AN EXPONENTIAL HORN SPEAKER

Radio Record, Volume I, Issue 48, 15 June 1928, Page 13

AN EXPONENTIAL HORN SPEAKER

FINE example of exponential horn of the folded type is now on the market in New Zealand. This pattern, which is fitted with a speaker unit of high quality, is capable of very fine quality reproduction, and when housed in a suitable cabinet, forms a useful and attractive piece of furniture. A number of these have been landed by Messrs. Thos. Ballinger and Co., Victoria Street, Wellington, where a demonstration will be given.

Browning-Drake Connections, [TN the Browning-Drake circuit as originally published, B negative lead was connected to A postive. It has been found advisable to connect B negative to A negative, and thus keep both negatives at earth potenital. Such change would be necessary in the case of adding a potentiometer across the filament of last. valve to cut out A.C. hum as mentioned in another column. Position of Loud Speaker. IZERE are various kinds of "howling" which can be set up in a re- ‘| eeiving set, and which are frequently dealt with in relation to the circuit arrangements and to the set itself, bul a low-frequency howl sometimes arises owing to purely acoustical reaction between the loud speaker and the valves, especially if the latter are inclined to be microphonic. Sometimes this effect is very troublesome, and I have known cases of amateurs seeking for a remedy for this trouble with no idea of the true cause, ‘The action in cases of the type referred to is similar to that which occurs if you place the earpiece or receiver of an ordinary line telephone against the transmitter. If the loud speaker is facing the set and

i ihe Ferry pen oR, in close proximity to it, a loud note’ from the speaker, if it happens to be ‘of shott the xight pitch, may piroduce considerable vibrations in the valves, and thereby in the filaments, this having the effect of increasing the note in the loud spédker, and so on. The remedy, is simply to turn the loud speaker in a different direction and/ also, if necessary, to remove it further away from the set,