Feet (not Spikes) for Speaker Stands

[zeon]

One solution to spikes touching the floor is Something Solid s missing link feet, which floats the stand on a
tensioned rope arrangement, thus spikes not touching the floor at all. Worked well for me with good sound improvement,
though can be fiddly if speakers moved around on a regular basis. See Deco audio website for info.

 

[Tony L]

The problem with steel spike/wood or spike/concrete interface is impedance mismatch. For s better energy transfer into wood, a layer of material that has stiffness modulus in between of the two materials is needed. I use graphite/epoxy pads, with very good results.

Though surely that logic starts from the premise/acceptance that you want to use a spike? Why do you want to use a spike?

 

[Darren L]

what you describe is not constrained layer damping. This is a very specific structure comprising very thin layers (the layer to be damped) and the constraining layer, sandwiching a viscoelastic (ve)layer, which also must be very thin. All layers must bend, which effects the damping, so that shear forces are set up in the ve layer. Your structure is just a structure, which may comprise some form of damping, although not cld.

Okay, a misnomer on my part, though I can't find any reference stating that it 'must be a very thin layer' and in context of a room I would suggest the 25mm slab and >25mm carpet and underlay are fairly thin layers.
Anyway regardless of the terminology used I've found this sandwich method to be a very effective & practical solution.

 

[Helen Bach]

yep, the cld thing can be very confusing, there are lots of mentions on audio sites, most of which is incorrect.

To work, layers must be thin, by which I mean mm thicknesses. Cld works by the layers bending, which stretches the thin viscoelastic layer, which provides damping. If any (or all) of the layers do not bend, there is no cld. I have some tape made by 3M, which they describe as a damping tape, and it is only 0.4mm thick (or should that be thin!).

Much of the confusion arises because the term is often applied to turntable plinths, the constructions of which are never based on the cld principle. HTH

 

[Darren L]

Yeah, the references I found were not on audio related sites but mechanical engineering sites
relating to the aerospace industry:

Constrained-layer damping is a mechanical engineering technique for suppression of vibration. Typically a viscoelastic or other damping material, is sandwiched between two sheets of stiff materials that lack sufficient damping by themselves. The ending result is, any vibration made on either side of the constraining materials (the two stiffer materials on the sides) are trapped and evidently dissipated in the viscoelastic or middle layer.

 

[ampedup]

The problem with steel spike/wood or spike/concrete interface is impedance mismatch. For s better energy transfer into wood, a layer of material that has stiffness modulus in between of the two materials is needed. I use graphite/epoxy pads, with very good results.

Dimitry, can you expand on this understanding. What do you see as the better method for speaker stand/carpet interfaces? Doesn't the speaker design have to be considered part of the system? For instance, LS3/5a and their lossy-designed cabinets surely would lead to different considerations of speaker support/speaker stand/carpet interfaces?

 

[DimitryZ]

Though surely that logic starts from the premise/acceptance that you want to use a spike? Why do you want to use a spike?

Spike is there to prevent speaker motion in response to driver motion. It helps the cabinet to serve as inertial ground for the driver.

It's the same reason Rega puts a very stiff brace between the spindle and arm - so the arm can correctly measure the groove.

 

[suzywong]

PS: IsoAcoustics do offer a threaded version but it's too expensive:
https://www.audiovisualonline.co.uk...ustics-gaia-3-threaded-isolation-feet-4-pack/
I mean, I can afford them but I don't believe they're worth that kind of money.

Couple of years ago, at the London Indulgences show, Naim-Focal did a demo where they lined up two sets of Focal speakers, one pair of which has these IsoAcoustics Gaia feet, the other spikes. they had the two left speakers positioned together side-by-side and similarly for the rights, so the inter-speaker gap between each pair would be the same. They could then switch between the two pairs "on the fly".

I suppose you can guess the result.......the Gaias made a significant difference for the better. Very obvious, and of course, eminently repeatable during that demo.

I'm tempted to try Gaia3 under the SBLs (currently using spikes & spike shoes onto ceramic tiles laid onto concrete), but at £400..........

 

[johnacurtis]

I used the M8 DIA. 30mm x 40mm long versions of these on my Shahinian Compasses. Absolutely brilliant to sort the bass boom through the house and tighten the bass notes up!
https://www.ebay.co.uk/itm/223700384876

 

[Helen Bach]

Yeah, the references I found were not on audio related sites but mechanical engineering sites
relating to the aerospace industry:

Constrained-layer damping is a mechanical engineering technique for suppression of vibration. Typically a viscoelastic or other damping material, is sandwiched between two sheets of stiff materials that lack sufficient damping by themselves. The ending result is, any vibration made on either side of the constraining materials (the two stiffer materials on the sides) are trapped and evidently dissipated in the viscoelastic or middle layer.

yep, not really correct, but better than many. The middle layer has to be viscoelastic. This is an example of a simple cld, but there are many others, becoming quite complex, but I think we don't need to go any further. Suffice to say, your structure (and mine) have more to do with 'The society for putting things on top of other things' as Monty Python once said!

 

[johnacurtis]

Ahh, they work better than my ability to paste a link that works!

 

[Tony L]

Spike is there to prevent speaker motion in response to driver motion. It helps the cabinet to serve as inertial ground for the driver.

That is a remarkably theoretical piece of thinking! The reality is the floor isn’t stable, the stand isn’t stable and therefore the speaker isn’t stable. Everything has some resonance. Also factor in the mass of the speaker/stand assembly and the frequency of energy in play - do you really think a typical bass-mid driver has the ability to shift a 5kg+ speaker on say a 20kg stand much in the audio frequency range. If all we listened to were single subsonic DC pulses every 30 seconds or so, then yes, you could probably set up sufficient motion to move the whole assembly more than a tweeter wavelength, but a speaker reproducing a wide-band multi-frequency signal just isn’t going to get moving further than it’s inherent cabinet/baffle resonance. A far better strategy to my mind is to prevent resonance being transmitted, generated or amplified by the floor or other surfaces.

It's the same reason Rega puts a very stiff brace between the spindle and arm - so the arm can correctly measure the groove.

I see your Rega and play my Well Tempered and Schroeder cards!

 

[DimitryZ]

That is a remarkably theoretical piece of thinking! The reality is the floor isn’t stable, the stand isn’t stable and therefore the speaker isn’t stable. Everything has some resonance. Also factor in the mass of the speaker/stand assembly and the frequency of energy in play - do you really think a typical bass-mid driver has the ability to shift a 5kg+ speaker on say a 20kg stand much in the audio frequency range. If all we listened to were single subsonic DC pulses every 30 seconds or so, then yes, you could probably set up sufficient motion to move the whole assembly more than a tweeter wavelength, but a speaker reproducing a wide-band multi-frequency signal just isn’t going to get moving further than it’s inherent cabinet/baffle resonance. A far better strategy to my mind is to prevent resonance being transmitted, generated or amplified by the floor or other surfaces.



I see your Rega and play my Well Tempered and Schroeder cards!

Tony, can you easily find the result plots from FEA that I published? They show how much the cabinet moves coupled to the stand via spikes and with resilient mounts. The stand was spiked to ground. There were also modal analysis results for both systems.

While floor is not rigid, it is the only ground available. Any mechanical transducer needs ground to work. It's either the floor or the mass of the speaker. It's better if it's both, especially if you have a good floor.

It's on page 4 of this thread:

https://pinkfishmedia.net/forum/threads/speaker-isolation.226791/page-4#post-3647901

 

[Rug Doc]

May sound silly, but as I see it, spikes are there to add mass to the cabinet, by including the floor/structure as part of the cabinet itself... It’s all about transferring the resonance to a larger mass, which is then more efficient at dissipating the energy.

The opposite is sorbothane treatment, which in itself is there to absorb the resonance.

Tonys little felt pads are doing a bit of both - it’s so difficult to know what’s best.. on a floating floor I’d be tempted to go for a sorbothane treatment (or felt pads!) on a concrete floor I’d use spikes to get to the larger volume of mass available.

 

[Tony L]

The interesting thing is there is now debate. Back in the ‘70s speakers were just plonked on the floor, bookshelves, piles of bricks or whatever was to hand. In the ‘80s we were conditioned to use spikes as Linn, Naim, Mana, Heybrook, Foundation and much of the audio press absolutely insisted on it. The only debate at that point was between low and high mass. Since that point we have recognised that speaker support structures certainly make an audible sonic difference, but it is far less clear what the best approach is. We still have spikes, far too many of them IMHO, but we also have suspension (Townsend, some speakers e.g. Audio Physics have sprung bases, MEGs are on very wobbly/springy un-spiked stands), we have Sorbothene and other compliant rubber supports, plus Blu-Tac and felt pads for the speaker/stand interface, and damping foam still seems to be the most widely used support in the recording industry (both for meter-bridge nearfields and soffit-mounted main-monitors).

The fact there is no consensus actually meets with my approval as to my ears the different approaches all bring different strengths and weaknesses and which is right will match one system/room and listener’s priorities, and not another’s. I certainly think it is one to experiment with rather than to blindly accept someone else’s theory. As ever if it sounds better it is better!

 

[Helen Bach]

May sound silly, but as I see it, spikes are there to add mass to the cabinet, by including the floor/structure as part of the cabinet itself... It’s all about transferring the resonance to a larger mass, which is then more efficient at dissipating the energy.

The opposite is sorbothane treatment, which in itself is there to absorb the resonance.

Tony's little felt pads are doing a bit of both - it’s so difficult to know what’s best.. on a floating floor I’d be tempted to go for a sorbothane treatment (or felt pads!) on a concrete floor I’d use spikes to get to the larger volume of mass available.

Hate to disagree, Rug, but mass per se doesn't damp. And transfer of vibrations will only be quantitative if mechanical impedances are close. Sorbothane will isolate the loudspeaker, as its mechanical impedance is too far away from that of the speaker or floor. Also, it will not absorb any energy, and dissipate little, as it deals best with shock rather than harmonic waveforms (music).

Tony's last paragraph is entirely apposite, in my opinion. So many different approaches to so many different situations. Although I don't go along with his final sentence. To me, it should read, 'if it sounds good to you today, it may sound pants tomorrow'.

 

[stevec67]

You can get carriage bolts in M6 or M8, look them up. They cost pennies in diy shops. You get a rounded head which might suit.

 

[joe9407]

I suppose you can guess the result.......the Gaias made a significant difference for the better. Very obvious, and of course, eminently repeatable during that demo.

I'm empted to try Gaia3 under the SBLs (currently using spikes & spike shoes onto ceramic tiles laid onto concrete), but at £400..........

I laid out the dough for the Gaia 3s a couple weeks ago and found that they're one of the very few audio tweaks that actually do "what they say on the tin". The Gaias are butt-ugly compared to the brass cones supplied with my speakers, but I'm afraid I don't want to do without the delicacy and clarity the Gaias have brought to the proceedings. They're well worth a try, particularly if you can find a used set.

 

[DimitryZ]

Hate to disagree, Rug, but mass per se doesn't damp. And transfer of vibrations will only be quantitative if mechanical impedances are close. Sorbothane will isolate the loudspeaker, as its mechanical impedance is too far away from that of the speaker or floor. Also, it will not absorb any energy, and dissipate little, as it deals best with shock rather than harmonic waveforms (music).

Tony's last paragraph is entirely apposite, in my opinion. So many different approaches to so many different situations. Although I don't go along with his final sentence. To me, it should read, 'if it sounds good to you today, it may sound pants tomorrow'.

Concept of mass damping is quite well worked out by one named Raleigh.

Adding floor mass to the speaker reduces the speaker cabinet parasitic movement in response to the driver accelerations. The cabinet is heavier than the cone, so it doesn't move a lot. But move it does - and we want it to move less. Increasing its' dynamic mass is what floor spiking does.

We can damp this motion with viscous damping, but it again needs a ground to work against. Heavy speaker stand may be enough, or not. But your floor is very heavy, the heaviest thing you have available in domestic environment.

Further, achieving very high damping ratio with bottom only isolators is very difficult to do. Even with naval cabinets isolated with HERMs, getting 20% damping is an effort. Coupling the speaker to a known very high mass rigidly is much more certain.

Finally, high frequency energy draining through the spike interface does require impedance matching, as pointed out previously.

Ideally, one gets reduction of low frequency cabinet swaying AND reduction of high frequency cabinet flexure. I also damp my woofer enclosures with Isodamp sheet....of course.

 

[Tony L]

But your floor is very heavy, the heaviest thing you have available in domestic environment.

I’m not convinced. In the UK at least most floors are wooden boards over joists, I’m not sure of the exact measurements, but from memory about 7” x 1/2” x pretty long. A floor is conceptually not hugely different from a giant guitar soundboard.

One of the reasons I’m a big fan of a good carpet plus underlay plus rug situation is to apply as much damping to the floor as is possible, as in most cases it is an obvious resonator (the other reason being I also view it as the ‘dead end’ vs. the ceiling acoustically).

Anyone who has ever owned a suspended turntable with a high centre of gravity (Linn, TD-160 etc) will know this only too well as in most UK rooms you have to tiptoe around like a cat burglar in a sleeping household or the turntable will jump. The floor is often not a stable or stationary structure. It has a bounce, one or more resonant frequencies or points of movement.

Sure, the Earth’s gravity tends to dictate that speakers and their stands end up on the floor, but we should not necessarily view that as an ideal, especially when it comes to physically coupling them and transmitting energy and vibration.