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THE
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plate in the four string region. I think that
the experiment ought to be tried.
On the other hand I do not think that any-
thing practical can be done in the way of
reducing the number of strings to the unison,
but on the other hand I should like to see
the twisted or plaited wire tried once more.
It might lead to some interesting facts and if
any one wants to go into it I should like
to hear from him. To twist such wire to three
or four to a strand is practicable, but would
involve rather careful preparation and would
be costly.
TENSIONS
Question No. 4. In your book on piano
building you state that the test average ten-
sion per string is 160 lbs. You have stated
since then that piano wrres are sometimes
used at a tension of 300 lbs. or more. What
does this mean ?
Answer: Average means average. Long
experimentation and much study since that
book was written shows that ideal results
can only be approached when the peculiarities
of each scale are determined on their own
merits. Thus, in the case of a nine-foot con-
cert grand with nothing save tonal efficiency
and mechanical perfection to be considered,
it would probably be best to start at the upper
end with No. 13 wire at about 135 lbs. ten-
sion. Two octaves lower this would become
150 lbs. Two octaves lower again the ten-
sion would be up to 160 lbs. (middle C). An
octave lower we should reach 170. An
octave lower we ought to be up to 200 and
from there onwards the tensions reached
would depend upon the conception held by
the designer as to the quality of the tone de-
sired and the general sonority of the lower
bass region. Other things being equal, the
higher the tension the fewer the harmonics
developed, since the higher the tension the
stiffer the string. Obviously the stiffeT the
string (so long as it is not rigid enough to
take on the properties of a rod) the less
readily will it break up into harmonic seg-
ments. Should, however, the stiffening be
carried far enough to cause the string to vi-
brate like a rod, the exact reverse of the
above process will take place.
STRIKING POINTS
Question No. 5. You say in your book that
for obvious mechanical Teasons the striking
point of hammer on string cannot be kept at
one-eighth of the string's length throughout.
What are the reasons?
Answer: The reasons are actually more
acoustical than mechanical, although one only
has to try drawing a scale with a hammeT
line set at one-eighth of the lengths all the
way from one end to the other, to see how
the symmetry of the design would be spoiled.
Acoustically, the reasons are even more com-
pelling. The treble strings above C 52 need
to be struck above the eighth node in order
that they may be encouraged to break up into
as many harmonic segments as possible. Even
at that they are too stiff to make much of
the harmonic process, and this in fact fur-
nishes the principal cause of the hard, short
metallic tone of the uppeT treble in even the
finest instruments. If the striking point were
kept at one eighth all the way to the C 88,
the upper treble would be very much less
powerful than it is. It would be less glit-
tering, but more feeble.
MUSIC
TRADE
REVIEW,
November,
1932
RADIO MANUFACTURERS TAKE STEPS
TO PREVENT UNFAIR COMPETITION
T meetings of radio industry leaders
in New York on October 20-21, in-
cluding the Board of Directors and
Receiving Set, Tube and Parts Divisions of
the Radio Manufacturers' Association, sev-
eral important and vigorous measures to im-
prove merchandising conditions and prevent
unfair competition were adopted:
Chief among these was unanimous adop-
tion by the RMA Board of Directors of a
foTmal resolution calling on radio patent
licensors, including the Radio Corporation of
America, to take adequate action against un-
licensed manufacturers.
This action immediately follows recent
numerous lawsuits instituted by holders of
loud speaker patents against many prominent
chain-store, furniture and other purchasers
of unlicensed products and is expected to re-
sult in similar action to protect receiving set
manufacturers against many unlicensed and
irresponsible manufacturers.
Receiving sets offered to the public by
RMA set manufacturers soon will bear an
RMA label certifying official Association ap-
proval and manufacture under RMA stand-
ards. Only manufacturers who are mem-
bers of the RMA will be permitted to use this
label on their products as another measure to
protect "legitimate" manufacturers. Radio
dealers and jobbers in intensive advertising,
and the public also, will be urged to buy
RMA "certified" receiving sets.
The RMA label, of attractive design either
in metal or paper composition, will ceTtify
official association approval by the RMA
Engineering Institute. Establishment of this
new RMA Engineering Institute was author-
ized by the Association's Board of Directors
at New York, October 21. The Institute will
be under the direction of Mr. Franklin Hutch-
inson, of New York, Chairman of the RMA
Engineering Committee, and will consist of
five leading engineers appointed by Chair-
man Hutchinson and approved by the RMA
A
CROWN
Question No. 6. What is the best practice
in regard to the elevation of the belly bridge
above the hitch plate to produce pressure of
the strings on the soundboard?
Answer: In order to cause the soundboard
to Tespond effectively to the motions of the
strings, it is best to bend the whole structure
to a curve of long radius, say 60 feet. This
is done, as every one knows, by heating the
wood of the board thoroughly and then glu-
ing to it curved rather than straight ribs and
bridges. If the curvature of both ribs and
bridges has been properly calculated, the
board will assume the proper shape. When
the piano is strung the pressure of the strings
will tend to flatten out this curvature some-
what. It is generally thought best to curve
the board so that when it is in place with
the plate fastened above it, before the strings
are put on, the line of the treble bridge shall
stand about 3 A" above the line of the hitch
pins and tuning plates. When the strings
are put on and pulled up to pitch the differ-
ence between the two levels is likely to be
reduced by about one-half to 3/16". Practice
Board. The Institute will give its approval
to receiving sets of RMA members which are
manufactured in accord with specifications
adopted by the Institute and the RMA Board.
The initial specifications under which the
RMA label may be used provide that:
1. All sets which,carry the RMA label shall
have been submitted to the Underwriters'
Laboratories for approval, except sets for
which the Underwriters have no require-
ments.
2. Sets shall cover the entire United States
and Canadian broadcast band.
3. Sets shall be noninterfering in accordance
with RMA standards.
4. Sets shall meet quality and performance
standards of the RMA.
The new RMA labels, copyrighted, are be-
ing prepared and will be available soon to
RMA set manufacturers. The date of their
initial distribution and use will be announced
well in advance to permit their use by manu-
facturers, for them to proceed with adver-
tisement to the trade and the public of the
new plan to certify sets of standard manu-
facturers. LateT on, to facilitate use of the
RMA labels, each manufacturer will be per-
mitted to secure his supply of RMA labels
after approval of his models by the RMA
Engineering Institute.
The Association proposes not only to pro-
mote sales of receiving sets bearing the
RMA label, but also to prevent infringement
or improper use by manufacturers not hold-
ing membership in the RMA.
The certification plan, establishing the new
RMA Engineering Institute, was developed
by the Association's Set Division, headed by
Arthur T. Murray of Springfield, Mass.,
Chairman, and the initial specifications for
sets sold under the RMA copyrighted label
were adopted at a meeting of a number of
leading engineers October 21 at New York,
with Chairman Hutchinson of the Engineer-
ing Division presiding.
differs, of course, to some extent, but the
figures given here represent a good average.
PERMANENT TUNE DEVICE
Question No 7. Was not a device patented
some years ago which aimed at keeping a
piano in tune permanently?
Answer: Yes, patents were issued in 1916,
or thereabouts, to A. J. Ostrander, of Lyons,
N. Y., upon a hydraulic device utilizing
Pascal's law of fluid pressure. In this device
each string is hitched to a piston working
in a cylinder filled with a viscous fluid. The
bank of cylinders is connected with a reser-
voir of the fluid. If any string rises or falls
in pitch the change is at once distributed
throughout all the other 230 or so strings in
the scale. Thus the tendency is for the pitch
to be constantly rising or falling by imper-
ceptible amounts evenly throughout the
whole scale. I have seen the apparatus in
action and do not hesitate to say that its
principle is correct. Mechanical difficulties
connected with the management of the fluid
do exist; but they could be worked out, I am
sure. It is too bad that this most fruitful
device has never been put to adequate test.