Zargon, your case is the special exception I mentioned earlier, namely: you have a transducer (subwoofer) that moves up and down, same as the (only) direction the floor can move. So naturally it can mechanically excite the floor (grab it and shake it) in that direction at 34 Hz or whatever. But a normal forward facing transducer can't do that because the floor can't respond to its forward-backward motion. A woofer or sub can of course possibly excite strong standing waves in the air in a room (not the speakers' fault, just a factor of the room dimensions) and these standing waves can excite the floor to resonate. My point is that to decide how best to accomodate a speaker, one has to look at how it might want to move and then figure out how best to restrain it.
Gammajo's analogy doesn't really apply to loudspeakers for two reasons. First a vibrator's action is usually rotational (semi-omnidirectional), and loudspeaker transducers are reciprocal, whether they're cones or electrostats. Second, a vibrator is designed to transfer energy to another solid (your body). But loudspeaker transducers must absolutely NOT do that (transfer any energy to the enclosure.) ALL their motion must go into vibrating the air. That is why the speaker enclosure or frame must not vibrate (resonate) or be able to physically move (like rock back and forth on rubber pads or a rug or a too-flexible floor.)
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Obviously even well constructed speakers vibrate or spikes would not work their way right through pennies placed underneath them.
Given all the divergence in answers, I decided to approach this logically through a hypothetical example. Please tell me where you think my reasoning is correct or incorrect. Lets say we place a vibrator on a kitchen table when the kids aren't home. In my example the vibrator is equivant to a speaker.
We turn it on (turn about is fair play). What will it do? It will clatter. This is equivilant of a poorly coupled speaker. Then we press down on it adding weight. Now it is coupled to the table and the table will act as an amplifier of the vibration - rather the disipate, the noise will get louder, true? This would be similar to a coupled speaker interacting with the wood floor. The speaker is now less vibratory but the table is magnifiying the sound.
Next we place an inert substance such as styofoam, sand, or rock between the vibrator and the table. We now get less noise. This suggests to me the best is to firmly couple the speaker to something rigid enough to reduce the speaker's vibration,and under this have something non-resonant so that the vibration is not passed to the floor. |
I had speakers with cones and down firing subs sitting on a suspended floor in a relatively new home. The floor has a resonant frequency of 34 hz, and I know because at that frequency the amplitude of the vibrations increases so much it shakes the chair and tickles my butt!
To solve it, I cross braced the joists, put a post under the center of the floor, and put a piece of slate between the cones and the carpet (isolation). This combination works very well indeed, and there is no visible movement of the speaker tops.
So, my experience and that of Fiddler are very similar, in that we both found isolation was necessary on a suspended floor. That does not mean coupling should never be used, as these same speakers on a concrete floor shine with just the cones. |
If the floor seems to be the offending item, I always recommend fixing the problem, instead of adding some other item into the mix to try to mitigate the floor problem.
Nsgarch has some good advice about locating the speakers over the joists, and there can be supports placed under the joists too. |
inpepinnovations - stick around here and you'll find out. Otherwise, just buy the cheapest new stereo you can find and enjoy how well it measures. |
Whether to couple, decouple and dampen, etc., is determined by experiment. Theory does not help because whether any result is positive or negative depends on a wide range of factors. With a suspended wood floor, coupling will mean that the floor will be able to better act as a resonant sounding board itself. That is good, if you want some bass/midbass warmth, and bad if you want to tighten up the bass.
I personally use a Symposium Svelte shelf under my speakers. This thin, multilayer platform is coupled to the whole bottom surface of the speaker enclosure for effective transfer of vibrational energy to the platform. The inner layer then converts that energy to heat. This is an effective way or reducing the shaking of the speaker itself (generally not a good thing for sonics), and dissipates this energy instead of transferring it to the floor. This tightens up the sound noticeably, which is a good thing in my system. |
Nsgarch, even though we "beat a dead horse" for a while, I do appreciate your willingness to offer your expertise. I have learned a lot from many like you here on the 'Gon who have always been eager to help.
And just as an aside, I don't believe "incompetants" is a word. But what do I know since I am not one of the...uh huh...brilliant ones :) |
Fiddler, as in all professions, there are some incompetants, many bright ones, but few brilliant ones. The fact that your problem was solved with a speaker change and not with a construction project is what led me to my conclusion ;~)) |
Nsgarch, you could be right, but I doubt it since I fixed the problem with decoupling like many others have here.
I might not have a minor in acoustics from MIT and I also don't have an engineering degree either, but I can tell when my car is spark knocking and how to fix it from the experience of others. But I certainly don't need to tear the engine down!
The fact is, I did cure the problem in my room without having to tear my floor up or re-engineer the joists as you suggested. But I guess if you can't find a simple solution like decoupling there's always the big hammer approach, huh? And btw, being a licensed contractor doesn't mean you are an experienced builder. You know there are licensed contractors and licensed contractors!
And I anticipated your, "There are architects and architects; sorry you didn't find a better one.", after your, "apparently you have a very under-engineered floor."
From your attitude, it appears that you are the only competent architect around. Too bad everyone just doesn't hire you. |
Fiddler, I am an experienced builder as well as a licensed architect. I also have a minor in acoustics from MIT, and trust me, you don't begin to know whereof you speak, your limited personal experience notwithstanding. There are architects and architects; sorry you didn't find a better one.
As for your resonant floor, speakers coupled to the floor can't possibly move the floor for the simple reason that, except for down-firing subwoofers, transducers only move horizontally and floors only move vertically. So whether you say 'bounce' or 'resonate,' the floor would have to move; and if it doesn't, then perhaps the floor isn't the culprit; it could have simply been a standing wave between floor and ceiling created by an identical frequency peak in your previous system's response curve.
My guess, after all you've described, is that your new system's response is such that the natural room oscillation (standing wave) that got excited by the previous system, now doesn't occur. |
Nsgarch, I have a 3 year old home and I seriously doubt it was under-engineered. Apparently you are missing the point. I don't have a bouncy floor. I have a resonant floor. They are the result of the same problem, just a long way apart. When I walk on the floor it is not bouncy. But certain bass frequencies made it resonate when I had rear ported speakers. Now that I have changed speakers to OB's and a Velodyne DD12, I don't have the same problem.
However, with my previous speakers, when they were coupled to the floor they made the floor resonate badly. One of the reasons you are reducing the resonance of your clients floors is that you are adding mass, not just stiffness. The more mass you add the lower the resonant frequency.
There's no sense in us going round and round here. If you will just take the time to do a search, you will see the resonance problem is very common to suspended floors. And I am sure that all of the guys who have reported a similar problem here and on AA didn't have "under-engineered" floors.
"My solution in such cases (when none other was possible or practical) was to add a couple more layers of plywood subfloor, with the sheets staggered and edge and face nailed very well. This acts like a stressed skin and keeps the floor from bouncing excessively."
I can promise you that if you do a search you will find a very "possible and practicle" solution to the problem other than the expensive, time consuming and unnecessary fix that you employed.
And I appreciate the fact that you are an architect, but when I built my business, both I and my contractor found many practical, economical and more effective methods of doing things than my architect had drawn and submitted. Any good contractor with a lot of real-world experience will take virtually any plan drawn by an architect and improve it. No intentional slam here, but like I said earlier, give me actual experience any day. |
Fiddler, apparently you have a very under-engineered floor which is indeed being "excited" by the sound waves in the air! Is it an old structure? I have cured this problem for clients (I'm an architect) who had intolerably bouncy floors due to undersized joists put in by a shady builder (joists can be "up to code" to carry the load, but they usually need to be bigger than that to resist bending)
My solution in such cases (when none other was possible or practical) was to add a couple more layers of plywood subfloor, with the sheets staggered and edge and face nailed very well. This acts like a stressed skin and keeps the floor from bouncing excessively.
Frankly, I don't believe attaching the speakers elsewhere (like the ceiling) will keep the sound waves in the air from exciting the floor, as it is right now. |
Wellfed,
Now you've gone and done it, the Big Fat Dots are relatively inexpensive, so I suppose I am going to have to break down and try them. Still curious, how does the hardness compare with a hockey puck? Thanks, Tim |
Nsgarch, thanks for the feedback, but number 1, 2 & 3 won't work simply because the floor is being excited by certain frequencies. The problem is not floor flex, per se. The floor is acting like a drum head. It doesn't much matter where you strike the drum head, it will still resonate. Until the frequency vibrations are sinked to something with a much lower resonant frequency (such as, the ground or a concrete pad on the ground), they just rumble around until they dissipate. So moving the speakers over joists won't make a big difference. Believe me, I tried.
Stiffening the floor would cure the problem, but most effectively if it is stiffened by applying pressure from the floor to the ground, i.e. using floor jacks and posts or footings and pilings. These solutions simply change the resonant frequencies and the problem can be eliminated. But the simpler solution is to decouple the speakers. Do a search for actual results.
And according to other users, hanging a speaker from a single chain does not produce any movement of the speaker when the speaker is playing. I personally have no experience with this, but that is what has been reported from actual use. |
Fiddler, if this is what's happening in your case:
"All coupling does to many suspended floors is excite the floor which creates a delay in the sound traveling in the floor and it muddies the bass badly."
Then it's because the wood floor is flexing (what you call "excite") underneath the speaker allowing the woofer motion to rock the enclosure back and forth. Remember, it only takes 1/16" of deformation (flex) in the floor for a 5 foot tall speaker to rock back and forth as much as 3" at the top! There are three possible solutions:
1.) (the easiest) reposition the speaker so the front and rear spikes/cones/feet are on top of, or very close to, the (two closest) joists themselves (as discussed earlier)
2.) If (1.) isn't possible for some reason, then put blocking (little cross joists) between the two joists right under the speakers and/or put posts (or jacks) from the ground to under the floor where the speakers sit.
3.) If (1) and (2) aren't possible, the best solution (a bit of a hassle to do nicely, but works great!) is to run a brace (aluminum tube or plastic PVC pipe works well) from the top-back of the speaker to either the wall behind, or back down to the floor at least 4 feet behind the speaker, and secure it.
Any of these solutions will keep those woofers from rocking the cabinet instead of your ears. An additional benefit will be better highs and mid-range transients.
Hanging speakers can work also, except the chains or cables need to be splayed enough to insure that the speakers don't sway even a little. That's sort of an ugly tour-de-force don't you think? |
There are many threads on Audiogon and AA about suspended hardwood floors.
I tried many solutions on my suspended hardwood floor and the only thing that worked was to decouple the speaker from the floor. Coupling the speaker to my suspended hardwood floor was a disaster. All coupling does to many suspended floors is excite the floor which creates a delay in the sound traveling in the floor and it muddies the bass badly.
You will find in the many threads here and on AA that the vast majority of suspended floor owners had much better success with decoupling. I know...I searched every thread available and the over-whelming consensus was coupling was bad, decoupling worked. All of the theories you will hear are great, but there is nothing like actual experience. Search "suspended hardwood floor" and "suspended floor" here and especially on AA and you will find a lot of "actual experience" from owners with suspended hardwood floors, not a bunch of theories. That is not to say that coupling may not work on "any" suspended floor, but the preponderance of evidence from owners is that coupling is not good.
And as far as movement of a speaker goes, there are also those here or on AA who have suspended their speakers from the ceiling with absolutely no movement of the speaker when playing...none, zilch. Once again, theories are nice, but actual experience is soooo much better. |
Newbee, you raise an interesting point which I think is long overdue for discussion:
There are absolutely no vibrations or "resonances" to be DRAINED from a loudspeaker. And if there are, then its cabinet/enclosure (or stand) is poorly designed.
The object of using spikes/cones under speakers (as opposed to components) is to "mass-couple" the speaker to the ground. "Mass-couple" is just a fancy term for "hold it down tight!" and steel tie-downs with big bolts would work great too, if you didn't mind looking at them.
The only thing that should move/vibrate in a loudspeaker is the transducer(s) itself -- and 99% of those only move forward and backward. And the only thing the transducer should impart its vibrations to is the air -- not the cabinet, or the stand, or the floor.
With components, especially turntables, transports, and amps (because of tubes and especially transformers) it can be desireable to "drain off" micro-vibrations thru a mechanical "diode" like cones, or ball bearings, etc. But speakers do not require this. With loudspeakers, the use of cones and spikes is merely a way of securing the cabinet (or frame, in the case of electrostats) to the ground so that ALL the energy of the transducers is transferred to the air, and none to the cabinet, floor, etc. |
Aball, how do we know what our ears are capable of measuring if we can't measure their capability with instruments. What instruments are we using to measure the fact that we can't hear sounds at 40kHz?
If there is any effect from speakers systems 'moving' 0.1mm due to vibrations, that effect cannot be detected by the ear and in any case would be smaller than if your ear (the measurement device)moved a similar amount. |
Mitch2,
Herbie's Big Fat Black Dots provided considerably richer and somewhat more detailed sound vs. the Audio Points in my setup. |
Here are a few thoughts, for what there are worth.
IMHO the only vibrations which originate in a speaker that are 'necessary' to drain are those which by reason of construction and materiels creat a resonance at some particular frequency, if that resonance actually effects sound quality (some speakers are voiced to include resonances). In order to 'drain' the vibrations at any particular frequency (where the resonance occurs) wouldn't you have to have materiel which would be capable of passing vibrations in that frequency as opposed to having a similar resonance frequency which might then compound the problem? If that is correct how do you select the materiel used to connect the speaker and the floor?
What I think might actually be in play, which is not discussed much, is the benefit of isolating speakers from the floor. Again IMHO most of the vibrations which occur in the rooms and floors are the result of airborn loading from the speakers. When the speaker is fully coupled with the floor these vibrations are being fed back into the speaker which causes a change in perceived sound quality and may actually increase the degree of resonance of the speaker in its resonance frequency.
As I said, just some random thoughts..............
Just a few thoughts, I'm sure most of you have the answers and they are not revelant. |
The reason there isn't much scientific research about this kind of thing is because our measurement equipment isn't as good as our ears. Maybe in the future we will have test gear that will be able to measure more subtle effects that right now are only detected by humans. |
Hopefully, we will someday see more of scientific research
about hi-fi matters. As it is , many people seem to be in a dark zone, where they are prone to fall for Wodo , because they hope to obtain something positve,but they wouldn´t .
Vibration control is an area, quite possible to apply research to . Let it be competition, but let there be more objective guidelines, on what is best under different circumstances. This could be obtainded, if we,- the consumers, only asked for more of this, and the market, in this case the manufacturers would provide it. As it is ,
I don´t find the situation to be satisfying , especially when it comes to cables and accessories. Spikes has long been a given item , and a holy cow, because nobody questioned it. Now some people seem to realize that there are alternatives, but in this situation , some not serious enough manufacturers turn up , and the confusion goes on.
You may ask us what to use, but we maybe not have the best answer. And it´s interesting to see , that a proposual that is based in a study I do have seen , is easely neglected! Spikes never give an improvement(compared to rigid feet,placed direct on the floor),but sometimes worsens things.Properly decoupled speakers, based on the theory of lowpass and highpass filter theory, often give an improvment, but never worsens things. You may wiggle a decoupled speaker back and forth , by hand . Common sense can be a limit in understanding, Thus , is it possible for the bass driver to wiggle the speaker? |
Markphd Thanks for the reminder I will look up the old thread |
Hi Gammajo. I thought your handle was familiar. You posted a thread on 02-06-05 titled "Spikes versus wall coupling". There are over 40 responses on that thread on vibration isolation, some from pros in the field. If you revisit the comments there, I can't add anything more. My posts on that thread also contain a reference to a website which have pictures of, and sell, Superspikes. |
Mt thats an interesting suggestion. I like the sand part as it should not transfer vibration and the price is right |
On my hardwood floors I tried most of the suggestions listed here. What I found worked best for me and my floor was to use the small clear soft plastic (Home Depot or Lowe's) furniture floor protectors. Along with the sand in the bottom, they don't move either from speaker play or family walking (kids running/jumping) nearby. |
The listening areas in all my houses have had oak floor over subfloor over wood joists. I have found cones to perform fine with my larger sized speakers. I also have used Sound Anchor stands with all of my speakers for added weight, stability and protection of the speaker base. I like cones better than skinny spikes or rubber type footers. Wellfed, I find it interesting you like the Fat Black Dots better than Audio Points, and would be curious to hear what improvements you noticed. BTW, are the Black Dots similar in substance to a hockey puck, harder, or softer?
To protect the floor, I have used Sound Anchor Cone Coasters [http://www.soundanchors.com/page20.html], a stainless steel disk with a small point for the cone tip and a special teflon type pad on the bottom. These also allow you to slide the speaker around to position it without damaging the floor.
I wouldn't worry too much about positioning over the joists. You have large heavy speakers with an 11 by 24 inch footprint, so your floor/subfloor combination should distribute the load over at least two to three of the floor joists regardless of your specific positioning. If the house is old, so that the subfloor was not originally glued down, you may want to use some fasteners from underneath to anchor the subfloor to the tops of the joists in the area of the speakers (this is commonly done to eliminate floor creaking in older houses). Another thing you can do if you can get to the underside of the floor, is to add perpindicular bracing between joists in the area of the speakers.
A last consideration nobody has yet mentioned on this thread is that some have reported good results using Symposium Svelte Shelf platforms under speakers. They can also be used between speakers and stands, which I have been curious about trying. Let us know what works for you. |
MarkPhd Thanks for your input. I have been scanning threads for awhile but found them confusing, particularly when you add in the different needs of different components and types of flooring, so I thought I would post just for my speaker application.
Frankly I still am confused. I guess there is no clear consensus of spikes versus Tenderfeet type cones. It would seem to me that spikes if they are indeed able to draw out vibration from the cabinet would then vibrate the wood beneath and the adjoining spikes would act as a megaphone and transmit it back to the cabinet. Yet any type of soft rubber would allow the cabinet to move (jiggle). It leaves me wondering why something that is more inert and sound insulating yet not metalic such as styofoam would not work better.
WTB do you know who sells superspike? |
If you want the speakers to stand as still as possible while playing, spikes are the least likely item to do the
job! Quite the contrary to many peoples belief, they act as a "tuning fork" and excite floor resonances. These floor resonances will be perceived as delayed sound, that is in no way in harmony with the origional sound.
Decouple the speakers from the floor ,and you are more likely to obtain a good result. Don´t just use rubber feet,instead try some "soft" feet that are made from a material that is in accordance with the weight of your speakers. You have to weigh your speakers at their front and back to order the right stuff.Here in Sweden , there is a brand called "SD-foten" , but there are more brands than this one. The resonance frequency of the decoupled speakers should be in the vicinity of 8 Hz , I think.
An Italian reviewer thought he heard doppler-distortion, when using such devices as SD-foten , (because he was able to rock the speaker back and forth). Talk of expectaitions ! Measurments has shown the opposite to be true.Even a Swedish hi-fi magazine that was sceptical at first , did find it possible to place a coin on its "edge", play loud while the coin was still standing. If plain physics would role , instead of marketing "hype" , good sound would be more common.
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Nsgarch - Got it, if the speakers do not rock back and forth over a single joist, they will rock better on the music. |
Hello Gammajo. There are lots of threads on vibration isolation that you can research on Audiogon. I'll agree with everybody else who have posted comments to the effect that speakers should not move (except for the drivers), so rubbery feet are not too good. I also believe that cones (Tenderfeet for example) are better than spikes. Both sit on a point at the speaker/floor interface. However, a cone places the speaker closer to the floor on a broader base. It isn't as wobbly as a spike. In my view, an excellent product for hardwood floors is the Superspike. It's an integrated spike and pad to protect the floor from the spike tip. The speaker is on a spike but you can move it around without putting little spike holes all over the floor. |
Gammajo, here's the deal on speaker placement over joists:
Assuming the joists are running the short way across the room (and that you have your speakers facing the long way) take care to place the front and rear spikes of the speaker(s) as close to adjoining joists as possible. In other words, if the front and rear spikes were actually 12" apart, then the front spikes should be right on top of one joist and the rear spike on top of the next joist to the rear.
Or another example, if the F and R spikes are 16" apart, then the fronts should be 2" in front of one joist and the rear 2" behind the next joist to the rear.
You can locate the joists pretty easily with an electronic stud finder if you can't actually get under the floor and see them.
That is what I meant by "cunning" speaker placement relative to the joists. |
Chadnliz -Thanks for the encouragement- its an expensive experiment for me but finally getting to listen to great speakers with great equipment ignited a lust for improvement and you have to start somewhere.
Thanks everyone for the suggestions which fairly clearly eliminate rubber products. The joist supports on 12 inch centers were designed to have a large grand piano placed anywhere with no support underneath for a 30 foot span, so the floor feels completely rigid to the jumping test. I had not heard of the black dots - looks to be an intriguing material.
I have some cermaic tile pieces about the size of the speaker bottom, may compare the stock spikes on these to the balck dots. |
I highly recommend Herbie's Audio Lab Big Fat Black Dots. These were an improvement over the Audio Points brass cones previously used in my system. I have a fairly rigid engineered truss floor covered with plywood and oak flooring. Herbie's Audio Lab |
Speakers to perform their best MUST NOT MOVE AT ALL (meaning the tops should not wave around, even a silly millimeter!). So rubber is OUT! Spikes are best, but if you are on a wood floor, you have to be cunning about where you place the speakers relative to the supporting structure, in order to minimize the rocking motion that can result from the floor flexing (spikes won't help with that problem.)
So, how far apart are the trusses? |
I used rubber under my home theatre speakers (Athena s3/p3) and the sound was awful, affecting the bass the most.(bloaty, slow, and absolutely no punch, kinda like: bbllaaahhhhh) I used big heavy cones, and the improvement was immediate. Sorry, I do not recall the brand. |
Not that this helps but congrats on your new speaker, it should be a nice jump from your Polks! |
