DIY sand filled turntable feet

[Arkay]

Fascinating thread - I'm glad it got revived. I posted recently asking about sealed sand boxes as isolators: although the boxes are not made of rubber, a lot of the same theory applies to them.

The "bounce/no bounce" concept was a nice reminder, too, as I'm considering some "hand/wrist therapy balls" I found in a kind of clearance-goods shop as possible isolation tweaks. I think I'll go back and try bouncing a few of them, first, to see if they pass this first hurdle! :yes:

 

[onwardjames]

I'm thinking some nice hacky sacs might work??

No, really.....:scratch2:

Phenomenal thread, JimmyNeutron!

 

[Copa1934]

OMG!

I didn't see anything posted on "how" to compact the sand in these projects so I'd like to offer up an orbital sander. Most all have a foam/rubber pad and should be safe to run on most any type of surface. Sander should provide more than adequate vibration to compact sand, at least the finer sand being used in these projects.

I'll have to give this idea some thought since I have rotted isolation feet on my TT at the moment.

 

[iceman79]

Under each feet I place hockey pucks that have 3 self adhesive clear vinyl pads under each puck.
I know it works good as the sub is close to my stand.

 

[Spalls]

Regarding the comments about compacting the sand: compacting the sand will only facilitate the transmission of vibrational energy through the media. I am very familiar with this. Keep the sand loose, and periodically loosen it as it consolidates over time. Compacting the sand will increase point-to-point contact between the particles and effectively make the sand behave more like a solid. Keeping the sand loose will make it more effective as a damper. Over time the sand will consolidate, assuming that it IS actually subject to vibration. Hence, the need to loosen it over time.

 

[elcoholic]

This is correct. The more compact the sand, the better it transmits vibration due to increased granular point-to-point contact. For those of you not in the earthmoving business, the most effective way to compact granular soil (such as sand and gravel) before you put a structure, road, etc. on it is to use a vibratory compactor.

Excellent point. Then you also know that the practical limit of soil compaction is 90%. So the questions that occur to me are - What's the compaction limit of common sand? At the limit is it still an effective mechanical filter? While were in the garden center at Home Cheapo, what about grabbing some vermiculite?

If I may please offer a not so casual observation about this whole thread:

Here we have a guy who admits to not having a stellar background in theoretical physics or engineering posting about his solution to a problem using good old fashioned commen sense. Lots of different takes on the subject have been posted, but not one iota of impolite or unfriendly verbage has surfaced. Rather, a good discussion about the topic that makes it easier for others to understand the issues. This is what sets AK apart from many, many other online forums I have visited.

Amen Brother!

I don't know yet. I won't have any serious time to test them until this weekend. I only really have 1 "VERY UNSCIENTIFIC" method to use as a test - doing jumping jacks a few feet from where my turntable sits LOLOLOL!!! I know, I know. Hey, Newton discovered the law of gravity by having an apple bong him on his noggin! Anyway, I'll put it to the test this weekend. I will say that as it stands right now with my sand filled iso-feet and sand box I don't hear any thumping from the speakers when I apply my very incredulous jumping jacks test. I don't have any methods for accurately testing and measureing the results, so as always take my results with a grain of salt, your mileage may very, not responsible for damage, some hidden fees may apply, etc.

Jimmy

Are you set up to rip vinyl? If so you can record your thumping about and compare the graphic results. Just place the stylus on a stationary record's lead in. Even if your recording chain isn't NBS traceable, it is fairly repeatable and will show you relative results. Especially so if you use a sand bag or a can of chili dropped from a standard height on a standard spot. You could also point a speaker at the turntable, put on a suitable reference recording, say John Bonham's Moby Dick at volume 8 and record the bombardment.

 

[Orange juice]

Sweet feet, and great discourse. Long live AK!

 

[MRL_Audio]

Just picked up a PX-3 today. Great deal. However, needs feet. I am using this design. Have seen nothing better. Thanks Jimmy! Agree with OJ. Long live AK!

 

[Oilmaster]

Regarding the comments about compacting the sand: compacting the sand will only facilitate the transmission of vibrational energy through the media. I am very familiar with this. Keep the sand loose, and periodically loosen it as it consolidates over time. Compacting the sand will increase point-to-point contact between the particles and effectively make the sand behave more like a solid. Keeping the sand loose will make it more effective as a damper. Over time the sand will consolidate, assuming that it IS actually subject to vibration. Hence, the need to loosen it over time.

What about mixing the sand with particals of a different (soft) material, not to mention a mix of different partical sizes, so that a self-dampening property is created? Let's call it hybrid particals :scratch2:

 

[kotofei]

If cork is such a good vibroioslator, would it be a good idea to pack feets with small cork pieces instead of sand?

Nice feet!! I read somewhere on this site a few months ago that cork was
a very good isolation material and my cd player had developed a skip at
high volumes caused by my speakers. I was at Walmart one day and spotted
some sheets of cork board so I bought some and put 2 ea 1/4" sheets under it.
No more skip!!! I plan to cut some discs off another sheet and put under
my turntable feet or replace the feet all together with a stack of cork discs but have not got around to it yet.
Think about about what a cork ball would do thrown against a wall as compared to a rubber ball.

 

[Dan D.]

I'm thinking some nice hacky sacs might work??

No, really.....:scratch2:

Phenomenal thread, JimmyNeutron!

I was thinking the same thing as James. My daughter's toybox has a bunch of small bean-bag style balls made of a spandex-type material for stretch etc. These things do NOT bounce, and I would think any compacting of whatever is in there would be voided out by the fact that they flex and stretch. Besides...they have goofy faces on them, it'll add character. I'll try this on my exceptionally moody cd player. Great stuff, Jimmy.

 

[joemg]

I know this is an old thread... but it got me thinking. How would Chromite or Zircon sand work in these designs?

they are 94 and 98% heavier than sand per volume respectively.

http://www.6mmbr.com/sandcomparison.html

being that you don't need very much for the feet, the cost factor shouldn't be a big deal.

 

[RickeyM]

I missed this thread originally but I'm glad it got resurected. I have a Technics SL1200 that has those feet with springs in them. One of the feet even has the spring missing. I won't embarass myself by saying what I'm using for feet now but I will be making a pair of "Jimmy Feet" real soon!

 

[Marty Socal]

How would lead birdshot work in these feet? It's really inexpensive at the local gunshop.

 

[joemg]

How would lead birdshot work in these feet? It's really inexpensive at the local gunshop.

I was also thinking of that (though, there are no local gunshops in NYC, lol).

My thinking was that the birdshot isn't as fine as sand... but what do I know, i've never see it in person. Am I incorrect?

 

[RickeyM]

How would lead birdshot work in these feet? It's really inexpensive at the local gunshop.

Too coarse I'd wager.

 

[JimmyNeutron]

My 2 cents on the bird shot. While I'm no scientist I would wager it would not be a good idea for isolating waves. First, the shots are large in size, so with so few in a small space they could begin to act as a single metal shot. Second, they are metal, and metal vibrates. I don't think it matters that there are 20 in a small foot or 20,000. Metal is metal and will transmit waves faster than sand. Sand has a great property in that it is soooooo small that it actually disperses the sound waves, thus making the wave loose energy and momentum. Most of the wave dissipates in the foot. Try this, fill 2 small bowls with bird shot, and sand. Then tap the top of the bird shot with your finger. The energy will travel to to outter most shot easily. Do the same with the sand. The tap stays in the middle without disturbing the sand at the edges. That's good isolation.

Chromite or zircon? Sorry, I've never heard of this. Post your results here if you try them.

Remember, if you do make the sand filled Iso-feet, don't compact the sand inside, let it move a bit freely - leave a little bit of space. You need that space for the sand to move around in and dissipate the waves.

Jimmy

 

[Spalls]

It is nice to see that this thread is still moving along...

With my current turntable isolation project (soon to be posted - stay tuned!) I am still going to use my old Audio Technica spring leveling feet but I will be separating the plywood turntable mounting base from the MDF sub-base with sandwich-size bags filled with hydrated bentonite clay. This stuff has the consistency of thick cold cream / axle grease. I like to think that it will work quite nicely in combination with a couple of other tricks.

The non-hydrated bentonite is on the right (looks just like crushed rock - just asking for a high school prank...) and the hydrated form is on the left.

 

[Marty Socal]

#12 birdshot is .050" diameter lead balls. Costs a little more than I remembered, $44 for 10 lbs. Metal prices have skyrocketed!
http://www.midwayusa.com/product/814885/bpi-lead-shot-12-10-lb-bag

The size comparison of #12 shot is about that of coarse sand.
http://en.wikipedia.org/wiki/Particle_size_(grain_size)

There is also a shot size called "Dustshot", it's even smaller, but I could not find the specs.

My thinking was that as a mechanic, I've used dead blow hammers that are filled with lead shot. They don't bounce when you hit something with them, basically they transmit all of their energy into the object being hit.
http://en.wikipedia.org/wiki/Dead_blow_hammer

The lead shot is very dense, and soft. It takes a lot of energy to get it to move, compared to lighter material. It would be interesting to figure out a way of testing the difference, if any that it would make.

In the mean time, I'm going to fab up a set of the sand filled feet, as my $15 Pioneer PL-12D is missing two feet!

 

[Fishead]

I missed this thread originally but I'm glad it got resurected. I have a Technics SL1200 that has those feet with springs in them. One of the feet even has the spring missing. I won't embarass myself by saying what I'm using for feet now but I will be making a pair of "Jimmy Feet" real soon!

You can get brand new feet for your SL1200 here:

http://compare.ebay.com/like/380333493519?var=lv&ltyp=AllFixedPriceItemTypes&var=sbar&afsrc=1

Maybe you already know that, but I'm curious as to whether these feet will fit the PX-3??? Have started a new thread about it but so far no answers....

Thanks,

Andreas Novak