NDS floating sub chassis noise

Posted by: Audiofool on 15 January 2014

While there was no music playing, in a silent room, I bumped into my audio cabinet ever so lightly and heard the NDS sub chassis make a light metal tapping sound. Similar but not exactly like knocking on the outside of the NDS case with your knuckle. I was able to recreate this sound by moving the NDS on it's shelf with a short quick move of the NDS or walking right in front of my HiFi rack when the room is silent. My listening room is on a suspended wood floor (2nd floor room), combine that with a 200 pound person walking right next to the HiFi and there is some floor flex and soft mechanical noise coming from NDS. I assume this noise is the NDS sub chassis moving on it’s springs and hitting the NDS outer case? Is this normal? It kinda freaks me out to hear something clanging around inside the NDS like a loose part in a $11,000 USD piece of HiFi gear.  Does your NDS make a mechanical noise when you bump it or move it in a quick jerking manner? Is this normal for units with a floating sub chassis?

Posted on: 15 January 2014 by Peter W

I think this is normal. I could certainly feel the sub chassis bouncing around when I remove NDS from the Fraim to clean the glass shelves.

Posted on: 15 January 2014 by MangoMonkey

The more interesting question - how much bounce around before there is damage... - maybe someone from Naim can answer this question....

Posted on: 15 January 2014 by Audiofool
Originally Posted by MangoMonkey:

The more interesting question - how much bounce around before there is damage... - maybe someone from Naim can answer this question....

+ 1

Posted on: 15 January 2014 by james n

Might be worth reading the manual 

 

Moving the unit with the locking bolts out needs to be done with care.

 

Moving it in a quick, jerky manner whilst unlocked is a tad daft... 

Posted on: 15 January 2014 by Harry

As above. The internals are designed to move around and the odd clonk can ensue. Same for the 552. I have initiated some soft vertical clonks when setting up but I wouldn't subject it to a sideways jerk or sharp vertical movement, just to see what happens. I expect they are bolted together strongly enough and suspended generously enough to take a fair bit of movement, but why would I push it deliberately? It can't be any worse than lifting or walking (on a bouncy floor) past a suspended TT.

Posted on: 15 January 2014 by Audiofool
Originally Posted by james n:

Might be worth reading the manual 

 

Moving the unit with the locking bolts out needs to be done with care.

 

Moving it in a quick, jerky manner whilst unlocked is a tad daft... 

 

 

Yes I read the NDS manual BEFORE it came out of the box. Once the transport screws were removed the NDS has never been on anything other than a flat solid surface right side up. 

 

The side to side jerking was me just pivoting the NDS as it sat on a shelf to trouble shoot the sound. I fear my initial description of what I did was far more violent then what actually occurred. 

 

Bottom line it's not possible for me to walk past the front of my HiFi rack without the NDS making an internal tapping sound. OK maybe I can walk past the front of the HiFi without the NDS sound IF I walk like a stealthy audio ninja. But that ninja stuff is much harder than it looks.  

 

These are NOT violent shocks or vibration to the NDS.  No handstands or jumping jacks mind you. No kids jumping off chairs etc. I don't have any children which is why I can afford a high end stereo.    This internal NDS rattle is just me walking past the NDS on a less than rock solid floor. The NDS sits on it's own shelf in a heavy wood (MDF) rock solid piece of AV furniture.
 
My HiFi rack is not wobbly or flimsy. It's quite solid as it often supports my full weight as I lay on top of the cabinet to get to the wires in the back of the cabinet. 
 
And yes I know that a high mass HiFi rack in not desirable. That's just what I have for now. 

 

Posted on: 15 January 2014 by Audiofool
Originally Posted by Harry:

As above. The internals are designed to move around and the odd clonk can ensue. Same for the 552. I have initiated some soft vertical clonks when setting up but I wouldn't subject it to a sideways jerk or sharp vertical movement, just to see what happens. I expect they are bolted together strongly enough and suspended generously enough to take a fair bit of movement, but why would I push it deliberately? It can't be any worse than lifting or walking (on a bouncy floor) past a suspended TT.

Understood. It's just that I can't walk past the NDS without it making a soft metallic tapping sound. Is it possible that the NDS sub chassis has come off it's springs or has been unseated from it's normal correct position and that's why it makes this mechanical nose when presented with the slightest of vibrations? Seems to me there would be more room for the sub chassis to move inside the NDS without bumping into something and making a noise? I've had turntables on this very same cabinet and I can walk past the turntable without any audible effect in the record playback. I have an email into naim on this NDS rattle question. I will update all when I have a response. Thanks to all for the input.

 

Signed,

 

A Tad Daft

Posted on: 15 January 2014 by dzambolaja

Check with spirit level that your NDS is dead flat?

 

Bobby

Posted on: 16 January 2014 by Audiofool

Thanks to all for the ideas and feedback. I'll update when I hear back from Naim support.

Posted on: 16 January 2014 by Audiofool
I can tell you that I have heard spring noises with sprung sub-chassis gear a number of times when the floor is not a solid one.
Woodfloorboards do move a bit, and the sub chassis will briefly respond.
 
In my experience with Naim suspension systems, mechanical noises are caused by normal movement of the springs inside their shallow wells (in the bottom main chassis
plate) … as the sub chassis bounces. The springs are captive but NOT fixed in place on purpose.  They just rest in their wells, so they can jiggle 
around a bit noisily.  I have not seen an instance where the subchassis is actually off it's springs or rubbing against other parts. There are end stops for
the subshassis that prevent that from happening for the most part (with possible exception of the unit being flipped upside down and shaken without the transit bolts in).
FYI,  if you hear heavy clunks without spring bouncing noises when you carry the NDS around, that would be a sure indication the sub chassis is off it's springs.
 
If there is quite a lot of energy going through your floor, even if it's not sudden jumping etc.  … but  large weight shifts: Depending on the overall Physics
you might get a resonant response from the sub chassis that is more pronounced. It's normal bouncing frequency is a few times per second (intentionally out of the audio bandwidth like a Turntable).  It's conceivable under these circumstances that the sub-chassis might hit the end stops (or their pillars) causing tapping noises. 
If you were to carry the NDS around you can hear what that sounds like.
When you are listening to music though, as with a turntable on suspended flooring, naturally it would be best not to walk around. :-)
 
BTW, rock solid shelving transmits floor energy very well. Think of newtons balls. :-)    The released ball swings down and hits one end of a row. The energy
transmits through the solid middle balls without them moving, and the opposite end free ball receives virtually ALL the energy and moves in reaction.
Lijewise, the movable part of the NDS is receiving ALL the energy stored in the floorboards with your every step.
 
Hope your NDS is sounding great!
 
Regards,
 
Chris
avoptions
Posted on: 16 January 2014 by Tog

It could be me - but don't you think you are being a little over sensitive?

 

You might need to get out more!

 

Just a thought.

 

Tog

Posted on: 17 January 2014 by Audiofool
Originally Posted by Tog:

You might need to get out more!

  

Tog

 

Tog in first 17 days of this year you have posted on this forum on 13 of those days for a total of 61 posts... and I'm the one that needs to get out more?!

Posted on: 17 January 2014 by dayjay

I suspect that post come quite close to proving his point? 

Posted on: 17 January 2014 by Audiofool
Originally Posted by dayjay:

I suspect that post come quite close to proving his point? 

Tog's post is like the pot calling the kettle black. 

Posted on: 17 January 2014 by sheffieldgraham
Originally Posted by Audiofool:
Originally Posted by Tog:

You might need to get out more!

  

Tog

 

Tog in first 17 days of this year you have posted on this forum on 13 of those days for a total of 61 posts... and I'm the one that needs to get out more?!

He who lives by the sword, dies by the sword.

Well researched and well said.

Togs comment was un-called for.

 

"Just a thought" doesn't mitigate the comment.

 

 

 

Posted on: 17 January 2014 by Tog

I was suggesting a degree of of hypersensitivity - clearly not the case

 

Tog

Posted on: 18 January 2014 by analogmusic
 with the NDS costing as much as it does, it's normal to be concerned about it.
 
I would be.
 
 
 
Originally Posted by Tog:

It could be me - but don't you think you are being a little over sensitive?

 

You might need to get out more!

 

Just a thought.

 

Tog

 

Posted on: 18 January 2014 by MangoMonkey
Originally Posted by analogmusic:
 with the NDS costing as much as it does, it's normal to be concerned about it.
 
I would be.
 

+1 . I don't think it's normal for it to make those noises just because someone's walking around on a wooden floor. I suspect there's something wrong with the tolerances.