The effect of vibration on the music playing system or

how to detect it, what effect does it have and do you need to bother...

I'm not talking about footfall but this may be an issue with some sources.

The vibrations I have in mind are mainly structure bourn, through the floor. Lets assume that for the purposes of this thread that the sound replay system is effected by these issues, otherwise there would be no point in the discussion.

The best way I've found to detect these vibrations is by the use of a doctors stethoscope.
I use this by creating a sound impulse in the equipment and stand, then listening to the various effect altering the variables of the structure make.

IMO
The effects of the structure bourne sound waves or rather why does my cdp sound better if I reduce the ammount of vibrational energy getting to it....so my hypothesis goes something like this if some of the vibrational energy impinging on the cdp and its constituent parts is absorbed by the player, its a well known that many components are "microphonic" this includes capacitors, any coils [wire], probabley the crystal ....etc this mechanical energy will be converted into heat or electrical energy. Don't believe me ? you try vibrating a wire in an magnetic field and read off the current generated. These "stray" electrical impulses must effect the performance of the player ......As I say this hypothesis does fit the observable results. I suspect though this is only one of any number of reactions audio equipment have to stray vibrational energy. Just the vibration on delicate mechanisms ie the optical read systems of cdp must have an effect?

As all substances vibrate on a molecular level, it doesn't seem unreasonable to think that adding more energy may effect that substance ...and may increasing the molecular vibration [the measure of which is of course temperature].

Are vibrations entering a cdp good or bad ? well I've never heard a cdp sound better if its put in a high vibration environment. So I'm going to err on the side of caution and say vibration is detrimental to its performance ...this of course only applys to cdps I've had direct contact with...and include most of the ranges from these makers sony denon quad naim marantz arcam plus one or two individual units from cec esoteric wadia. Each of these players sounded better once the structure bourn vibration had been controled/reduced. This of course is only anecdotal but pretty damn compelling all the same.

What can you do about it.....or a long and boring series of floor tappings.

this is where the stethoscope comes into its own. First listen to the floor and then create a repeatable sound impulse [screw handle driver tapped on the floor does it for me] make certain the impulse intensity is pretty even. Then listen to the equipment stand or the cdp if its sat on the floor. In the various systems I've tried this is clear straight away that the vibrational energy [the sound ] heard has changed ...remember that energy can't be created nor destroyed so something has happened to some of it. The over all level [volume] of the transient is much as it was but I usually hear a slight loss in the hi freq component of the impulse. As you get further up the stand and listen to higher shelves there is a further reduction in this component.

A recent experiment involved placing the cdp on an upper shelf of an equipment stand ....and carrying out the initial impulse tests [placing the stethescope on the cdp and the bare shelf, the impulse was via the floor] and then sitting the cdp on various feet and different materials.

The following tings were tried ....

extra shelf materials

5mm rubber sheet
20mm close cell foam mat
10mm granite sheet [tesco's finest work top protecter]
6mm mdf
18mm mdf
6mm glass
beech [?] butchers bloc

equipment feet

davidf's cones and discs
vecteur cones
tenderfeet cones
audioquest sorbthane feet
various homemade feet
bubble wrap[large]

These were used in isolation[pun intended] and in combination

It was clear that some had zero or next to zero effect on the impulse test these included.

6mm mdf
6mm glass [hint of a ring in the impulse]
tenderfeet
vecteur cones [very small change]

Items that attenuated the amount of impulse heard, not all did the same thing and of course some were more effective than others.

sorbthane
davidf's feet
closed cell foam
bubble wrap
granite
18mm mdf [small]
homemade feet [to a lesser or greater degree]
rubber sheet

I've not tried to discriminate between isolation and coupling, this was just to see if a range of materials will effect the level of and form of vibration reaching the player.

After a long period of testing, combinations of material ie constrained damping were tried, it was clear some combinations were rather more effective than others.

the best was, granite sheet with rubber on top with mdf on top of that , sat on a set of davidf's feet provided the very best attenuation , closely followed by the same with the closed cell foam instead of the rubber. The downside was that this was rather too thick and not especially asthetic.

The Attenuation was rather interesting in overal volume terms this reduced the transient by about 30% but if you considered the actual freq responce very little high freq was getting through.

What effect does this have on the sound of my current cdp ?
Its an obvious difference its as if the noise floor has been lowered and the music lifted out of a background mush. There'll be someone along in a minute that will tell me I heard no such thing ...which of course is odd because I did lock the front door so how they got in and from where they were able to listen I'm not certain!

Oddly the most effective items tended to be the cheapest ..bubble wrap [but its not pretty].
closed cell foam [bright blue....now wait a minute]
davidf's feet..far ahead of the commercial feet in sonic gains from the cdp.
other conclusions... it obvious that mass is good and certain complient materials form a barrier against vibration transmition.

If you've not tried any of this you could be in for a treat so how about finding out how much your systems being held back ?

 

What can you do about it

I put the source equipment in a different room from the one I listen in. No interference at all.

 

Interesting stuff pete,from small acorns......

 

a guy I knew years back (before i got into hifi) had some massive speakers and the backs of them were concrete based...from what I remember - they sounded lovely...

 

I now have my system in a redundant fireplace which is pretty much isolated from the rest of the (wooden) floor, and is shielded from the speakers (on either side) by virtue of being within a brick structure.

I can concentrate on the musical vibes :MILD: ...or at least I would if my amp hadn't just given up the ghost.....again

S'alright now, fuses blown probably due to my dodgy diy cables!

 

I always find it interesting how the audio industry gets all hot and bothered about this subject.
Anyone who is interested in this subject can look as far back as the 1930's. Pay particular attention to the vibration isolation methods used for high-accuracy, high-sensitivity optical galvanometers.

 

That was an interesting note pete....and thanks for the mention of the cones.

Pete introduced me to this subject perhpts two years ago (about).

I had contacted him in the first place requesting his cables......and got talking hifi; breifly, pete suggested i took up soem of these ideas as a low cost method (importantly) to sonic improvements.

I have dabbled quite a lot with this and now focus mainly on the ball bearing /cones combinations. I can comfirm the benefits pete speaks of.

In trueth I would (at one time) have been fairly sceptical (along I think with a few others!) about the validity or relevance of this subject on hifi sonics........IMO the results can be startling...



( I should add that Pete/Zanash has been an absolubed mine of knowledge on the subject.........he has never been too busy to help with me it )

 

I'll look it up.

Thank you.

 

Wouldn't it be more productive initially to excite the environment with sound rather than a hammer and then look at the electrical output rather than listen to the stand with a stethoscope?

You could short circuit a lot of assumptions that way.

Paul

 

Zanash,

Very interesting.

I noticed you never mentioned a bike inner tube? Also, although I don't dispute your findings one bit, I'm a bit concerned about the Tesco granite block, if it's the same one I have, black & looks fab, it rings like a bell. Place it on an inner tube & hit it with your finger. You won't believe it until you try. I appreciate the rubber may compensate for this though, sounds a bit like placing a mouse mat on the granite. Any vibration must find a way to earth though, unless it's possible to totally suspend the piece of equipment, I guess the quicker the vibration/energy reaches earth is important.

 

Good stuff Pete. Ignore this stuff at your peril folks.

The stethoscope is a very useful bit of kit for anyone into hifi. When you came round it was really interesting to check the resonance signature of the loudspeaker cabinets I'd built and to see if decoupling was having any effect.

Since your visit I picked one up off of ebay. And have been going around listening to how much things are affected by such vibrations. I don't have much to worry about with the speakers but the PC really sings when tapped and other things in the room are equally problematic.

Also try playing a high level, fullrange and very short duration sine sweep whilst listening to various bits of kit with the 'scope. You can literally hear them ring after the signal has long(comparatively) since died away.

 

paul, yeh you're right a scope looking at the electrical output on a steady state noise tone would be best.

but a stetho' is only £5 from ebay...

 

You can also use one of those piezo loudspeakers like you would find in a musical card. Connect its terminals up to a high-gain mic pre-amp. Stick it on the surface in question (some thin double sided tape is good) and you can record the resonance patterns of things. Then of course you can FFT them, CSD them and anything else you like-em.

You can also buy piezo tape called 'PZT' that can be stuck on to things so I gather. It is used in some instrument pick-ups such as for violins. But I have yet to find a place to buy any.

 

Interesting stuff.

I think if you can work out the frequency your trying to eliminate it might be worth trying some different density Sorbothane as they do a number of varying density for specific applications/frequencies. Loads of scientific/medical equipment use Sorbothane for damping.

 

Great responses .....

I agree with everything .....?

tried inner tubes a while back [15 years] none had survived to be able to try in this tranche of tests....they were effective but I was not certain I liked the effect on my cdp of the time.
There are many other things you can do to ....I've floated on of my equipment shelves on strings and also tried magnetics but thats been rather hit and miss.
System in another room is a very good solution if you can do that...I can't. though that still can't prevent any self generated vibrations [one of my cdps has a noisy transformer] but a little case loading and damping shifts the frequency of the vibrations.

peizospeakers yep thought about it but you can't get much simpler than the stethoscope .....

a laser pointer may work as well using a swinging mirror or glass of water to magnifie movement.

 

I think that Pete knows my opinion on vibration control, but for everyone else, then yes I do believe that it can have a dramatic effect on some equipment.
The most influential things I've heard were:
- The inner tube. Have to say that I didn't like the effect at all, seemed to really slug the system in question.
- Stillpoints. This uses a cone which is tipped by a low friction ball bearing. The implications being that it allows smooth motion in the horizontal plane, but prevents vertical motion. To me this was like adding a better PSU to a system, or lowering jitter in a CDP. It cleaned up the sound and simply made everything a little better. Not cheap, but in the context of an expensive system, good value.

The other thing I did notice was that pre-amps and CDPs seemed to really benefit, whilst the PSUs I've tried Stillpoints under, weren't improved at all. Make of that what you will.

 

Zanash, a project for you to try if you fancy...

How about getting a small microphone capsule and embedding it in a shelf. Then fix a speaker motor (or I thought one of those rumble things for home cinema would work) to the bottom of the shelf over the same spot as the mic. Feed the mic output to a small amplifier (maybe t-amp?) which in turn is connected to the motor. Adjust amplification and phase until vibration in the shelf picked up my the mic is actively canceled out by the motor. This would reduce any vibration in the shelf, whether it comes from the ground, air or the player.

Just an idea pretty un-thought out

 

Having played with oak and ebony cones, with steel bearings, at the instigation of Pete, I am convinced of the benefits of sound footers.

The interaction of the footer with the surface may be relevant, but I find on my Lack table surface that a BB cupped on top and bottom by concave metal cups is definitely more detailed than with the wood. Soft absorbing feet I find rob the sound of dynamics, as seems to occur with inner tubes, by the related tales.

If anyone is interested I may be able to get my local engineer to knock up some more, in a metal of your choice. I am using hardened steel, plain steel, aluminium and hard plastic, but only enough to go under my system at present. They are self-centering, but with a decent degree of lateral low-friction movement.

A last thank you to Simon for causing me work in trudging around machine shops to find someone with a CNC lathe willing to use it. Once I had tried the above mentioned style of footers I could not go back to wood.

Ian

PS the best results I found were under my SB+, with the pre in second place. The power amp, previously straight onto acrylic on a wood platform, also sounds better for 3 cups etc, but I could not face AB testing with a 110lb amp. Once it is in, it stays.

 

I was looking through this recently....


http://www.noteworthyaudio.co.uk/Equipment_supports.html


.......though I see you've tried the string/nylon chord idea pete?



"Having played with oak and ebony cones, with steel bearings, at the instigation of Pete, I am convinced of the benefits of sound footers.

The interaction of the footer with the surface may be relevant, but I find on my Lack table surface that a BB cupped on top and bottom by concave metal cups is definitely more detailed than with the wood. Soft absorbing feet I find rob the sound of dynamics, as seems to occur with inner tubes, by the related tales."


The interection between ball and cone is highly influencial (IMO)....tot he overall sound....

....to an extent where a recent mod that should have worked .....hasn't!

I have undoubtedly increased the highs and lows of the system but also robbed the sonics of something that was there previously....but is seemingly not now!







Indicates one two more changes during my next break!


edit.... just thinking;

I used beech for the cones....I suspect thats where the fault lies. Its very hard and as has been noted this can give different effects. I use oak mostly which I think works better.

 

I find music sounds a lot better through the speakers.

Michael.