|
Audio Asylum Thread Printer Get a view of an entire thread on one page |
For Sale Ads |
108.38.55.213
This is a progress photo of my new TT isolation base. The idea is pretty basic- inertial mass sitting on damped foam spring pads. The stone is "green" marble- I bought an old table and had it waterjet cut.
One wrinkle is that I'm adding a ¼" aluminum plate to the underside of the stone slab adhered with a layer of viscoelastic polymer sheet ("Hushmat"- around 3/32" thick) to provide "constrained layer damping" to the stone. CLD primarily is designed to dampen flexure, which implies less "drumhead" vibration response in the slab. This should reduce surface acoustic waves on the slab also. Stone is pretty well damped internally but this will make it totally "dead." The ratio of stiffness (varying as the the modulus of elasticity x the cube of the thickness ) factors in- it seems to me you want the E x I ratio to be in the range 1:20 - 1:10 for the damping plate : stone, although there's no definitive guideline (sez the Naval Undersea Warfare Research Station paper I read).
The base will go under my sweet little Sony PS-X55S table. It's a good, solid DD and on these types of tables the only way they control transmission of vibration from the surface they sit upon is via their elastomeric feet. This should assist the feet. My current shelf is undamped steel plate and is quite "lively."
The isolation I chose feet are industrial units made by Wagner. I researched them pretty well and they seem good for this purpose. They are rated at a maximum load of 50psi and thus the whole assembly wall only load them lightly. We'll see how it goes in that regard. I believe the performance would be better nearer the design load. These blocks appear very similar in overall construction to Mapleshade Isolation Blocks, although I can't attest to the material characteristics. They are around a buck each, so it's not an expensive experiment.
The small valence in the front isn't connected to the plinth and will be foam-taped to the shelf, just for appearance. All edges are as-waterjet-cut and appear smooth, a small amount of ripple. Finishing them with clear lacquer today. They look very nice that way.
I'll report back how it sounds. Since I worked pretty hard to get here, it will be a glowing report about "midrange bloom" and superb "PRAT," undoubtedly.
Follow Ups:
I really like the sony dd tables. Going up the chain to top tts8000 gives improvements in audiophile characteristics and bass. ..but dang it, mid range is almost same..actually more pronounced in mid table ... So aactually bit more involving on initial listens. Wonder if twaaking the mid tables takes them almost to top.
Put those blocks on something because they stain whatever you place them on. So a small wooden or metal square is advisable.
There is this Phono hobbyist in the UK that has taken it upon himself to test and publish from his website the damping factors of various materials to be used in this hi-fi hobby. His moniker is Cats Squirrel. He posts at forums like DIY Audio and Vinyl Engine with his opinions and results.
His test method seems to be that he gets a sample of the material to be tested. Then from a specified distance drops a steel ball on the material. Meanwhile an accelerometer has been fitted to the sample material to induce a signal from the material, upon being hit, to electronics instruments he has hooked up downstream.
He has amassed quite a list of measures. Probably worth a look if you seek a support structure that won't ring like the proverbial bell.....as will marble. Link below.
-Steve
How do I make sense of his chart. It looks very interesting.
One of VPI's first commercial product was a base very similar to yours, (though not nearly as good looking)
Thanks for the compliment- it needs to have what the call "Spousal Acceptance Factor."
The project was inspired by my "vintage" (antique?) VPI / Denon DP-75 which has a massive plinth suspended on tall soft springs, set in a wooden base frame. It provides excellent isolation, theoretically, but not always in practice. In my previous himes it was superb but its performance depends on the resonant characteristics of the floor and here in my new little condo Bearcave it performs poorly in response to footfalls.
.
Before you place the turntable on top, give it a simple rap test with your knuckles to make sure it's dead. I built a table for my Sota Millennia Turntable and I put the slate top on some felt pads. When I rapped on it with my knuckles it range like a bell. I removed the felt pads and replaced them with a layer of Sorbothane. That worked great!
Edits: 04/28/16
That's the plan- an impulse like a knuckle rap will excite its fundamental mode strongly, like ringing bell (hopefully, not like that!) I also might set a bare woofer on it, sprinkle it with very fine salt- or something like that- sweep some test tones, and see if any standing wave patterns appear in the dust. It would sure as hell look scientific- got a white lab coat I can borrow?
.
Post a Followup:
FAQ |
Post a Message! |
Forgot Password? |
|
||||||||||||||
|
This post is made possible by the generous support of people like you and our sponsors: