www.roksan.co.uk

[GABSTER001]

Hello,

I get the impression that some of the improvements in the recent Xerxes design evolutions are in no small part due to improved energy absorption and dissipation in the more recent designs.

Clearly, damping any internally induced resonances in the turntable body should result in less colouration reaching the cartridge.

If this premise is true then the original Xerxes should benefit from any modifications that improve the damping of key components like the top and bottom plinths or even the platters.

I have access to high performance self adhesive damping material that can be applied to a surface to form a very effectively damped constraint layer structure. It is used to damp resonances in aeroplane skins.

I am dying to try this treatment on the top and bottom plinths of my original Xerxes to see if it actually results in cleaner less coloured sound, as the theory would suggest.

However, I am cautious and would appreciate any comments or input from any one who has tried similar treatment and what the results and learnings were, before I go ahead and potentially regret the move.

Any thoughts or words of wisdom?

[Guy Pettigrew]

Is this treatment reversable? If not, then I'd be very wary about trying it.

Guy
_________________
Know what's important, go for it, and value it when you get it.

[GABSTER001]

Hi Guy,

Thanks for your reply. That is the concern I have too, not sure how reversible it is.

It is a very special type of pressure sensitive adhesive backed aluminium tape.

The tape can be removed but I have no idea if the adhesive will come off clean or remove some of the wood surface with it.

I bought a spare plinth from ebay (Fantozzi) with the view of experimenting at some stage without destroying the original plinth.

Based on my understanding of the theory, reducing internally induced self resonances can only lead to lower colouration. Only problem is that some of these colourations may actually sound pleasing and removing them may well lead to a cleaner but less pleasing sound.

I wonder if any one has experimented with this??

Thanks again and best regards.........Gaby

[Spartacus]

Hi Gaby

A quick and easy way to test if you are experiencing resonances from the Xerxes chassis is to remove the 'picture frame' (the outer casework) and see if you notice any differences. It's fastened by 4 allen bolts on the underside of the deck and the Xerxes will perform quite normally without this. It will remove one likely source of energy reflection.

Once you have done this you will see that the xerxes plinths are made of quite porous looking mdf which looks more like it will damp things down rather than resonate. The finish on the top plate is a veneer only. If you tap the top plate you will find that it really doesn't resonate like solid wood.

I'm not sure of the product you are thinking of applying but would expect that any adhesive will be difficult to remove from the plinths and you would need to be wary of adding mass especially to the peninsula supporting the arm and bearing which as we know can be prone to sagging.

I have never felt that the Xerxes was in any way smeared or lacking in transparency or particularly coloured and it has been described as being if anything, very CD like in its presentation. If you do feel that its performance is being compromised in any way I would look at ensuring set-up etc is spot on and then perhaps look at the turntable support for possible resonances.

All the best S

[GABSTER001]

Hi Spartacus,

Thanks for your feedback. The original Roksan must suffer to some extent from internally induced resomances, whether we hear them as nastry sounds or not.

The modifications to the design over the years to the current Xerxes20+ and TMS3 would suggest that this is the case since most of the design changes are to do with improving damping and isolation.

All constraint layer damping does is reduce any internally induced resonances by converting vibration and resonant energy to heat energy in the viscoelastic adhesive layer. It is no different really to what the BLOBS do in the Xerxes and TMS designs and one notices that as the design evolved and improved, there has been more use made of these damping BLOBS and treatments.

Even Roksan's own Upgrade Plinth uses constraint layer damping. If it is good for the upgrade plinth, what would happen if the same energy control treatment was applied to the top and bottom plinths ?

The theory is sound and has actually been implemented by Roksan and other leading TT designers to refine and improve their designs over the years.

The risk is that some of these inherent internal resonances may actually contribute to what we may like about the sound and removing them, though less coloured, may actually sound worse.

It is a fine tuning process at the end of the day - how much damping to apply and at what frequencies to get best sound improvement - which is the one thing I don't have the time or the resources to do properly.

If any one has experimented and can offer suggestions it would be great.

Thanks again Spartacus and best regards....................Gaby

[GABSTER001]

Hello all,

Just as an update, I was hoping for more input from Roksan on this topic but in the absence of it, I have decided to go ahead and follow the science.

I have finally modified my original Roksan Xerxes with constraint layer damping applied to both the lower and upper plinths.

They are now dead as rock when subjected to the knuckle test.

I have no idea what the impact on the sound is though as the deck is still being put back together with the rest of the recommended Roksan upgrades (new blobs - new oil - new belt - upgrade plinth)

I will let you know how it sounds.

Regards to all

[GABSTER001]

OK, my original 1988 Xerxes with all the latest modifications AND my own constraint layer damping treatment applied to both the lower and upper plinths has finally been set up with a Denon 103R cartridge and has been playing for the last week or so.

Apart from the constraint layer damping the other "own" modifications I have done were to replace the two solid metal tubes on which the motor is mounted with suitable highly rigid and compressed springs. I had to do this as I was finding it impossible to get the correct belt alignment with the limited adjustment possible on the original motor mounting setup.

I have also modified the antiskate spring arrangement to allow for easier adjustment to the thread length and tension of the spring. Basically I created my own O rings by cutting cross sections off silicone tubes used as fuel line on nitro operated model aeroplanes and model cars. For string I used the black string used to secure O ring guides on fishing rods. It looks identical to the original Roksan antiskate string.

Using a sowing needle, I threaded a piece of this string through one of the silicone O rings at one end and through the other silicone O ring at the other end. On the spring side I basically pushed the bare wire spring arm through the same hole in the silicone O ring as the string. This now can slide up and down the length of the spring arm and allow for fine adjustment to the antiskate tension, as per the current design of the Roksan antiskate assembly. The other O ring goes over the notched metal arm . Apart from the ability to slide the O rings up and down to adjust tension, I am also able to pull the thread through the silicone Oring and easily increase or shorten its length. Long story but saved me the time and money to get a new Roksan Antiskate Spring assembley. Works like a dream...

After all of this, the sound quality is incredible, Thank God, the best my Xerxes has ever sounded since I bought it over twenty years ago.

Of course it is hard for me to tell which upgrade or modification has contributed to what difference in sound since I did everything at the same time.

However, I am particularly pleased that the constraint layer treatment appears to have worked as I can hear nothing in the sound that is detrimental and much that is significantly improved.

In particular, the improvement in the natural decay on acoustic instruments is incredible. There is increased silence around the music and a much greater sense of the natural decay around musical instruments.

Also there is a much greater sense that the music now seems to start and stop immediately with no hint "overhang" which I was detecting slightly before all the modifications went in.

I find the musical experience complete and compelling. So much so that I find myself for the first time listening to entire records with no temptation to get up and change records or songs. The sound is so satisfying I have fallen asleep a few times while listening to music at night.

Above all, I am extremely satisfied that I have taken a big risk carrying out my own, non reversible, modifications and they seem to have worked. Thank God..

Over and out..

Gaby (Sydney - Australia)