| Subject: | Re: [RESOGUIT-L] Reso cones and tone (was DelVechio Guitars?) | | Date: | Tuesday, May 1, 2007 12:42:30 (-0700) | | From: | Richard DeNeve <richard_d13132 @.....com>
|
Dennis,
I'll stick my oar into this pond, and probably will
get it snapped off by the admittedly polite
alligators!
--- Dennis Poague <poague@metalink.com.br> wrote:
> Greetings from Brazil,
(snip)
> I have been lurking and waiting to post since I
> have questions for all
> the Reso Luthiers about making cones. I have had
> the luck to be shown by
> a DelVecchio worker how to spin their cones. I even
> got to spin a couple
> on their lathe...peace of cake.
What is
> the secret to the magic
> cone? So far I have come to three major answers
> from
> some kind luthiers that have answered>
> First I tried to discover the alloy John
> Quarterman. I have been told that as the
> best guess he uses a
> 6061 fully annealed (T1) alloy about .07inch
> think???.
John is somewhat secretive about his product - and
probably should be. I have microscopically examined
and spectrographically analyzed metal from the "QC-1"
cone. The metal looks to be a sandwich of darker
metal between two lighter clads. Alloy 7075 is an
aircraft alloy which contains other elements that make
it liable to more rapid corrosion than most others.
So they but a thin layer of soft purer aluminum on
each side to protect it from corrosion. The amounts
of copper and zinc in the QC-1 aluminum, about 1.5% to
2%, are also consistant with alloy 7075. Alloy 6061
has little or no copper, and less thans 1% zinc. Mr.
Quarterman has told me his alloy is NOT 7075.
Quarterman cones I have from 3 different sources and
from as far back as 25 years have metal that is
10/1000 (.010) inches thick. Some sections are
stretched somewhat thinner in the spinning process.
> Next I was told by the BelTona reso luthier in New
> Zealand the the
> secret is not the alloy but the shape of the cone:
> height versus
> diameter..better tone the higher the center.
When you think about it, the cone is a speaker, both
bass and treble. (Some builders - including me -
regard the guitar body as a bass reflex speaker
cabinet, the size of which considerably effects guitar
tone, but this is another topic.)
The volume of sound the cone produces depends on the
amount of distance in and out various sections move,
under force from string vibration. This is governed
by the real and apparent mass of the resonating system
(including mass of the spider and strings, as well as
down-pressure from the strings pre-stressing the
system), the size of the cone's surface area, the
stiffness of the metal, and the radius of the roll
around the rim of the cone.
The greater the radius of the roll around the edge of
the cone, the more it will move in and out, and the
greater volume it will produce. Except that if the
radius is too great, it will not be strong enough to
support string down-pressure, and will collapse into
the guitar. (John P. Quarterman told me that most
guitar designs place about 65% of the maximum
down-pressure his cones will withstand.)
A larger cone diameter than the "standard" 10-1/2 or
10-9/16 inches should give more bass response. But it
takes more energy to produce lower frequency sound at
the same apparent loudness to the human ear, and there
is only so much energy available from a plucked
string.
The central part of the cone, the raised portion, acts
as a tweeter and midrange speaker. It's "crossover
frequency" is probably at least in part due to its
base diameter. Make it bigger, you should increase
midrange sound, likely at the expense of high treble.
The angle of this central cone part should also affect
sound quality. It needs to be steep enough to
efficiently transmit vibration to its base, but flat
enough to fit under the spider above, and to push
sound waves up rather than sideways.
(Don't forget that the screw transmits treble to the
central part of the cone, and the legs transmit lower
frequencies to the edge. I have had spiders that were
too stiff, causing treble to suffer, and so soft that
little sound went to the cone edges.) Everything is a
trade-off or a compromise.
An arched surface is stronger than a flat surface. A
cone with straight sides will absorb more of the low
to midrange frequencies as they force air movement.
The parabolical or spherical sides of the Beard and
QC-1 cones bend less to this air resistance, and seem
to have a fuller sound. I also think that, like a
telescope with a parabolic mirror that focuses light
to a central point, the rounded inner surface of these
cones focuses sound up and out more efficiently than a
straight-sided cone does.
> Now I also believe that the tools used as well as
> the attention by the
> spinner has some influence on the quality of the
> cone tone. I mean that a
> seasoned cone spinner can make a better sonding cone
> that the Korean (
> Chinese) ??? machine made cones.
Many aluminum alloys will "shelf anneal," that is,
they will gradually lose their hardness from being
formed over time. Heat speeds this process. Hardness
imparted by alloying other elements like silicon,
carbon, zinc, etc., does not anneal away (unless you
approach the solution temperature of the metal.).
OMI used to form some of their cones by stamping them
instead of spinning, and most cones from the 30s were
stamped. In general, they had good sweet tone, but
not much volume.
Some people think that very sharp edges at the roll
and where the spider rests add to tone. As long as
there was at least a small curvature, I have not
noticed a difference, but have never flattened out
these areas to test this. Sharp angles on your chuck
(the form against which you spin the alumuinum) and
your forming tools increase the likelihood that you
will thin the metal too much at these sharply bent
areas, and cut through it.
>I plan on
> making my own cones once I have all the answers.
Once you do, please share with the answers us! There
is only so much energy available in a plucked string.
If that energy is rapidly dissipated into a large
light surface (think banjo head) the sound will be
loud but short-lived. If the surface is stiff, heavy
and large, you will produce less volume but a lot of
sustain. If the vibration goes elsewhere (e.g. neck
movement, absorption into the cone support or bridge
inserts, etc.) you will lose both. Laws of physics
dictate that there IS a limit. Folks like you can
perhaps help us move closer to it.
> I love this forum and read all the post
> everyday...if I can´t
> get the answers from youall here I guess I will try
> Resonation or
> Acoustical Guitar Luthier forum next...
> I am just waiting for the answers to start spinning
> and bulding so I too
> can becom a Master ConeHead luthier.
I don't know if there ever could be "the" answer.
Most of us do what we think is the answer for us, and
for the sound we are trying to achieve. I make two
body styles of guitars that have two distinctly
different sounds, using the same basic construction
techniques and identical metal parts. I do some
things other luthiers are free to adopt - but haven't
- and they do things that I respect, but do not want
to incorporate into my guitars. But there are a good
many luthiers out here making a lot of good sounding
guitars. Come and join us, and enjoy the venture!
Dick DeNeve
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
|
Re: [RESOGUIT-L] R
Reply to this message