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DIY CLD Plinth Design--A measured Approach
DIY CLD Plinth Design--A measured Approach
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Old 18th June 2021, 11:26 AM   #231
cats squirrel is offline cats squirrel  United Kingdom
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I'm sure it would be better, as mdf is not a nice material for hifi projects. However, the best situation is just one thickness of Permali/Panzerholz, 15mm - 25mm thick. If you wanted to use resin/bentonite, then I would suggest just the resin, not a mix of resin/b and P. If you want a 'skirt', then I would suggest connecting it to just one layer of P (upper or lower, not both). Bracing is not a good idea, as it increases the resonance frequency, and if too much bracing is used, the whole panel acts as though it was the thickness of the bracing+panel.


There is much to commend the two thin panel approach. HTH
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Old 18th June 2021, 12:01 PM   #232
warrjon is offline warrjon  Australia
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I'm in the planning phase of building another pimped SP10mk2.

What I'm trying to achieve is to house a platter and DD motor that are 155mm from top of platter to bottom of motor housing without having the platter sat high. There is also a gap between the motor mounting flange and bottom of platter of 35mm.

If I use resin/b it will r/b only no P.

You mentioned a two thin panel approach. What's your opinion on 2x 15mm panels with MDF or other timber connecting the 2 together around the edge.

Top panel will mount the arm with a 320mm cutout for the platter and lower panel will mount the motor.
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Old 18th June 2021, 01:06 PM   #233
cats squirrel is offline cats squirrel  United Kingdom
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not mdf, but other (highly damping) stiff material. If you do as you suggest, you have a panel with a clamped edge (actually four clamped edges). That will dictate how the panels will vibrate. However, if you use four 'pillars' to support the top panel, the result will be virtually the same. But I would suggest separating the tone arm (pod) from the turntable. Not so critical with the SP's, but a useful thing to do. It allows easy swapping of tone arms, if that's your thing.


Click the image to open in full size.simple plinth by cats squirrel


DO NOT use any soft (compliant) material in the design of the plinth, except underneath the total bottom panel.
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Old 20th June 2021, 03:37 AM   #234
hjam is offline hjam  Canada
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Default That wild and crazy Panzerholz

Quote:
Originally Posted by cats squirrel View Post
Hi Hugh....

There is something wrong with your Panzerholz waveform. What was the resonance frequency?
Cats Squirrel,

I've had similar results to yours for Vinyl and Acrylic. But I'm finding Panzerholz is a difficult. Maybe it's a good sign...

https://www.monoandstereo.com/2014/1...of-kaiser.html

Rainer Weber has an interesting comment in the above link.
" The young modulus is different in the 3 directions but the density is constant. Therefore the speed of sound is different in each direction leading to a high dispersion of energy so that resonance can not build up so easily. "

I've found that for very soft hammer taps, it does not really break into an oscillation. Hit it hard and it's a very wide spectrum. Somewhere in the middle starts to get close to how other materials behave.

In a plinth, I'm guessing most of the vibration is at lower levels than any of the hammer taps, so it's well behaved.

Hugh
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Old 20th June 2021, 11:19 AM   #235
cats squirrel is offline cats squirrel  United Kingdom
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Hi Hugh,


remember that if vibrations are not readily attenuated, then if instigated by harmonic vibrations (like music or motors) then there will be energy left over from the previous cycle. If this happens, vibrational amplitudes can build, in some cases by quite a significant amount. I seem to remember that some materials with little damping can have the vibrational amplitudes build by 20 times or more.


Hammer taps provide the signal which we can measure (hopefully). Measuring the damping factor of a material provides a first step to choosing appropriate materials (except those who put aesthetics first!).
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Last edited by cats squirrel; 20th June 2021 at 11:26 AM.
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Old 20th June 2021, 11:08 PM   #236
warrjon is offline warrjon  Australia
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Hi CS,

What is your opinion on this version. This uses a 24mm Permali top. The RED is Permali fixed to the underside of the top for motor mounting. The GREY is an MDF skirt for aesthetics and mounting the feet. Or would I better to leave the skirt off and make the 3 motor mounting circles the same size?
Attached Images
File Type: jpg Plinth idea.jpg (65.5 KB, 117 views)
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Old 21st June 2021, 04:53 AM   #237
JohnnoG is offline JohnnoG  United Kingdom
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The Method to myself looks similar to other designs I have seen.
Whilst Looking at the Design as a Diagram, I can see one additional option that could be considered.
The Skirt could remain as a Separate Part and maintain the aesthetitic.
The Skirt can have a Footer on the Base and at the interface with the Plinth, a Small Space can be created between the Top of the Skirt and the Plinth using for example a Threaded Spike, or another type of adjustable Support, with any preferred choice of Contact Surface for the Plinth.
This will add another level of control for levelling and Preferred Isolation.
The last choice would be if either the Plinth or the Skirt Wall will have the Female Thread Part inserted to receive the adjustable Male Thread.
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Old 21st June 2021, 12:48 PM   #238
cats squirrel is offline cats squirrel  United Kingdom
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Quote:
Originally Posted by warrjon View Post
Hi CS,

What is your opinion on this version. This uses a 24mm Permali top. The RED is Permali fixed to the underside of the top for motor mounting. The GREY is an MDF skirt for aesthetics and mounting the feet. Or would I better to leave the skirt off and make the 3 motor mounting circles the same size?

as I have mentioned several times, I would NEVER use mdf in any design.
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Old 12th July 2021, 09:00 AM   #239
Studley is offline Studley  United Kingdom
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Quote:
Originally Posted by cats squirrel View Post
not mdf, but other (highly damping) stiff material. If you do as you suggest, you have a panel with a clamped edge (actually four clamped edges). That will dictate how the panels will vibrate. However, if you use four 'pillars' to support the top panel, the result will be virtually the same. But I would suggest separating the tone arm (pod) from the turntable. Not so critical with the SP's, but a useful thing to do. It allows easy swapping of tone arms, if that's your thing.


simple plinth by cats squirrel


DO NOT use any soft (compliant) material in the design of the plinth, except underneath the total bottom panel.
Re your comment about compliant material. Does that mean you would not recommend replacing the pillars in that design with 4 squash balls and that you would be better off if the pillars were panzerholz?
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Old 12th July 2021, 12:09 PM   #240
cats squirrel is offline cats squirrel  United Kingdom
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depends on how squashy the squash balls are going to be. Too compliant ( yellow spot) and the answer is no, but 'hard' (blue spot) and you may get away with it. Not sure about green or red ones. I am sure Panzerholz pillars would be better.
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