New-York tribune., 1922-11-26
Hints ON Using
Loud Speaker
Inn Receiver
Two Distinct Types of Loud
Speaker i'm Use, but Both
Need Correct Output From
Receiver to Work Well
Bet Must Suit Speaker
Success Depends ON Amount
of Asnplificasion From
the Radio Receiver Used

Practically every radio Fan desires
to reproduce the concerts and other
entertainment from the broadcasting
stations on a loud speaker, and thus
eliminate the necessity OF wearing
head telephones. In addition, with 9
good loud speaker 1t Is possible foI
many TO hear the entertainment In an
ordinary sized room, provided, OF
course, sufficient volume Is obtained
from the receiving set.
There are quite number Of things
that have to be taken into considera-
tion before success can be obtained
with q loud speaker, and 1t Is my pur-
pose TO outline these governing con-
ditions as FAR as possible. There lie
probably TO more abused instrument in
radio apparatus than the loud speaker,
and yet In the majority OF cases IL is
not TO blame.
In the first place it should be clear.
ly understood that loud speaker cam
not operate unless 1t Is given she right
ter how expensive or how we'll built
the loud speaker may be itself, It will
not work unless the receiver IL is con-
nected to is suitable FOR It.. In other
words, a sense Of proportion has TO be
maintained.
Two Types of Speaker
Roughly speaking, there are two
main types Of loud speaker in actual
use at the present time, first, those
which use an eieetro-magnet and
those which employ permanent mag
net. In the former. type large mag
" attn GofA ta ah tad Nv 70
strong current through coll which
has steel core. The denae magnetic
Aux is then employed 60 assist the
comparatively weak currents obtained
from the radio receiver. The latter
type uses a permanent magnetic field
for the same purpose, but relies more
on The output Of the receiver.
II is in connection with the lat
ter type, however, that certain pYecau-
tions must be taken In operation. Fol
general average results 1t will be
necessary TO employ at least two stages
Of auto-Yrequency amplification in ordsy
TO obtain loud speaking results. and iu
some cases ONE Or both Of these will
utilize power tubes.
Under the circumstances, therefore
il must be realized that there 10 q very
strong direct current component In che
plato circuit OF the last vacuum tube
to which The loud speaker Is attached
Ii this current should how through the
speaker In such way that IL sets up q
small! magnetic field opposed 10 that OF
the permanent magnet 1t will in time
denagnetize the speaker and go loves
its efficiency. This Of course applies
equally we'll to the ordinary head tele-
phone.
Speaker Must BE Joined Right
One Of the important things to be
observed in this type Of instrument
therefore, Is the correct polarity OF
have already realized this point and
are now marking the telephone, or
loud speaker, cords in distinctive
manner, 60 that the fan will know
just which way to connect them in
his set, II you are in doubt about it
take only those so marked.
II as q result OF the condition out
lined the loud speaker Or head tele-
phones have lost some Of their eff
cheney, this can be restored by very
simple expedient. Il consists solely
Of reversing the leads from their pres
ent connections, and then passing
rather more current them normal FOR
short time until the efficiency is
again restored. From this description
il will be readily deducted that II the
speaker or phones are correctly Joined
up TO the set the plate circuit current
will at all times be assisting the per
manent magnetic field, and thus AID In
keeping it permanent"
In nine cases out of ten gquealinG,
bowling loud speaker !s not at fault.
The trouble lies with the receiver, and
the fan in his endeavor to obtain
louder tones in his speaker has
overloaded his radio receiver and
thrown it into the bowling state.
Amplifying Conditions
In some cases loud speaking results
are attempted with two stages Of
amplification using the regular vacuum
tube Of the U. v. 2o1 type, when the
output from the detector Is at it's
lowest possible, due either to distance
from the broadcasting station or other
local causes. In such cases the tubes
in question cannot possibly fugnish
sufficient amplification to operate the
speaker. In these cases it is either
necessary to add one or more stages
OF The radio frequency amplification or
else use five-watt power tubes in the
audio frequency side.
OF course, 1t should be understood
that the radio frequency amplifcation
builds up the carrier wave and all that
goes with 1t, so that the detector can
get in IFS work more efficiently. Radio
frequency amplihcation will not give
loud speaker results alone. Roughly
speaking, it increases the range Of a
set.
Increasing the amount Of B battery
voltage on the plates Of the radio frc-
quency ampliAer tubes will help in
some cases, but this cannot be carried
beyond certain point. Where the five
watt power tubes are used, if the elec-