The Challis messenger. (Challis, Idaho) 1912-current, 1924-11-26
Providing Use Type Baldwin pbo,. and
Threench Diaphragm Could Be Modified Other combIoatns

speaker, without "chatteringr Chat.
tering Is caused by sending so much
current through the coil that the
armature strikes the pole pieces as II
swings. This dlstorts the sounds bad
~ as 1t prevents the diaphragm from
responding fully to the current.
Ihere are two methods Of decreas-
Ing this tendency to chatter First.
norm may be placed in front Of the
diaphragm. Under this condition the
diaphragm has to move a much longer
column Of air with 1t, and hence a
given current will not produce as
much swing Of the armature, thus
iessening the chattering. The second
method is to Increase the size of the
dlahpragm, so 1t must again move
more air, which results In less chat
terlng, as before. These methods may
De used Independently, or together.
There Is at least one loud-speaker on
the market using Baldwin phone at
tached to plaster "horn," with the
standard size diaphragm. At the
one man built, using the stretched
head Of a banjo-mandolin as the
diaphragm, no horn at all being used.
1t Is probably better to combine the
two methods If large sound output
Is desired. To do this satisfactorily,
the new diaphragm must be supported
in the proper position relative to the
rest of the phone. A small brass frame
is best used for this purpose. Draw
ings for such a frame are reproduced
herewith. The parts consist of two
disks, bar and the necessary machine
screws, bushings, etc This particu-
lar design is for a type &C" Baldwin
phone and three-inch diaphragm. 1t
could be modified for other combina-
lions.
Description of Parts.
The parts may be best described by
taking up the assembly of the device.
Disk A is 312 inches in diameter, with
four holes around the outside through
which machine screws pass to hold A
and B together. There is a deep
groove turned in A as shown, in which
a piece of fine rubber tubing is laid to
form one support for the diaphragm.
This groove is deep enough so that the
will be very close to A. A
one-half-inch or five-eighths-inch hole
is drilled at the center of the disk for
the sound to come out. The horn used
must come TO this size at the small end
without any sudden changes in size,
and must be firmly attached. No
specific directions regarding the horn
will be given, as some will wish to
mount the unit directly on a phono-
graph tone-arm, while others will pre-
fer a regular horn Disk B is also 315
inches in diameter, and is tapped to
receive the machine screws which hold |
A. B carries a somewhat shallower
groove opposite that in A, in which
second piece of rubber tubing is laid
to form the other support for the |
diaphragm. A pinch or 1a-inch hole |
Is cut in the center of B, as the air
must not be confined behind the |
The bar c is fastened to |
In the same way as A is. The Baldwin
phone unit is removed from its case
and fastened TO c by small bolts
through the holes S, S. The lever con-
1ecting the armature to the diaphragm
goes through the hole I. The brass
lsed should be quite thick, say De-
.ween DOS inch and OPS inch.
1t is necessary, of course, 20 remove
he old diaphragm from the Baldwin
,hone, and the old lever.
Mica diaphragms may be purchased
llready cut to size. and one-eighth-
nch rubber tubing Is also easily pur
York Sun.