| IZHAKKATZ |
Hi all,
Could any one give me the cons and pros of sand vs lead.
I've attached my planed platter and splint design with cavities for send/lead.
Any remarks on the geometry of the cavities?
Thanks |
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| rcavictim |
| If I'm not the exception you may get more people to look at your picture if you post it as a .jpg. For me to open a zip file is so much effort changing screens and having to get out my secret .zip decoder ring, I just cannot bother, even if it is something I'd really like to see. The other problem I fear is to go through the un-zip process it leaves a trail of memory consuming garbage in my computer after I finish viewing. Some folks like zip. I never got used to liking it. |
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| rcavictim |
| As a general reply to your question. Lead is just dead weight so will make something it is attached to have a lower resonant frequency. Sand on the other hand while doing the same through the mass factor can also absorb vibration and convert some of it harmlessly to heat. |
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| analog_sa |
Zipped bmp is indeed pathetic.
I have a personal dislike towards sand - it seems to rob music of life and dynamics when used in platforms and will probably do the same in a turntable.
| quote: | | convert some of it harmlessly to heat |
Nothing harmless about that. It's clearly frequency specific and as other types of excessive damping doesn't sound good IMO.
Based on successful commercial designs lead or oil/lead seems to be a successful combo and will provide reasonable damping and great inertia. Plus, it's bad for the environment which is another hint it may sound good :) |
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| IZHAKKATZ |
Thank you for your replies,
I've drawn my TT using Autocad 14.
I can not export to Jpg.
Any other sugested formats?
Thanks
Izhak |
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| rcavictim |
.gif
You could print it locally from Autocad. Scan print with flatbed scanner making a .jpg. |
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| Brett |
| quote: | Originally posted by analog_sa
I have a personal dislike towards sand - it seems to rob music of life and dynamics when used in platforms and will probably do the same in a turntable.
Nothing harmless about that. It's clearly frequency specific and as other types of excessive damping doesn't sound good IMO. |
I disagree strongly. My TT's are on a large sandbox, with lead/oil/sand plinths on two of them.
| quote: | | Based on successful commercial designs lead or oil/lead seems to be a successful combo and will provide reasonable damping and great inertia. Plus, it's bad for the environment which is another hint it may sound good :) |
It is good, but I can't see how it's bad for the environment when it's enclosed in a case. |
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| analog_sa |
| quote: | | I can't see how it's bad for the environment when it's enclosed in a case. |
Absolutely. That's what i tell my wife whenever she finds my mercury stash. |
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| Geek |
| quote: | Originally posted by IZHAKKATZ
Thank you for your replies,
I've drawn my TT using Autocad 14.
I can not export to Jpg.
Any other sugested formats?
Thanks
Izhak |
Go to http://www.xnview.com and download XnView - a great little freeware image viewer, tweaker and converter. If you don't need the viwing or tweaking, just get Nconvert.
1-bit binary PNG or GIF will be the absolute smallest size for a linedrawing. |
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| IZHAKKATZ |
Thanks Geek,
That was very helpfull.
I've attached the file in jpg.
If I'll use lead it seems like I need to decrease the lead vol. or it would be too heavy. (for both platter and splint)
Izhak |
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| fdegrove |
Hi,
One major advantage of lead over sand is that you can use it as a solid block.
Lead has a Q of around 3 Hz as a solid which should be low enough for all things audio.
I don't know the Q of sand but its damping properties come mostly from the fact that it's a grainy structure composed of solids randomly disposed with aircavities inbetween which tends to break up and spread resonance.
One can safely assume that the damping properties will vary according to the mass it's supporting, probably also with granularity of the type of sand itself.
Sand also tends to shift depending on where the highest mass is located, lead won't do this in it's solid form.
Note that lead can also be used in a form known as leadshot where it will behave similarly to sand and adapt more easily to the shape it is supporting.
In some applications such as as a filling material for loudspeaker stands it is asier to contain than sand as it can be had in far coarser grains than sand would.
Cheers,;) |
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| IZHAKKATZ |
Thanks Frank,
I've thought that the sand damping is mostly because of Q energy transfered to heat by the movment of the particals against one another ?
can anyone explain Why do people add oil to the lead shots?
Regards
Izhak |
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| analog_sa |
| quote: | | Why do people add oil to the lead shots? |
So they don't rattle? |
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| Variac |
Actually sand is available in as coarse a size as you want.
It's called gravel at a certain point , but that is more of a semantic distinction. Yet most people don't go for coarser sand. I think they believe that the sand is damping by converting energy into heat as Izhak states. Most people I've heard of that use lead shot mix it with the sand for the same reason.
Melting it and forming a block lowers theresonant frequency, but probably doesn't damp much EXCEPT that it's attached to something else (the tube of the stand?) some there will be constrained layer damping. |
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| fdegrove |
Hi,
| quote: | | I think they believe that the sand is damping by converting energy into heat as Izhak states. |
It surely will but it's rather slow at that.
What you can compare it to IMO is the type of damping materials used inside loudspeaker cabinets that have a foamy, cellular structure.
These tend to diffract soundwaves but I doubt these to be very effective at very low frequencies though.
The use of leadshot in speakerstands has of course another advantage; lead is much heavier than sand.
Combining both sand and lead makes perfect sense, it all depends on what it is you want to achieve I suppose.
Cheers,;) |
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| Variac |
| And knowing what it is you are trying to achieve ;) |
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