in the shape of plates. The side
faces 6 do not prevent atmospheric agents from undesirably entering
such a plate like member. Therefore it is convenient to submit such
a second plate-like member to a previous drying process and then to
seal the side faces 6 with a sealant 6' such as a synthetic resin
of the vinyl type, for example, which exist on the market.
Referring now to FIG. 2, it may be appreciated that the rear face 4
of the first plate-like member 1 defines a marginal portion 7 which
circumscribes a figure portion 8 of particular shape, similarly to
the pinna of a human ear. This figure portion 8 is dome shaped-as
may be better seen in FIG. 3-- and a portion of maximum height 9 is
at a zone out of the geometric center of said figure portion 8. The
portion of maximum height 9 includes preferably a recess 10 to
which the electromagnetic or driving unit 11 (FIG. 2) is to be
connected and which is mounted on a bridge 12 the ends of which are
supported by the marginal zone of the first plate-like member 1
--actually this bridge is mounted on a frame which is not shown,
since the bridge and the electromagnetic assembly do not form part
of the present invention and are merely described for informative
purpose.
It will be understood that upon vibrating the electromagnetic
assembly 11, vibrations will be transmitted to the recess 10 and
thereby to the figure portion 8. The zone of maximum height or
thickness 9 therefore receives the vibrations from the
electromagnetic assembly. Conveniently the marginal portion 7 is
flat and defines a plane parallel to the front face 2 and the zone
of maximum height 9 of the figure portion 9 is tangential to said
plane. The marginal portion 7 forms a marginal vibration damping
portion and is capable of damping the majority of the vibrations
which are transmitted through the electromagnetic assembly 11 to
the figure portion 8. However the low frequency range vibrations
have the tendency to propagate through the marginal portion 7.
It may also be appreciated from FIGS. 2 and 3 that the figure
portion 8 forms with the marginal portion 7 an endless side wall
13.
The second plate-like member 5 has a cut-out portion in its center
portion, the shape of which is substantially equal to that of the
figure portion 8, so that the endless lateral wall 14 becomes
coplanar with the side wall 13. It is advisable that said lateral
wall 14 is subjected to the same sealing process by means of the
synthetic resin as the side faces 6.
The second plate-like member 5 is adhesively connected, for
instance by means of a synthetic adhesive of the vinyl type, to the
rear face 4 which defines the marginal portion 7 of the first
plate-like member 1 and in this embodiment the plate 5 projects
beyond the side faces 3 of the first plate-like member 1. Since the
object is to enhance the low frequencies by using the theory that
the low frequencies are transmitted by the first plate-like member
1 in the vectorial channels (see my above cited patent)which start
from the electromagnetic assembly 11 towards those portions of the
side wall 13 which are the remotest ones from the electromagnetic
assembly 11, it will presumably be sufficient that the second
plate-like member 5 projects beyond the first plate-like member 1,
in the pertinent vectorial zone.
Eventually it will be possible to insert through the second
plate-like member 5 in the zone corresponding to one of the
marginal portion 7, preferably a zone having a large surface, a
tweeter (not shown ) specially useful for obtaining particular
stereophonic effects.
With regard to the example shown in FIG. 3, it may be appreciated
that the plate-like member 1' includes a portion 1" of smaller
size, but which is similar to the plate-like member 1' and which
may be used for producing the tweeter device. In this embodiment
the marginal zone 7 is provided in the rear face with a channel
member 15 which insulates vibrations and which is conveniently
filled with a resilient material 16, which does not attack the
material of which the member 1', 1" is manufactured. If the last
mentioned member is manufactured of polystyrene or polyurethane
then a silicone rubber, may be used such as the one known by the
trade name SILASTIC produced by Dow Corning. Portion 1" defines
likewise a side wall 17 and the pertinent marginal vibration
damping portion 18, as well as a figure portion 19. In this
embodiment the second plate-like member 5 has a second opening
formed by an internal endless lateral wall 20. Apart from that, the
second plate-like member 5 covers also the marginal portion 18,
although it is not necessary that it is adhesively adhered thereto.
Thus the portion of the second plate-like member 5 corresponding to
the portion 1", performs the role of the portion of the plate-like
member 5 which projects beyond the plate-like member 1 in the
example corresponding to FIGS. 1 and 2. In this embodiment it is
not necessary that the plate-like member 5 projects beyond the side
walls defined by body 1', 1".
Finally reference has to be made to FIG. 4, wherein a first
plate-like member 1 is shown, having also the marginal vibration
damping portion 7 and the figure portion 8 provided with the recess
10. On the marginal portion 7 a resonance box 21 is arranged
consisting of a first plate member 22 the peripheral portion of
which is linked through a perimetrical cross band member 23 with a
second plate member 24. First plate member 22 has a cutout portion
22' whose size and shape are substantially equal to that of the
figure portion 8, the relationship and positioning of plate member
22 relative to figure portion 8 being substantially the same as
that of plate-like member 5 described in connection with FIGS. 1
and 2. Second plate member 24 is also provided with a cutout
portion or mouth 26 aligned with cutout portion 22', the area of
cutout portion 26 being less than that of cutout portion 22'. In
this manner, the internal free edge portion 24' of second plate
member 24 overhangs the figure portion 8. In the illustrated
embodiment internal free edge portion 24' overhangs the entire
periphery of figure portion 8 between the members 22, 23 and 24 a
chamber 25 is formed. By varying the size of the projecting portion
of the first plate member 22 with regard to the marginal portion 7,
the volume of chamber 25 may be changed. Another way of changing
said volume is by varying the size of the perimetrical cross band
member 23.
Upon transmitting vibrations to the first plate-like member 1
through the electromagnetic assembly (such as assembly 11 of FIG.
2) part of these vibrations of the low frequency range are
transmitted through the figure portion 8 into the marginal portion
7 and therefrom by contact to the first plate member 22.
The mass of air which vibrates behind the rear face corresponding
to the figure portion 8 is in part forced to enter chamber 25,
because the second plate member 24 faces a portion of the rear face
of the first plate-like member 1. When the electromagnetic assembly
11 starts to transmit high frequency vibrations corresponding to
the high tones, these may freely project through the mouth 26
defined by the free edge 24' of the second plate member 24 and
therefore substantially do not enter the chamber 25.
Thus the chamber 25 operates as a resonance casing for low
frequencies and a special colour and shade is achieved for these
low frequencies.
If desired the mouth 26 may be covered by a lid 27. Obviously the
members 22, 23 and 24 may be made of many kinds of materials, but
are preferably made of wood of the type used for producing violins
and other musical string instruments. In some cases it may be
interesting to replace the wood by other materials such as
plastics.
It is not necessary that the resonance casing 21 defines a mouth 26
of similar shape but of smaller area than the shape of the figure
portion 8. In some cases it may become even interesting that the
resonance casing is only provided in the vector zone corresponding
to the low frequencies.
It is also possible to make holes 27' (of any shape) in the second
plate member 24, and/or in the cross band member 23 (see hole 28)
in order to connect the chamber 25 with the outside atmosphere to
thus vary the sound characteristics.
It will be obvious that modifications may be introduced in this
invention upon carrying it out into practice as far as certain
structural details are concerned, but always without departing from
the fundamental principles which are clearly specified in the
following claims.
* * * * *