On Oct 29, 3:51*pm, "Arny Krueger" wrote:
wrote in message
...
On Oct 28, 5:17 pm, "Arny Krueger" wrote:
wrote in ...
Clamps don't improve isolation. They do couple the records to the
vinyl which achieves two things depending on the nature of the
platter. 1. They improve the stiffness of the vinyl
Must not be what you mean, because you can't change the stiffness of
vinyl
without changing the vinyl itself.
No it is exactly what I mean. Hold a vinyl record in the air and try
to flex it. It is quite easy. Now place it against a platter and
couple it with a record clamp. It won't flex in the direction of the
platter. so it is effectively stiffer.
However, this is not a real-world example because we *never* hold a vinyl
record in the air and try
*to play it. Well, maybe some crazed enthusiast has tried it, but I don't
know about it! ;-)
One does not need to hold a record in the air. If a record is not
completely coupled to a platter there is air underneath it when it is
being played.
What a clamp might do is mechanically couple the vinyl to something that
is
stiffer than it is, which would make the vinyl part of something that is
stiffer. Stiffening would raise the resonance of the vinyl sheet,
which
would probably move it into a frequency range where its vibration would
be
more audible. So, just because the LP is stiffened, is not necessarily an
advantage.
That is true. That is why platter design is a lot more complicated
than just making it out of the stiffest material out there.
Technical measurements seem to show that platter material is not all that
important - many things will work.
What technical measurements show that platter material isn't all that
important. I'm sure many turntable designers would like to be privy to
those technical measurments. One need look no further than the trouble
many makers of high end turntables go through over this to get the
impression that many of them think this is a critical issue. It would
seem the folks at Continuum would vehemently disagree with you on this
issue.
http://www.continuumaudiolabs.com/caliburnplatter.html
"We have built a database of properties and measurements which now
allows us to "virtually" model any platter design and determine the
sonic signature by matching it to similar signatures from prior
listening tests."
The desigers at Continuum don't strike me as a bunch of crackpots or
snakeoil salesmen,
http://www.continuumaudiolabs.com/aboutus.html
Check out
John Loton: Physics and structure design
Jihn Veitz: Metalurgy and Engineering
Dr. Neil McLachlan: acoustics design
Here is some of what they have to say.
"Many people may consider building a turntable is not rocket science.
Read on!
Turntable design has gone through some interesting developments over
the years.
The Caliburn’s design process began with the analysis of existing high-
end turntable designs to identify their strengths and weaknesses.
We took away the aesthetic considerations and concentrated on the
physical properties of a material and it became apparent that the
sonic signature of a turntable is greatly affected by the selection of
materials.
In the search for the perfect turntable material, Continuum Audio
Laboratories analysed many commonly used materials in existing
turntables such as:
Wood based products -
MDF, Chip Board, StoneWood, Marine Ply, Natural Timbers, both Hardwood
and Softwood, exotic and native etc.
Plastics -
Acrylic, Methacrylate, Glass Fibre Composites, Carbon and Kevlar based
composites, epoxies, urethanes and other uncommon materials.
Glass/Ceramics/Stone -
Naturally occurring or man made.
Metals -
Titanium, Aluminium, Magnesium, Tungsten, Stainless Steels, Copper,
Brass, Bronze, and a host of other metals.
We often see references to aeronautical alloys such as 2024-T3, 6061-
T6 and 7075-T6 which have material properties that are well known and
published.
So too are Stainless Steel alloys and the family of advanced metals
and ceramics such as Titanium Magnesium and Tungsten, Amorphous Metals
etc.
We also looked at a range of Magnesium Alloys and determined that
commercially available Magnesium Alloys were not perfect for
turntables either.
Challenging problems often require the creation of purpose specific
materials
Caliburn advanced metallurgy
The Caliburn uses advanced metallurgy and composites engineering used
in the aerospace industry, to create purpose specific materials to
achieve a level of performance never before realized from analogue
reproduction systems.
We sought the assistance of some of the finest metallurgists to
discuss our unique needs.
In conjunction with materials engineer, John Vietz (see Design Team),
these specialists worked out a formulation for a unique alloy
specification, which has been tailored to address the needs of a
turntable and tonearm combination.
We realised early on that to build stiffness and damping into a design
required the use of metals which behaved differently to carbon fibre
composites, wood based products, masonry (granite, marble etc) and
plastics.
This led to the creation of a new alloy using Magnesium as the primary
material with trace elements of other alloying materials to create the
right mix of properties.
To verify our design we then prototyped the Caliburn turntable shape
out of readily available aeronautical alloys and compared that to an
identical prototype using our newly forged “Caliburn” Magnesium Alloy.
The result was a significant improvement in real world audiophile
performance between the purpose built “Caliburn” Alloy and the
commercial alloy.
Spatial information retrieval, timbre and tone accuracy, absence of
high frequency distortion etc etc."
It seems like some pretty legitimate scientists and engineers did some
pretty extensive research and drew very different conclusions from
yours. It is fair to point out that their research is not, to the best
of my knowldge, made public. But that is understandable since they are
developing proprietary technology. I could understand their reluctance
to share the sepcifics. OTOH this would be one elaborate hoax
involving the reputations of legitimate engineers and scientists if it
were all B.S.
Platters
and mats need to be damped *and need to be carefully designed with
careful choice of materials to insure complimentary internal resonant
frequencies. You don't want a platter that rings like a bell.
Actually, I've had several platters that rang pretty nicely if I held them
in the air. Some were made out of steel sheet and also die cast aluminum or
similar metal.
Well I
don't. There are some designs out there with some pretty stiff
undamped light weight platters. I tend to find these designs to be
noticeably unpleasantly colored. You will find this a common design
feature in the Rega line of turntables. Sorry Arny. Nothing personal.
But I don't like the Regas.
I posted both a frequency sweep (well known means for exciting resonances)
and a dynamic range test of a Rega atwww.pcavtech.com. See any resonances
in actual use?
I couldn't find the test. But even if I did how would you figure what
variances are due specifically to the effects of platter resonances? I
am assuming you did not get a razor flat frequency response.
2. they allow for better damping of the vinyl.
This would only happen if the vinyl were put into more intimate contact
with
something that is itself dampening. The degree of clamping would need to
be
optimized, not too little, not too much. If the record is clamped to the
damper too tightly, then the damping due to sliding between the two
elements
would be lost.
You are absolutely right here. that is why we often find the most
successful designs incorporate clamps that are specifically designed
to go with the platter.
"Going with the platter" does not ensure what I am talking about. *However,
there's plenty of evidence that exotic matched and damped platters are
solutions looking for problems.
Could you show us this evidence?
If you have a stiff, well damped platter, those
characteristics will better transcribe to the vinyl when better
coupled to the platter.
If this vibration of the LP has no audible effects, then dampening this
vibration will have no audible effects.
That is true but we can't get around the fact that the stylus is
riding the vinyl.
Actual tests would show any problems that were audible.
What actual tests are you refering to?
Clealry any added vibration to the vinyl will be fed
directly into the stylus.
Only if it happens to an audible degree. Ever wonder why exotic LP playback
equipment provide zero technical tests for their products,
I would be more interested in independent test results.
and Stereophile
has AFAIK only done one? *Technical testing would not show a real-world
advantage for a lot of expensive tool work and materials. It's audio
jewelry, plain and simple.
Something is responsible for the unique sonic signatures of all
turntables and pickup arms.
Also the stylus is putting energy directly
into the vinyl. If the vinyl is flexing that is very bad. If it is
taking that energy that is being directly applied to it and reflecting
it back because the vinyl is coupled to a stiff undamped platter that
rings like a bell, you have yet another significant coloration.
turntable design is a pretty complicated endeavor.
Actually, there's nothing at all inherently complicated about turntable
design. Nothing new of technical significance has been seen in decades.
I suggest anyone who believes this carefully comb the Continuum
website. Links are already provided.
When measuring the frequency response and noise from a LP, these
vibrations
should have some measurable effects. I can't remember seeing any, and see
no
signs of them in the published test results we have discussed. Note that
these measurements *do* pick up vibrations that are very tiny. Many of
the
vibrations that we *can* measure are masked by other sound sources
including
the music that is recorded on the LP.
How do determine what is causing what when you look at your
measurements?
Well, we know what was put on the test record.
Not exactly. We don't know what distortions or their exact source went
into the cutting and plating and pressing of any test record.
The input to the cutting
lathe is reported by the engineer who made the recording. The contents of
the recorded disk can be determined using a microscope.
How?
*We're hoping that
when we play the test record, the input to the cutting lathe is what comes
back. If something is missing or else shows up, then that's not good.
Any given test record is subject to any shortcomings of the cutting
engineer or the specific equipment used. There is no getting around
that fact. I am confident that the latest HFN test record is at least
one of the best ones out there though.
Vis-a-vis these alleged vibration problems, that can't be detected: When
evidence of a problem is so universally absent, there is no causality to be
determined. I can explain why *it doesn't happen. I can't explain why it
should happen.
I think the folks at Continuum along with a whole host of other
turntable designers would disagree.
There are the folks at SME
http://www.sme.ltd.uk/content/Model-302-1314.shtml
Here is something they say about the subject
"the design of the Model 30/2 takes special account of sonic
considerations and with equipment of comparable quality can provide a
listening experience that allows L.P. sound to be re-assessed. Detail,
resolution, and neutrality are of a new order with a dynamic range
that does justice to the original sound.
The laws of physics decree that the higher the mass and stiffness of a
body the less it will flex and vibrate - and this is reflected
throughout the Model 30/2.
The sub-chassis is machined from 19mm thick aluminium alloy plate and
weighs approximately 17kg while the base with its four supporting
pillars adds a further 16kg. This offers the high mass and stiffness
required for uncoloured reproduction further aided by efficient
extensional damping of both components to reduce the amplitude and
duration of their vibrational modes.
In conventional turntables metal supporting springs often contribute
significantly to colouration. Sometimes even their size and nature can
be identified by an experienced ear!"
The thing is isolation and damping achieve
similar results, the reduction of added vibration to the system.
I'm surprised that clamps don't help flatten records out. One of the
rather
obvious problems of the LP is jitter or FM distortion due to the LP not
being perfectly flat.
Thank you for adding that. Clamps also help flatten out records.
But, they only help somewhat - they are not a solution.
It is ironic that so much is made of jitter in digital equipment that is 100
dB down or more, and so little is made of similar jitter from LPs that is
only 30 to 50 dB down. Another Mulligan, I think. :-(
It seems you are trying to make very little of it. Clearly it is a
priority to any number of high end turntable designers and
manufacturers.