Blu-Tack – Alternatives and speaker coupling / de-coupling

[NetGeek]

I have been using Blu-Tack to “de-couple” my bookshelf speakers from the metal stands they sit on. I just placed an order from AudioAdvisor for another pair of Energy Stands and they are out of Blu-Tack and I have not been able to find it locally.

What does everyone else use for their Bookshelf Speakers? Is there another similar product that can be found at a Office Depot? I like how Blu-Tack holds the speaker firmly to the stand, I use one package per pair of stands and put it around the entire edge of the top speaker plate, not just in the four corners and it seems to have a really strong hold..

And speaking of coupling & de-coupling, what is really the difference and when is one used over the other? I hear people talking about how audio-spikes on floorstanders or speaker stands “couples” the speaker/stand to the floor; I would think that by having a very small area of the speaker (the tips of the points) touching the floor that this would isolate, or “de-couple” the speaker?

 

[MacManNM]

I have been using Blu-Tack to “de-couple” my bookshelf speakers from the metal stands they sit on. I just placed an order from AudioAdvisor for another pair of Energy Stands and they are out of Blu-Tack and I have not been able to find it locally.

What does everyone else use for their Bookshelf Speakers? Is there another similar product that can be found at a Office Depot? I like how Blu-Tack holds the speaker firmly to the stand, I use one package per pair of stands and put it around the entire edge of the top speaker plate, not just in the four corners and it seems to have a really strong hold..

And speaking of coupling & de-coupling, what is really the difference and when is one used over the other? I hear people talking about how audio-spikes on floorstanders or speaker stands “couples” the speaker/stand to the floor; I would think that by having a very small area of the speaker (the tips of the points) touching the floor that this would isolate, or “de-couple” the speaker?

Sticky-tac is available at most office supply stores. I use felt pads, they seem to work ok.

You want your sub and floor standers to couple to the floor. This helps propagate the lowest bass notes. The bookshelves don’t play that low so there is no real need to couple them. I use the felt pad only to eliminate annoying rattles and the like.

 

[mtrycrafts]

You want your sub and floor standers to couple to the floor. This helps propagate the lowest bass notes. .

Please explain this

 

[MacManNM]

Please explain this

I don't think so Tim

 

[mtrycrafts]

I don't think so Tim

I didn't think you could. Just not in you, Joe.

 

[JoeE SP9]

I have been using Blu-Tack to “de-couple” my bookshelf speakers from the metal stands they sit on. I just placed an order from AudioAdvisor for another pair of Energy Stands and they are out of Blu-Tack and I have not been able to find it locally.

What does everyone else use for their Bookshelf Speakers? Is there another similar product that can be found at a Office Depot? I like how Blu-Tack holds the speaker firmly to the stand, I use one package per pair of stands and put it around the entire edge of the top speaker plate, not just in the four corners and it seems to have a really strong hold..

And speaking of coupling & de-coupling, what is really the difference and when is one used over the other? I hear people talking about how audio-spikes on floorstanders or speaker stands “couples” the speaker/stand to the floor; I would think that by having a very small area of the speaker (the tips of the points) touching the floor that this would isolate, or “de-couple” the speaker?

I have heard that spikes on speaker stands operate like a diode. They allow vibrations to go from the stand to the floor but not the other way. I don't know if this is true. I do know that spiking my speakers improved the sound.

 

[MacManNM]

I have heard that spikes on speaker stands operate like a diode. They allow vibrations to go from the stand to the floor but not the other way. I don't know if this is true. I do know that spiking my speakers improved the sound.

The spikes are pretty much for a carpeted floor. They help prevent movement of the speaker (newtons third law of motion). This movement primarily occurs when playing the deepest/loudest bass notes, where the excursion of the woofer is the greatest.

Preventing the speaker from moving improves imaging, and will increase bass.

The bookshelves don't really need them because they really shouldn't be playing those deep bass notes, and usually the friction of the rubber feet on a hard surface is enough to keep them from moving.

 

[MacManNM]

I didn't think you could. Just not in you, Joe.

Come on Tim, explain this to us idiots.

 

[WmAx]

Sticky-tac is available at most office supply stores. I use felt pads, they seem to work ok.

You want your sub and floor standers to couple to the floor. This helps propagate the lowest bass notes.

I'm not sure what you mean by propogate the lowest bass notes. Unless you just want the floor to vibrate[for feel] as much as possible. It should be noted that many wood construction floors[with wood joices] may have a rather high amplitude resonance that may be excited by direct coupling. I have come across several such floors. I typically use a suspension platform with a very low resonant frequency, so that this resonance is excited as little as possible.

The bookshelves don’t play that low so there is no real need to couple them. I use the felt pad only to eliminate annoying rattles and the like.

 

[claudermilk]

Back to the original question, try a crafts or fabric store. I found some stuff like blu-tack there & it holds really well (like if I put a bead all the way around, the speaker & stand would be a permanent single unit!).

As for the spikes, they helped stabilize my stands since they are now resting directly on the slab under the carpet & pad--no more scary wobbling.

 

[WmAx]

The spikes are pretty much for a carpeted floor. They help prevent movement of the speaker (newtons third law of motion). This movement primarily occurs when playing the deepest/loudest bass notes, where the excursion of the woofer is the greatest.

Movement is directly proportional to the opposing mass. In the worst case scenario, a free-hanging speaker[in a vacuum and with zero mechanical friction losses] with 40 gram cone moving 8mm will move a 40 kilogram cabinet by an opposing 0.008mm. I'm not aware of what impact on the sound 0.008mm[or ten times that] of movement can have. The speaker cones are moving, several magnitudes more, compared to this, while at the same time radiating sound.

Preventing the speaker from moving improves imaging, and will increase bass.

How will it improve imaging? The mechanism through where bass will be increased substantially, is through the effect of feeling the vibrations[sort of like the bass shaker transducers] better through the floor and/or where such vibration excites the floor structure resonant frequency[leading to possible additional coloration]. It is completely subjective, as whether one likes this effect or not, I suppose.

-Chris

 

[WmAx]

I have been using Blu-Tack to “de-couple” my bookshelf speakers from the metal stands they sit on. I just placed an order from AudioAdvisor for another pair of Energy Stands and they are out of Blu-Tack and I have not been able to find it locally.

The blue-tack will have a higher resonant frequency, some midrange transmission will still occur. If the speaker is not so heavy as to compress significantly, you could use a 2" thick piece of cushion foam, or a piece of very thick shag carpet. These will decouple a broader frequency band, but probably be too ugly and will not offer much stability. The choice of material[and effective filtering frequency] is entirely dependant on the resonant frequency of the stands. If the stand is metal, the resonant frequency is probably in the upper midrange or even lower treble, which means that blue-tak would work sufficiently. If the construction is wood, the resonant frequency may fall into the lower midrange, in which case the effectiveness of the blue-tak may be questionable.

And speaking of coupling & de-coupling, what is really the difference and when is one used over the other?

Coupling's main function is to offer maximum stability. De-coupling is used to prevent vibration transmission to the stand or floor, or even just the mechanical connection where the stand touches the cabinet, that may otherwise cause audible effect(s).

-Chris

 

[MacManNM]

Read post #9. It's basic physics dude.

I'm not sure what you mean by propogate the lowest bass notes. Unless you just want the floor to vibrate[for feel] as much as possible. It should be noted that many wood construction floors[with wood joices] may have a rather high amplitude resonance that may be excited by direct coupling. I have come across several such floors. I typically use a suspension platform with a very low resonant frequency, so that this resonance is excited as little as possible.

Unless it's a down firing sub this isn't that much of an issue. I should have said front or side firing speakers.

 

[MacManNM]

Movement is directly proportional to the opposing mass. In the worst case scenario, a free-hanging speaker[in a vacuum and with zero mechanical friction losses] with 40 gram cone moving 8mm will move a 40 kilogram cabinet by an opposing 0.008mm. I'm not aware of what impact on the sound 0.008mm[or ten times that] of movement can have. The speaker cones are moving, several magnitudes more, compared to this, while at the same time radiating sound.

Life is not lived in a vacuum! I guess every time I've stood in front of a large driver and felt the bass, it was because it was coupling through the floor to my chest.

Thats why it's called Sound PRESSURE Level. In a vacuum it wouldn't tend to move, but lets insert the forces of air pressure into the equation too.

How will it improve imaging? The mechanism through where bass will be increased substantially, is through the effect of feeling the vibrations[sort of like the bass shaker transducers] better through the floor and/or where such vibration excites the floor structure resonant frequency[leading to possible additional coloration]. It is completely subjective, as whether one likes this effect or not, I suppose.

-Chris

There is no bass imaging. It improves midrange and high frequency, by the cabinets not moving around. Bass shakers are sub sonic. Off axis response can vary quite a bit, a few mrad of movement could change the imaging drastically.

 

[rschleicher]

Being simplistic about it (the only way I know how), you want the speaker drivers to vibrate, and nothing else, to avoid harmonics, distortion, and other un-controlled sounds.

In a perfect world, you could get this by having the drivers 100% rigidly mounted to an infinitely heavy (actually "massy") mass. In reality, the masses of the speaker cabinet itself, and the mass of the stand and/or floor it sits on, are finite, and the "mountings" aren't perfectly rigid. So, you go for a compromise. Too soft a coupling between the speaker and its stand (or the floor) and you get energy absorbtion and loss of sound (basically the whole speaker cabinet will move in reaction to the speaker drivers). Too rigid and you get the stand and/or floor vibrating.

A speaker cabinet or a stand laying on carpet is too soft, so spikes are used to pierce the carpet layer and connect at least to the backing of the carpet, or possibly part-way through the carpet pad. But spikes on a wood or other hard floor would be too rigid, so either you use rubber feet or something else to provide a little damping.

The advantage of Blu-Tack between a small speaker and its stand is that it is a somewhat more rigid coupling to the larger mass of the stand, than simply laying the speaker on the stand (due to its tackiness). But, the putty-like consistency also provides some damping of high frequencies. If you have speaker stands that came with the speakers, and actually clamp to the speakers (or attach via some threaded mount), then this is even more rigid. Usually this will be better, as long as the stands have pretty high mass, and if there is still a little damping of higher frequencies between the speaker and stand. (Higher mass moves the resonance frequency down.)

 

[WmAx]

Life is not lived in a vacuum! I guess every time I've stood in front of a large driver and felt the bass, it was because it was coupling through the floor to my chest.

Thats why it's called Sound PRESSURE Level. In a vacuum it wouldn't tend to move, but lets insert the forces of air pressure into the equation too.

You stated Newton's 3rd law as the reasoning behind coupling in one of your first posts.

I used the theoretical condition of a vacuum with free floating object, because this offers the most movement, due to opposing mass. In reality, the surrounding air and the issue of the object sitting on a surface[with gravity and contact to the surface offering much additional friction] will reduce the movement to a tiny fraction of the theoretical amount I posed.

Now you are [apparently] claiming that the cone is moving enough air to move the enclosure. Is this correct? If so, please offer some proof that the cabinet is moved any sufficient amount in any realistic circumstances, as to have a negative impact on sound quality. If this is your opinion, then that's cool, but it's not an issue I have seen proven[by any credible source] to be a real concern in any normal circumstance. Perhaps in the very unusual situation, where one has a very high excursion, very large diameter woofer, in a tiny and light enclosure, a very small noticable movement may be achieved due to the air disruption[as opposed to a resonant mode at the coupling of the floor and subwoofer, for example hard feet or direct contact of the cabinet bottom with the hard floor, which is not the same] if said woofer is driven at very high amplitudes.

It improves midrange and high frequency, by the cabinets not moving around. Bass shakers are sub sonic. Off axis response can vary quite a bit, a few mrad of movement could change the imaging drastically.

I'll need two things in order to accept this as probable:

1. An accurate measurement of movement in a situation where the cabinet is not solidly coupled to the floor. [let's say using soft rubber feet as opposed to spikes].

2. Corrolary perceptual research that demonstrates that the degree of movement in the relevant axis, in itself, will cause any significant degredation or change in audio.

-Chris

 

[WmAx]

Being simplistic about it (the only way I know how), you want the speaker drivers to vibrate, and nothing else, to avoid harmonics, distortion, and other un-controlled sounds.

In a perfect world, you could get this by having the drivers 100% rigidly mounted to an infinitely heavy (actually "massy") mass. In reality, the masses of the speaker cabinet itself, and the mass of the stand and/or floor it sits on, are finite, and the "mountings" aren't perfectly rigid.

What is(are) the real consequence(s) of having imperfect mountings, that are not perfectly rigid? Source of data?

So, you go for a compromise. Too soft a coupling between the speaker and its stand (or the floor) and you get energy absorbtion and loss of sound (basically the whole speaker cabinet will move in reaction to the speaker drivers). Too rigid and you get the stand and/or floor vibrating.

The cabinet will move? By how much? How much will cause audible issues? What is the source of data on this?

-Chris

 

[MacManNM]

You stated Newton's 3rd law as the reasoning behind coupling in one of your first posts.

I used the theoretical condition of a vacuum with free floating object, because this offers the most movement, due to opposing mass. In reality, the surrounding air and the issue of the object sitting on a surface[with gravity and contact to the surface offering much additional friction] will reduce the movement to a tiny fraction of the theoretical amount I posed.

Now you are [apparently] claiming that the cone is moving enough air to move the enclosure. Is this correct? If so, please offer some proof that the cabinet is moved any sufficient amount in any realistic circumstances, as to have a negative impact on sound quality. If this is your opinion, then that's cool, but it's not an issue I have seen proven[by any credible source] to be a real concern in any normal circumstance. Perhaps in the very unusual situation, where one has a very high excursion, very large diameter woofer, in a tiny and light enclosure, a very small noticable movement may be achieved due to the air disruption[as opposed to a resonant mode at the coupling of the floor and subwoofer, for example hard feet or direct contact of the cabinet bottom with the hard floor, which is not the same] if said woofer is driven at very high amplitudes.



I'll need two things in order to accept this as probable:

1. An accurate measurement of movement in a situation where the cabinet is not solidly coupled to the floor. [let's say using soft rubber feet as opposed to spikes].

2. Corrolary perceptual research that demonstrates that the degree of movement in the relevant axis, in itself, will cause any significant degredation or change in audio.

-Chris

It's not just the cone, or the air. Its a combination of vibration breaking the friction, the cone movement, the air movement and a few other variables. So I guess you are saying we could mount our speakers on ball bearings and it wouldn't make a difference?


Also any movement of the cabinet robs performance from the setup. How many watts does it take to move a 80 lb speaker cabinet 0.015" which is a little more realistic number than the one you came up with, since I just measured it. This translates into 7.45 watts of power, not taking into account friction. When the coefficient of friction is included this goes up. I didn't do that calculation because there are too many variables to mess with.

This alone is worth using spikes or coupling the cabinet to the floor.

 

[WmAx]

It's not just the cone, or the air. Its a combination of vibration breaking the friction, the cone movement, the air movement and a few other variables. So I guess you are saying we could mount our speakers on ball bearings and it wouldn't make a difference?

Ball bearings...that would be just fine under normal circumstances...except that it would not be practical, since the speaker would be easily moved by accident[a feather-light touch, for example].

Also any movement of the cabinet robs performance from the setup. How many watts does it take to move a 80 lb speaker cabinet 0.015" which is a little more realistic number than the one you came up with, since I just measured it.

I doubt the accuracy of your report, it does not add up. Nor could I come close to replicating it, with extreme conditions[that were used in order to give you the benefit of the doubt]. Did the speaker have a 500 gram cone, or some other unusual circumstance? Did you purposely measure at a resonant mode related to the coupling[which is another matter]? What was the coupling you used? Such a value of movement as you report is not supported by any calculations of which I'm aware, under any normal application.

Since you pose the ball-bearing example, I did just that. I took an old 10" car subwoofer, threw it in a spare, half-completed subwoofer cabinet, which weighed in at 38.6 lbs on a digital scale. I placed a sheet of acrylic down onto a piece of smooth wood on a level surface. I then placed 6 ball bearings on the acrylic. I then placed another layer of acrylic on top of the ball bearing. I placed the cabinet on top of this second sheet.

http://www.linaeum.com/images/sm1.jpg

At this point, the cabinet could be moved with a feather-like touch[no suprise].

http://www.linaeum.com/images/sm2.jpg

I then used a 20Hz sine wave, and adjusted the amplitude until the speaker cone moved +/- 6mm (12mm total travel). I placed a tape measure, with tape, onto the bottom piece of plexi, so that it aligned the measurement marks under the cabinet.

http://www.linaeum.com/images/sm3.jpg

The mm units will make it easy to see a 0.015"(0.381mm) movement by eye. I also video taped the action using a macro lens, so that I could review it on a monitor/zoomed. No visible movement with bare eye viewing. NOt on the video, either. 0.015" of movement did not occur. Not even close. And this, at high amplitude, with a relative light-weight enclosure, set on ball-bearings for minimum friction in the axis of speaker/air movement.

Why should I be worried about movement this small? It's even less[alot less] when it sits, even on soft rubber feet, as compared to ball bearings. Let's assume it was 0.0025"(0.127mm) total movement, since it might be tough to see that by naked eye inspection. That's 0.5% total of the 12mm travel. So, 0.5% of the energy is wasted[on ball bearings]. The movement is not enough to have any effect on even 20kHz signals, so imaging, etc., is a moot point.

Your test result was not repeatable[in an extreme circumstance, favoring your claims].

-Chris

 

[MacManNM]

Ball bearings...that would be just fine under normal circumstances...except that it would not be practical, since the speaker would be easily moved by accident[a feather-light touch, for example].




I doubt the accuracy of your report, it does not add up. Nor could I come close to replicating it, with extreme conditions[that were used in order to give you the benefit of the doubt]. Did the speaker have a 500 gram cone, or some other unusual circumstance? Did you purposely measure at a resonant mode related to the coupling[which is another matter]? What was the coupling you used? Such a value of movement as you report is not supported by any calculations of which I'm aware, under any normal application.

Since you pose the ball-bearing example, I did just that. I took an old 10" car subwoofer, threw it in a spare, half-completed subwoofer cabinet, which weighed in at 38.6 lbs on a digital scale. I placed a sheet of acrylic down onto a piece of smooth wood on a level surface. I then placed 6 ball bearings on the acrylic. I then placed another layer of acrylic on top of the ball bearing. I placed the cabinet on top of this second sheet.

http://www.linaeum.com/images/sm1.jpg

At this point, the cabinet could be moved with a feather-like touch[no suprise].

http://www.linaeum.com/images/sm2.jpg

I then used a 20Hz sine wave, and adjusted the amplitude until the speaker cone moved +/- 6mm (12mm total travel). I placed a tape measure, with tape, onto the bottom piece of plexi, so that it aligned the measurement marks under the cabinet.

http://www.linaeum.com/images/sm3.jpg

The mm units will make it easy to see a 0.015"(0.381mm) movement by eye. I also video taped the action using a macro lens, so that I could review it on a monitor/zoomed. No visible movement with bare eye viewing. NOt on the video, either. 0.015" of movement did not occur. Not even close. And this, at high amplitude, with a relative light-weight enclosure, set on ball-bearings for minimum friction in the axis of speaker/air movement.

Why don't you do it correctly. Use a dial indicator (affixed to the wall or any surface with a lot of mass) to the top portion of the speaker cabinet. Im sure doing the experiment in the proper fashon will yield similar results. I also did not measure woofer excursion, I played a random tone burst with frequency content from 20-20k. Power input was around 40W rms.

Why should I be worried about movement this small? It's even less[alot less] when it sits, even on soft rubber feet, as compared to ball bearings. Let's assume it was 0.0025"(0.127mm) total movement, since it might be tough to see that by naked eye inspection. That's 0.5% total of the 12mm travel. So, 0.5% of the energy is wasted[on ball bearings]. The movement is not enough to have any effect on even 20kHz signals, so imaging, etc., is a moot point.

Your test result was not repeatable[in an extreme circumstance, favoring your claims].

-Chris

Why don't you do the calculation. Lets assume the cabinet does move 0.015". The amount of movement, needs converted to total energy the amp is wasting to move the enclosure. Assuming an 80lb cabinet, can you please run the numbers and tell me how much energy it takes to do this?