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Hi, making a platform for my Kuzma, given no suspension, when I stamp my wooden floor, get a thud, but does this mean that sound vibrations more subtle are affecting playback? 

 

Re design, current version is 20mm ply on 8mm accoustic board on 2mm carbon fibre board wrapped in Carbon n fibre, on 6mm  sorbothane feet (have removed metal feet) . But it's still not suspended.....

 

Ideas appreciated

IMG20210424103757.jpg

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Have you taken a look at Barry Diament's pages? He's a passionate believer in sound of less than 10Hz affecting the listening experience. As a result there are two schools of thought in rack design, I generalise because this is SNA and I don't want to spark a tribal conflict, but to the best of my limited knowledge there's the "mount it on pointy feet" and the "decouple utterly" approaches. Diament is of the latter school. He goes for big solid feet on racks, and then decouple at the component. For example in your situation to decouple the options for under your rather nice platform could be 3 squash balls, or a half-inflated wheelbarrow tyre inner tube or one of those inflatable rings that can be used on chairs or beds to provide cushioning, or (and apparently best) 3 metal ball bearings each on a shallow metal dish.

 

Your ears should be the judge.

 

Search for Diament here on SNA; or google "Barry Diament isolation" on ordinary text google, and again on google images.

 

 

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1 hour ago, philwill1971@gmail.com said:

Hi, making a platform for my Kuzma, given no suspension, when I stamp my wooden floor, get a thud, but does this mean that sound vibrations more subtle are affecting playback? 

 

Possibly.  :(

 

1 hour ago, philwill1971@gmail.com said:

Re design, current version is 20mm ply on 8mm accoustic board on 2mm carbon fibre board wrapped in Carbon n fibre, on 6mm  sorbothane feet (have removed metal feet) . But it's still not suspended.....

 

Ideas appreciated

IMG20210424103757.jpg

 

Your TT rests on a bench - as mine does.  :)

 

But what supports the bench?  Does it have feet resting on your floor ... or is it wall-mounted?

 

If the former ... then, unfortunately, footfalls will upset your playback.  :(

 

Andy

 

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40 minutes ago, andyr said:

 

Possibly.  :(

 

 

Your TT rests on a bench - as mine does.  :)

 

But what supports the bench?  Does it have feet resting on your floor ... or is it wall-mounted?

 

If the former ... then, unfortunately, footfalls will upset your playback.  :(

 

Andy

 

Hi Andy, yes the bench has four feet with some acoustic 10mm material as padding direct to the floor, I'm ok with not banging my feet on the floor, but was thinking more so of the speaker sound, esp sub feeding back through the TT.

27 minutes ago, ThirdDrawerDown said:

and an Australian take on Barry Diament's "Hip Joints" and inexpensive substitutes, including from Ikea

https://hifiauditions.wordpress.com/2019/03/28/vibration-magic/

 

 

Fun reading, thanks

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1 hour ago, ThirdDrawerDown said:

Have you taken a look at Barry Diament's pages? He's a passionate believer in sound of less than 10Hz affecting the listening experience. As a result there are two schools of thought in rack design, I generalise because this is SNA and I don't want to spark a tribal conflict, but to the best of my limited knowledge there's the "mount it on pointy feet" and the "decouple utterly" approaches. Diament is of the latter school. He goes for big solid feet on racks, and then decouple at the component. For example in your situation to decouple the options for under your rather nice platform could be 3 squash balls, or a half-inflated wheelbarrow tyre inner tube or one of those inflatable rings that can be used on chairs or beds to provide cushioning, or (and apparently best) 3 metal ball bearings each on a shallow metal dish.

 

Your ears should be the judge.

 

Search for Diament here on SNA; or google "Barry Diament isolation" on ordinary text google, and again on google images.

 

 

THanks, will definitely try tyre option

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3 hours ago, philwill1971@gmail.com said:

Hi, making a platform for my Kuzma, given no suspension, when I stamp my wooden floor, get a thud, but does this mean that sound vibrations more subtle are affecting playback? 

 

Re design, current version is 20mm ply on 8mm accoustic board on 2mm carbon fibre board wrapped in Carbon n fibre, on 6mm  sorbothane feet (have removed metal feet) . But it's still not suspended.....

 

Ideas appreciated

IMG20210424103757.jpg

 

Give up the Morris dancing, it is overrated anyway.

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On 07/05/2021 at 9:19 PM, ThirdDrawerDown said:

Have you taken a look at Barry Diament's pages? He's a passionate believer in sound of less than 10Hz affecting the listening experience.

Totally agree with his view.

 

Any erroneous signal will modulate onto the audio and smear the sound. Subsonic filters will remove the low frequency fundamental from the output but do not remove the intermodulation products from the signal.

 

This example is an EPA100 with a Stanton 881s on an SP10.  The first plot shows the stock EPA100. The second plot the CW and stub have been replaced The sub is threaded and made from brass and Stainless CW locks rigidly to the stub, viscous damping has also been applied. The 8.5Hz AM sidebands are all but completely gone. This was audible as improved clarity even though I  can't hear 8.5Hz.

 

300Hz_OEM.thumb.jpg.257cb77506c66a97e287864c698e58fb.jpg

 

300Hz_CW_damp2.thumb.jpg.a878bd33464c799376e4b213e1552060.jpg

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30 minutes ago, Warren Jones said:

Totally agree with his view.

 

Any erroneous signal will modulate onto the audio and smear the sound. Subsonic filters will remove the low frequency fundamental from the output but do not remove the intermodulation products from the signal.

 

This example is an EPA100 with a Stanton 881s on an SP10.  The first plot shows the stock EPA100. The second plot the CW and stub have been replaced The sub is threaded and made from brass and Stainless CW locks rigidly to the stub, viscous damping has also been applied. The 8.5Hz AM sidebands are all but completely gone. This was audible as improved clarity even though I  can't hear 8.5Hz.

 

300Hz_OEM.thumb.jpg.257cb77506c66a97e287864c698e58fb.jpg

 

300Hz_CW_damp2.thumb.jpg.a878bd33464c799376e4b213e1552060.jpg

What do you think of the weights that Magna Audio turns to put on top of the bearing tower (sorry!) of arms like the FR-64? Also larger nut for the arm pillar under the armboard (ie N-60 or B-60 for the FR-64)? 

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3 hours ago, Warren Jones said:

CW and stub have been replaced The sub is threaded

Interesting post. Sorry to ask, but I face dozens of abbrevs and TLA every day. Sub? Stub? CW? Regretfully asking the obvious.

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Stub = the bit that goes into the back of the tonearm that the counterweight is fixed to

 

CW = counterweight.

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Posted (edited)
6 hours ago, crtexcnndrm99 said:

What do you think of the weights that Magna Audio turns to put on top of the bearing tower (sorry!) of arms like the FR-64? Also larger nut for the arm pillar under the armboard (ie N-60 or B-60 for the FR-64)? 

I had a quick look at that and I would want see before and after measurements as I do not see any benefit of adding a weight to the top of the post. IMO it would be better to add damping to the bottom of the post like in a resin/bentonite plinth.

 

Vibrations traveling down the arm from the cartridge, some will reflect back to the cartridge at every joint even if the material is the same, so adding a weight seems illogical. It may lower the frequency at which the system resonates which is not a good thing as low frequency has more energy to control.

 

It's interesting there are no measurements to show before and after effects of adding the weight.

 

Edited by Warren Jones
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The purpose of my post was to highlight that vibrations outside the audio band (8.5Hz in my case) modulated onto the audio signal are audible. If you can damp/control these vibrations then clarity will improve.

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9 hours ago, Warren Jones said:

This was audible as improved clarity even though I  can't hear 8.5Hz.

Interesting, hey.

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I'm in the process of doing a write up on the mods I did to my arm that can be applied to any tonearm. stay tuned

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On 12/05/2021 at 11:41 PM, warweary said:

Ah, u found a way.  How solid is the wall mounting?

 

Wall mount reasonabe solid on 18mm Oak, but will be adding a platform ontop when ready. Just wish there was a measuring device.

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  • 2 weeks later...

Wasn't sure where to post this, and since we're already talking about TT platforms and isolation...

 

My Lenco build is fairly solid but not a mass-loaded design. Design is Lorifcraft-style 48mm birch ply top plate sitting on stone spheres in acrylic squares on felt, which in turn sit on sticky-out bits in each corner of the hardwood plinth/'frame'. It sits on a cut-off of stone bench top I have had for a good while. Currently the feet are Rega feet. My question > 

 

Given the fairly inert table and the high-mass of the stone platform it sits on, are isolating feet (Gaiia III) or spikes a better route? Do spikes, based on the assumption that the stone platform is the more inert of the two structures, win? Or do the praised Gaiia feet, isolating the TT from the stone platform, make any sense?

 

After recently witnessing the impact of source upgrades with a new tonearm, I think optimising all aspects of the TT is a worthwhile endeavour :thumb:

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The cheapest bit of test equipment I use is a stethoscope, very useful for listening to things like plinths etc to estimate effects of damping / isolation.

 

Stone has mass and it takes more energy to excite a heavy mass, this is the reason that mass works in a lot of cases. BUT at some frequency the stone will be transparent to vibration what this frequency is anyone's guess so isolation would be the best option.

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Posted (edited)

My next upgrade: spike feet for TT. My phenomenal sounding LP12. Even the dog sits up and takes notice.

1CABE8DD-4AD8-4A03-B24C-78D438824469.jpeg

Edited by davidSun
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Protecting the Linn from vibrations is well known to help.

Be aware though that Ivor specifically recommended against spikes on the t/t itself. From the feet up it was designed to route vibrations away from areas of significance.

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33 minutes ago, davidSun said:

My next upgrade: spike feet for TT. My phenomenal sounding LP12. Even the dog sits up and takes notice.

1CABE8DD-4AD8-4A03-B24C-78D438824469.jpeg

Don't use spikes on the turntable. Your best bet for the Linn is a light but rigid wall shelf.

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