Designing speaker stand

[Nuukular]

Hi, I hope I found the right forum for this type of question. I have been working on the design for a speaker stand and have come across a few issue where I have not been able to find the right solution so far.
Probably the best way to start this is by sorting a few of the most important requirements. First off, the stand has to be as sturdy as possible. In my opinion this is most important in the direction the speakers are moving. Secondly, the resonance frequency of the system should be as low as possible - if possible below the audible range.
So far I have come up with a design that from the way it looks is based on a commercially available product, as I like that concept. However, that stand is not available in the height I need it, so I will have to come up with my own interpretation of it.
This image shows the basic design, which mainly consists of two arrays of aluminium tubes. The amp is placed in between the tubes. Top and bottom plates are stainless steel.
stand4.jpg

This image shows one array of tubes removed.
stand3.jpg
What I was looking for, is to preload the tubes with the threaded rod inside of 3 of the 5 aluminium tubes. This initial design featured a little gap between each of the tubes, so there would be no problem in case the tubes would start to resonate a little. Each tube should be filled with sand, to minimize vibrations.

After thinking about everything some more, it struck me that this construction will probably not be sturdy enough. So I came up with the idea that the sturdiness (especially in the direction the speaker moves) could be improved by connecting the tubes to each other, distributing the applied force on a broader area. However, this currently is my main issue. I do not see an easy way, how I could attach the tubes to each other. I don't think glue would be an option, since the area it can be applied to is much to small. I don't see any practical way I could use screws for that. Last option would be to weld the tubes to each other, but that would be a rather complicated procedure. I would love to hear any input on that issue.

While looking for alternatives, I thought about using square tubes instead of round ones. Even though they probably will not look that nice in the end, it would probably be possible to glue them to each other as there is pretty large area to apply the glue to. What do you think about that?

I would very much appreciate your thought on these issues, as well as on the general design.

Edit: Please let me know if the images are too small. Seems like they are resized automatically.

[PinkertonD]

Hi and welcome. I actually have several thoughts!

Gotta say I am perplexed. "the direction the speakers are moving," what does that mean? Are you suggesting the very light cones of the speaker will have sufficient inertia to move a 50-lb metal stand? Your ears would be bleeding before they would even think about moving the stand. In fact probably the neighbor across the road and down two blocks, ears will be bleeding before that.

Do some research on the resonant frequency of various diameters and thicknesses of the tube you think might be good. The lowest audible frequency generally heard by the best of human ears is around 20Hz. I can't see many tubes getting that high unless they are 0.010"-walled spring steel.

It all sounds like a very complicated approach to sitting a couple of speakers on the floor.

Just what are you trying to achieve?

Do the stands go from floor to ceiling or what?

[Kelly_Bramble]

Just what are you trying to achieve?

X2

The sand would absorb the sound and mute the effects I think

[jboggs]

And make it much heavier.

You might want to check this company out. They are one of many that offer extruded aluminum structural components, kind of an "Erector Set for grownups". I have used their stuff for several projects in the past.
http://www.8020.net/Default.asp
http://www.8020.net/casestudy.asp

[Nuukular]

Gotta say I am perplexed. "the direction the speakers are moving," what does that mean? Are you suggesting the very light cones of the speaker will have sufficient inertia to move a 50-lb metal stand? Your ears would be bleeding before they would even think about moving the stand. In fact probably the neighbor across the road and down two blocks, ears will be bleeding before that.

well, I've got to admit, I've actually never thought that this would matter in the past, until a speaker designer proved me wrong by actually doing listening tests when placing speakers on different stands. Sure, this will not matter too much when talking about typical consumer audio systems. However, I guess I should have probably added that I am talking about a situation which involves professional high end audio components in first place; and actually every little bit matters in order to achieve the most ideal listening environment. I think in the end we are talking about two things: An impulse that is initiated by speaker which is trying to move air as fast as possible and creates a force in the opposite direction, which is applied to the stand. That's why usually speaker stands should be as sturdy and heavy as possible, as every little movement of the speaker will result in coloration of the sound. The other thing is the vibration of the enclosure and the stand which will for instance happen when a constant sinusoidal tone is played.
Honestly, I do not have any actual data of what forces will apply here, but I think this actually might only be modelled by an approximation, as we are trying to create a system that has ideal properties - at least as much as possible.

It all sounds like a very complicated approach to sitting a couple of speakers on the floor.

Just what are you trying to achieve?

I agree that this is complicated... but that's kind of what creating a perfect listening environment always is...

What I am trying to achieve is to create a speaker stand that will not limit my current reproduction setup, while still allowing to integrate the amp in the design in order to keep cables as short as possible.

[Nuukular]

And make it much heavier.

You might want to check this company out. They are one of many that offer extruded aluminum structural components, kind of an "Erector Set for grownups". I have used their stuff for several projects in the past.
http://www.8020.net/Default.asp
http://www.8020.net/casestudy.asp

I think the sand will not only make the system heavier and dampen resonances, it will also lower the resonance frequency of the system.

Thanks for the links - looks like fun stuff. However, I currently don't see how that would improve the sturdiness of my current ideas or make them easier to assemble while still maintaining the sturdiness I would achieve by gluing square shaped tubes together.

[PinkertonD]

Well, having spent several years of my working life in anechoic chambers involved with the design of broadcast Monitor speakers (as in professional sound studios) for several UK manufacturers, I felt I may have been suitably experienced to leap in here.

Illusionists make one believe what the Illusionist wants them to see. Similarly, a speaker designer, may encourage you to "hear" what they want you to hear.

Good luck with the project.

[jboggs]

So, it sounds like this is for your own use, and not meant to be portable. True?

[RWOLFEJR]

I don't hear so well anymore and my dash speaker in my 71 Ford seems to work fine by me...
And I'm inclined to agree with Dave on the sales illusion thing. I'd guess most folks can't hear to the levels the audio can be reproduced to anyway.

But...
If exact or precise reproduction of a sound is what you're after. And I'm just thinking out loud here so don't beat me up on this... But maybe you need to look into a way to suspend the speakers in mid-air? Hover speakers... Maglev speakers...

If this makes you a fortune feel free to share...

Good Luck,
Bob

[Kelly_Bramble]

I'd guess most folks can't hear to the levels the audio can be reproduced to anyway.

Not me - my hearing has been going south for years!

[Nuukular]

Well, having spent several years of my working life in anechoic chambers involved with the design of broadcast Monitor speakers (as in professional sound studios) for several UK manufacturers, I felt I may have been suitably experienced to leap in here.

Illusionists make one believe what the Illusionist wants them to see. Similarly, a speaker designer, may encourage you to "hear" what they want you to hear.

Good luck with the project.

In case you were having the impression that I ment to be disrespectful, that has not been my intention at all. I honestly appreciate everyones input on my questions. Probably my standpoints and believes are not the same as yours, but if it weren't the case that I would be uncertain about certain aspects, I would not have taken the time to write such a posting in first place. I think things like that are best solved by using actual data or calculations to support a standpoint. Unfortunately I haven't found any reliable information about the forces that are involved in such a case and I haven't had the time and patience to thoroughly do my own calculations that would provide a reliable foundation for being sure about what's going on in extreme cases. If you have any actual data on how the stand affects the reproduction quality of a speaker, or any calculations about the forces involved in such a case, I would highly appreciate it, if you could post some of it.
About your second point... I know that there are lots of guys, especially in the world of audio, that try to sell their magic gear, which apparently isn't much more than a big collection of buzz words. I am also aware of that the mind is too easily tricked into what one wants to believe. I've had to realize that more than once, actually.. However, the experience I described had nothing to do with anyone trying to sell his stuff. I just made the experience that someone made a good change to my listening environment by changing a few minor things about the way I had mounted my speakers quite some years ago. However, this clearly hasn't been a scientific test, so that actually bring me back to my initial problem of not knowing for sure which parameters in what quantity a good stand has to fulfill and if my design is good enough and what would be the best method to assemble it.

[jboggs]

In my opinion, and its been a lot of years since I took any courses in vibration analysis, if you want the surroundings to have the least impact on the performace of the speakers, you do one of two things: you either make the surroundings as light as possible (as in the suspension suggestion), or you make them as heavy as possible (Support the speakers in a concrete monument). The theory being that you create an order of magnitude difference in material density between the speaker bodies and their surroundings. I know both suggestions are equally unfeasable, but am I way off in my understanding of the situation?

[RWOLFEJR]

Hi Nuukular,
Gotta say I can relate to the way you think. I often find myself going through thoughts or calculations to optimize or verify some design or process to the umpteenth degree. That's why I pop on this site. It's fun to see what folks are working on and maybe be able to offer some input or learn something from input others offer up on their projects. My knowledge on vibration is very limited and I've been watching this thread more for the learning aspect.

Also meaning no disrespect... and bear in mind my lack of experience in this... I'm wondering if any additional noise generated through the stand could ever be heard above the sounds blasting out of the speakers? Just thinking maybe there's no point in worrying about what might be produced because of the inability to detect it from the position of the listeners. Maybe the added sound could only be heard from behind the speakers or off to the side and then... maybe only from inches away? Just thinking that it'd be time wasted to fix something that might not be broken?

Then on the complete opposite side of that thought... Could any additional output from the stands be desirable in any way? Sort of like a subwoofer using your floor to generate rich lows with small inputs to "enhance" the experience. Unless maybe you have a cracked floorboard or a loose board throwing out a sour buzz. I would guess that most of any sound generated by the stand would be transmitted into the floor rather than coming off the tubes etc.?

When working on sound barriers for a couple of very loud pieces of equipment here in our shop I went to businesses involved in supplying materials for reducing sound to learn what would be required to quiet things down. What I learned from three sales reps and some searching around is basically the extent of what I know about noise. Sound deadening is easier when you're dealing with a small range of frequencies. It's tougher when it's the broad range you're looking at. What works for higher frequencies doesn't do much for lower and visa versa. Dense kills lows and fluff kills highs...

I'll toss some more fuel for thought out there... Slow at work today...
Maybe sit the speakers on gel pads of some sort? Gellin' like a felon... Maybe encapsulate all but the exit of the speakers in oil... like a liquid filled gage dampening the needle. Maybe consider lead sheet and / or aerated metal sheeting covering on the stands? (That stuff is functional and also looks really nice)

Here's something that might be neat to try. An experiment... What about hanging a speaker or two from a few chains on hooks at the four corners of the speakers and cranking them up and see what happens.
Maybe build stands heavy enough to handle the weight and hang the speakers from fluid or rubber "shock absorbers" or isolators so their attachment doesn't transfer into the stand to the floor... with that cracked board that only the guy in the front row can hear but it drives him nuts.... bzzzzz....bzzzzz...bzzzz.

Might look at sound cancellation companies and see what testing methods they are using for quantifying differences and apply similar to your designs or changes in the design.

Good luck,
Bob

[Nuukular]

Thanks for the suggestions. That approach using gel pads is definitely something one might want to consider, as it even has found its way into "professional" audio as a commercially available product. To me this approach does not make too much sense, as I feel the best option is to try to prevent the speaker enclosure from moving as much as possible. I guess the same thing applies for the approach of suspending the speaker enclosure (if I understood it correctly)... I think, the enclosure should be mounted as sturdy as possible, so that the driver is able to do its work translating as much current as possible into air movement. By making the stand as heavy as possible and to have a low resonance frequency, you are trying to prevent it from having any impact as much as possible. Yeah, well... the resonance of the floor might be another thing, especially in case when your floor is kind of light... but I guess this is one of the last issues you will be dealing with... At least I have never found that to be of any sort of major problem.
Bob's idea of using parts of the room in order to enhance your reproduction system is kind of interesting, but I guess trying to design a room to compensate for issues that your speakers have, will be much more costly in end. I guess you will be better off buying better speakers that suit your needs...

So, I spent some more time thinking about my design. I guess I will end up using square tubes instead of the round ones. I will glue the tubes to each other and fill them with sand. That way they should have a high inner damping and provide enough sturdiness. I will use 3 threaded bolds for 5 of the tubes in order to mount the top plate against the bottom plate... I think I found a supplier which provides 50x50x2mm square stainless steel 1.4301/V2A tubes at a reasonable price. Maybe I will be overdoing it a little this way, but I couldn't find any prove that less would be sufficient as well (let's not forget that is still kind of a very complex topic).. And the costs will stay way below the commercially available alternatives... At that point right now, I even can't think of any way of making that design more sturdy, without thinking about just building it of concrete or something similar... and that is something I definitely do not want to do....
And that's how it maybe one day will look: stand2.1.jpg