Rubber Feet Seem Like a Scam

[mike7877]

At least a lot of the ones I'm coming across on the biggest, least scamm-y platform we have... (o ya, the tl;dr is at the bottom in point form if you're not interested in science)
So I just spent the last 20 minutes perusing a plethora of silicone speaker support pads/ plinths and whatever else, finding things that look very overpriced for what they are, scrolling through description sections which don't often exist, actually. ..You click "more details/info" or whatever it says in blue text where you're supposed to click to expand at the usual 3-5 bullet points at the top of the page (why usual? because there's less here... or sometimes, ..yes.. , none.

Something about when there aren't enough words... it bothers me -I can't help it - especially if it's important, and ESPECIALLY if it's on purpose. Then I can't help myself... I just, start, thinking. If you put 10lbs of force onto little rubber foot like that... it's a bit bigger than you'd expect a usual foot would be (one picked for grip and scratch protection (ie. the usual and obvious) vs. vibration isolation (which is insane)), It's like 7/8" x 7/8" or 20mmx20mm - a bit bigger than those 9x3.5mm rubber drawer stoppers lol.
So its sides with surface area are or 4 sq. cm (cm2) per side, and volume 16 cu. cm (cm3). OK, from here, now... because my speakers are just under 40lbs, that means each foot is getting a little less than 4.5lbs - let's call it 4 for math purposes.

We have 4kg on each surface area, together being 8cm3
and 4kg is compressing that cube, 0.25kg/250g per cu cm3

I dunno... rubber and silicone has lots of variables to consider. How malleable is it, probably being most important. It behaves a little like a liquid as welll, but only a little. I think that's the part we're hoping the vibrations to enter and then interfere with each other is the fluid aspect, and then let the low malleability be the resistance which stifles and (hopefully) extinguishes vibrations before they reach the other side.

The cubes I'm looking at claim "up to 15lbs", so the designers probably would expect people with 8-17lb loads to end up with them. While sound dampening performance is within the designed range: specification until at least 15lbs-performance would be a little better a bit below 15lbs, the optimal performance. Maybe 12.

It would be bad for someone to have a 40lb speaker, and instead of using 15(x4=60lbs total for 40, they instead got the 25lb package thinking "they'll be even softer then, absorb more, eh!"
When too much compressive force is on the damper, the compressive and tensile stress work against each other, effectively hardening the material. But as long as the tensile strength can endure the excess weight, the material will survive.
And just the same in the opposite direction, if you get the 150lb set for the 40lb speaker, there won't be enough weight to make the very solid and very very viscous state change into that sweet spot where there's enough softness between the compression and tension that the vibration can enter and then the friction can make heat instead of noise.


I haven't seen any of the manufacturers going into the science of these foots beyond "recommended weight"

Well, I don't trust final specifications from random, faceless people on Amazon making company names of random letters because they have to start new companies all the time for ....some, reason..... It's not even a specification like "with this much weight and full contact area, attenuation at 25Hz is <3dB, 50Hz is: 4dB, 100Hz: 5dB, 250Hz: 5.5dB, 500Hz: 4.5dB, 1kHz 4.0dB, 1.5kHz: 3.5dB, 2k: 3.0, 5k: <3dB. And then they give the same frequencies at two other weights - if it's rated for 15 max, maybe you'd check 14, 11, and 8lbs, plotted on the same chart, along with the properties of the rubber - how malleable is it? Taking a standard size, pretend it's 30x30mm, how much crushing weight does it take (with full top and bottom contact) to compromise the rubber's integrity: specifically, when did that crushing (which is just stretching in another direction) result in a visible rip?

So if we had that number always taken of a 30x30 cube of rubber-like material designed for 20-200 pound speakers, that would be something real. to look at (if they're honest about it...)
How accurate it is across different sizes, and if there are other or aspects that are important that I haven't thought of yet and probably can't think about with my knowledge base lol.


If you know how these feet work: the physics of all the the relevant properties of rubber for damping, how they affect one another and have the talent for explaining things really well, that would be incredibly enlightening to me and I'm sure many people (to know what properties of a rubber foot pertain to the weight it's best for damping. And how increasing and decreasing weight changes from optimal. Are there discernable upper and lower shelves? If so, how much does damping vary once you reach them (within reason - not feather light and not damaging). How does increasing or decreasing the weight from the default, change the frequency attenuated to the highest degree? And this frequency... what's it called, the inverse resonance? haha. Oh, and finally, size - you know more than me what'd be best to say about size, I just want to hear about how it affects things, and shapes, how they might affect things - I've seen hemi-spheres, pyramid-type looking things, cubes, cylinders... Tall vs short?

Obviously the topic could be discussed in useless depth for our speaker isolation purposes, but as a formal physics person, you know how far too far is lol


To those who don't have the knowledge (or the spare cycles if you do),

- do you have isolators?
--if you do, what are the speakers on? The floor? Stands? Are the stands on the isolators? Were they sitting with a large contact area, like the bottom against a desk?
---are they not on speakers, but your turntable or amplifier, or both (or some combination of them and your speakers. or other equipment - it could be anything)
- do you like them? How do they affect the sound of whatever you use them on?
- rephrased, what is something you found out about isolators from installing and using yours that was an unexpected surprise - not that it went against what you wrote, but it came out of nowhere




Edit: removed junk sentence at bottom I didn't see lol

 

[wwenze]

I just know they stop scratching

 

[OCA]

They will only help rising tweeter to ear height if you need that with your seat.

 

[Chrispy]

Only reason I used rubber cabinet feet on my DIY subs was to prevent movement...they worked fine for that. Speakers on stands I find something like museum putty/blutac works fine

 

[mike7877]

Only reason I used rubber cabinet feet on my DIY subs was to prevent movement...they worked fine for that. Speakers on stands I find something like museum putty/blutac works fine

40lb total weight, 9x10x17 inch constrained layer box (with personally applied, strategically set bracing, upgraded hardware to fasten the drivers (T-nuts and m8/m4 (W/T) - the cast iron baskets and machined alloy front plates can take it!
>20lb woofer, the expected (and respected) double stacked front panel, placed on equally heavy, stylish standss.
I have some half thickness drawer stops (rubber feet) in each corner which are crushed from maybe 3mm to 1.2mm (especially at the front under all that woofer!)

I think, in my situation, any damper would be a complete waste, no matter how ideal for the size.

If you've got 6 minutes to read what I wrote, I outlined a way that these types of things can be publicly categorised for public use (and not just coincidentally enthused at the right moment physics nerds with speakers with very little freedom to improve otherwise - I'm thinking like Physics student with studio monitors on the two flimst LDF (not M, L-DF) rickety in the air, he's tired of the noise radiated from the bottom of his $350 powered pair's lively box - its 6x8" surface is in contact with the 12x16" shelves, effectively tripling the 250-700Hz range... And that's only the worst problem until the whole thing starts vibrating around from the bass, rattling sharply like phone damaging itself while receiving a text naked on granite (Ouch!)

Anyway, I think you should read it - it's a bit rough because I'm not a physician physicist, but probably neither are you so maybe this is the best way for you to understand (I was also slightly tired so don't think I'm normally into feet like this, I'm not. I just.. don't feel like trying to shorten what I already tried so hard to make as short as possible so people would read it, understand, and have no questions because that's a real time saver for the topic and future people who stumble across. Not so much me... but it's less fragmented in time and clouded by distraction

 

[mike7877]

I just know they stop scratching

You had nothing to add so you referenced my joke to let me know you read it!

Or.. ...you didn't..
And our funny are just similar.

I liked my first assumption more - at least that way, if your brain realised something in the background after -while you were doing other things (like brains tend to do from time to time) - something could have been coming... At least there could have been potential for an indirect contribution to progress).

 

[Roland68]

I generally don't use silicone or rubber under my devices or speakers. If it comes with something like that, I remove it and place it on something very hard.

 

[MAB]

There are tests. The ones that are executed carefully (controlling for mic and speaker position, which is critically important), show tiny measurable differences, way below audibility. Ethan Winer for example:

Testing Loudspeaker Isolation Products

ethanwiner.com

Ethan points out how critical it is to get the speakers and mic into same position between runs, otherwise measuring placement changes, which turn out to be order of magnitude larger than type of feet. I find millimeter position changes are much larger difference than type of feet.

I've also measured the impact of different feet on an old hardwood floor, since people often struggle with bouncy floors and end up endlessly chasing a solution, often spending big on fancy feet.

Tower speakers on hardwood floors: spikes on discs/coins? Sorbothane/silicone pads? Springs?

From what I gather it seems to not matter much for a regular concrete floor, but what about tower speakers and subwoofer for a pier and beam type house ?

www.audiosciencereview.com

The differences are down to run to run. Wind, traffic, and mic placement repeatability play a larger role in run to run measurements. I also measured distortion:

Tower speakers on hardwood floors: spikes on discs/coins? Sorbothane/silicone pads? Springs?

From what I gather it seems to not matter much for a regular concrete floor, but what about tower speakers and subwoofer for a pier and beam type house ?

www.audiosciencereview.com

Once again, the differences are negligible, differences are run to run repeatability. If you have a bouncy floor feet won't help, placement may help.

I have put sand in stands to explore how controlling resonances in stands, which also allegedly have a big impact on sound. To be clear, stands are just tall feet. I measured tiny changes between sand and no-sand, way below threshold of audibility. In other words, no difference.

Springs Under My Speakers: What's Happening?

LOL, let's keep going, prove that you have a window. I want proof Purite Audio even made that post before it's worth answering. Could have been hacked. Or his wife posted while he wasn't looking.

www.audiosciencereview.com

I did very carefully control for mic and speaker position between filling with sand, controlling to within a couple millimeters, which is the most important and the hardest part of the experiment (as Ethan Winer mentions in his excellent test). Controlling for position was not done in many of the other 'tests' in that "springs under my speakers, what's happening?" thread, which is why the thread never actually answered it's own question.