Quick vibration-isolation project

[dyche01]

For various space reasons I occasionally find it necessary to place a turntable on the same surface or in the same bookshelf as the speakers and I have been thinking about good ways to better isolate the turntable from the speakers. Night before last, as I picked my way through the basement shop I saw a 1 3/4" slab of oak leftover from an abortive coffee table project. Whipping out my tape measure I realized that sawing it in half would give me the perfect-sized platform to hold a turntable. So, finally giving up on the coffee table, I sawed it in half.


The wood was very rough and uneven, so I ran it through my buddy Peter's drum sander about 50 times to make both sides perfectly flat and parallel.



After that, I routed the edges and sanded the surfaces multiple times, starting with 120 and ending with 320 grit.


Next, I used a 1 1/4" spade bit to drill holes near the corners just large enough to wedge part of a squash ball into.


I routed out the edges of the holes to improve the fit.



...and then finished the surface with a great poly-urethane finish called 'The Good Stuff' (no affiliation).

 

[dyche01]

Squash balls are an old trick we used to use for vibration isolation of microscopes but I am pretty sure I have seen some other people use it for turntables.

Here are the balls in place.


And here are a couple of shots of the final product in situ.




And here it is with the AR turntable I just scored from @mkane

 

[guiller]

Great job!!

 

[808_state]

Nice! Have you considered taking both slabs and making a super platform with maybe spike feet beneath the bottom slab? I'm considering doing this with cutting boards.

 

[dbxdx5]

Nice work. Love that you were able to repurpose some wood you had on hand.

 

[beatcomber]

As an aside, I'm concerned that the Scott tube amp isn't getting enough ventilation.

 

[sqlsavior]

Nice work!

 

[vaathi]

Cool looking Isolation platform. Shout out from fellow Bay area Aker. I got Scott 399 too.

 

[dyche01]

Cool looking Isolation platform. Shout out from fellow Bay area Aker. I got Scott 399 too.

We should get together for a Scott listening party!

 

[petehall347]

nice job .better looking than my chair cushion idea .

 

[IPADave]

Nicely done! Functional and pleasing to the eye.

-Dave

 

[mkane]

The 'Good Stuff ', thanks.

 

[mbskeam]

looks nice.....

 

[dyche01]

I wanted to get a general idea of how well this vibration isolation platform works so I used a giant Electro Voice corner speaker (with a 15" woofer) to test it out. Vibration sensing was performed by a cute iPhone app called VibSensor (no affiliation).



I collected 40 seconds of vibration data with the phone sitting either directly on top of the speaker or on the vibration isolation platform. The music in both cases was a section of bass-heavy electronic dance music from YouTube. The results without the damping platform were actually interesting by themselves. For orientation, the x- and y-directions are both parallel to the top surface of the speaker while the z-direction is perpendicular to that surface.


Interestingly, the forward-backward vibration mode (y-direction) was much larger than either the side-to-side (x) or up-and-down (z) motions, meaning that the speaker has a stronger tendency to rock back-and-forth than side-to-side. There is also a strong peak just below 40 Hz, which looks like some sort of resonance.

With the damping platform, both the side-to-side and up-and-down motions drop down to the noise level of the iPhone (i.e. the levels of vibration that you measure when no music is playing at all). The forward-backward motion is still detectable but is decreased by 20- to 100-fold, depending on frequency.

 

[Dmitry]

Have you taken the measurements of the AR turntable both on and off the isolation platform?
Please post them!

 

[dyche01]

Have you taken the measurements of the AR turntable both on and off the isolation platform?
Please post them!

As soon as I get the time!

 

[Andre Garcia]

Nice project.
Why do you use four legs instead three?
I made my own using a 3/8 natural stone tile and sorbothane pads. I will try the app and see what is the result.
Thanks for the info!!

Andre.

 

[sqlsavior]

I'm impressed with your measurements, too. Nice to have objective feedback.

Is the Y direction in line with the woofer axis?

 

[dyche01]

I'm impressed with your measurements, too. Nice to have objective feedback.

Is the Y direction in line with the woofer axis?

Thanks! And you are right, the y-axis is parallel to the woofer axis. It is also the smallest dimension of the cabinet.

 

[arcsound]

Nice job! I have been trying to reduce the footfall vibration (on concrete slab with plywood sub-floor) picked up by my DD TT sitting on top of a glass/wood/steel rack. It was picking up not only footfalls, but rapping on tables nearby, and likely vibrations through the air from the floor mounted speakers. I tried a couple different weight Vibrapads, as well as foam blocks and some other home-brew rubber-based isolators, all with little success. Then I tried squash balls. Someone on AK mentioned cutting them in half for stability, but I felt like trying them whole, to create two minimal contact areas, above and below (like you did), and just stuffed them under the useless OEM feet. The difference was impressive. No numbers but tap testing seems like at least 10 dB down, compared with no isolation. The TT will sway if perturbed, but will quickly damp to stop, probably no more motion than my Thorens with its spring suspension. Cheap fix!