[Ckaz]

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

 

[nikongod]

Hockey pucks are pretty stiff, try them!

 

[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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Hockey pucks are pretty stiff, try them!

 

[Prog Rock Man]

 
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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.

 
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.
 

 

[InnerSpace]

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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.

 

[JerryLove]

Quote:

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.

 

[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.

 

[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.

 

 

[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.
 

 

[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.