"John Phillips" wrote in message
...
On 2006-09-27, Keith G wrote:

I'm in the process of chopping a nice little DD deck:

http://www.apah69.dsl.pipex.com/show/Chopper.JPG

Which is already much better since I removed the dodgy 'suspension' and
clamped it directly to a piece of, er, kitchen worktop - which has
produced
a much richer and 'fatter' sound already, but I need some feet which will
work at least as well as (and look better than) two bath sponges and a
packet of Fusilli...??

Nick G has mentioned squash balls which, sitting in little wooden rings,
would work but I'm curious about wooden cones, which I can buy for a
coupla
hundred quid or make for about 50p (still not decided...) - what I want
to
know is which way up for best 'isolation' (energy dissipation) - points
up
(from a concrete paving slab) or points down...??

I have tried out squash balls cut in half under certain bits of kit [1].

In a previous career in semiconductor devices, the group I worked in used
to mount vibration-sensitive kit on solid slabs which were suspended on
compliant air-filled rubber "springs". This certainly worked.

[1] I couldn't hear any difference with the half-squash-balls under
anything I had (but I don't use my Thorens/SME/AKG these days so I
didn't try that).


I'm not the least bit surprised to hear it - I'm on a little 'trail' of my
own, atm....

What Thorens, btw...??



[2] Optical lithography kit which aligned wafer and mask to sub-micron
precision.


I had one of those once - unfortunately the wheels fell of it...

:-)

"Ian Iveson" wrote in message
...
Keith G wrote

I'm in the process of chopping a nice little DD deck:

http://www.apah69.dsl.pipex.com/show/Chopper.JPG

Which is already much better since I removed the dodgy 'suspension' and
clamped it directly to a piece of, er, kitchen worktop - which has
produced a much richer and 'fatter' sound already, but I need some feet
which will work at least as well as (and look better than) two bath
sponges and a packet of Fusilli...??

Nick G has mentioned squash balls which, sitting in little wooden rings,
would work but I'm curious about wooden cones, which I can buy for a
coupla hundred quid or make for about 50p (still not decided...) - what I
want to know is which way up for best 'isolation' (energy dissipation) -
points up (from a concrete paving slab) or points down...??

Any Stress Engineers here? (Or I'll take the opinion of an ordinary
engineer who is at least a little bit wound up.... !! ;-)

Clamping the opposite of decoupling. Perhaps you could use clamps?

A thin layer of blu-tak or well-chewed gum under each corner should spread
the mass evenly and secure the deck against sideways forces and, er,
rocking couples.


Ooh, er....



Or bolt it down, as has been suggested, if you are inclined to worry about
high-frequency performance of blu-tak. Low frequencies won't be a problem
if the blu-tak is thin.

Cones don't dissipate energy unless they are squidgy. Squidgy cones are
unstable. Stiff cones dissipate compressive and sideways *forces* quite
well, if your objective is to raise something heavy above the ground so it
doesn't sway about. Think bridges, derricks, and the like.


Derrick's what...??



Generally pointy end up: the idea is to ensure that the cone is in
compression such that the supported weight, combined with relatively small
sideways forces, maintains the line of force from the point within the
boundary of the base, so every part of the cone is always in compression,
so the bridge doesn't fall over, even in a gale. This assumes that the
ground itself is stiff and that the bases cannot slide, and also means
that the supported weight doesn't need to be so stiff, because the pointy
ends cannot apply rocking couples to it, or vice-versa. Also to relieve
the points from the weight of the cones themselves, and because they are
easier to build that way because otherwise it is hard to climb, even with
a ladder. I guess that's why the Pyramids are point up.


I thought that was a 'Masonic' thing...???

(???)


In all these applications, the sharp end
should be effectively pin-jointed so whatever is resting on it can't
slide.

Just as cones spread force in one direction, they concentrate it in the
other. Hence they tend to make an effective pin-joint because the point
embeds itself under compression if the surface is relatively soft. If you
use them pointy-end down, as in spikes, then the bases must be prevented
from sliding. Whatever you are supporting must also be structurally stiff.

Quite what this has to do with your application I don't know. It only
makes sense for big things, so you don't waste time and materials on
unnecessarily bulky supports, reduce forces from wind and/or tide, and let
ships through. For coupling to a hard surface, thin blu-tak is better than
spiking, and chewed gum is even better, although it takes longer to run
in.


Do you recommend any particular flavour...??



Better still would be to embed the whole deck in cement. That would
relieve the bending forces on it between supports due to its weight. Not
good for cooling though.


OK, thanks for that - very reassuring to know I'm not the only nutter
here..!! ;-)

On Wed, 27 Sep 2006 21:55:16 +0100, "Keith G"
wrote:


"Don Pearce" wrote


Well, squash isn't a word that comes to mind looking at those - don't
like the look of those shears either, especially in context :-(


They ain't shears, they're scissors...

Right, in acknowledgement of the interest shown by your own good self, you
shall be the first to hear how this little experiment went:

First, you've seen my balls:

http://www.apah69.dsl.pipex.com/show/balls.JPG


Now, by means of a secret method, they are made up thus (note the interest
shown by the DLL who has nothing better to do):

http://www.apah69.dsl.pipex.com/show...&%20Friend.JPG

Here is the deck on the 'Spunj Feet' (which have just about the right amount
of give):

http://www.apah69.dsl.pipex.com/show/Spunj%20Feet.JPG

And now on the 'Bolly Feet':

http://www.apah69.dsl.pipex.com/show/Bolly%20Feet.JPG


A quick comparison (sighted, because I need help with the lifting/placement)
brought the following reaction from my resident, totally neutral 'Golden
Ears' - 'Wow! Much more 'airy' and tuneful!!'

??? ('Sonorous' was also said a little while afterwards! ;-)

Now, guess which way round that was...??

Comparisons not yet started in earnest and they will be done as 'blind' as
possible with anybody who is up for it......



In that case you just need to rest the deck straight down. The balls
won't be contributing anything except perhaps a bit of wobbliness and
a tendency to go skidding off the stand if someone coughs.

d

--
Pearce Consulting
http://www.pearce.uk.com

"Don Pearce" wrote in message
...
On Wed, 27 Sep 2006 21:55:16 +0100, "Keith G"
wrote:



Comparisons not yet started in earnest and they will be done as 'blind' as
possible with anybody who is up for it......



In that case you just need to rest the deck straight down. The balls
won't be contributing anything except perhaps a bit of wobbliness and
a tendency to go skidding off the stand if someone coughs.


The deck flumped directly onto the stand is an option I hadn't thought of
and which will be tried. It's no big deal, it's just me trying out ideas,
although there's not much doubt that taking the 'springing' off has improved
it and tightened it up noticeably!!

I will get a couple of people to hear the options and throw out an opinion -
'can't tell' will be a valid response, but I could *see* Swim was taken
aback somewhat when I swapped to the balls after the sponges after only
about a minute both ways.

If they hold up under this rigorous testing I shall need a name to market
them - also, they cost 15p a corner (you only need 3) so some idea of price
would be handy?

Say $199/£199 a set and call them Brittany Spheres?

(Swim has just suggested 'Airy Bollies'....!! :-)

In article , Don Pearce
wrote:
On Wed, 27 Sep 2006 10:57:21 +0100, "Keith G"
wrote:



Totally unstressed today - but here we go anyway.

Wooden cones wont dissipate any energy to speak of, whichever way up you
put them.

i became curious about the 'cones and spikes' some years ago. Looked at the
work on vibration in solid structure.

Three things emerged:

1) That with a cone there was no inherent reason for thinking one way up
was different to the other *unless* the materials/surfaces they seperated
have very different acoustic properties. In which case, those surfaces
determine what is going on anyway. (Here 'different' as in 'carpet' versus
'steel' rather the relatively minor differences between most solids
involved.)

2) That the actual shape doesn't matter much unless it caused plastic
deformation of the surfaces it contacts.

3) That oak had acoustic properties surprisingly similar to metals. So
choose oak if you like the look of it.

Oh, and,

4) The cones/spikes tend to transmit vibrations about as well as most
ofther shapes of similar overall size. They are all much smaller than the
wavelengths involved so tend to act as a 'lumped element'.

So if you want isolation/damping, then your deciding to go for squash balls
makes more sense. Oak cones may be prettier, though. :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

In article , John Phillips
wrote:
On 2006-09-27, Keith G wrote:


I have tried out squash balls cut in half under certain bits of kit [1].

In a previous career in semiconductor devices, the group I worked in
used to mount vibration-sensitive kit on solid slabs which were
suspended on compliant air-filled rubber "springs". This certainly
worked.

[1] I couldn't hear any difference with the half-squash-balls under
anything I had (but I don't use my Thorens/SME/AKG these days so I
didn't try that).

I have found a half squash ball works well when I squeezed one in between
the top of my DVD recorder and the shelf above it. This dampens down the
vibrations and means I can't now hear the rattling of the tinny lid as the
disc is whirled around.

Above said, I did also take of the lid and fit 'dedsheet' (from Wilmslow
Audio) inside the case and this also reduces the rattles and transformer
buzz.

[2] Optical lithography kit which aligned wafer and mask to sub-micron
precision.

Half inflated bicyle tyres in between two flat plates of wood come to mind
here... :-)

Slainte,

Jim

--
Electronics http://www.st-and.ac.uk/~www_pa/Scot...o/electron.htm
Audio Misc http://www.st-and.demon.co.uk/AudioMisc/index.html
Armstrong Audio http://www.st-and.demon.co.uk/Audio/armstrong.html
Barbirolli Soc. http://www.st-and.demon.co.uk/JBSoc/JBSoc.html

On 2006-09-27, Keith G wrote:
"John Phillips" wrote in message
...
I have tried out squash balls cut in half under certain bits of kit [1].
...
[1] I couldn't hear any difference with the half-squash-balls under
anything I had (but I don't use my Thorens/SME/AKG these days so I
didn't try that).
...

What Thorens, btw...??

Nothing exceptional. TD160 Mk1 bought new the late 1970s.

--
John Phillips

Keith G wrote:

The deck flumped directly onto the stand is an option I hadn't
thought of and which will be tried. It's no big deal, it's just me
trying out ideas, although there's not much doubt that taking the
'springing' off has improved it and tightened it up noticeably!!

I'm a great believer in mass. Lightweight stuff can work if it's done right,
but it's easier to get a result with over-engineering - heavy **** is always
harder to move. You could bolt the deck down onto a heavy slab of something
(black granite?) with some sort of damping between that and the concrete
slab.

My little Kef Q Compacts (200 quid, 10" high bookshelf jobbies) weigh 4kg
each, but, with the sand filled stands, they're about 20kg. When I tried
them full range with one amp, I was surprised at how much depth there was in
the bass, and at how solid it was. (I cut the low end at 200Hz in the
tri-amped set up.)


--
Wally
www.wally.myby.co.uk
If it ain't broke, fix it until it is.

"Wally" wrote in message
...
Keith G wrote:

The deck flumped directly onto the stand is an option I hadn't
thought of and which will be tried. It's no big deal, it's just me
trying out ideas, although there's not much doubt that taking the
'springing' off has improved it and tightened it up noticeably!!

I'm a great believer in mass. Lightweight stuff can work if it's done
right,
but it's easier to get a result with over-engineering - heavy **** is
always
harder to move. You could bolt the deck down onto a heavy slab of
something
(black granite?) with some sort of damping between that and the concrete
slab.


Yes and no...

I don't think mass per se is the whole answer. There is the unscientific
term 'musicality' to take into consideration and I'm pretty certain
overdamping and too much 'mass coupling' can do as much damage in this area
as too little....


My little Kef Q Compacts (200 quid, 10" high bookshelf jobbies) weigh 4kg
each, but, with the sand filled stands, they're about 20kg. When I tried
them full range with one amp, I was surprised at how much depth there was
in
the bass, and at how solid it was. (I cut the low end at 200Hz in the
tri-amped set up.)


.....when I loaded my Paladins with lead shot it killed them! I reduced it by
degrees until I ended up taking it all out again! Also, there are (were?) a
number of speakers that fly in the face of convention ('knuckle test' for
cabinet resonance) like the thinwall Rogers Studio Monitors I had, which
were very good speakers in their own way.

FWIW, I am also beginning to think plywood really does make a better 'horn'
speaker than MDF, but I'm a long way off a conclusion yet....!!

On 2006-09-28, Jim Lesurf wrote:
In article , John Phillips
wrote:
I have tried out squash balls cut in half under certain bits of kit [1].

In a previous career in semiconductor devices, the group I worked in
used to mount vibration-sensitive kit on solid slabs which were
suspended on compliant air-filled rubber "springs". This certainly
worked.

[1] I couldn't hear any difference with the half-squash-balls under
anything I had (but I don't use my Thorens/SME/AKG these days so I
didn't try that).

I have found a half squash ball works well when I squeezed one in between
the top of my DVD recorder and the shelf above it. This dampens down the
vibrations and means I can't now hear the rattling of the tinny lid as the
disc is whirled around.

Above said, I did also take of the lid and fit 'dedsheet' (from Wilmslow
Audio) inside the case and this also reduces the rattles and transformer
buzz.

Interesting. I might try that with a PC I have, to quieten it down a
bit more.

[2] Optical lithography kit which aligned wafer and mask to sub-micron
precision.

Half inflated bicyle tyres in between two flat plates of wood come to mind
here... :-)

The air-filled rubber springs we used were a little like short shock
absorbers and did have bicycle-tyre-style valves to allow them to be
pumped up to the right pressure. I am sure bicycle tyres would have
been less costly. IIRC we actually connected them permanently to a
regulated air line to keep the pressure correct.

The slabs we used were made of a medium-weight composite material of
some kind which sounded rather "dead" when rapped. I assume that was
part of the anti-vibration design.

--
John Phillips