The Challis messenger. (Challis, Idaho) 1912-current, 1923-01-24
PRESERVING TONE
IN LOUD SPEAKER
How This Can Be Done and the
Maximum Amount of AmpIi-
ficati0n Obtained.


: received signals Is obtained and tn
necessity Of wearing the head phone
Is eliminated. The loud speaker ais
permits u greater number of people t.
hear the concert, as with head phone
the number hearing the concert Il
limited to the supply Of head phones
while with the amplification the mum
Der Of people hearing the concert 1.
limited to the range of the device.
tThere are several problems involved
In obtaining the maximum amount OF
application, and yet at the same time
preserving the original tone so that II
will retain its pleasing qualities.
Most of these problems are involved
in the maintenance of the quality OF
The received tone, as 1t Is compare
lively simple matter to amplify the
received signal sufficiently.
III order to eliminate or minimize
loud speaker distortion, it is necessary
to know the causes involved. The
source Of the trouble may be In the
amplifier, in the loud speaker itself,
or in both.
Amplifier distortion may be caused
by unequal voltage transformations In
the coupling transformer at different
radio frequencies. by the operation Of
the amplifier tube at the wrong point
OF Its characteristic and by overload
Ing the tube to the point of saturation.
For good application Of telephone
signals, the inter-stage transformer
should be capable Of giving a uni
form transfer of voltage from about
200 to 5000 cycles per second. A good
many transformers now In use do not
do this, and their operation is one of
the principal causes for unsatisfactory
signals. For any particular plate vol !
tage applied to the amplifier tube there
Is corresponding value Of negative |
grid voltage which should be applied |
In order to operate upon a straight por-
ton Of the characteristic curve and
thus secure uniform application.
For connecting to the loud speaker,
especially when using power tube
for the last stage, it is preferable to
use ain intermediate transformer with
the proper constants, instead Of plac-
Ing the loud speaker directly In the
tube plate circuit. This keeps wind
Ing and prevents the polarzing effect
that it would have upon the dia-
phragm.
A two-stage amplifler will general
ly give enough intensity to operate a
loud speaker in an ordinary living
room, while the loud speaker mechan-
ism itself may be Of the head tele-
phone type with q suitable horn. Some
receivers operate very well at moder-
ate intensities, but when very strong
signals are applied to them they vi
)rate so violently that the diaphragms
nit the pole pieces and produce harsh
sounds instead Of good reproduction !
If the original signals. To handle the
proper amount Of energy, therefore,
he construction must be such that rea-
onaby strong vibrations will not G
orce the diaphragm to its limit Of a
ravel. The material and shape Of the 0
diaphragm are also important in de- n
the resultant tone qualities, r
ince whatever natural periods Of vi e
ration 1t may have will bring out GER e
min tones In greater proportion than II
hey should be to the remaining tones II
musical selection. b
The size, shape and material Of the "
orn are likewise important factors IL
l the final result. The high natural y
eriod of small horn will tend to ac
the higher tones to the ex-
fusion of the lower ones. The ma
srial from which the horn is made Y,
Mould be some substance which will b,
OF vibrate and produce rafting re
FUNDS. 81,
Thus we see that in order to pro- al
1ce Il combination of amplifier and d,
nd speaker which will give pleasing OF
,sults. II Is necessary to choose the bl
lrious parts with care and assemble W
lem so that they will give true re- az
Of the original signals. FL