The primary mode may not be the lowest present mode, but it will only be apparent if the pick-up's own curve is known over the desired frequency band.

As for spikes, I see no reason to use them on a suspended wood floor, but in any case the idea is to get the frame itself down to "one mode" if you can, and then deal with that one mode by going back and forth between targeting the dominant mode directly and spreading it out, backed up by listening, of course.  If felt on broader contacting feet works to reduce the transmission of floor-generated/borne noises, then...  Yes, the cartridge-on-an-LP method is very effective at amplifying noise that affects the stylus under those "static" conditions.

Again, you might gain something by fastening the rack to adjacent walls and adjusting the tension and/or damping of those connections. In any case, you'll want to prevent swaying of a TT support, and likely a CD transport, as well, and it might even damp some noises that enter the frame from the floor, just like standing there and poking it with your finger.


Best regards,
Paul S

For some reason I cannot post pics, they wont upload to the server so I cant select them.

The way Aurios work is with 3 ball bearings rolling inside a round chanel, something like an inverted doughnut...top and bottom.
On the center they have a bolt that allows for some movement but wont let the whole contraption get dismanteled, in case, lets say, of a big hit on the side.  Each ball bearing is held in place by a thin plastic circle that hold the bearings in a triangle shape.

The main thing is they work very nice and slide sideways with a lot of ease.
There is no way they will damage the bottom plate of any piece of equipment, imho.
They couple to the shelf, with a big area and some felt, and to the equipment on top with a ball bearing: I have used a small brass cone here and heard no change.


I dont use the sand inside the posts that make up my rack,  I could, but I see no need just yet.I used pretty thick material.

Each shelf of the rack is supported by something like a sand box, with a lot of area and about one inch deep of sand, 
each shelve has its own sand box: this gets rid of a lot of vibrations.  Let say Each shelf couples to the rack via sand.
The easiest and fastest way for me to do it, was to use Plywood shelves,  I know, not my first choice.
The idea was to use them temporarily untill I ordered some Marble or Granite shelves cut to size.
I havent got around to ordering the heavy shelves...

For my TT I use a 2 inch slab of Maple, I detach it from the shelf with Sorbothane, and form the TT plinth with Brass cones.
It works pretty good and it is still sensitive to added weight on top.   If I jumpt right next to the rack I will hear a thump if the record is playing.
My listening room is made of brick and mortar with concrete floors.

Jorge wrote:

For some reason I cannot post pics, they wont upload to the server so I cant select them. The way Aurios work is with 3 ball bearings rolling inside a round chanel, something like an inverted doughnut...top and bottom. On the center they have a bolt that allows for some movement but wont let the whole contraption get dismanteled, in case, lets say, of a big hit on the side.  Each ball bearing is held in place by a thin plastic circle that hold the bearings in a triangle shape. The main thing is they work very nice and slide sideways with a lot of ease. There is no way they will damage the bottom plate of any piece of equipment, imho. They couple to the shelf, with a big area and some felt, and to the equipment on top with a ball bearing: I have used a small brass cone here and heard no change.

Hard to imagine without a picture. What does the ball touch at the top? Directly the equipment or another puck? This felt below the lower puck doesn't sound right to me: one wants here very hardcoupling to the shelf to set the ball in motion with a slightest micromovement.

Jorge wrote:

I dont use the sand inside the posts that make up my rack,  I could, but I see no need just yet.I used pretty thick material.

If you ever feel need, be carefull!

Jorge wrote:

... The idea was to use them temporarily untill I ordered some Marble or Granite shelves cut to size. I havent got around to ordering the heavy shelves...

I'd avoid granite. It rings.

http://www.newport.com/Granite-Optical-Structures/139776/1033/info.aspx

Marble...maybe but a selected one. If you go through all the stone pains why don't you rescue some

vulcanic slate from n old biliard/snooker table like I did? There is  reason English snooker players moved from once traditional

marble tables to vulcanic slate (Itlian slate) ones. Better damping. And the color!! My pics don't do the justice to the stone,

it's just hypnotically beautifull, with absolutely no graveyard pretensions! Some people even think it's plastic, until they touch it.

Jorge wrote:

For my TT I use a 2 inch slab of Maple, I detach it from the shelf with Sorbothane, and form the TT plinth with Brass cones. It works pretty good and it is still sensitive to added weight on top.   If I jumpt right next to the rack I will hear a thump if the record is playing. My listening room is made of brick and mortar with concrete floors.

Paul S wrote:

Again, you might gain something by fastening the rack to adjacent walls and adjusting the tension and/or damping of those connections. In any case, you'll want to prevent swaying of a TT support, and likely a CD transport, as well, and it might even damp some noises that enter the frame from the floor, just like standing there and poking it with your finger.

N-set wrote:

I'd avoid granite. It rings.

N-set wrote:

A very approximate calculation shows that in my case I should have the profile fundamentals around 20Hz, so perhaps what I take as subsonic vibrations are actually 20Hz, poorely damped due to the added sand mass.  I've ordered a dirt-cheap guitar piezo and try checking that.

N-set wrote:

Rings=poorely damped, due to its crystaline structure. Take a granite tile with two fingers, put your ear close to it and knuckle. Observe the sound. Repeat with other stones to compare. For that reason it's neither used in nanolabs anymore (see e.g. the Newport link) nor in, say, billiard tables, not ot mention TT plinths. But looks good on graveyards

Paul S wrote:

I wonder how much hitting the rack feeds the floor/cavity(cavities).