DIY turntable isolation

It has always amazed that after spending thousands of dollars on a turntable, it is still very susceptible to skips. Why cant they engineer it into the table?
Instead you have to take your expensive TT and place it on something corny like tennis balls or a cutting board etc.
To me its like putting hubcaps on a Ferrari.
Not trying to put anyone down, hell I use a piece of carpet padding under my TT.
Just something I always thought was odd, and it really takes away from the appearance.

 

That is what I call excellent DIY based on solid physics.

 

It does

 

Thanks very much. I talked to an engineer at Barry Controls before constructing this, and he helped quite a bit. He told me that Mark Levinson had talked with Barry Controls about using the SLM1A's in a turntable project, but it never came to fruition.

 

Do you know what the resonant frequencies are in both the horizontal and vertical axis?

 

Does everyone use isolation mainly for stability, to prevent the needle from jumping during room traffic?

 

It's to prevent vibrations from getting to the TT. Any vibrations in the audible range that reach the stylus/ record interface will generate audible distortion that is not the good sort.

 

Do bananas ring? Just curious. It seems that I misunderstood the whole concept of ringing. Where I thought there was a dull thump, there must have been ringing.

 

Sorry, I don't know about the resonant frequencies. I tried to do a calculation using a test record 20 years ago, but either my technique was terrible or the resonant frequency was less than what the record measured, because the test failed.

 

Actually they do but not nearly as much as hard wood slabs. And yes, a dull thump is ringing. Any noise you can hear is ringing.

 

If anyone really believes that any solid object is acoustically dead or actually capable of even decent vibration isolation within the audible frequency range here is an experiment. All you need is a hammer and a stethoscope. Put the stethoscope on one end of the object and hit the other end with the hammer. Do you hear anything through the stethoscope? That would be the transmission of vibrational energy within the audible frequency range. Now please don't actually do this. You will damage your hearing. That is how bad solid stiff objects are at acoustic isolation. OTOH with a well engineered suspension system you CAN actually do this test. You will hear something. With a top flight suspension system tuned to a low enough resonant frequency you won't hear much. That is what real acoustic isolation actually sounds like. The physics and the math are both pretty simple when it comes to this subject. You simply absolutely need compliance in the system to convert vibrations in the audible frequency range to a frequency that is below the audible range. Stiff is the opposite of compliant. Stiff objects are really good at vibrational transmissions. That's why you really really don't wan to do my stethoscope test with stiff objects.

 

To lean down the bass and keep the sound tight.

 

The sound / bass seems excellent and I never in my audio history witnessed a need for additional isolation other than the table's provisions. I always place on sturdy furniture though.
All this discussion just makes me wonder. I'll probably do some A-B compares of the same title on vinyl and CD to see if I have any bass issues.

 

I foolishly replaces the feet with spikes. The stock feet had thin sorbothane pads, and had started to show wear. I put some big fat dots (Herbies) on the stock feet to replace the original pads. It was surprising because the full sounding bass became tightly focused, and although I didn’t have one-note-bass before, I found I now had a whole bunch of texture and flesh on the bass notes that had been missing. I've changed speakers since then, but continue to ammend my ideas about how bass should sound.

 

As you say the resonant frequency does increase with stiffness or density of any substance (with other factors) The resonant frequencies in the bass region most affect tracking ad sound of a turntable. If the mechanical resonances are low enough in amplitude, then their effects have a minimal or no effect on the reproduced sound. Mass is most effective in reducing amplitude ie: a thick slab of marble less resonant then a thin one.. The planet Earth has a resonant frequency, which probably does not affect the sound of a turntable. Speaker cabinets have resonance, a fundamental resonant frequency with higher order harmonics. A speaker cabinet more massive is better than a less massive one. The density must vary, as then the resonances spread out and dampened as much as possible. The speaker cabinet should not produce any sound of its own, as also true for a turntable base, and platter and arm.

I understand (or think I do) how air suspension isolates a mechanism from outside resonances (but does not reduce the resonances of the isolated component itself) For example, an air bearing isolates the platter from the plinth, however the platter, record, and the arm must have sufficient mass and intimate coupling without compliance to perform well.

The original AR turntable suspension isolates the sub-chassis from the base. (I think well below 20Hz) AR claimed in its advertisement literature, a person could strike the top of the deck with a hammer without any effect on tracking and sound. I actually tried this with a hammer with a single layer of masking tape on the head.. to not damage the finish. Their claim is true. So it is reasonable to deduct the AR turntable would not benefit by air suspending the base.

 

My wife makes mine ring.

 

I've often wondered that too. I think Dual, in the 60's, seemed to be moving in that direction...then it--for some reason--became unfashionable to do so.

Perhaps the thinking is that every room is different, and different cartridges track differently and are affected differently, so it's best left to the end user. But then, in the very late 1970's when they were developing the 'level playing field' concept of the P-mount cartridge and arm, why didn't they address this at that time also? You would think that once it got down to 'one cartridge fits all', the differences between turntables and cartridges would be within a small enough tolerance level to attempt to do this. Maybe the answer to that was the development of the CD player...by the time P-mounts became prevalent, nobody was paying any attention to vinyl anymore.

Maybe those bright young men over at U-Turn feel like taking on another challenge, eh?

 

I had footfall and rumble issues with my VPI Scout, and then my VPI Prime. They were resolved completely with a $88 solution:

- Boos Block 24 x 18 x 2 1/2" solid Maple cutting board from amazon: $86.00
- 8 isolation blocks from amazon: $0.25 each. (They are essentially the same as the ones two other audio retailers sell for $25 a set of 8).

Problem completely solved, and the TT sounds great beyond my old baseline.

 

I

This looks smart. I've always used the Target shelving (wall mount) for my tube amp and turntable and never had an isolation issues that I know of.

 

Can you post a link?

I'm not turning 'em up on Amazon and would love to try some.

Thanks!

 

Here are the blocks. Amazon seems to have run out. http://www.westsidewholesale.com/di...=18283950120&gclid=CI2NvrGsisQCFQ4dgQodq3IA8A


The cutting board went up a bit too. I bought mine on December 3rd for $79.95, they are now over $120. They'll come back down I'm sure.

John Boos RA03 24-by-18-by-2-1/4-Inch Reversible Maple Cutting Board

 

In addition to Boos, Kobi and Grizzly also make "affordable" maple butcher blocks. Both can be found on Amazon.

 

Thanks!! ^^

 

Acoustic feedback affects sound quality throughout the entire audible spectrum. This isn't just an issue in the bass region it's just a harder to solve issue in the bass region but if there isn't some sort of compliant suspension somewhere in the system you will get feedback well beyond the bass and it will cause problems. Mass helps with isolation but not that much in reducing the amplitude of the feedback. That feedback is already going through things like massive concrete floors. It's not like an additional 20 lbs of stiff wood is going to stop it. put your ear to any slab of wood and knock on it. You will hear plenty of transmission of that knock regardless of the mass of that wood.

 

Somewhat off-topic, but Marc Morin (marcmorin) on AudioKarma offers an AR upgrade service. One of his more effective mods is mass-loading the T-bar with 4 lbs of some sort of metal, and then installs Linn springs to support the extra weight. Without this mod, AR-XAs can sound a bit lite, but the mass-loading really adds some oomph to the AR's sound.