Turntable Isolation Journey

Just like in life- too much of a good thing can be a bad thing. Too much dampening can deaden the sound. That is especially true when working on room reflections. Too many reflections muddy the sound but too few makes the sound dead/dull.

If you look at a chart of a spring mass system, the response ratio is about one below the natural frequency, then wants to shoot to infinity (constrained by physical limitations and dampening) at the resonance point (the natural frequency) and then falls below one and lower as the frequency input goes well above the natural frequency. So the spring mass system is absorbing the energy that is being put into it via airborne or mechanical vibrations through the floor.

Think of a car. A car’s suspension system is simply springs. The shock absorbers are pistonic dampeners that keep the car from bouncing at its natural frequency while driving down the road. If you have ever driven over an old bouncy suspension bridge at just the right speed the spring action of the bridge can interact with the car’s suspension and make for quite an exciting ride because the car’s suspension will interact with the bridge.

You might wonder why then if speakers are sitting on springs for isolation from the floor shouldn’t they start bouncing around and dancing across the floor like an out of balanced washing machine on spin cycle? They don’t because the spring suspension system is tuned for a natural frequency around 3 Hz and speakers are not typically able to go that low. Also, the mechanical energy output of the speakers is still way below that crazy washing machine on spin cycle.

One more thing before you I start to annoy you all. A turntable tonearm is also a damped spring/mass system. The stylus in mounted to a cantilever which is mounted to a spring in the phono cartridge. The cartridge also has a dampener- typically a tiny o-ring. Phono cartridges have a compliance figure- that is the spring rate. The tonearm has an effective mass. It is not the same as the total mass of the tonearm and counter weight because the tonearm is mounted on a pivot. Knowing the compliance of the phono cartridge and the effective mass of the tonearm (always provided in the manufacturers specifications) one can calculate the natural frequency of a phone cartridge and tonearm system. Why is that so important? The goal here is to have a system natural frequency around 10 Hz. That’s because if the record has a warp- that is at 0.5 Hz (33.33 rpm) or 0.75 Hz (45 RPM) we don’t want the tonearm to have a resonance response near that frequency. And on the other side- the music frequency response starts at 20 Hz so we do not want the tonearm to respond at that frequency either. With the wrong set-up the tonearm will fly right off the record. Been there, done that.

@mulveling One very important material that is being overlooked in your list of Materials, is the B25 Panzerholz (Densified Wood), it is the most upper layer of the Tiers produced and is the one used to support all of the critical mechanical components required for the TT to function. 

It is for the best, to not overlook the magic that this material brings, when used for the role to connect all the critical mechanical operating parts together. 

I would even encourage as an investigation that Densified Wood to be used as a exchange material for the Base of the Sota TT. 

The Link will give an indicator as to the values offered from a Phenolic Impregnated Densified Wood.

https://www.lessloss.com/page.html?id=80

@pindac

The 1.5" thick brown wood layer in these Clearaudio Innovation and Ovation tables is panzerholz :)

I’ve been admiring the Taiko audio panzerholz platforms. And I’ve definitely wondered if a nice slab of panzerholz atop the Townshend platform might be a good idea.

@tonywinga Yes, I was aware the tonearm mass + cartridge compliance forms its own spring system, which can be difficult to deal with. Even when you’re right in the "ideal" 8 - 12Hz range, what they don’t tell you is that footfalls (etc) can very easily excite this resonance until you’ve properly addressed structural issues and isolation in a setup. I could observe this excitation very plainly -- by both sight and sound. Finally now with rack bracing, the Townshend, and (to a lesser degree) hockey pucks, this excitation no longer occurs :)

Probably the worst case of feedback I’ve ever observed, even worse than this small room setup (before current solution), was with one of those Clearaudio full-magnetic bearing tonearms ("Concept", "Clarify", and "Verify") on a Clearaudio table, on a suspended wood floor, near the speakers. The magnetic arms act like their own spring system, and good god their interaction with other non-ideal system factors is just pure nightmare fuel! The hybrid-bearing "Magnify" arm (rigid in one direction, magnetic in the other) was a LOT better in this regard, at least. It looks like Clearaudio has either discontinued or de-emphasized these models in their line -- no surprise to me!!

@mulveling This conversation for myself is now heating up, P'holz gets me all fired up. 

More importantly, I retired from building a system many years ago, and took on the task of working with interfaces that the system is dependent on, Electrical, Mechanical and Acoustic have all been thrashed out. This Subject under discussion on P'holz, is where I am now at with a New Material being utilised for Mechanical Interfaces and it is superseding all other choices for materials that are in use.

The Taiko Sub Plinths are very good in my view, as they are P'holz, but are even better for one other thing, they really show how much money can be saved when sourcing the Panzerholz Material B25 Cross Grain Structure oneself. If a Fibonacci Arch is routed into the acquired board of P'holz, then the Taiko is almost mimicked. By acquiring the P'holz oneself, they can be assured the Spec' for the material is the one that is most desirable, as tests available to be seen to confirm this.

How the P'holz is acquired and how much is to be paid is for oneself to decide on, getting the Spec' correct is very important.

As a guideline my last purchase of the same P'holz as above was for a Board of a dimension 2mtrs x 1mtr ( 6' 8" x 3'3") which cost £850. This could be cut to produce 10 Boards @ 500mm x 400mm ( 20" x 16"), coming in at £85 per Board that can be used as a TT's Plinth, Plinth/Chassis or Sub Plinth.

I have been using two Tiers of P'holz as a Sub Plinth, seated on and separated by AT-616 Footers. Depending on the weight of the Audio Device, I have a selection of footers to be used to separate the device from the Top Tier.

This support method has been taken to other homes as well and loaned for demonstrations, it is a unanimous agreement that betterment is to be had when utilised. Usually the assessment is that unidentified smearing is discovered as having been removed, as it is replaced by new insights to detail being presented, that is a very attractive outcome as the initial observation.

The Sub Plinth Assembly has been used under a variety of different Drive TT's, where it really shone in a unexpected way, was when it elevated a Garrard 401 to new heights. The method has also undoubtedly honed the presentation for the better from other TT's. A few who have been present during Dem's and have an interest in P'holz are now using P'holz as Sub Plinths in their own systems.

There has been similar outcomes, but not as noticeable when used with CDP's and CDT's > DAC's, the biggest audible tidy up being when Valves are present in the Digital Device.

A Valve Power Amp' that had been Imported and demo'd at a local HiFi Group event was considered to be mediocre, but OK for the retail price. When put on the P'holz Sub Plinth Assembly the Amp' become much more gathered in the lower registers and was quite unrecognisable, as the Mid's and Highs were very present as a result. 

I will suggest two uses for P'holz in your system, one will be easy to accept, the other a little more difficult, but very doable.

The idea of the extra tier added to the Townshend Sub Plinth, is the easiest to accept and will in my view be very valuable as a addition. If the material used as the additional tier is a Phenolic Resin Impregnated Densified Wood, that is produced with a Cross Grain Structure for the laminations, a compression to 50% of the original thickness is also desirable, there are other Brands of Phenolic Resin Impregnated Densified Woods that achieve this, but P'holz B25 is meeting this Spec'.

Note: It is not just the Densified Wood Material that brings on the magic, it is also the footers used as separators. The P'holz can be tweaked to a much more personal taste through trials on different footers. As stated in a earlier post, I have found the Solid Tech 'Feet of Silence' to be ideal for my unique preferences, there are much cheaper variants of these that are worthwhile trying out.  Another friend has settled on 'Sorbo Hemispheres' as their choice for a Footer, and another is using Knock Off 'Stillpoint Ultra 6's'. Trials will bring one to their own selections to suit their preferences. 

If the added tier is produced, I feel that there will be a giant step taken for your TT, to become a rival to the advanced in design sibling the 'Wood'.   

The next suggestion, and maybe not too easy to digest, but one I can't but help feel will transform the good impression further is to investigate the TT's Sidebar Tonearm Support.

I have been involved in experiments where the P'holz has been produced as a Headshell and a mount for a TA, (not a design that resembles a conventional Base Plate) Each has been A/B compared to previously used methods and each new method for a mechanical interface, has added something very special to the sonic.

Note: These changes are small, but are wanted to be maintained as they add to the attraction of the listening experience.

If the Sidebar can be swapped out for the B25 material, I do believe there will be a WTF moment from the impression being made.

Additionally, if this route is taken and a machining service is utilised to help produce the items, do ask for any waste materials to be turned into Cone Footers, this will not be regretted.     

When you stack springs you create lateral instability, bad news for turntables. The Sota turntable was special because it was the first turntable to hang from it's springs instead of sitting on them like the AR XA or the LP12. This is also the method copied by SME, Avid and the Basis Inspiration. Hanging the turntable is a much more stable system. Only a suspension tuned to less than 3 Hz will isolate a turntable from environmental rumble. Sota also uses a magnetic thrust bearing. It is compressed by the weight of the platter to a very high frequency and damped by very thick bearing oil. As @mulveling suggested it is not in any way a suspension that will isolate the turntable from anything as it does not include the tonearm and cartridge as well as the frequency is too high. This is the argument against using such a bearing as it detaches the platter from the tonearm in the vertical direction. Functionally it does not due to compression and the oil.