Where do classical vinyl records get their rumble from?

@pindac 

... the spindle is seated upon non-metal low-friction material, and the spindle is contained within non-metal bushes which are custom measured to the spindle and allow very low micron tolerance. Combining these control measures is also another substantial contribution. 

I am in full agreement that measures put in place to improve how the Spindle interfaces with the bearing housing and platter will substantially reduce the noise floor, resulting in a major improvement to the end sound; details, dynamics and envelope become discernible and easier to detect their presence in the structuring of the produced sound.     

Explains in part why the Holbo has such a low noise floor.  The 5-kg mass of the platter is supported on a 10-micron (I think) layer of air.  The non-metallic spindle is made of engineering plastic (Delrin) and is only needed to centre the platter against the slight pull of the drive belt.  With the drive belt removed, the platter takes about 3 minutes to stop from 33-rpm.

Placing the 625-gram puck on the edge of the platter is enough to ground the 'hovercraft effect' even with the air on.  It is used during final levelling of the tonearm support shaft to stop the platter rotating, while the arm bearing is still floating freely on a 10-micron cushion of air.

In this thread, Holbo has claimed a 100-fold reduction in noise compared with 'normal' bearings.  I am sure this contributes to me hearing low level recording artefacts that are masked on most systems.  It also brings to the fore musical detail that is otherwise lost.

@faustuss 

Thanks for that review of the DS Audio DS003 optical cartridge.  I had seen it before, but this detail escaped me:

Says Aki, ’In the 2nd generation vibration system, the distortion rate was consistent regardless of the stylus pressure, but in the 3rd generation, the distortion rate decreased when the stylus pressure was increased.’

@billstevenson This is great corroboration of the ’clearer sound’ effect I noticed when adding your 5-gram weight, which as a by-product increased tracking downforce by about 50% because the balance weight reached its limit. 

Compliance (vertical/lateral)

15cu / 18cu

This is the first time I have noticed vertical and horizontal compliance reported individually, but the frequency is not specified, and I didn’t know what cu meant .  It is higher than the 7cu at 125-Hz I saw in another review, which I previously used for the Vinyl Engine calculations.

I’ve seen a lot of negative discussions about using Sorbothane with audio components so I’m avoiding

Maybe you could turn your negative hearsay into a positive by explaining what you would use instead?

Calm down, only informing what I discovered which may be helpful.

Early on, I thought Sorbathane was an ideal and affordable option to mitigate unwanted vibrations. But after combing forums, many reported it negatively affects the Sonics. Seems that not all vibration mitigation devices work well with the internal micro vibrations of electronic components.

I use a HRS RXR rack with RXR vibration reduction isolation platforms. Seeking another stand alone platform for my 61kg (135lb) integrated. HRS seems best but a tough budget reach. Also plan to add CMS Center Point Footers which after sonic roller coaster it settles to great sonic improvement. Guessing it somehow harmonizes the micro vibrations- a bit over my head. Personality, I do not need to understand the process as I’m primarily interested in price/positively increased Sonics. 

@richardbrand is this the Mahler 7 recording you referenced earlier in this thread?

@kennyc 

I also use HRS. I have two EXR 21’ x 19" racks (3-shelf, 4-shelf). My 145 lb Clearaudio Master Innovation sits on one rack, but I additionally have a M3X2 isolation base under it. I also use a R3X isolation base under my Boulder phono-stage (along with HRS's largest damping plate on top).

I can play anything without worry about rumble and other acoustic feedback, even with my full range floor standing speakers and REL six-pack.

Isolation is key to getting great performance and minimal interference out of vinyl, IMO.