The Ely miner. [volume] (Ely, Minn.) 1895-1986, 1924-11-14

netized throughout by the perma-
nent magnet. the upper being north,
/ the lower south. And since like poles
/ repel, while unlike ones attract, the
end of the armature which has be-
/ come the north pole will tend TO move
up, while the other will at the same
| time try 10 move down. Thus, both
will contribute to exert a force on the
diaphragm and to move it in accord
/ ance with the current.
Cause of "chattering."
Practically, the Baldwin phone Is
| sometimes fails TO deliver sufficient
volume. when operated as a loud
| speaker, without 'chattering" Chat
tering is caused by sending so much
current through the coil that the
armature strikes the pole pieces as 1t
swings. This distorts the sounds bad
ly. as it prevents the diaphragm from
responding fully TO the current.
There are two methods of decreas-
ing this tendency to chatter. First.
horn may be placed in front of the
diaphragm. Under this condition the
diaphragm has TO move a much longer
| column of air with it, and hence a
given current will not produce as
much swing Of the armature, thus
lessening the chattering. The second
method is TO increase the size of the
diaphragm, so Ii must again move
! more air, which results in less chat
| tering, as before. These methods may
be used independently, or together.
There is at least one leHd-speaker on
the market using Baldwin phone at
tached TO a plaster horn" with the
standard size diaphragm. At the
other extreme, l know of a speaker
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, a bar and the necessary machine
screws, bushings, etc. This particu-
| lar design is for a type &C" Baldwin
phone and a three-inch diaphragm. 1t
/ could be modified for other combina-
! tons.
Description of Parts.
The por-s ,,,o,- I,a hast laSor;had H.
! taking up the assembly of the device.
| Disk A is so 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
piece of fine rubber tubing is laid TO
| form one support for the diaphragm.
| This groove is deep enough so that the
| diaphragm 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 10 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 De gwen, as some Will WISH 10
mount the unit directly on a phono-
/ graph tone-arm, while others will pre-
| fer regular horn. Disk is also ga
| inches in diameter, and is tapped to
receive the machine screws which hold
/ A. B carries somewhat shall0wer
/ groove opposite that in A. in which
second piece OF rubber tubing is laid
I TO form the other support for the
diaphragm. A pinch or 21a-inch hole
| is cut in the center of B, as the air
must not be confined behind the
! diaphragm. The bar c is fastened IN B
| in the same way as A is. The Baldwin
phone unit is removed from its case
and fastened to C by small bolts
I through the holes s, s. The lever con-
Meeting the armature TO the diaphragm
| goes through the hole t. The brass
used should be quite thick, say be-
tween 0.0S inch and Obs inch.
1t is necessary, Of course, TO remove
| the old diaphragm from the Baldwin
| phone, and the old lever
Mica diaphragms may be purchased
already cut to size, and one-eighth-
inch rubber tubing is also easily pur-
chased.-New York Sun
I made by soaking a strfp OF cloth I'm