# Ideas for speaker isolation on the cheap?



## Ckaz

I've just ordered my speakers and I would like to be able to have some form of speaker isolation, but I don't have the money to buy anything too special. My speakers are the Monitor Audio Silver RX1's, and I don't have the space for stands so they will be sitting on my desk.
   
  I've heard that cutting squash balls in half works well, and I've got plenty of those. Wouldn't it make the speaker extremely unstable though?
  Any other ideas?
   
  As a sidenote, what exactly is the purpose of speaker isolation. I I know for components its to reduce vibration (or so I thought), but my speakers will be sitting on a solid desk and won't be experiencing any of that. So yea, whats the point?


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## jilgiljongiljing

Eh I dont see half cut squash balls being very helpful for speakers, maybe the really heavy ones, but not for bookshelves. I would just stick some feet under them and keep them on your desk. I'd just make sure the speakers are all the way to the front of the desk, or just a tad behind the edge, but not more. If you push them back further you are going to get reflections from the desk and its not going to sound very good overall.
   
  But one question, if they are on your desk, will you be working at your desk when you listen to them? Cos those arent quite nearfield monitors, and will need some space to sound nice and big. You are going to limit its capabilities if you listen nearfield.


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## Ckaz

There are certain situations where one has to make compromises in regards to maximum performance, and real life practicality.
  I'm going to have them near the rear of my desk. I will be listining to them in a nearfield setup.
  I know that I can get better performance by doing otherwise, but it simply isn't a possibility. I auditioned the speakers at a position somewhat similar to what I would have at home, and decided that I liked them like that. End of story.
   
  And I've heard quite a bit online that cut-in-half squash balls are a great way to go when you need to spend as little money as possible. Why do you say otherwise?


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## dura

I made a thread about sonic design feet some time ago in this forum.


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## p a t r i c k

Quote: 





ckaz said:


> I've just ordered my speakers and I would like to be able to have some form of speaker isolation, but I don't have the money to buy anything too special. My speakers are the Monitor Audio Silver RX1's, and I don't have the space for stands so they will be sitting on my desk.


 

  
  Hi
   
  When listening to speakers in near-field position, such as at your desk , then the most important thing is that you listen on axis.
   
  If you simply place the speakers on your desk then I think you should prop them up so that the speakers are pointing at your ears.
   
  The difference in sound quality between on-axis and off-axis is massive.
   
  I am always seeing pictures of people who have some hi fi speakers for their computer. They just plonk them on the desk, but any benefits in sound qualtiy are lost immediately because they listen off axis.
   
  I think that the quality from those Monitor Audio speakers will be very good on-axis.
   
  Maybe you could prop them up with books at the front, something like that?
   
  You could raise them up from the desk with books as well if you like.


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## jilgiljongiljing

Patrick is right, I was referring to it not working because it will not be at the right level. Also, while it might reduce vibrations, its not going to be all that stable, and especially in a desk setting where things move around a lot, the last thing you want is your speaker falling face down onto something sharp, or even sideways and get scratched. I find that any potential benefit you might get from the squash ball technique is outweighed by lack of stability, just my 2 cents. If this were however a scenario where things are heavier and wider, then relative stability is more. I have tried a similar technique for isolating drums from the ground and it sort of worked, I can see it working for that scenario, but not really all that much for a bookshelf on a desk. I'd rather you raise it to have the recommended ear level listening position, on a flat solid, heavy surface.
   
  As for the near field listening, no need to get so defensive, I was just stating what is frequently discussed and recommended. If you feel you like the sound of these particular speakers in that setting, good for you, but in all honesty, you'd do a lot better with studio monitors since they are designed for nearfield setups. For a similar price of an RX1 you could get some very good monitors that will do a remarkable job in such a setting. I was just trying to help.


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## drewfus420

spring for $40 Auralex MoPads


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## p a t r i c k

I got so carried away with my "listen on-axis" thing that I forgot to mention my gold plated isolation suggestion.
   
  Here it is:
   
  Use two bicycle inner tubes. Small ones, obviously, 349 or smaller. Inflate the tubes a little, so that they are soft. Cut out two squares of MDF and put those on top of the bicycle tubes. Place speakers on those squares of MDF.
   
  This will give excellent isolation and it will provide, I suspect very good support for the speakers.
   
  The squares of MDF could be some quite nice wood if you prefer. You could use pine Timbre Board and apply wax polish. It will look pretty good.
   
  You'll find you hardly see the inner tubes.
   
  I haven't done this on a desk myself but I have created speaker stands for the floor where full size tubes are used. I put an octagon shaped chipboard panel on them and then build a simple light wooden structure on top up to the speakers.
   
  The great advantage for the speaker of a structure like this is that there are so few available standing waves in its design. This means that the stand will not accentuate given frequencies.


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## jilgiljongiljing

That sounds like an interesting idea, I will try it out sometime.


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## Prog Rock Man

Blobs of blue tac, two at the front and one at the back in the middle. You will isolate the speaker from the table, it will stop the speaker from moving about and you can use more at the front than at the back to point the speakers slightly up. I used blue tac to secure speakers to stands and it worked very well. I see no reason why it should not be as effective on a desk.


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## nikongod

Im not sure I would go to great lengths to isolate speaker: most people try to couple the speakers to whatever they are sitting on.
   
  Blu-tac is nice because it wont scratch like a spike. Be careful though! It does tend to harden into a baked on chewing gum residue.


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## InnerSpace

Quote: 





ckaz said:


> As a sidenote, what exactly is the purpose of speaker isolation. I I know for components its to reduce vibration (or so I thought), but my speakers will be sitting on a solid desk and won't be experiencing any of that. So yea, whats the point?


 
   
  Technically a speaker should be locked securely in place to a heavy structure that acts as a "mechanical ground".  If you introduce any kind of compliance under it, then the movement of the cone will be able to move the cabinet to some degree, compromising the acoustic output.  I would try them directly on the desk, possibly with something heavy on top holding them down.  If the desk is flimsy and you get buzzing, use the hardest and densest material available to cure the problem - maybe hard rubber washers from the hardware store.  Anything soft, squishy, or compliant is your enemy in this situation.


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## Prog Rock Man

Blue tac can be kept from hardening by replacing it every so often. Once squashed down it is far from soft and squishy and your speaker will not move. Something heavy ontop is also a good idea, but only once the bottom is secured.


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## Rdr. Seraphim

Hmm... never had Blu-Tak harden, even after multiple years of use.


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## Rdr. Seraphim

X10! NEVER use an inner tube type of platform for speakers! It's sometimes Ok under electronics, but I've found that constrained layer dampening works best (see http://www.marigoaudio.com/), uh, at a considerable cost 
	

	
	
		
		

		
		
	


	




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innerspace said:


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## p a t r i c k

Quote: 





innerspace said:


> Technically a speaker should be locked securely in place to a heavy structure that acts as a "mechanical ground".  If you introduce any kind of compliance under it, then the movement of the cone will be able to move the cabinet to some degree, compromising the acoustic output.  I would try them directly on the desk, possibly with something heavy on top holding them down.  If the desk is flimsy and you get buzzing, use the hardest and densest material available to cure the problem - maybe hard rubber washers from the hardware store.  Anything soft, squishy, or compliant is your enemy in this situation.


 

 No I don't think this is good science or good practice.
   
  The mass of the cone is far too light to move the speaker cabinet.
   
  I think that creating secure points of fixture for the cabinet only sets up nodes for resonance.
   
  So, with the regular dynamic speaker design, I think that they are best placed on compliant surfaces.


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## p a t r i c k

Quote: 





ckaz said:


> As a sidenote, what exactly is the purpose of speaker isolation. I I know for components its to reduce vibration (or so I thought), but my speakers will be sitting on a solid desk and won't be experiencing any of that. So yea, whats the point?


 


 Well, placing speakers on a desk surface will couple the desk surface to the speaker enclosure.
   
  The desk surface will start transmitting the vibrations of the speaker enclosure.
   
  Those vibrations are for the most part no wanted, they will muddy bass and suchlike.
   
  So, if you are to put speakers on a desk surface then it is probably best to isolate them from that surface.
   
  I think my bicycle innertube method is a very good way to do that 
   
  However make sure that the speakers are pointing at your ears.
   
  You could use small bicycle innertube, square of wood, and on top of that a pile of books.
   
  Better still, if you like DIY, would be to have a small bicycle innertube, square of wood and a light wood construction above that to raise the speaker so that they are the same height as your ears.
   
  Remember that the bicycle inner tube is only to be inflated to a very small degree, just enough air so that it lifts the speakers.


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## InnerSpace

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p a t r i c k said:


> The mass of the cone is far too light to move the speaker cabinet.
> 
> I think that creating secure points of fixture for the cabinet only sets up nodes for resonance.
> 
> So, with the regular dynamic speaker design, I think that they are best placed on compliant surfaces.


 

 OK, let's erase Isaac Newton from history and abandon decades of established audio practice, then.  It's a good job Frank Whittle didn't think hot gas was "far too light" to move an airplane.


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## p a t r i c k

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innerspace said:


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 If you give it a bit of thought you will see that my comment is entirely an application of Isaac Newton's laws of physics.
   
  I am writing about the "standard" dynamic speaker design where there are drive units in an MDF baffle which may be either infinite or ported.
   
  The cone will not be moving the speaker baffle as a whole, so there is no need to prevent that kind of movement.
   
  The cone instead creates vibrations within the structure of the speaker baffle.
   
  If you create fixing points with the baffle what then happens is that those simply become nodes for resonance.
   
  So, to prevent nodes of reference you use compliant materials.
   
  The most usual material of course is blue tak which people use between the speakers and speaker stands.
   
  The reason people often use big heavy speaker stands is not to bring that weight or to bear on the speaker, but to have a stand which itself does not resonate. They then decouple the speakers from the stand with blue tack to prevent it from vibrating.
   
  Personally I would never use big heavy stands in the first place, because lightweight stands will not resonate if they are placed on very compliant surfaces themselves.
   
  So, the speaker stands I have created myself in the past for speakers sit on full size bicycle inner tubes inflated just enough to raise the speaker and stand off the ground. The tubes are kept at a very low level of inflations.
   
  The stands themselves were light wooden structures.


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## InnerSpace

Quote: 





p a t r i c k said:


> The cone will not be moving the speaker baffle as a whole, so there is no need to prevent that kind of movement.
> 
> The cone instead creates vibrations within the structure of the speaker baffle.


 

 No, sorry.  If the cone is forced forward, the baffle is forced backward.  That's Newton's third law.  The vibrations within the baffle are caused by sound waves within the enclosure.
   
  The more perfect your inner tube suspension, the less acoustic output achieved.  Better to save money on the suspension and just turn down the volume.  Same effect.


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## nikongod

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p a t r i c k said:


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 So wrong. 
   
  The trend of "people who can sell anything they build" towards cabinets that weigh in the 300lb range, and are SPIKED to the floor is not an accident. The speakers DO set up resonances in lightweight cabinets, and by coupling the speaker to the floor you increase its mass several-fold. A light speaker on a suspension is free to sway to the music in a manner mildly related to the actual signal. Some call this distortion.
   
  Rigidly couple the speaker to whatever its sitting on. If the speaker is on a stand rigidly couple that to the floor. 
   
  By all means, experiment with any manner of suspension you can think of, but the rule of thumb says to rigidly couple speakers to the floor. Start off following the rules.


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## Rdr. Seraphim

Here's an excellent article on speaker resonance and isolation/mechanical coupling: http://www.stereophile.com/content/sound-surprise-loudspeakerstand-interface.


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## p a t r i c k

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innerspace said:


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 Well, no, sorry, and I am not writing "sorry" in a rude manner. If you give this a bit of thought you will start to see it.
   
  The cones moves forward and then moves backwards again.
   
  So for the speaker cabinet as a whole to follow the cone it must be able to accelerate at the same speed as the cone.
   
  As the cone is vibrating and the cabinet as a whole is too great a mass to follow that vibration it does in fact, just sit there.
   
  So there is no need to stop the cabinet from moving as a whole.
   
  The issue with speaker cabinets is vibrations within the cabinet itself.
   
  The best way in most cases (of the common MDF box as either infinite baffle or ported design) to prevent resonances is to make sure that the surfaces the cabinet is sitting on are compliant.
   
  The problem with fixing cabinets rigidly of using a lot of weight to pin them down is that this simply creates resonance points within the cabinet structure.


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## p a t r i c k

Quote: 





nikongod said:


> So wrong.
> 
> The trend of "people who can sell anything they build" towards cabinets that weigh in the 300lb range, and are SPIKED to the floor is not an accident. The speakers DO set up resonances in lightweight cabinets, and by coupling the speaker to the floor you increase its mass several-fold. A light speaker on a suspension is free to sway to the music in a manner mildly related to the actual signal. Some call this distortion.
> 
> ...


 
   
  Please do not be rude and try to understand.
   
  There is no benefit in increasing the mass of the speaker cabinet.
   
  The speaker cabinet as a whole will not move to follow the driver.
   
  The reason why speaker stands are sometimes sold with a very heavy mass is simply to stop the stand itself from conducting vibration as I have described. It is not to add mass to the speaker.
   
  If you rigidly attach the speaker to these very heavy stands then all you do is set up resonance points within the speaker cabinet where you have rigidly fixed the speakers.
   
  So, the best way to place the speaker on these stands is to use blu tak, which of course is common practice and a good one.
   
  Those heavy stands come with spikes for the floor, but these are a good way to make sure the stands are stable in most carpeted homes.
   
  With respect to this issue of speaker stands, I very much favour using lightweight stands and using large bicycle inner tubes (700 C) at the base.
   
  The bicycle inner-tubes prevent points of resonance and you will find, I think to your surprise, that the lightweight wooden structure, vibrates very little.
   
  This, of course, is because vibration requires nodes. If you don't provide the nodes there will be no vibration.
   
  The most classic way to describe this is the example of a 12 inch ruler. You clamp this ruler to a desk and then you can make a very nice "twang" sound.
   
  If, however, you undo the clamp, you cannot make a nice "twang" sound with the ruler any more because there is no longer a node as a reference.


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## InnerSpace

Quote: 





p a t r i c k said:


> With respect to this issue of speaker stands, I very much favour using lightweight stands and using large bicycle inner tubes (700 C) at the base.


 

 Patrick, I honestly think you're conflating two separate issues here.
   
  To follow an input voltage accurately, the speaker cone must move with reference to an immoveable chassis and cabinet.  Imagine for a moment a speaker floating in zero-gravity outer space, fed with a wireless signal.  There will be no acoustic output because there is no medium through which sound waves may travel, but even in the presence of such a medium there would be no output anyway, because the cabinet would be free to move backward as the cone moves forward, and vice versa, and hence there would be no net movement of the cone.
   
  That's basic Newtonian physics.  Every action has an equal and opposite reaction.
   
  So to preserve as much net movement of the cone as possible, rigidity of everything _except_ the cone is essential.  Conventionally it is achieved through mass, clamping, spikes, etc, and it's a good thing - except that it opens the door to problems of an unrelated type, i.e. as well as draining vibrations caused by spls trapped within cabinets, it also to some extent stores them and then releases them in a frequency- and time-smeared fashion.  Unfortunately, greater mass = greater energy storage, so yes, there have been entirely creditable attempts to design rigid mountings out of low-mass materials, which store less energy and release it quicker.  But notice that the basic requirement is always rigidity first.
   
  The approach you champion seems to concentrate on preventing secondary vibrations leaving the speaker cabinet and stand, but at the expense of global rigidity.  The logical consequence of your approach would be to "move up" your suspension principle - i.e. to design an extremely lossy gasket and mount it between the speaker basket and the baffle, so that the speaker chassis was free to move with respect to the baffle with no impediment at all in any direction ... it would be just hanging there, isolated by a jelly-like material.  Do you think that would work well?


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## Ckaz

K.. so I should use blue tack between the speakers and the desk? I don't want to end up damaging the speakers though..


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## InnerSpace

Quote: 





ckaz said:


> K.. so I should use blue tack between the speakers and the desk? I don't want to end up damaging the speakers though..


 

 IMO, get eight faucet washers from the hardware store and use them.  Best all-around compromise between all the various desiderata discussed above.  In the real world, they'll work very well.


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## JerryLove

Quote:


innerspace said:


> OK, let's erase Isaac Newton from history and abandon decades of established audio practice, then.  It's a good job Frank Whittle didn't think hot gas was "far too light" to move an airplane.


 
   
  You are equivocating. The force exerted to accelerate the cone on a speaker is very small and short relative to the mass of most speakers. Therefore, the ability of non-resonant pressure to move (move in the sense that anchoring the speaker would prevent such movement) a speaker based on equal-and-opposite force and be ignored in practical listening.
   
  While this may not move a speaker in the conventional sense: the force is sufficient to create waves that transmit through the material of the speaker. This occurs both directly from the pressure exerted on the magnets which is then coupled to the speaker enclosure (some speakers actually place viscoelastic gaskets to try to decouple the driver basket from the cabinet) and as the result of soundwaves moving inside the cabinet.
   
  These resonant modes are why so much effort is placed in bracing, internal cabinet shape, and cabinet materials. The goal being to prevent waves from propigating and creating sound.
  
  A desk has not been designed to avoid resonance. The more solidly you couple a speaker to a desk, the more you turn the speaker into a transducer. It is, in short, a bad idea.
   
  A better solution would be the use of acoustic isolation via a viscoelastic material to convert the difference in vibration between the desk and speaker into heat. I believe "peel-n-seal" at Home Depot does this.


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## JerryLove

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> Originally Posted by *p a t r i c k*
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  Perhaps not directly (adding lead shot to the bottom of a cabinet won't do much good), but indirectly the things which dampen resonance usually add weight.
   
  Quote: 





> With respect to this issue of speaker stands, I very much favour using lightweight stands and using large bicycle inner tubes (700 C) at the base.


 
  Lighter weight tends to mean less dampning and (unless very non-rigid) high resonance modes.
   
  Quote: 





> The most classic way to describe this is the example of a 12 inch ruler. You clamp this ruler to a desk and then you can make a very nice "twang" sound.
> 
> If, however, you undo the clamp, you cannot make a nice "twang" sound with the ruler any more because there is no longer a node as a reference.


 
   
  In fairness: a counter example would be a musical instrument like a triangle. Suspend it in air and you can make a nice "ding". Hold it or attach it to anything and the sound goes away.


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## cyberspyder

I have concrete stands decoupled from the ground with four hockey pucks and the speaker on top, decoupled from the stand with some 3M polyurethane feet, it works pretty well. The stands are spaced 2.5 feet from any wall in any direction.


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## Ckaz

Unfortunately, stands aren't an option. I need to have them on my desk.
  What about hockey pucks?


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## nikongod

Hockey pucks are pretty stiff, try them!


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## cyberspyder

Thing is, pucks need alot of weight on them to be effective, hence why I have them under my stands, they're too stiff for just a regular bookshelf.
  
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nikongod said:


> Hockey pucks are pretty stiff, try them!


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## Prog Rock Man

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p a t r i c k said:


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  Tell that to my Logitech ipod dock, which when playing Groove Armada has 'walked' itself off a shelf due to the vibrations caused by the speakers. That is an extreme case, but otherwise, as you say p a t r i c k, you want to stop vibration, which is caused by the speaker and its cabinet obeying Newton's Laws from transmitting to the surface.


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## InnerSpace

Quote: 





jerrylove said:


> You are equivocating. The force exerted to accelerate the cone on a speaker is very small and short relative to the mass of most speakers.


 
   
  No, equivocation implies a measure of ambiguity, and I'm unambiguously on the side of Newtonian physics here.  The force exerted on the cabinet by the cone is exactly equal to the cone's mass times its velocity squared.  (Duration, e.g. "short", is irrelevant here.)  The cabinet's mass will be much greater than the cone's, and therefore the square of the cabinet's resulting velocity will be proportionally much smaller, but it will be far from insignificant in a discipline where we try to track the tiniest waveforms with accuracy.  But hey, I agree, this isn't the science forum.


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## JerryLove

Quote:


innerspace said:


> No, equivocation implies a measure of ambiguity, and I'm unambiguously on the side of Newtonian physics here.  The force exerted on the cabinet by the cone is exactly equal to the cone's mass times its velocity squared.  (Duration, e.g. "short", is irrelevant here.)  The cabinet's mass will be much greater than the cone's, and therefore the square of the cabinet's resulting velocity will be proportionally much smaller, but it will be far from insignificant in a discipline where we try to track the tiniest waveforms with accuracy.  But hey, I agree, this isn't the science forum.


 

 Very well. Let's get technical.
   
  The cone, tube, and voicecoil actually are simply a passive weight being pushed and pulled by the magnetic interaction with the driver. The cone is not hard-coupled to the enclosure (the surround flexes greater than the extrusion of the cone), and so while there might be a little push-pull from the surround: the bulk is coming from the speaker magnet.
   
  Neither the magnet, the speaker cage, nor the enclosure are perfectly rigid... so this pressure does not propigate instantly. Every part involved flexes and, in the process of flexing, converts energy into heat and noise.
   
  So let's tie this in to how you have equivocated:
   
  The suggestion had been to form a very solid contact with a large weight (notice that this would not affect newton: so your argument in favor of it is already flawed since you've made no attempt to qualify the sonic impact of the two arbitrary setups).
   
  Such coupling will not effect the flexing of the basket and enclosure from the magnet until, at least, the wave hits the coupling point. Given that the material of the desk is an unknown, and therefore wave propigation in it is unknown, it's pretty clear that the movement being discussed is the movement of the average cabinet rather than the movement of waves along the cabinet.
   
  The cabinet is not sitting in free fall in a vacuum. Even if it were: the frequency of many of the waves would cause counter waves to occur before propigation had completed (we'd need to know a lot more about the cabinet, cone, materials, and actual sound to determine a cutoff point).
   
  In fact, since the average movement of the cone is zero (it moved back as much as it moves forward), to be able to actually move the cabinet of simple action-reaction would be a violation of several laws of momentium.
   
  Indeed: the activity of "speaker walking" depends entirely on traction between the speaker and the floor.
   
  So now that I've shown that you are mixing average movement with "vibrating in place"; it' is apparent as we look at non-rigid connectors (rubber feet), that they are superior at damping vibration to hard connectors.
   
  So yes, a cone move a speaker. This movement is irrelevant. The cone, and sonic pressure also vibrate the cabinet. This movement is not irrelevant... and can cause signifigant coloration. This coloration will be exascerbated by a hard coupling to another resonant object. This is one reason I advise against hard coupling.
   
  Here's another. Let's imagine that your speaker cabinet and desk have different resonances. Certainly I have a pair of speakers here with an MDF outer-wall and concrete inside. What would happen if the MDF and concrete were tightly constrained to one another? I would have a concrete&mdf wall with a resonance. Instead these two materials are attached by an elastic interface. Because of this, the MDF and concrete have separate resonances. they are, however, softly coupled and attempt to transfer resonance across the membrane (if they were hard coupled: they would resonate in sync). Since every transfer results in the loss of acoustic energy, and since the dissimilar resonant modes mean that transfers are constantly occuring, I have a far less colored cabinet as a result.


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## Somnambulist

Cut up and stick together a couple of sheets of foamboard/foamcore? A1 sheets would give you plenty of material to make a stand, not sure how effective that would be though.


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## p a t r i c k

I've been away in Romania where it is very cold. I'm back in UK now so I will add this post. It's quite long so it is value for money 

I don't read hi fi magazine or blogs these days. In fact I haven't done for over 15 years.

I forget that the mags and blogs are full of spurious myths. Like all myths they are sustained by repetition. Each mag or blog author reads the myth in the other publications and is reinforced in his/her belief.

The readers of the blogs and magazines immerse themselves in the myths and come to believe them to be true as well of course.

So, now to the more prosaic issue of supporting speakers.

The myths that I am reading in this thread are old. I remember them being repeated 30 years ago.

I will now try to unpick them. Please note that for all of these points I when I write "speakers" I am referring to the common "bookshelf" speaker design in which the drivers are mounted in a cabinet of MDF. The cabinet either forms an infinite baffle or is ported.

The myths I see repeated here are that speakers need to be "secured" in some way. That heavy mass stands add mass to the speaker. That adding mass to the speaker is desirable. Etc. etc.

These myths are very wrong and do not become right simply by their repetition.

Now to try and explain how to minimise unwanted resonances from a pair of speakers. It is best to think of the possible resonances in two forms.

(1) The speaker resonating as a whole.

(2) Resonances within the structure of the speaker.

Please don't lose these two basic forms from your mind.

The first thing to comprehend is that (1) simply does not happen. There is a lot of (2) but none of (1). However the nonsense physics seen applied in many hi fi magazine articles and blogs is written believing that (1) is the issue to resolve.

So, why is there none of (1)? The answer is simple. The frequencies of the driver are very much higher than the resonant frequency of the speaker as a whole. Because the driver is oscillating for it to move the speaker as a whole, then the speaker as a whole would need to be oscillating as well, out of phase to 180%. But to move the whole speaker at those high frequencies would require absolutely vast amounts of energy so it just stays put.

The behaviour is quite different from how the speaker as a whole would react if the driver were producing a constant force in one direction. So applying Newton's laws of physics without comprehension is not going to help understand this. Much better to apply Newton's laws of physics _with comprehension_.

Now to the issue of (2). Although the oscillation of the driver cannot move the speaker as a whole it will set up resonances within the structure of the speaker. When you play music and touch the speaker you will feel resonances in the cabinet and this is of course, (2).

Speaker manufacturers dedicate a lot of time to resolving (2). The most usual method is to make sure that (2) is an even spread across the frequency range.

Now to speaker stands. Unfortunately people buy speaker stands believing they are trying to solve (1). They don't understand that the issue to resolve is (2). 

The heavy speaker stands will have no impact on the problem of (1) because the problem does not exist in the first place.

People often think that they want to add mass to the speaker in some way. This will bring no benefits and, of course, the heavy mass speakers stands don't add mass to the speaker in any case.

Even if adding mass to the speaker were desired, how could the speaker stand do so as the speaker stand is not actually connected to the speaker. It is not bolted to the stand for example. The speaker just sits on top of the stand, most usually Blu Tak is used between the speaker and the stand.

So, why have a heavy speaker stand? Well the actual advantage is that the mass dampens the structure of the speaker stand. The problem to solve of course is not (1), but rather (2) and mores specifically the transmission of (2) to the speaker stand. So the high mass might reduce the amount of (2) in the speaker stand.

The problem with using heavy mass to dampen transmission of (2) is that the mass requires a greater structure. This structure must have some rigidity to carry that mass and so nodes of resonance are created. (2) will thrive of those nodes for resonance.

Now to understand how better to deal with the problem of (2). First we cannot improve on the work carried out by they actual speaker designers. They have done their job with the cabinet design. What we don't want to do is create the possibility of (2) being transmitted into our stand. How to combat this transmission? Well first we can come to understand that resonance requires nodes. If you think, for example, about ruler clamped to the edge of a desk. You will be able to make a nice "twang" sound with that ruler by flicking the free end. However if the ruler is not clamped to the desk you will not be able to make any sound. The clamped ruler has a node for resonance at the clamped end of course.

An ideal would be to have the speaker freely floating with no nodes of resonance whatsoever. This would eliminate the possibility of (2) being transmitted to the "stand". Nobody, to my knowledge, has manufactured a speaker which is freely floating but Roksan made a speaker in 1985 with a floating tweeter unit. This was the Roksan Darius.







In the picture of the Darius you can see that the tweeter is mounted on a small panel and this is held in suspension by four springs. The suspended tweeter unit is completely stable because the resonant frequency of the tweeter unit as a whole is so much greater than the frequencies generated by its driver.

Totally suspending the whole speaker is desirable but not practical. Instead a more conventional stand must be designed but the structural objective is to have as few resonant modes as possible. The lower the number of nodes, the lower the potential resonance.

I created speaker stands about 20 years ago, were very successful in reducing transmitted resonance. I will describe them to give some idea of the kind of stand that would be suitable.

On the floor are place two large (700 mm diameter) bicycle tubes. One for each stand. On top of the tube I put hexagonal chipboard boards. These are hexagonal because I can't cut circles. The boards' diameter is just a bit larger than the tubes'. On top of each board goes a light wooden structure made with PAR (Plained All Round) lengths. This has no panels and is a small tower up to the base for the speakers. The base is not a panel but simply four short lengths of PAR. The bicycle tubes are inflated just enough to lift the assembly with speakers off the ground.

This design is not perfect, there are still structural nodes, but it is very good indeed as can be evidenced by simply touching it while the speakers are playing. You will feel surprisingly little resonance within it.

For the original poster the best way to isolate speakers from the desk is to use compliant materials. I think that bicycle tubes with very little inflation are ideal in my experience. You can buy small tubes from a bicycle store and use squares of wood. The speakers can be further lifted above that with a light wooden structure. These simply produced stands will be very effective and far more advanced than the clodding things currently sold as speaker stands.


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## p a t r i c k

*InnerSpace* writes:

_The approach you champion seems to concentrate on preventing secondary vibrations leaving the speaker cabinet and stand, but at the expense of global rigidity._

I'll refer you to my "value for money" posting I've just put up, but there is no "global rigidity" issue at all.


*InnerSpace* writes:

_The logical consequence of your approach would be to "move up" your suspension principle - i.e. to design an extremely lossy gasket and mount it between the speaker basket and the baffle, so that the speaker chassis was free to move with respect to the baffle with no impediment at all in any direction ... it would be just hanging there, isolated by a jelly-like material. Do you think that would work well?_

Well yes! This would be superb. However this can't happen because a seal has to be made with the baffle.


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## InnerSpace

^^ Oh, dear.  Patrick, you lost track of the argument while you were away.  We weren't talking about resonant modes.  Briefly, we were talking about this: the only important pathway here is the passage of soundwaves between the speaker diaphragm and your eardrum.  For optimum transfer of information, keep your head still and the speaker basket still.  Simple as that. You figure out a way to keep your head still, and we'll figure out a way to keep the speaker basket still.


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