Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This patent application -for an industrial in~ention re-
: fers to a mult1ple loudspeaker with a pie~oelectrie "twee-ter",
held up by a means of support ~hich allows the rear wave e-
mitted by the ceralnic disk and respective conical diaphragm
to be fully exploited, usiny the main loudspeaker cone as a
reflecting surface, without overloading the moving coil of
the latter.
For further explanation of the loudspeaker, according
to the invention, we -feel it is necessary to give a brief
description of the currer1t technological situation in the
field of acoustic reproducers.
In order to faithfully reproduce high frequencies, a
'loudspeaker should have a fairly small cone, while on the
other hand, low frequency reproduction requires a cone of
considerable dimensions; therefore when an optimuln perform-
' ance needs to be obtained,instead of using just one loud-
speaher intended to reproduce the whole range of audio-
'frequencies with fidelity, an enselnble o-f several loud-
speakers suitably arran~ed is usually adop~ed: some with
large dimens~ons suitable for low fre~uency reproduct~on,
normally called "woofers", bthers wi~h sma'll dimensions
suitable for high frequency reproduction, normally called
"tweeters".
The multiple loudspeakers' group includes bi-phonic
coaxial loudspeakers which have t~lO reproduction appliances
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totally independent of each other but coaxially mollnted,
one equipped with a bigger cone, the other equipped with a
smaller cone placed imlllediately in front of and on the same
axis as the bigger cone.
In some bi-phonic coaxial loudspeakers, a piezoelec-
tric "tweeter" is adopted, namely using a ceramic ~isk ge-
nerator of sound waves, situate~ inside a small protection
and support baske.t, whicl) is a~tached to a part o-F the main
loudspeal<er Frame (i.e. the bigger loduspeaker), according
to various construction solutions: in some models the basket
is supported by an axia'l pin, while in o-ther models a sup-
port bracket is adopted made up of one or more radial spokes
the end of which is to be positioned and fixed on the main
loudspeaker basket.
Both construction solutions just described present some
comlnorl problems and some specific problems.
For example the abovementiorled central support pin is
not mechanically reliable; especially taking in-to account
the econornic material used for its manufacture which is
mainly p1astic barely resistant -to the ternperature, i-t can
bend laterally until it -touches the main loudspeaker coil,
which results in friction between -the parts which come into
contact with each other and inllnediately causes an in-
admissible crack'lin~ noise, iF not at the very worst, the
hlockage oF the bigger cliaphragll1.
Moreover hoth suppor-t systems mentioned do not allow
30 the installation of the "twee-ter" completely inside the main
loudspeaker diaphragm in such a way that the edges of the
-two maxilTIum diameter sections of the two cones are actually
; coplanar. l'his is due to the overall dilnensions of the pro
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tection and support basket o~ tilt-~ piezoelectric "tweeter".
Ilowever the most serious probleln, which can occur in
both systems examined so far, lies in -the -fact tha-t clue to
the presence of the aforenlentioned support basket~ the sound
waves emitted from the rear by the ceramic disk and by the
conical diaphragm of tlle piezoelectric tweeter cannot be
fully exploited. If these sound waves could be reflected
forwards, the actual raciiation impedarlce of the sound
sourcewould be increased.
UearincJ this in min(l, an alternative to the two above-
mentioned solutions has already been proposed, whereby the
support of the piezoelectric tweeter is in a coaxial posit-
ion in front of the main louclspeaker cone.
According -to this alternative solution, the piezoelec-
tric tweeter is not situated inside a basket, but its cera
mic disk is fir1nly juined to the mobile suppor-t of the main
10udspeaker coil, the diaphrac~ of which can then act as
a reflecting surface for tht! radiations emitted from the
rear by the tweeter cone, but not for those radiations emit
ted by the ceramic disk fixecl-to the rnobile support of the
main loudspeaker coil.
In additlon to the limited exploitation of the waves
emitted from the rear by the piezoelectric tweeter, the last
solution indical:ed obviously brings about an overloading of
the mobile support of the main loudsl)eaker coil. Even if
3U this ;s mir~ lal, an increase in the si~e of the magnet is
nevertheless necessary, which leads to a notable increase
in the final production cos-ts.
The ainl of this inven-tion is to provicle a means of
support for the piezoelectric"tweeter", which, without over-
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loading the Inobile supporl of i:he nlain lou(lspeaker coil, allows the exploitation o-F the radiation emitted from -the rear
by the ceramic disk and that emitted by the cone. The dia-
phragln behind -the main loudspeaker acts as a reflecting sur
face, and furthermore the overall dilnensions o-F the piezo-
electric~ltweeterllare limited in such a way that the whole
of the latter can fi-t into the Inairl loudspeaker cone.
~ccording to this invention, the solution is based on
the fact that the piezoelectriclltwee-terl~is placed in front
of the mairl louclspeaker cone withollt the usual support and
protection baske-t. A different Ineans of s~lpport is used
instead, which does not intercept or clisturb radiation e-
mitted fro!n the rear by -the piezoelectric"tweeter"or ob-
struct the forward reflection oF said radiation by the mainloudspeaker diaphragm.
In accordance with a preferred embodi~ent of the in-
vention, relating to the field of coaxial biphonic loud-
speakers, the piezoelectric ~Itweeter~ wi-thout a basket, is
suppor-ted by a spide~shaped bracket witll radial spokes, the
ends of which are fixed to the Inain loudspeaker basket.
In accordance with an alternative e~bodiment of the
invention, in the field o-f coaxia1 bi-phonic loudspeakers5
the piezoelectric"tweeter~lis Fixed on the back of the pro-
-tection grille which usually covers the hole on the front
oF the panel on which the lolldspeaker is Inounted.
In order to provide Further explanation, the descript
; ion of this invention proceeds with re~erence to the en-
closed drawings in which two preferred embodinlents of the
invention at re~erence are schelnatically illustrated, to be
applied in the field o~ bi-phonic, coaxial loudspeakers.
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Fig. 1 is a section witll the axial plan of a bi-phonic,
coaxial loudspeaker, in accordance with -the invention and
with its preferred embodiinent.
Fig. 2 is a section with an axial plan of a bi-phonic
coaxial loudspeaker in accordance with the invention and
with an alternative embodiment.
~ith reference to the abovementioned figures, the loud
speaker at reFerence is made (Jp of two independent reproduc
tion devices coaxially ll~ounte(l, an~ in conformity ~ith tra-
ditional construction nletho(ls For bi-phonic coaxial loud-
speakers.
The main moving-coii loudspeaker suitable for the re-
: production of medium to low frequencies is made up of a bas
ket (1), which suppor-ts the cone diaphragm (2) internally
~; and the centering device (3), which while allowing -the coil
to move lonyitudinally, ensures that it is always perFec~y
centered in the air gap and that it does not touch the two
pole shoes; the external one being ring shaped (4) and the
internal one cylindrical (5).
Number ($.) indicates an ant-i-dust plate which closes
at the front -the mobile support sleeve (9) oF the coil, not
shown in the figure.
With reference to Fig, 1, the other smaller piezoelec-
tric loudspeaker suitable For high frequency reproduction~
30 is characterized by the fact that it is nlade up of the ce-
ramic disk (10) and its respective cone ~11) only, which
are held in a position coaxial to and in front o-f the dia-
phragm (2) of the main louclspeaker, by means oF a support
nracket (12) which in turn -is made up of a central annular
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flange from which one or 1nore radial spokes branch out, le-
vel with the flange, the encis of which are linket1 up with
the main loudspeaker support baskel; (1).
More precisely, at the point where the diameter is
greates-t, the cone (ll) of the piezoelectric"tweeter" is
glued by its edge -to a spo)1~e ring (13), ac-ting as a damper,
which in turn is glued onto the back of the afore1nentioned
central annular flange.
~lith reference to fi~ure (2), according to an al-terna-
tive embodimen-t o-f the invention, it can be noted how -the
piezoelectric"twee-ter"is supported in a coaxial posi-tion in
- front of the n~ain loudspeaker diapi)rag1l1 (2) by means of the
protection grille (14), ~Ihich usually covers the hole on
the front panel on which the loutdspea~er is mounted.
In this alternative version, th sponge ring 113), I:o
which the edges of ~he piezoelectriC"t~Jeeter"COne (ll) are
to be attached, is sluecl to a surface especially provided
for the purpose, on the inside of the grille (14). Said
grille, as per the example pu-t forward by the construction
solution in Fig. 2, could even have a horn(l5) on the out
side of the opening of which, the aforementioned sponge
rintl (13) may he glued.
Needless to say l;his ciescription refers to the enclosetl
drawings, reprocluceti For exi)lanatory purposes only, and re-
lating to the Illanufacturt-! of bi-phonic, coaxial loudspeakers.
It is, however, obvious that the invention may be applied
i1~ the iield of )~lultiple loucispeakers in general, not neces
sarily bi-phonic and/or coax-ial, without actually deviating
from ti~e concept of this invention and the protection affor-
ded bv this industria1 patent ~i~ht.
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