[0001] This invention relates to an improved construction of loudspeaker which incorporates
what is known as a ring radiator. Loudspeakers which incorporate a ring radiator have
an annular diaphragm which is held clamped at both its inner and outer peripheries
and which is. vibrated by the movements of a coil which is coupled to the diaphragm.
[0002] One conventional construction of ring radiator for a loudspeaker comprises a diaphragm
element formed as an annulus having generally horizontal inner and outer webs and
a substantially V-shaped valley zone between them. The inner and outer webs are rigidly
clamped by support washers. A separate tubular former carries the coil windings. Conventional
practice has been to secure the wound former to the apex of the valley zone of the
diaphragm by means of an adhesive using a butt joint. In order to improve the adhesion,
the tubular former is sometimes provided with a tongue,to provide an increased surface
area for adhesive contact with the diaphragm.
[0003] This conventional form of construction has a number of disadvantages. Firstly, it
is a relatively fragile construction, relying as it does upon a butt joint to secure
the wound former to the diaphragm. Secondly, with this form of construction the former
has to be wound first with the coil, and this delicate combination then has to be
brought up to the diaphragm and secured thereto. This involves handling problems and
the possibility of damage to the components. It is also not easy to wind the coil
on to the tubular former. Furthermore, it has also been found that with this form
of construction the response characteristics often include undesirable resonances,
primarily due to poor coupling between the coil and the diaphragm through the butt
joint.
[0004] It is an object of the present invention to provide an improved ring radiator for
a loudspeaker, and also an improved method of manufacture of such a radiator.
[0005] In accordance with the present invention there is provided a ring radiator for a
loudspeaker, comprising a radiating element having annular inner and outer portions,
and a former carrying a coil and positioned radially substantially at the junction
of said inner and outer portions, wherein said former is integral with at least one
of said inner and outer portions.
[0006] In a preferred embodiment of the invention, the coil former is formed integrally
with one of said inner and outer portions and the other said portion is secured to
said one portion, preferably by an adhesive lap joint.
[0007] Preferably, the element which constitutes the coil former is provided with a circumferential
lip or return at the end remote from the radiating element, in order to prevent the
coil turns from becoming detached.
[0008] Also, in accordance with the present invention there is provided a method of making
a ring radiator for a loudspeaker which comprises the steps of producing a tubular
former integrally with at least a portion of an annular radiating element, and thereafter
winding a coil on said former.
[0009] In the preferred method in which the former is integral with just one portion of
the annular radiating element, the coil is wound on the former and then the wound
component is secured to a further portion of the radiating element, for example by
means of an adhesive lap joint.
[0010] The method of construction in accordance with the present invention, and the product
produced thereby, has considerable advantages as compared with the conventional arrangement.
The ring radiator of the present invention is tough and robust, and is much less liable
to damage than the conventional radiator. Additionally, because of the direct coupling
of the coil to the radiating element one achieves a much smoother response, without
the undesirable resonances which characterise conventional ring radiators. Furthermore,
the winding of the coil is greatly simplified with the form of construction of the
present invention, resulting in more consistent performance, less wastage, and ease
of handling with automated assembly machinery.
[0011] The ring radiator of the present invention is particularly suitable for loudspeakers
which operate within a frequency range of 2KHz to 16 KHz, although these frequencies
are not to be taken as being limiting frequencies.
[0012] In order that the invention may be fully understood, one preferred embodiment of
ring radiator in accordance with the invention will now be described by way of example
and with reference to the accompanying drawings, in which:
Fig. 1 is a schematic view, taken as a section through one side of the ring, of a
known construction of ring radiator; and,
Fig. 2 is a view, similar to Fig. 1, of a ring radiator in accordance with the invention.
[0013] A conventional construction of a ring radiator is shown in Figure 1 of the drawings
which is a schematic sectional view through just one side of the ring radiator, the
section through the diametrically opposite side being the same. In this construction,
the diaphragm element 10 is formed as an annulus having generally horizontal inner
and outer webs 10a and 10b respectively and a substantially V-shaped valley zone.
The inner and outer webs 10a and 10b are rigidly clamped by support washers 12. A
separate tubular former 14 carries the coil windings 16. Conventional practice has
been to secure the wound former to the apex of the valley zone of the diaphragm 10
by means of an adhesive using a butt joint as indicated at 18. In order to improve
the adhesion, the tubular former 14 is sometimes provided with a tongue, indicated
in broken lines at 20, to provide an increased surface area for adhesive contact with
the diaphragm 10.
[0014] Referring now to Figure 2, it will be seen that the annular radiator here comprises
an outer annular portion 22, and an inner annular portion 24. Clamping washers 26
are shown for each radiator portion, but these are optional. The outer annular portion
22 comprises a horizontal web or limb 22a, a sloping limb 22b and an upturned tongue
22c. The inner annular portion 24 comprises a horizontal limb 24a, a sloping limb
24b, and, integrally therewith, a portion 24c which constitutes a tubular former for
the windings of a coil 28. The tubular portion 24c has a flange or return 24d which
serves as a seat for one end of the coil windings to prevent turns of the coil from
becoming detached.
[0015] In manufacture, the one annular radiator portion 24 is first produced by a suitable
shaping process. The coil 28 is then wound on that element 24, using the flange 24d
as a stop. The other, outer annular portion 22 of the radiator is then presented to
the wound element so that the tongue 22c makes a lap joint with the face of the sloping
limb 24b of the element 24. A suitable adhesive is used between the two parts to give
a strong joint. It will be appreciated that because one has surface-to-surface contact
here, as compared with point contact in many of the conventional arrangements, one
can achieve much better adhesion and a more reliable joint.
[0016] The material of the ring radiator of the present invention may be any suitable material,
for example bake- lised cloth, aluminium, a plastics material, etc.
[0017] Although in the preferred embodiment described above the portion 24c which constitutes
the former on which the coil is wound is integral with the radially inner portion
of the radiator, it could alternatively be made integral with the radially outer portion
22 of the radiator. Alternatively, it could be made integral with both portions 22
and 24 of the radiator, in which case no separate jointing steps would be necessary.
1. A ring radiator for a loudspeaker, comprising a radiating element having annular
inner and outer portions, and a former carrying a coil and positioned radially substantially
at the junction of said inner and outer portions, characterised in that the former
(24c) is integral with at least one of said inner and outer portions (22,24).
2. A ring radiator as claimed in claim 1, characterised in that the former (24c) is
integral with one (24) of said inner and outer portions, and the other said portion
(22) is secured to said one portion by an adhesive joint.
3. A ring radiator as claimed in claim 2, characterised in that the joint is a lap
joint providing surface-to-surface contact between an annular tongue (22c) on said
other portion (22) and an annular surface on said one portion (24).
4. A ring radiator as claimed in any preceding claim, characterised in that the former
(24c) is tubular and is provided with a circumferential lip (24d) at the end remote
from the radiating element.
5. A ring radiator as claimed in any preceding claim, characterised in that said inner
and outer portions of the radiating element each comprise a flat web portion (22a,
24a) and a sloping web portion (22b, 24b) with said sloping web portions defining
a substantially V-shaped valley at the bottom of which the former (24c) is located.
6. A method of making a ring radiator for a loudspeaker which comprises the steps
of producing a tubular former (24c) integrally with at least a portion of an annular
radiating element, and thereafter winding a coil (28) on said former.
7. A method as claimed in claim 6, characterised by making the former (24c) integrally
with one annular portion of the radiating element, then winding the coil (28) on the
former, and thereafter securing the wound component to a further annular portion (22)
of the radiating element.
8. A method as claimed in claim 7, characterised . inthat the wound component is secured
to said further portion (22) by an adhesive lap joint.