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Spider27

Improving vertical isolation for Suspended turntable

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What would be the ideal way to improve vertical isolation for suspended turntables other than wall mount option?

 

I recently got AR XB turntable and it has great isolation from horizontal movement or vibration (it does not skip when I bang on the plinth which is impressive) but terrible on vertical movement.

 

When I even slight jump or step on the ground hard near the turntable, then it skips.  Turntable is currently sitting on a IKEA solid timber chopping board with spike feets as isolation base that is sitting on top of AV rack. I have other turntables that are non-suspended design but they are less prone to vertical vibration than this AR XB turntable. This is surprising to me because I always thought that suspended design is less prone to both horizontal and vertical vibration...

 

At present, I have not put any dynamat or any damping materials but kept stock form. If damping is required, do I need to damp underneath the top plate or T-Bar sub chassis?

 

Any suggestion would be greatly appreciated.

 

Thank you.

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Posted (edited)

Suspended designs provide excellent acoustic isolation but have no protection from footfalls. Damping the sub-chassis won't change that.

 

Try putting a wedge between whatever the turntable is sitting on and the wall. This will eliminate the rocking that causes the footfall issue.

Edited by Telecine

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Posted (edited)

Ceiling mount? Just 4 hooks on the trusses and some wires to a turntable platform should fix any ground floor problem, unless there is a floor above. Or if you are on the ground floor you could  sink a post into the ground below and cut a hole out in the floor boards.

My preference is to have a wall shelf on an external wall preferably one sitting on a bearer.

Any thing else on a suspended timber floor is totally inadequate.

Edited by awty

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1 minute ago, Telecine said:

Suspended designs provide excellent acoustic isolation but have not protection from footfalls. Damping the sub-chassis won't change that.

 

Try putting a wedge between whatever the turntable is sitting on and the wall. This will eliminate the rocking that causes the footfall issue.

Thank you very much for your suggestion. May I ask what you mean by wedge? Are you referring this one?

 

566x566

 

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Anything of a suitable size to jam between the wall and what the turntable is sitting on (rack, buffet, etc).

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Posted (edited)

Any suspension has limits in its movement.

You will certainly stop this floor bounce if you wall mount the XB.

May I suggest the easiest fix is don't jump near the  TT.

I have an XB and it is rock solid but I have concrete floors.

I had a Thorens 150 that suffered from the bounce problem

I tried concrete flag stones and other solutions but only wall mount fixed the problems with the flexing wooden floors.

As an aside I built an equipment cabinet around the wall mount so it looked like it was in the cabinet.

Edited by Colin Rutter
Syntax

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What is the floor structure? Floor boards? Sheet? Does the skip happen when in line with a rack leg, or anywhere in the vicinity?

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Just now, t_mike said:

What is the floor structure? Floor boards? Sheet? Does the skip happen when in line with a rack leg, or anywhere in the vicinity?

it is floorboard and carpet on top and whenever I step hard around the area where rack sits on, it skips. 

I put a large 18mm thick plyboard on the carpet and put the AV rack on top and it helps skipping a bit but it is not completely prone to hard stepping or running around. 

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Posted (edited)
7 minutes ago, Colin Rutter said:

Any suspension has limits in its movement.

You will certainly stop this floor bounce if you wall mount the XB.

May I suggest the easiest fix is don't jump near the  TT.

I have an XB and it is rock solid but I have concrete floors.

I had a Thorens 150 that suffered from the bounce problem

I tried concrete flag stones and other solutions but only wall mount fixed the problems with the flexing wooden floors.

As an aside I built an equipment cabinet around the wall mount so it looked like it was in the cabinet.

100% agree with Colin. There is no substitute for wall mounting. By sheer dumb luck, I am able to make use of an unused brick fireplace/hearth for my turntable. It is independent of my wooden floor and is effectively part of the wall. 

Edited by Bisguittin
typo

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13 minutes ago, Spider27 said:

May I ask what you mean by wedge? Are you referring this one?

image.jpeg.7dcfeaf1cb334db7a6d7ba456df4cca4.jpeg

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Posted (edited)
2 minutes ago, Rocketfrogs said:

image.jpeg.7dcfeaf1cb334db7a6d7ba456df4cca4.jpeg

That's what he should get for buying a suspended design to use without a wall mount with wooden floors ;) 

 

Given he is in Victoria, he will have to apply it to himself as punishment.

Edited by Telecine

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3 minutes ago, Spider27 said:

it is floorboard and carpet on top and whenever I step hard around the area where rack sits on, it skips. 

I put a large 18mm thick plyboard on the carpet and put the AV rack on top and it helps skipping a bit but it is not completely prone to hard stepping or running around. 

As a cheap and easy experiment, try bracing the ply with full length pieces of wall framing timber. Floor boards can "rock" over the floor joists, causing the boards to take on an s shape (down where you step causes up on the other side of the joist). This acts on a single leg to cause an up/down movement. A plinth can average this out, making it difficult for a single board to have an effect. This is what has happened when you used the ply underneath. By adding the braces you make the plinth more rigid, further protecting the table from single board movement. If this doesn't help, then I'm afraid the whole floor is springy, and only a wall mount will fix this.

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Posted (edited)

Best fix is to buy a SOTA Turntable. You would have to drop a weight on it to get it to skip. Superbly designed sprung turntable. Even the very original model is virtually impervious to footfall. You drop the dust cover down full force and it won't skip. Even bang it with your fist.

 

 

Edited by kelossus

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Posted (edited)

With my LP12 I did try the old half inflated bicycle tube isolation trick to some success.

Edited by kelossus

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4 minutes ago, kelossus said:

With my LP12 I did try the old half inflated bicycle tyre isolation trick to some success.

I can imagine it would work nicely on other components but wouldn't it be too bouncy for TT since TT requires stable non moving base? 🤔

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Be careful adding any suspension under a suspended TT, you will end up with resonance between the 2 springs. I had an Lp12 and a very light stand will do the job. My LP12 sat on a Linn deck stand which worked well.

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Posted (edited)
22 minutes ago, Spider27 said:

I can imagine it would work nicely on other components but wouldn't it be too bouncy for TT since TT requires stable non moving base? 🤔

I have no idea really. Not an engineer or have even a remote understanding of the physics involved. The method I described has been recommended by people much smarter than I so I followed like a sheep.

Edited by kelossus

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Guest ianttt

Thorens used to fit foam dampeners to their springs to help alleviate this problem.Worth a try perhaps.Susp_Tim_Bailey

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1 minute ago, ianttt said:

Thorens used to fit foam dampeners to their springs to help alleviate this problem.Worth a try perhaps.Susp_Tim_Bailey

Thank you for the tip......I might have some sponge around and will try it. 

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1 hour ago, Spider27 said:

Thank you for the tip......I might have some sponge around and will try it. 

 

Won't do a thing, unfortunately (Thorens didn't use that foam to eliminate footfall problems).  :(

 

You need a wallshelf; if you're renting and can't drill holes in the wall ... then you have a biiig problem.

 

Andy

 

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Posted (edited)
12 hours ago, andyr said:

 

Won't do a thing, unfortunately (Thorens didn't use that foam to eliminate footfall problems).  :(

 

You need a wallshelf; if you're renting and can't drill holes in the wall ... then you have a biiig problem.

 

Andy

 

 

Edited by ianttt

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The problem is that both wood and springs absorb energy through deformation quite well, and then return it in an undamped manner. In suspended wood floor, the energy is absorbed locally and returned locally- ie. it bends under your feet and the bending-unbending moves close objects that are light enough to  move. This drops your TT, with it’s platter, and when the floor moves up again, the platter compresses the springs before being boosted back upwards beyond its initial position. At this stage the springs are stretched to some degree, and will snap back adding speed the normal gravitational fall. As the cartridge end tonearm is not fixed to the record, it will only fall at the speed determined by gravity (more or less), and will lose contact with the record, given a big enough injection of energy from the footfall. Non suspended tables don’t get that extra spring-back, and often aren’t so badly effected.

 

The energy absorbed by almost all vibration absorbing devices, furniture, etc. is orders of magnitude less than that transferred by a 100kg person into a lightweight wooden floor, and from there back into the hi fi rack. The suspension springs and vibration absorbers work within a range of a mm or two of movement  before being overwhelmed. If you walk on a wooden floor, often it will move much more that this.

 

This is why having a very heavy, non elastic material like concrete that acts as a sink for the energy your body weight puts into it, moving little and not returning the movement to the hi fi rack elastically, is much less associated with skipping with footfall. Wall mounts are structurally somewhat separate to the floor structure of a suspended wooden floor and hence don’t move significantly when the floor moves. These are both the only real solutions that allow you to dance next to your record player.

 

Sorry if that is a bit of a ramble. Hope it explains why vibration absorbers are great for isolation from small energy inputs like bass noise, etc., but not so good for even lower frequency but much higher energy inputs like footfalls.

 

Justin

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1 hour ago, Juzbear said:

The problem is that both wood and springs absorb energy through deformation quite well, and then return it in an undamped manner. In suspended wood floor, the energy is absorbed locally and returned locally- ie. it bends under your feet and the bending-unbending moves close objects that are light enough to  move. This drops your TT, with it’s platter, and when the floor moves up again, the platter compresses the springs before being boosted back upwards beyond its initial position. At this stage the springs are stretched to some degree, and will snap back adding speed the normal gravitational fall. As the cartridge end tonearm is not fixed to the record, it will only fall at the speed determined by gravity (more or less), and will lose contact with the record, given a big enough injection of energy from the footfall. Non suspended tables don’t get that extra spring-back, and often aren’t so badly effected.

 

The energy absorbed by almost all vibration absorbing devices, furniture, etc. is orders of magnitude less than that transferred by a 100kg person into a lightweight wooden floor, and from there back into the hi fi rack. The suspension springs and vibration absorbers work within a range of a mm or two of movement  before being overwhelmed. If you walk on a wooden floor, often it will move much more that this.

 

This is why having a very heavy, non elastic material like concrete that acts as a sink for the energy your body weight puts into it, moving little and not returning the movement to the hi fi rack elastically, is much less associated with skipping with footfall. Wall mounts are structurally somewhat separate to the floor structure of a suspended wooden floor and hence don’t move significantly when the floor moves. These are both the only real solutions that allow you to dance next to your record player.

 

Sorry if that is a bit of a ramble. Hope it explains why vibration absorbers are great for isolation from small energy inputs like bass noise, etc., but not so good for even lower frequency but much higher energy inputs like footfalls.

 

Justin

Thank you for sharing the info. Very informative indeed. 

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I am inclined to wall mount the turntable by purchasing wall brackets and HDF board.

 

The reason that I was trying to avoid wall mount all along is that nearest wall studs are not ideally located (between speakers) but more like right above one of the speakers. I wish I can move speakers but speakers needs to be there since my listening position cannot be altered in great deal.

 

For those of you who have wall mounted, is your wall mount just above AV rack between speakers or is it off centred?

 

I am a bit concerned that it would look weird after turntable mounted quite off-centred when other components on the rack right on middle between the speakers.

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