DE1002396B - Coaxial loudspeaker - Google Patents

Description

The invention relates to coaxial loudspeakers which have two separate voice coils, one for playback higher frequencies and one for reproducing lower frequencies. These speakers come together used with filters that divide the frequency range of each system into the desired frequency band.

In the coaxial loudspeaker according to the invention, two oscillating coil systems are available, each have an air gap.

The one, inner air gap is concentric to the other, outer air gap and also in same magnetic circuit.

In loudspeakers of this type, the air gaps have been arranged so that they are with respect to the magnetic Flow in series, d. H. both are penetrated by the same lines of force. '

The invention is intended to create a particularly simple way of distributing the magnetic flux between the two air gaps. In addition, it should be achieved that for the magnetic core, which is common to both vibration systems, only insignificantly increased amounts of additional magnetic material can be used in order to achieve the necessary magnetic flux in the two annular air gaps. This not only simplifies and facilitates the manufacture and assembly of the loudspeaker, but also achieves a considerable reduction in production costs. ■ ' ^:

According to the invention, the coaxial speaker of the aforementioned type is designed so that the outer Air gap between a central pole core and an annular one Main pole plate and the second inner air gap of one connected to the central pole core Auxiliary pole core and an auxiliary pole plate are formed and the auxiliary pole core a smaller one Has diameter than the central pole core and lies at the front end of the latter, while the auxiliary pole plate is in magnetic communication with the outer air gap in such a way that part of the magnetic Flow in the outer air gap goes through the inner air gap.

A preferred embodiment of the invention is described below with reference to the figures.

Fig. 1 shows a section through the axis of the loudspeaker according to the invention and

FIG. 2 shows a part of the section according to FIG. 1, in particular of the auxiliary magnet system, in an enlarged manner Scale.

The unit shown in the figures consists of a main magnet system known per se, which is a Pot-like housing 1 made, for example, of soft iron, coaxial loudspeaker

Applicant:

Goodmans Industries Limited,
Wembley, Middlesex (Great Britain)

Representative: Dr.-Ing. H. Leithäuser, patent attorney,
Essen, Bertoldstr. 9

Claimed priority:
Great Britain 5 March 1954

John George Carter, Ashford, Middlesex

(Great Britain),
has been named as the inventor

a central pole core 2 and an upper main pole plate 3 (outer pole plate). The main pole 3 is fixed to the edge of the housing 1 and forms with the pole core 2 an outer air gap 4. The pole core 2 is composed of the magnetic core 2 ° and the other core 2 ^b, which together and to the housing 1 by a central screw bolt 5 are firmly connected. For the purposes of the invention, an annular groove or recess 6 is provided on the upper outer edge of the core 2 ^b in such a way that parts are removed from both the peripheral surface and the front surface of the core, so that an additional short auxiliary pole core 2 ^C is created, which protrudes from the upper limit of the core 2 ^b and has a smaller diameter than this. Inside the groove 6, an annular auxiliary pole plate 8 (inner yoke plate) made of soft iron or a highly permeable alloy is attached to a non-iron spacer member 7, which is fitted into the groove and is designed as a support ring. The Hilfspolplatte 8 disposed is thinner than the outer main pole 3 and so that their top surface is approximately in a plane with the upper surface of the main pole 3 and the pole core 2 HiIfS ^C. The outer edge of the inner auxiliary pole plate 8 is aligned with the outer boundary surface of the core 2 ^b , but has a certain distance from the latter. The inner edge of the auxiliary pole plate 8, on the other hand, forms with the auxiliary pole core 2 ^C a second, but smaller (inner) annular air gap 9 which is concentric with the (outer) annular air gap 4.

s \ - :; t; ; ■ ·; · 609 770/272

In this way, the auxiliary pole plate 8 and the auxiliary pole core 2 ^{C form} an additional magnet system, part of the magnetic flux penetrating the air gap 4 being passed through the auxiliary pole plate 8 via the inner air gap 9. The proportion of magnetic flux which is branched off via the air gap 9, it can be determined from the outset by the axial position of Hilfspolplatte 8 with respect to the core 2 ^b.

Inside the outer air gap 4 is the voice coil 10 for the conical membrane 11, which is tuned to low frequencies and which in turn can be suspended in the usual way in a membrane basket 12, on the rear of which the magnet system is located. The voice coil 13 for the tweeter diaphragm 14 is arranged within the inner air gap 9. The membrane 14 preferably consists - and as also shown - of a dome-like or dome-like structure which arches over the auxiliary pole core 2 ° and is itself covered by a perforated cover 15 or the like. The tweeter system is attached to the front of the central pole core 2 as described below:

The tweeter diaphragm 14 is carried by a centering device 16 which is clamped between two annular disks 17 which are located in a recess provided on the upper side of the auxiliary pole plate 8. The pole plate 8, the annular discs 17 and the support ring as a spacer member 7 are held by a number of non-magnetic bolts in a certain position, the ^east through the entire system into the Kern2! Protrude, as shown beil the location 18th These bolts advantageously also serve to hold the cover 15 in its position. For this purpose, spacer rings 19 are provided between the cover 15 and the annular disks 17. The tweeter system can also have a small horn 20, which is optionally held by the same screw bolts. The centering device 21 for the bass system can also be held by the same bolts by placing it between the flanges of the cover 15 and. of the horn 20 is pinched.

It should be noted that the illustrated embodiment of the invention can be modified in various ways. It is thus possible in practice to omit the spacer 7 entirely for acoustic reasons and to replace it with spacers made of non-magnetic material. Furthermore, the recess 6 (FIG. 2) can be designed in various ways. It is also possible to manufacture the auxiliary pole core 2 ^C as a separate component and then to fasten it with screws, which has the advantage that a highly permeable material can then be used for it. Finally, the invention can be applied in the same way as to permanently dynamic loudspeakers of the annular gap type as well as to electrodynamic, externally excited loudspeakers.

Claims (2)

PATENT CLAIMS: 1. Coaxial loudspeaker in which a first voice coil system with a first (outer) air gap and a second voice coil system with a second (inner) air gap are provided and the inner air gap is arranged concentrically to the outer air gap and also in the same magnetic circuit, characterized in that, that the outer air gap (4) from a central pole core (2) and an annular main pole plate (3) and the second inner air gap (9) from an auxiliary pole core (2 ^C ) connected to the central pole core (2) and an auxiliary pole plate (8) are formed and the auxiliary pole core (2 ^C ) has a smaller diameter than the central pole core (2) and is located at the front end of the latter, while the auxiliary pole plate (8) is in magnetic connection with the outer air gap (4) that part of the magnetic flux in the outer air gap (4) goes through the inner air gap (9). 2. Coaxial loudspeaker according to claim 1, characterized in that the distance between the auxiliary pole plate (8) and the central pole core (2) by a non-magnetic spacer, for. B. Ring (7) or the like. Is secured, dias is mounted in a recess (6) at the front end of the central pole core (2) and ^{encloses the auxiliary pole core (2 C} ). Considered publications:
British Patent No. 445,935;
RCA Review, Dec. 1949, pp. 490 to 503. 1 sheet of drawings © «19 770/272 2.57