JPH0434877B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A so-called "double concentric" type of loudspeaker includes a pair of coaxial voice coils, one of which drives a cone for low frequency reproduction, while the other drives a horn load at the rear of the loudspeaker. Drives a high frequency diaphragm. The voice coil is, for example, British Patent No. 893838
Acting within individual cavities formed in annular rear and front plates forming part of a magnetic system comprising a ring magnet as exemplified in GB 2015300 and GB 2015300. .
In this type of loudspeaker, mid-band frequencies are reproduced by the superimposed effect of a horn-loaded high frequency diaphragm operating near the lower limit of the frequency response and a lower frequency cone operating near the upper limit of the frequency response. As a result, speaker performance in this frequency band leaves room for improvement.

The invention is based on the principle of including an additional cone between the speaker horn and the low frequency cone, which is designed to respond to the intermediate frequency range. And this, according to the invention, comprises three separate transducer units covering three frequency bands and driven by individual coaxial voice coils, the low frequency unit being in front of the loudspeaker. The high-frequency unit consists of a horn-loaded diaphragm at the rear of the speaker, and the intermediate-frequency unit has an axially extending annular portion and a radially extending annular portion formed along the rear surface. From an intermediate frequency unit consisting of a cone supported by a chassis whose axially extending annular portion fits closely within the central opening of the front plate of the magnetic assembly serving as part of both the high frequency unit and the intermediate frequency unit. This is made possible by the following configuration.

When an intermediate frequency unit is mounted in place, it is inevitable that it will be subject to considerable magnetic attraction which increases the difficulty of accurate centering.
The axially extending annular portion can be inserted into the central opening of the front plate, while the rest of the chassis is still separated from the front plate and its magnetic attraction is such that the radially extending portion is connected to the front plate. Providing an axially extending annular portion overcomes this difficulty to a large extent since it is considerably lower than the maximum value it reaches when in contact. During the remainder of the mounting operation, the unit as a whole is guided by the cooperation between the outer surface of the axially extending part and the intermediate opening surface, so that it is precisely centered when it reaches its final position. It remains as it is. As a result of this configuration, the low frequency cone can be spaced from the mouth of the horn to leave a gap for the insertion of the intermediate frequency unit, and the low frequency cone and its associated magnetic assembly can be spaced apart from the mouth of the horn to leave a gap for the insertion of the intermediate frequency unit. The assembly can be mounted in place on the frame before installation. The intermediate frequency chassis is then installed and then moved into an axial position until the rear axially extending portion of the chassis engages the opening in the front plate as described above.

The elements are preferably designed such that the magnetic attraction exerted on the chassis of the intermediate frequency unit is sufficient to hold this unit in place without the need for additional fixation. This has the further advantage that the unit can be prefabricated and then installed in place as a stand-alone unit. However, in some cases bolts or other forms of fasteners may have practical limitations.
What can be called a so-called triple concentric loudspeaker, i.e. the low and intermediate frequencies are reproduced by a separating cone, which is designed for optimal performance over the frequency range in question, thus improving the overall performance of the loudspeaker. Without losing the main advantages of the configuration according to the invention, the theoretical concept of a loudspeaker, which can be provided to complement the magnetic attraction, can be provided.

As previously mentioned, the high frequency diaphragm and the intermediate frequency cone share a common magnetic system similar to the previous dual concentric type loudspeaker. However, the low frequency cone requires a separate magnetic system, which is preferably mounted in front of the platform on the chassis provided for its support. This is in contrast to the usual means employed by cone-type speakers when the magnetic assembly is attached to the rear of the chassis platform. The front attachment of the present invention is
It facilitates mounting the intermediate frequency cone in the space between the low frequency cone and the mouth of the horn, and also helps maintain a relatively smooth profile at the junction between the two cones. A smooth profile is also maintained between the mouth flare of the horn and the mid-frequency cone, similar to what is normally done between the cone and horn of a dual concentric speaker.

The magnetic system for the low frequency cone should consist of a ring magnet in the usual manner with an annular front and rear plate, and the rear plate should be assembled in one piece with the platform as described above. It is fixed to the chassis platform facing forward. Furthermore, the magnetic system should include a central annular pole piece extending from the rear plate and cooperating with the edge of the central aperture in the front plate to form an air gap for the voice coil of the low frequency cone. This central magnetic piece will surround the chassis for the intermediate frequency unit.
And you may need to shape it to match that.

The leading edge of this pole piece will extend forward between the outer edge of the intermediate frequency cone and the inner edge of the low frequency cone. In order to achieve a smooth transition between the two cones, this leading edge must be relatively thin or shaped to form a smooth transition surface. A small annular gap between the inner surface of the pole piece and the chassis helps form additional support for the intermediate frequency chassis, excludes dust from the internal cavity, and provides a damper on the chassis to prevent unwanted acoustic output due to vibrations. It can be conveniently closed by a forming annular spacer of elastic material.

An example of the triple concentric speaker of the present invention will now be described with reference to the accompanying drawings.

The loudspeaker consists of three basic sections: a high frequency section 1, an intermediate frequency section 2, and a low frequency section 3.
The high frequency section 1 is driven by a diaphragm 6, which with its associated magnetic system is very similar to that illustrated and described in GB 2015300; Therefore, it will be explained relatively simply. It includes a group of ring magnets 7, mounted between annular rear and front plates 16 and 12, respectively.
8 and 11. Central pole piece 14
has a central interior defining a horn 15 in communication with the diaphragm 6 and is attached to the outer plate 16 by an integral flange 17.

The intermediate frequency section 2 is in the form of an independent unit comprising a chassis 21 supporting a cone 22 by internal and external suspensions 23 and 24, respectively. The chassis 21 is made of a material such as a mild steel plate that is permeable to magnetic flux and has an outer protective coating. The voice coil 25 is supported by a homer 26 of considerable axial length that extends out of the front of the horn 15 to the suspension 23. An axially extending portion 27 is formed on the rear surface of the chassis 21 and fits closely within the central opening of the front plate 12 of the magnetic assembly, thus serving as a centering guide during assembly and Center this unit as a unit when complete. It also limits the radial width of the air gap. Furthermore, the chassis includes a radially extending annular portion 28, which rests on the surface of the front plate 12 and is held thereto by magnetic attraction. A thin layer 29 of non-magnetic material is provided between portion 28 and the surface of plate 12 to reduce forces on the chassis, facilitate its removal when necessary, and form a damper. The outer surface of the chassis 21 can be fitted with acoustically resistive material 30 that fits into openings in the side walls of the chassis to provide damping.

The installation of the intermediate frequency unit 2 in place represents one of the final stages in the assembly of the loudspeaker, and in particular follows the installation of the magnetic assembly of the low frequency unit 3. The need for this arises from the associated formation of units 2 and 3, as will be explained in detail below.

The unit 3 consists of a low frequency cone 31 driven by a voice coil 32 acting in an annular gap between a central open surface in an annular front plate 33 and the outer surface of an annular pole piece 34. The magnetic system further includes a ring magnet 35 and an annular rear plate 36. This assembly is
Platform 3 forming part of the main chassis 38 supporting an outer suspension 39 for the cone
It is attached to 7. Contrary to the usual method
The magnetic assembly is attached to the chassis platform 3.
7 is mounted at the front rather than the rear of the low frequency cone 31, with the working air gap located immediately after the outer suspension 24 for the intermediate frequency cone.
This allows a relatively smooth continuous formation of the intermediate frequency cone 22. An inner suspension 40 for the low frequency cone 31 is attached along its outer edge to an annular bracket 41, which in turn is attached to the front plate 33. As mentioned above, parts 33, 34, 3
The magnetic assembly consisting of 5, 36 must be installed in place before the installation of the intermediate frequency unit 2, but the low frequency cone assembly can be installed after the intermediate frequency unit and the manufacturing is normal. Good morning. Nevertheless, the installation of this cone assembly is not hindered by the intermediate frequency unit, which can be removed, replaced and operated when necessary without removing the cone assembly.

The magnetic assembly is attached to the chassis platform 37 by bolts, one of which is indicated at 42 and extends from the rear of the platform 37. These can be threaded through magnets 35 and into internally threaded holes in front plate 33. As shown, plates 33 and 36 are attached to magnet 35 by adhesive.

A non-magnetic spacer ring 43 is mounted between the edge of the aperture in the rear plate 36 and the front plate 12 of the high and intermediate frequency section magnetic assembly. This ring, which can be conveniently constructed from three or more washers of a specially defined thickness (although not shown as such), is designed to accommodate the axial depth of the intermediate frequency unit. It has the function of physically separating two magnetic assemblies. The rings are mounted concentrically around mounting bolts, one of which is shown at 44, which holds the magnetic assemblies for the high and intermediate frequency units to the plate 36. This arrangement is MF cone 2
2, a cavity defined by the LF pole 45, the LF plate 36, and the MF plate 12, and a rear cover 51 attached to the rear extension 50 of the main chassis;
allows free movement of air to and from the air following volume defined by the space encompassed by. choosing a dome shape for the cover 51 rather than a flat disc to achieve rigidity;
Thus, responses resulting in unwanted acoustic emissions are minimized.

In order to bring the inner edge of the low frequency cone 31 close to the outer edge of the intermediate frequency cone 22 and to form a smooth transition between the two, the low frequency magnetic system, in particular the central pole piece 34, is connected to the intermediate frequency cone 22.
It needs to extend after part 1. in this way,
Comparison of pole pieces in which the leading edge of the pole piece 34 is sloped outward at 45 to match the shape of the chassis 21 and the inside of the air gap fits just inside the outer suspension 24 for the intermediate frequency cone 22 It can be seen that the target is limited by the thin extension 46. The narrow annular gap between the inner surface of part 46 and the chassis 21 is closed by an elastic bead 47, and this provides a slight additional support to the chassis 21 and also to prevent dust from entering the associated cavity. Seal the gap.

The associated formation of the chassis 21 and pole piece 34 allows the portion of the pole shoe 34 to be behind the portion of the chassis 21 and, as shown, in the assembled position, remove the low frequency magnetic assembly without first removing the chassis 21. It means that it is impossible. Conversely, if the chassis were installed first, it would be impossible to install the low frequency pole assembly in place.

As just explained, instead of making the extension 46 of the pole piece 34 relatively thin, the portion 46 is instead made thicker, leaving only a narrow gap between the inner edge of the cone 31 and the outer edge of the cone 22. , and 2
It can have a front surface shaped to form a smooth transition between two cones. This not only provides a large cross-sectional area for the passage of magnetic flux and avoids the risk of magnetic saturation, but also ensures that the chassis 21 does not extend in front of any part of the pole piece 34, allowing greater freedom in the order of assembly of the elements. Shashi to bring 21
allows you to design.

[Brief explanation of drawings]

The accompanying drawing is a longitudinal cross-sectional view of a triple concentric speaker according to the present invention. In the figure, 1, 2, and 3 are high frequencies, respectively.
Coaxial transducer unit covering intermediate and low frequencies, 6 is a horn load transfer plate, 1
2 is a front plate, 15 is a horn, 21 is a shell, 22 is a cone, 27 is an annular portion extending in the axial direction, 28 is an annular portion extending in the radial direction, and 31 is a cone.

Claims (1)

Claims: 1 comprising three separate transducer units each covering a low frequency band, an intermediate frequency band, and a high frequency band and driven by individual coaxial voice coils, The low frequency unit consists of a cone at the front of the speaker;
The high frequency unit consists of a horn-loaded diaphragm at the rear of the speaker, and the intermediate frequency unit has an axially extending annular portion and a radially extending annular portion formed along the rear surface, and the axially extending annular portion. consisting of a cone supported by a chassis which fits closely within the central opening of the front plate of the magnetic assembly which serves as part of both the high frequency unit and the intermediate frequency unit; A loudspeaker characterized in that both rear parts are formed from a metal that is permeable to magnetic flux and are held in place by magnetic attraction exerted by a magnetic assembly. 2. The rear portion of the intermediate frequency unit chassis is held in place solely by magnetic attraction exerted by the magnetic assembly.
Speakers listed in section. 3. A loudspeaker according to claim 1 or 2, wherein the low frequency unit has a magnetic system mounted in front of the platform on the main chassis supporting all three units. . 4. The magnetic system of the low frequency unit surrounds the chassis for the intermediate frequency unit and extends between the former for the low frequency voice coil and the outermost edge of the intermediate frequency cone, and extends between the outer edge of the intermediate frequency cone and the low frequency cone. 4. A loudspeaker as claimed in claim 3, including a central annular pole piece terminating at its leading edge in a portion shaped to form a smooth transition with the inner edge of the pole piece. 5. A speaker as claimed in claim 4, in which the leading edge portion of the annular pole piece is relatively thin so as to leave only a narrow gap between the two cones. 6. A loudspeaker as claimed in any preceding claim, wherein the radially extending annular portion engages a front plate of the magnetic assembly.