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Tapping on my table

Searched some threads and did not find an answer specific to my question, so I will try here.  My system is in my basement, which is a concrete slab with wall to wall carpet ( and carpet pad).  My TT is a Music Hall MMF 9.1 which has 3 plinths separated by sorbothane spacers.  The TT sits via its conical feet directly on a Salamander cabinet holding my amp and cd player plus some albums.  Total weight of the cabinet, equipment and albums is at least 150 lbs.  The TT weighs 40 lbs.

I have never experienced any issues with vibration, i.e when walking around while playing an lp.  I had assumed the concrete floor and thick carpet, along with the heft of the cabinet and contents, provided excellent isolation.  However,  this morning I inadvertently tapped the top of the cabinet while listening to an album and there was a very subtle but distinct thump emanating from the speaker.  Clearly the TT is not isolated from the cabinet even if the cabinet is isolating the TT from the floor.

Is there a good inexpensive solution to solve this isolation issue?  I do not want to lose the leveling benefit of the TT's feet - I have some Herbies cones under my cd player, but these would eliminate the leveling capability.
sjtm
geoffkait's avatar
geoffkait
23,365 posts
 

raymonda
Magnetic feet, airblatter systems, vibraplane or what I use......a home made sand box with about 75lbs of sand. The last option is fairly inexpensive. e.g. less than $50.00.

You don’t see sandboxes much these days but they were ubiquitous 25-30 years ago. Good on ya, mate. Bright Star, who later went on to make air bladder stands, made sandboxes for placing on the top of components, too, as well as underneath. I’m high on sandboxes, too, especially when substituting perfectly round pure glass microspheres for the sand, which is kind of gnarly by contrast.

bdp24's avatar
bdp24
9,735 posts
 

The Bright Star sand box was named Big Rock, and came in many different sizes. I found silica "sand" at a building supply yard for eight bucks for a hundred pound bag. Silica is a non-organic man made product similar to sand, used for sand blasting, etc., and comes in many different grades (size of the granules). I used Grade 60, which is granules of very small size. Their very small size allows more granules to fit in a cubic inch, thereby providing more absorption and dissipation of vibration. Anything higher in grade that 60 was almost a powder.

The "sandboxes" Bright Star made for placing on top of components (to damp chassis resonances and vibrations) were named Little Rock, also offered in various sizes. They actually were filled with some kind of granules (neither sand nor silica) that provided not only damping, but also magnetic shielding.

ct0517's avatar
ct0517
2,041 posts
 

sjtm
I have never experienced any issues with vibration, i.e when walking around while playing an lp. I had assumed the concrete floor and thick carpet, along with the heft of the cabinet and contents, provided excellent isolation.

from my past experiences, the key imo is you want to turn your cartridge/system into a type of stethoscope for your room. Also poured concrete slabs are far from perfect containing air pockets. Your rig could be on one of them. How to find out ?

sjtm
Is there a good inexpensive solution to solve this isolation issue?

There is an inexpensive way and it can be kind of fun too.

With system on mute and set to the lowest volume.
Place record on the platter - not spinning - and lower your stylus onto it.
Unmute and slowly start raising volume to what represents a loud level for you.
Your cartridge/system has now become a stethoscope to your room.

So ....standing near the stand, start jumping up and down .......like you have won the lottery. (waving arms optional)
Dance in front of, beside, and behind it if possible. Is anything heard through the speakers when you do this ?

If yes your turntable stand is not on good ground. Move to another spot.

Good luck.

terry9
2,326 posts
 
There are two issues here, IMO. First is the stability of the cabinet, which is a function of construction, TT mass, and the ratio of the height to the smaller of depth and width. The second is sinking transients to ground.

The solution which I found, because my 150 lb TT dictated it, was to lengthen the width of my cabinet to 40 feet, by the simple expedient of bolting it to the frame of the house. This also served to sink transients to the frame and thence to the concrete foundation. Problem solved. Of course, the wife doesn't yet know there are holes in the Louis XIV desk ...
stringreen's avatar
stringreen
6,443 posts
 
A good trick to try is to use a turnbuckle attached to the wall and cabinet...tightening the buckles.......amazingly effective.
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