In my engineering degree we studied the effects of vibration and movement on adjacent objects and machines, it is clear that one moving and / or vibrating object creates energy that has effects on adjacent objects and machines. This is particularly the case if objects are close, creating the same energy and coupled. As hifi electronics and speakers are extremely sensitive machines there is certainly resonant effect in both directions. The most obvious way is to de couple the objects, this is most often performed by separation (distance), interference (place something between them), or isolation ( de couple one or better still both, from the energy pathway). In a small room and with the need to have speakers relative close together to get proper imaging then de coupling is likely to be the preferred solution.
To couple, or not to couple, that is the question
There seems to be a fundamental difference of opinion between those who would couple their speakers to the floor (e.g., with spikes), and those who would decouple them (e.g., with springs). I’ve gone both ways, but have found that I prefer the latter; I’ve currently got Sorbothane feet attached to my tower speakers, so that they wobble or "float"—much like the Townshend Platforms videos show for that similar, but more expensive, approach. My ears are the final arbiters of my listening experience, so they rule my choices. But my mind likes to have a theoretical explanation to account for my subjective preferences.
That’s where the question comes in. A very knowledgable audiophile friend insists that what I prefer is precisely the opposite of what is best: that ideally, the speaker enclosure should be as rigid and immovable as possible so that the moving cones of the drivers can both most efficiently and most accurately create a sound front free of the inevitable colorations that would come from fighting against a moving cabinet. He says that transients will be muddied by the motion of the cabinet set up by the motion of the speaker cones. And this makes perfect sense to me in terms of my physical intuitions. It’s perhaps analogous to the desirability of having a rigid frame in a high-performance vehicle, which allows the engineers to design the suspension without having to worry too much about the complex interactions with a flexing chassis.
Am I just deluded, then, in preferring a non-rigid interface between speaker and floor? Or does it depend on the kind of floor? (I get that most advice seems to favor decoupling from a suspended wood floor, and coupling to a slab; my floor is hardwood, but not exactly "suspended" as the underflooring structure is very rigid.) Or are there trade offs here, as there usually are in such options: do I gain something (but what, and how?) even as I lose something else (i.e., clean transients, especially in bass tones)?
The ears will win this contest, but I like to have my mind on board if possible. So thanks for any input you may have on this question.
@aewarren I tried both on basement concrete and springs sound better there too.
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Millercarbon! So good to have you back! This is sufficient "theory" to satisfy my curious mind. That is, it's a clear and reasonable explanation of how and why decoupling may work the acoustic wonders it does work, as far as my ears tell me. In fact, it's because of your advocacy for Townshend podiums a year ago or so that I was led to try decoupling, albeit cheaply with Sorbothane. But I'm willing to believe I could improve things even more by at least going to Nobsound springs. Someday, perhaps. Again, welcome back. We've missed your wit and wisdom on this forum. |
Snilf, you are not deluded, and your friend (and anyone else lauding coupling) is misunderstanding the big picture. Yes in theory, in the perfect world of imagination (utopia, literally “nowhere”) then being fixed and unmoving is the way to go. Only problem, we live in the real world. In the real world when the speaker cone moves one way the speaker cabinet moves the other. The result is not what the couplers would have you believe, robbing the music of dynamics and detail. The mass of the cabinet is so much greater than the moving mass of the cone and coil this might as well be zero.
But the speaker is on the floor and so sets the floor to vibrating. Unlike the speakers the floor is not designed to be nonresonant. So now the floor is vibrating. The speaker is on the floor. Speaker and floor are a resonant system. Floor is connected to walls, walls to ceiling. In no time flat everything in the room is vibrating. All because you played some music. That’s with speaker coupled to floor. Speaker isolated from floor, now stops much faster. Where coupling obscures detail by getting lost in endless resonance, isolation reveals detail by reducing ringing. What you are hearing is with only a very limited and skewed form of isolation. Springs are much better. You can buy ordinary ones on Amazon for peanuts. But springs need to be tuned to the mass of the component to work well. This is a pita to find. So a better budget solution is Nobsound springs as then you adjust for load by changing the number of springs. This still leaves us with the problem of resonance. We have eliminated a lot but there’s still some because the springs aren’t damped. But too much damping and the spring reverts to something closer to sorbothane, which we don’t want. The optimal damping factor, at least according to Townshend, is only about 1%. This seemingly minuscule damping factor seems to be the main thing that accounts for the profound improvement of Pods and Podiums over Nobsound. That’s the theory. I never trust theory that much. So I tried all this stuff. All sorts of cones and spikes. Sorbothane. Ordinary springs, Nobsound, and finally Townshend. It’s not even close. But just in case you trust neither my theory nor my ears (which I always say do NOT! DYODD) then you can always check out the yt video where Max Townshend shows a seismic iPad that demonstrates visually and clearly exactly what I am talking about. |
I went from coupling to decoupling big time. I guess a lot depends on the construction and acoustic treatment of your room. In mine, fully acoustically treated with concrete flooring, coupling ended up resulting in too bright a sound. Now using thick maple boards with the spikes resting on metal coin like bases placed on top of thick soborthane hemispheres. Much easier on my ears, like tube vs. ss sound. The best part of that setup is I can adjust the speakers angles by simply sliding the maple boards around on top of the carpet. As the PBN Montana XPS weigh 214 lbs each, it's a wonderful setup. |
From the latest I've heard and been told the biggest problem is microphonics in our systems. It's amazing how the sound of electronics are literally changed by vibrations. And the largest source of vibrations is our speakers and coupling seems to be the best way to send vibrations from our speakers back into our systems. You can isolate each piece of gear but that seems to be putting the cart before the horse. So at this point after years of coupling(I did the first Stereophile review of speaker cones) I believe I have switched camps. |
Sniff- Did you surmise your speaker cabinets were moving or did you see them moving? My speakers are roughly 4.5’ tall- I use the rubber feet that came with them and the floor is Saltillo tile on concrete slab. I’ve never noticed a speaker cabinet moving regardless of the listening level. |
If you search back, you will find about 101 posts on this topic and many answers to wade through that both support and refute the benefits of decoupling. Folks around here have been decoupling speakers with things like hockey pucks well before the more recent craze of decoupling products became available. To your question about a "theoretical explanation" I have linked videos from manufacturers Townshend and Credo, as well as an article on IsoAcoustics Frequency Response Testing at the National Research Council of Canada, and a thread posted about springs on the dreaded Audio Science Review. I hope this helps - draw your own conclusions, and good luck convincing your "very knowledgable audiophile friend"! |
Thanks folks. But my question was more theoretical than practical: as far as practice goes, I’m sure my system sounds better with the speakers decoupled on Sorbothane feet. But the theoretical question remains: WHY? It would seem, as my "expert" friend argues, that a rigid structure for the drivers would be better. It makes intuitive sense that the motion of the speaker cones will necessarily move the entire speaker enclosure on that "floating" platform, even if in only very tiny amounts. This—again, it would seem—should "smear" transients, especially at lower frequencies, which should result in a subjective experience of reduced clarity, locational specificity, and so forth. Only Eric has addressed this, and he only very briefly. That having woofers closer to the floor would be better is consistent with my intuition here: the moment of inertia on a tall tower (49"), if the woofer(s) are mounted high, will be greater, and thus the movement imparted to the enclosure will be greater. As it happens, my speakers employ the "D’Appolito" array: two 6.5" woofers, one above and one below a dome tweeter, all three of them at the top of the tower. And yet, the speakers DO NOT sound smeared or compromised when standing on rubber. Why not? |
I agree with Eric, it is complicated and floor does transfer sound. I tried to couple (spikes) and decouple (Vibrapods) and cannot say one way is better than another - just different sound. I moved recently from wooden floor/basement home to one on the slab with ceramic tiles and resonances are completely gone, but it might be caused by different dimensions of the room as well - back wall 2x further away (less of the room effect at bass frequencies). Vibrapods and such make speaker less stable - important with kids. Spikes over large/wide granite slab on isolation (like Vibrapods) might work well. They also sell in gardening stores, heavy as hell, garden concrete columns/pedestals - very cheap and way better than stands (if you need them), as long as you can tolerate such atrocity in your room. |
I had always thought that the best possible situation was spikes thru the carpet into the concrete ( at my house) floor. With a LOT of urging, one evening I removed the spikes and replaced them with the GAIA feet from IsoAcoustics and realized that my preconceived notion was wrong. Bass was more pitch accurate and mid-range smear that I was unaware of was suddenly gone. These are rather large floor-standers (110 pounds each). I have no clue as to why the GAIA's make such an improvement over spikes, but they certainly do and are worth the time/effort to try. I have no affiliation with the manufacturer or distributor. |
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I do agree that you want the speaker to be unable to move back and forth, but the total answer is complicated. Big feet may prevent the rocking against the woofer motors. Floor standers with woofers close to the floor have less of this problem. Soft feet may make transmission through the floor less likely. The worst thing you can do IMHO is to rest an entire speaker surface against the floor. Everything else is probably going the right way. I just had the very unusual experience of "hearing" my kittie purring through the floor. She was resting on the carpetted floor, about 6" from the front leg of the couch and if I rested my head on the pillow of the couch I could hear her. So sound travels a lot more through the floor and other surfaces than we realize. |