SE328611B - - Google Patents

Abstract

1,003,608. Diaphragms; reverberation systems. AKUSTISCHE UND KINO-GERATE G.m.b.H. Jan. 2, 1963 [Jan. 15, 1962], No. 300/63. Headings H4J and H4R. A loud-speaker diaphragm comprises a substantially flat plate of foamed material said plate being susceptible to the formation of flexural waves therein, whereby reverberation is added to sound produced by its vibration. The diaphragm 1 (Fig. 1) may be rectangular (50 cm. x 100 cm.) with a rim 2 of smaller thickness than the remainder. The rim 2 is gripped in a frame 4 and damping material 9 of soft felt, wadding or soft rubber reduces the formation of standing waves. The diaphragm 1 is actuated by a dynamic driving system 5 secured to a cross-bar. The voice coil 7 may be centred by the diaphragm itself, or by a single centring ring 10 (Fig. 3) or by two rings 10, 11. The driving system 5a (Fig. 4) may be offset from the centre and the diaphragm may be mounted at its rim in damping material and backed by damping means 14, 15. One or both sides of the diaphragm 1 (Fig. 4b) may be covered with aluminium foil or plastics sheet which acts as a mounting. The diaphragm may be covered with damping material on one or both sides. The rear face of the diaphragm may be conical (Fig. 5, not shown). Ribs may be formed on the diaphragm surface. A plurality of driving systems may act on a single diaphragm (Figs. 6, 8, not shown). The diaphragm 26 (Fig. 7) may be fitted in a cabinet and cater for middle and upper frequencies while bass frequencies are radiated by bass loud-speakers 27, 28. The diaphragm 33 (Fig. 9a) may take up the entire front face area of a transistor radio, the driving system 32 being secured to a cross-bar 35 or to a triangular board (Fig. 10, not shown). The diaphragm may have a conical extension 39 (Fig. 11) to which the voice coil is secured. A conical diaphragm of " Duralumin " or " Pertinax " (Registered Trade Marks) may have an outer foamed diaphragm 41 (Fig. 12) and a foamed plug 42. Specification 827,302 is referred to.