A MUSICAL WONDER

Bay of Plenty Times, Volume LIV, Issue 9204, 9 June 1926, Page 2

A MUSICAL WONDER

m:w gramophone invention A great ileal of favourable comment lias been occasioned by the new “His Master's Voice" gramophone. In a trial recently made, between the best of the H.M.V. gramophones as at

present known ami the new model, it \\as found that the contrast was striking am! remarkable. For some years past, the Bell Telephone Company oi America has Iteen engaged in solving problems ol long-dis-tan.o audibility. Among them was the problem oi transferring sound waves, tr'm thin wirrs in underground rabies, to the thicker wires earned on poles in the open country. In the course oi their work on this problem, the company's exports found themsclvs delving deep into the mysteries ot .sound waves and elceirophonies. Among other tb jno it was discovered that the sound wa\e s were carried the more accurately fr mi a thick to a thin wire, if the transfer were effected by stages, thereby avodiing the severe resistance cl counter-waves ami backwash such as arise, for example, when water from a large pipe is toned through an abrupt joint into a narr ov channel. On the same principle. sound Irom the gramophone's diaphragm will be best transferred to the air .if the horn be long and straight, with the area ol its cross-section increasing in a constant radio. For drawing-room purposes, however, a ItMoot, or even a six-foot, horn is an impossibility Si the problem has been, how to gel the effect of a six-foot horn into a cabinet ]Sin square. An ordinary comb might serve, hut for the fact that, while a curve or elbow in a tulie ol one or two inches diameter, causes only miner distortions of the sound waves a curve in a round conch, when it ha s expanded to a diameter cf four or more inches. sets up cross currents and repercussions of sound waves that distortthe purity of the music, or clarity cl the voice. The new machine meets this difficulty with striking ingenuity.

in the ordinary H.AI.V. machine, (he sound waves set up by the mica diaphragm pass through a round! tube across the top of the machine down into the interior, and thence directly out into the air through a. box shaped like a pyramid. On the new machine the diaphragm of corrugated aluminium sets up sound waves which are carried across the machine by a carefully proportioned round tube, leading into a square pipe running half-way down the hack of the cabinet, 'flu’s square pipe then divides into two passages that carry the sound waves forward into the upper and lower halves of a wooden box occupying the middle range of the cabinet. This box is like two cpnvex shelved fitted together. Actually it contains four flat couches, two in the upper half, and two in the lower.

Inside each conch the sound waves are given space to expand horizontally, while the flatness of the conch prevents vertical expansion. Waves expanding horizontally only can bo sent horizontally round a corner without serious distortion. On emerging from the common egress of the two pairs of conches, the waves have now reached the lull width of the gramophone' cabinet. They then strike a ridge at the hack of the cabinet, and are bent upwards and downwards, following expanding curves that permit them to obtain vertical expansion. By the time they reach the front of the cabinet the waves have gained a full expansion, both horizontal and vertical, as if coming from a horn six-foot long, yet the expansion has all along been taking place in a passage whose cross section areas, have been increasing in a- constant ratio