ROHO

[Jamier]

     I pursued this thing after reading an old Bee Pre post of Doc's.He described the use of a pneumatic inner tube as the base of a plinth for reducing microphonics in tube gear. This is a ROHO Cushion. These are used by individuals who are wheel chair bound and the cushion helps to reduced the occurrence of pressure injuries caused by spending many hours seated in a wheel chair. I found this one on Amazon. It was sold as used but actually had never been used, it was in a factory sealed box.I paid $125.00. The prices are all over the map so careful shopping pays off.

    On top I place two pieces of limestone which have a combined weight of about 50 lbs. These cushions are designed to handle the weight of an adult man or woman so you could probably go higher than 50 lbs., but I just happened to have this stone left over from a counter top project so I used it.Also, I have no idea how much air pressure is in the cushion, I just pump it up until the sag is out of the cushion. I'll have to play with this to see if there is some optimal pressure, but I will need to come up with some way to measure it as the valve does not have a  stem like a tire does, so a conventional pressure gauge will not work with it.(BTW, mine came with it's own pump so if you pursue this, make sure you get the pump with yours).

    So far I have put several different components on it (including a Quickie) and the reduction in microphonics due to footfalls, etc. has been pretty impressive. I really haven't tried to fine tune anything, I just pumped it up, put the stone on it, pumped it to take the sag out and thats it. For scale, thats a Crack on it. I think I'll just build a wood base around it and call it good.
 

PS this one is a High Profile Cushion. They come in different heights and sizes but I figured this one would be an all around useful size.
Jamie

Here's some images:

[Doc B.]

Very cool! We are just starting to hand wave a bit about equipment rack kits here and this subject came up once again. Regarding "how much pressure", you probably want that bag to be maximally lossy - as squishy and sluggish as possible. So probably the lowest pressure you can get away with would be the place to start. In practice you might bump the stone with the gear on top and try to measure the frequency at which it wiggles. Generally the lower the better.

My thought at this point is that we might try something less expensive like scooter tire inner tubes, and provide platform boxes that one can fill with sand from the local Home Depot to keep shipping costs low. And of course the setup would assemble as easily as Kaiju cabinets.

[Jamier]

I think I will call this the "Be-Still". If you put a Bee-Pre on it you could call it a "Bee-Still".

Jamie

[Deke609]

That's pretty cool.  Is the heavy stone needed for inertial mass?  Or just for leveling?

I ask because I don't think my Macgyvered audio rack would like an additional 50 lbs. I'd like to use a wooden plank if I could.

Thanks,

[Jamier]

Inertial mass, definitely. I think Doc can explain this better than I. I tried to follow his guidelines from that old Beepre post. Initially, I tried just 1 piece of that stone but when I added the second
piece it became considerably more effective at quieting the microphonics. That's why I mentioned the weight bearing capacity of the cushion, I think you could easily put a hundred pounds on the cushion, its made to hold an adult human, maybe upwards of 200 lbs (?) I don't know exactly. I'm sure that information is available.

Jamie

PS: I think Newton's laws of motion apply here. The more massive an object is, the harder it is to get it to move. Right? Well, anyway, something like that.