Patent GB-1450310-A (GB)
Title: Speaker unit
IPC: H04R1/20
Filed: 1974-12-18
Abstract: 1450310 Loudspeakers SANSUI ELECTRIC CO Ltd 18 Dec 1974 [28 Dec 1973 (2)] 54628/74 Headings H4J and H4X A high frequency loudspeaker is mounted on the front baffle of a loudspeaker enclosure and has a diffuser assembly which radiates generated sound in a direction away from the baffle and also parallel to the baffle. An enclosure 10 (Fig. 1) has a woofer 12 mounted in an opening in the baffle 11. A diffuser 13 is bolted to the front face of the baffle 11 vertically above the woofer 12. A mid- and high-range speaker 14 is mounted centrally of the diffuser 13. If desired, a separate tweeter (not shown) is mounted in the baffle. The diffuser 13 has three sound radiating openings 15, 16, 17 (see Fig. 3) directed upwardly and to opposite sides of the enclosure 10 for directing sound from the speaker 14. Speaker 14 also radiates forwardly. A decorative cover 18 is of perforated metal sheet or is a frame on which is mounted acoustically transparent synthetic resin cloth. The diffuser has a front panel 20 (as in another embodiment shown in Fig. 8) and a diffuser body 21 both of which may be made of wood, die cast aluminium or moulded synthetic resin. Three exponential sound passages 24, 25, 26 (similar to sound passage 24 in Fig. 8) extend from the passages 27, 28, 29 and communicate with a central opening 23 to receive back radiation from speaker 14. The speaker 14 (Fig. 4) is of the moving coil type and has an aluminium frame 30 with a dished portion 31 and a speaker cone 33 with an edge 34 attached to the edge of dished portion 31. An annular damper 36 of silicone rubber sheet or synthetic resin is attached to the edge 34 of cone 33. A magnet assembly 32 comprises a central pole 37 and an annular permanent magnet 39 interposed between a disc yoke 38 and an annular yoke 40. The dished portion 31 has radially extending holes 42, 43, 44 which communicate directly with the throats 27, 28, 29 (Fig. 3). In an alternative diffuser (Fig. 6, not shown) the intervening space between the front panel (20) and the baffle 11 forms a single sound diffusion passage (46) which extends around the rear of speaker 14 and is filled with sponge rubber, foamed polystyrene or glass wool. An integral speaker frame (30) is formed by pressing the front panel and the speaker cone 33 and magnet assembly 32 are mounted on this. In yet another diffuser (Fig. 7, not shown) the speaker frame 30 is again integral with the front panel (20). The front panel (20) has an annular recess (50) located around the speaker 14 and projecting inwardly towards the baffle 11. An annular member (51) of configuration complementary to the recess (50) projects toward the recess (50) to form a throat. In a compound co-axial type speaker (Fig. 8) the woofer 56 is mounted on the rear wall of the diffuser 13 which is secured around an aperture on the front wall of the baffle 11. A large number of holes 57 extend through the diffuser body 13 and the front panel 20 to allow low frequency sounds to pass freely. Sound produced by the cone 33 of speaker 14 passes forwardly and in sideways directions through passages 24, 25, 26 as in the arrangement of Fig. 3.