And add a HUGE surface area out of time with the actual cabinet/drivers it sits on. One arrives at your bottom and the other at your ears. This has been known for years. You will receive the vibration to your bottom FIRST on a stim wall suspension or a non-friction peer-ATTACHED slab. This has been known about in all engineered concrete construction slab work. Especially in places with Bay Mud, tidal sub-soils like the west coast, and even in "Las Vegas Caliche" where you can feel the freeway on the Palace floor if not for sinking 140-180 feet of 6" reinforced torqued strand to thousands of pounds of torque. Those strands are on 4-foot centers and tie back the sides and basement flooring, holding up a 50-story building.
The building's upright structure is then set on huge decoupling isolators so the building can move within that secured vault (50-100 ft deep) as much a 2-5 feet side to side. They are moving very slowly all the time. Depending on the height, they can and do use strands and accumulators hooked from the bottom to the top for high winds.
Decoupling has been around and was practiced even on the Twin Towers. It was also used in sandy loamy soils in like Berlin, Germany, and perfected there at the turn of the 19th century.
Need to catch up a bit there.
Regards
As already posted above, the joist wood floor my smallish living room calculates out to 1800 lbs. Claiming the feet of an under one foot square, 32 lb floor standing speaker (random example, Polk ES50) materially alters the native resonant behaviour of this mass meets the extraordinary smell test.
What do you make of the Citroen hydro-pneumatic suspension? It was licensed to Rolls-Royce and Mercedes and others way back when, and outlawed in racing for its obvious unfair advantage...
I play the cello so I can address this part of the discussion. Some cellos have a rubber tip, though most have a spike that sticks into a wood floor. A rubber tip is hard rubber, so there would be no isolation. A cello puts out a surprising amount of acoustic energy, both into the air and via body vibration. Years ago I had a house with a finished basement, with carpet over cement. One day I was playing my cello which has a spike, and a friend was standing 2-3 feet away. He felt in his feet the cello vibrations that coupled into and through the cement!
Ice-skating and car suspension are really applicable analogies here wrt to decoupling and general physics. Next up is cannons and cannon balls!
And yet you seem to doubt structure born excitations.
By the way you said; "if anything, a large speaker would tend to damp the floor vibration by adding its own mass to the floor"
Added mass doesn't add damping it just adds mass, which changes the resonant modes of the floor, but it does nothing to "damp" them.
Not at all. I doubt that a competant loudspeaker cabinet flexes enough to create sufficient energy to benefit from isolation. That's totally different from a cello that obviously needs to vibrate and resonate in order to work at all. I'm sure you understand this difference, so I'm confused why you even brought that up.
This reminds me of a guy who sells speaker isolation products, and uses a video of a music box mechanism as proof that decoupling is needed for loudspeakers. The vibration of a music box mechanism is mean to be coupled to a larger surface, much like a tuning fork. But this guy is dishonest because he knows the difference between a music box and a loudspeaker, yet he uses that as an example anyway
As for a large speaker on the floor, you are correct that it will add mass. But it might also tend to push the floor down closer to its lower excursion limit, which would reduce its travel from coupled vibration. That's more what I was thinking, to possibly reduce or even stop any resonance.
It's not about cabinet flexure, it's about coupling a vibrating mass - as a lumped mass because the cabinet is solid - will couple to any structure on which it is mounted. One can isolate this vibration through feet isolators/dampers. That's my only point, but you seem to be disagreeing. I read your test and it backs up what you and I both believe is that this generally isn't worth doing. But physics says that it does something (and we need to get that right to begin with) and in certain circumstances, it could matter. (My other "only point")
Let's assume that the structure has "settled" and there are no more significant nonlinearities. (This is a virtual certainty.) Then the most that a massive sub would do on even a weak floor structure (it's mass being insignificant to the floors weight) is shift the resonance frequencies a little (very little) and with no change is the "Q". The resonances can't be "stopped" and "reduced" is a stretch. And that doesn't really change the physics of signal transmission through the floor.
IF large structural sound paths do exist, and you yourself have alluded to this, then the reason that this is such an issue is that these waves travel many times faster than sound in air. Thus it is possible to detect a vibration before your ear hears it. This can be very disconcerting and a problem that should always be resolved. For me its not an issue, so I don't study it much. My listening room is a corner poured concrete - typical midwestern construction - with damped walls apposing There are no structure borne issues.
Very interesting thread. Was just reading article linked in the above quote, and came across the following statement, "If these products really do affect the sound from a loudspeaker as claimed, it will be easy to prove using standard measurements of frequency response and ringing decay time."
Having tried one of the referenced products myself, namely, Primacoustic Recoil Stabilizers, with a pair of NS-10m near field monitors, I agree with the common subjective assessment that they tend to tighten up bass and improve imaging. Well, it turns out in more recent years the science of imaging audibility is something I have spent some time reading about and trying to better understand.
With the above in mind my question for @Ethan Winer would be, what science supports your claim which seems to be to the effect that if sound is affected by an isolator in such a way as can be perceived by humans (e.g. bass 'tightness' and or imaging), it it must only be from changes easily seen in frequency response and or ringing decay time?
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Why would harmonic distortion components be ignored? Physical surfaces are unlikely to be ideal resonators.
Actually physical surfaces, structures are most likely ( almost certainly) to be linear vibrators.