Microphonics

[Paul Joppa]

Reducing movement is a tricky business. Here are three technical points:

1) If the device you are addressing is the source of movement (speakers, for instance) then increasing their mass will reduce their displacement, at least at frequencies low enough that the whole moves as a rigid single entity. A massive support and/or platform, tightly coupled to the device, works this way. It does not change the energy, but a larger mass moves a smaller distance for the same energy.

2) Isolation does not reduce movement, it just keeps it confined to one place. In the case of a speaker, isolation keeps the cabinet's vibrations out of the floor, so the floor does not radiate sound. In the case of a microphonic preamp, isolation keeps the floor's movement out of the preamp so it doesn't ring.

=== notice the tricky bit here with speakers. Spikes will increase the cabinet's mass but will couple the cabinet's vibrations into the floor. Which is better? Kind of depends on the floor! ===

3) Isolation is not absorption. A pure-spring support reduces the motion (above its resonance) even if it bounces forever once set in motion. If it absorbs energy (damps the bounce so it dies quickly) it  provides less isolation at all frequencies. It's a tradeoff. Car shock absorbers are a familiar example.

[Grainger49]

Xavier,

My last three set ups were 1) on a poured concrete floor, 2) resting on the foundation wall and 3) on a load bearing wall.  I haven't had a problem with an LP skipping in a couple of decades. 

Your set up looks like it is on a load bearing wall sitting on a foundation wall.  I don't think you should have a problem from foot falls. 

It also looks like the air is being pushed away from your system.  The reflections will be a lower amplitude.  So Dan's suggestion of putting some absorbent material between the amps and the room, just to see if it helps, is pragmatic. 

[Demsy]

I have some extra sorbothane pads that I got from Jaques Riendeau for the Oracle Paris turntable suspension. I placed them under the Paramount as you can see from the picture. The sorbothane absorpts almost all of the vibration created underneath them, I can knock on the thin ply base or the stainless steel stand and almost nothing is transferred to the tubes. The 300B on this Paramount is more microphonic than the other side. I will change the ply with 8mm or 10mm acrylic and expect it to be even better.

[Jim R.]

Paul,

Thanks for the technical clarifications and explanations -- all makes perfect sense to me, and why, even if presented a bit differently, the mapleshade stuff does work as nicely as it does.  It also explains why it doesn't work as well for every situation.

People really just need to experiment as every situation is going to be different and I just wanted to give some of my own experience  as another alternative that people may want to try for themselves.  This stuff is not usually of the make or break kind of thing, but when done right and in the right proportion, can make a nice difference that I find makes my listening just that much more enjoyable.

-- Jim

[denti alligator]

Somebody recently recommended I try a slightly inflated inner tube with a 1" thick piece of plywood on top of it. The ideal is to get the inner tube inflated just enough so that the plywood (with whatever's on top of it) does not touch the surface (through the rubber). I mean to try this with my turntable, since it's on a glass shelf (not ideal for phono).

[adamct]

To quote from one of my favorite websites, The Online Photographer:

"(By the way, if you're wondering how to suspend an unsuspended [turntable] like the MMF 2.2 or the Regas, here's what you do. Go to the plumbing section of your local hardware mart and look for 1 1/2" pipe end caps in the plumbing section

[Grainger49]

Somebody recently recommended I try a slightly inflated inner tube with a 1" thick piece of plywood on top of it.  .  .  .   

Sam,

Microphonics are different than isolating turntables from room vibrations, IMHO!  As I posted above having a firm base that the table/furniture rests on is a cheap way to isolate the TT from the room.  I don't know the situation in your new place.  My table is in an oak shelf-unit which weighs 100 pounds empty.  My equipment can't weigh 30 pounds total, so mostly my isolation comes from the cabinet and the wall right behind it which is load bearing.  Even though it is on the second floor the wall below it is sitting on the foundation.  Just a lucky happenstance, not something I thought out.

With Joel Bain here I stomped on the floor in front of my table and I heard something but no skipping.  That is not a real world test.  I walk, I don't stomp.