[p a t r i c k]

 
Quote:

 
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.

 

[p a t r i c k]

Quote:

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.

 

[InnerSpace]

Quote:

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.

 

[p a t r i c k]

Quote:

Quote:

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.

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.

 

[InnerSpace]

Quote:

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.

 

[nikongod]

Quote:

 
Quote:

 
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.

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.

 

[Rdr. Seraphim]

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

 

[p a t r i c k]

Quote:

Quote:

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.

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.

 

[p a t r i c k]

Quote:

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.

 
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.

 

[InnerSpace]

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.
 
 

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?

 

[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..

 

[InnerSpace]

Quote:

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.

 

[JerryLove]

Quote:

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.

 

[JerryLove]

 
Quote:

Originally Posted by p a t r i c k 

Please do not be rude and try to understand.
 
There is no benefit in increasing the mass of the speaker cabinet.

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.
 
 

 

[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.