Using search I haven't found the info I was looking for... Seems like stands aren't a big scream ;/
I was thinking about a DIY of course for my friend's studio.
I thought of 2 ideas for the base of the stand:
either a triangle shaped base on which the whole thing will stand - why a triangle, to ensure all points will touch the floor evenly spread - at most minimum touching points. (A desperate try to decouple from the floor)
or... a circular base, which is of course the total opposite - where the whole thing touches the floor.
I'd have 3 pipes (filled with sand) attached to a middle pole, without leaving them detached from anything all the way.
2 questions arise:
- Is there a real advantage to the 'less touching points as possible' idea?
- What would be the most 'logical' way to create the base on which the monitors themselves stand? (If a simple wooden plate won't do it)
Thanks alot in advance...
happy new year everybody.
Philip
Stand design
Moderator: Aaronw
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Trip-
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Stand design
If you build it, it will...
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knightfly
- Senior Member
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
Man, I wish I had that much time on my hands 
Seriously, are you making an artistic statement or just want good-performing speaker stands? (Not trying to make any negative statements here, it just seems like that's a lot of extra work for no acoustic reason)
The important requirements for a nearfield speaker stand is that it
isolates speaker vibes from the floor some way,
doesn't move around,
doesn't introduce any audible resonances, and
puts the speakers at an optimum height.
In order -
Isolating vibes - this could be done at floor level, using some sort of damped elastomer such as butyl rubber; good part about this is that it causes the weight of the stand to be included in the weight of the speaker - in this version the mass-spring-mass would be floor (first mass) butyl rubber (spring) and the entire weight of the stand, sand-fill, and speaker (which would be solidly attached to the stand in this case)
Isolation could also be done at the junction between speaker and stand - in this case you'd have the sand-filled stand (and part of the floor) as the first mass, then something like a MoPad or butyl pucks (the spring) between the stand and the speaker (the speaker being the second mass) -
The problem with this arrangement is that most speakers aren't heavy enough by themselves to properly compress a high duro material to at least 10% of its thickness - a lighter duro (spongier) material, while allowing proper compression, will allow speakers to rock at higher listening levels due to the force of the cones moving back and forth.
One way around this would be to place heavy steel plates on top of the speaker to increase the upper mass of the mass-spring-mass assembly - this would keep MSM resonance lower, keep rocking to a minimum, and still isolate speaker resonances from the rest of the room.
The reason this isolation is important is that sound travels faster through solids than it does through air; so if your speakers are solidly coupled thru the stands to the floor, and thru the floor to your desk, then it becomes possible for the desk to radiate the sound to your ears BEFORE it gets there thru the air - this scenario will cause smearing of higher frequencies thru phase differences, and just generally cause muddier sound.
doesn't move around - Having a solid stand and speaker helps this - if your "spring" is located between the floor and the stand, it needs to be pretty firm. This means that to achieve low resonant frequency (subaudible) you need pretty heavy stands and speakers in order to get at least 10% compression of the spring material.
The reason for this is that ANY spring, be it metal or rubber or whatever, is ONLY a spring when it is NOT at either end of its travel. Example - take a spring from a Hummer or a Mercedes sedan, and allow someone to hold one end of it and hit you in the face with the other end - after you regain consciousness, you'll probably agree that it wasn't very "springy" - this is because it's designed to hold a 6000 pound car (or at least 1/4 of it) so in a free state, until you load it with about 600 pounds it acts as a solid piece of steel. It's the same way with rubber or butyl or any elastomer that's used as a spring - until you get away from the two extremes of travel, the material acts as a solid. This precludes it from becoming your spring in this mass-spring-mass assembly.
So the solution to this is either use fairly stiff (like 60 durometer) rubber under your stands so they won't rock, or put your "spring" further up the column so the "rocking force"(speaker cone movement) can't cause things to move as easily. This would be where the springy material is between speaker and the top of the stand.
doesn't introduce any audible resonances
These can be caused by insecure interfaces between speaker and stand (no pad of any kind), not enough mass on either side of the spring material to keep MSM at sub-audible frequencies, or using a 4-point base on the stand without having some sort of adjustment to keep all 4 feet firmly in contact with the floor.
puts the speakers at an optimum height
This is covered in the Acoustics forum - basically, you don't want your speaker's woofer to be within about 6" from the center of your room height, measured NOT from any acoustic absorber but from the hard surfaces - see "are my speakers in a null" in the acoustics forum for more on this.
One simple (if inelegant) way to accomplish all this is to buy some hollow concrete blocks, stack them up to about a foot below half your ceiling height, put some MoPads on top, add your speakers, and generate a slow sweep signal into the speakers while listening for resonances. Rattles will be caused by lack of firm connection between two objects, louder frequencies will be caused by either room modes (see the thread in acoustics again) SBIR (Speaker Boundary Interference Response - similar to modes but caused by speaker placement relative to walls/floor/ceiling) or not enough mass on either side of the MoPads (or other rubber product)
I'm not saying that your really attractive design won't work - if you follow the above principles and keep mass high and joints tight, those can be as good as any - it's up to you whether you want that much work or just want to "make noise"
Didn't mean to ramble so much, I hope some of this helps you figure out what you want to do... Steve
Seriously, are you making an artistic statement or just want good-performing speaker stands? (Not trying to make any negative statements here, it just seems like that's a lot of extra work for no acoustic reason)
The important requirements for a nearfield speaker stand is that it
isolates speaker vibes from the floor some way,
doesn't move around,
doesn't introduce any audible resonances, and
puts the speakers at an optimum height.
In order -
Isolating vibes - this could be done at floor level, using some sort of damped elastomer such as butyl rubber; good part about this is that it causes the weight of the stand to be included in the weight of the speaker - in this version the mass-spring-mass would be floor (first mass) butyl rubber (spring) and the entire weight of the stand, sand-fill, and speaker (which would be solidly attached to the stand in this case)
Isolation could also be done at the junction between speaker and stand - in this case you'd have the sand-filled stand (and part of the floor) as the first mass, then something like a MoPad or butyl pucks (the spring) between the stand and the speaker (the speaker being the second mass) -
The problem with this arrangement is that most speakers aren't heavy enough by themselves to properly compress a high duro material to at least 10% of its thickness - a lighter duro (spongier) material, while allowing proper compression, will allow speakers to rock at higher listening levels due to the force of the cones moving back and forth.
One way around this would be to place heavy steel plates on top of the speaker to increase the upper mass of the mass-spring-mass assembly - this would keep MSM resonance lower, keep rocking to a minimum, and still isolate speaker resonances from the rest of the room.
The reason this isolation is important is that sound travels faster through solids than it does through air; so if your speakers are solidly coupled thru the stands to the floor, and thru the floor to your desk, then it becomes possible for the desk to radiate the sound to your ears BEFORE it gets there thru the air - this scenario will cause smearing of higher frequencies thru phase differences, and just generally cause muddier sound.
doesn't move around - Having a solid stand and speaker helps this - if your "spring" is located between the floor and the stand, it needs to be pretty firm. This means that to achieve low resonant frequency (subaudible) you need pretty heavy stands and speakers in order to get at least 10% compression of the spring material.
The reason for this is that ANY spring, be it metal or rubber or whatever, is ONLY a spring when it is NOT at either end of its travel. Example - take a spring from a Hummer or a Mercedes sedan, and allow someone to hold one end of it and hit you in the face with the other end - after you regain consciousness, you'll probably agree that it wasn't very "springy" - this is because it's designed to hold a 6000 pound car (or at least 1/4 of it) so in a free state, until you load it with about 600 pounds it acts as a solid piece of steel. It's the same way with rubber or butyl or any elastomer that's used as a spring - until you get away from the two extremes of travel, the material acts as a solid. This precludes it from becoming your spring in this mass-spring-mass assembly.
So the solution to this is either use fairly stiff (like 60 durometer) rubber under your stands so they won't rock, or put your "spring" further up the column so the "rocking force"(speaker cone movement) can't cause things to move as easily. This would be where the springy material is between speaker and the top of the stand.
doesn't introduce any audible resonances
These can be caused by insecure interfaces between speaker and stand (no pad of any kind), not enough mass on either side of the spring material to keep MSM at sub-audible frequencies, or using a 4-point base on the stand without having some sort of adjustment to keep all 4 feet firmly in contact with the floor.
puts the speakers at an optimum height
This is covered in the Acoustics forum - basically, you don't want your speaker's woofer to be within about 6" from the center of your room height, measured NOT from any acoustic absorber but from the hard surfaces - see "are my speakers in a null" in the acoustics forum for more on this.
One simple (if inelegant) way to accomplish all this is to buy some hollow concrete blocks, stack them up to about a foot below half your ceiling height, put some MoPads on top, add your speakers, and generate a slow sweep signal into the speakers while listening for resonances. Rattles will be caused by lack of firm connection between two objects, louder frequencies will be caused by either room modes (see the thread in acoustics again) SBIR (Speaker Boundary Interference Response - similar to modes but caused by speaker placement relative to walls/floor/ceiling) or not enough mass on either side of the MoPads (or other rubber product)
I'm not saying that your really attractive design won't work - if you follow the above principles and keep mass high and joints tight, those can be as good as any - it's up to you whether you want that much work or just want to "make noise"
Didn't mean to ramble so much, I hope some of this helps you figure out what you want to do... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
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Trip-
- Posts: 21
- Joined: Tue Nov 28, 2006 6:39 pm
- Location: Israel
You don't rumble at all 
I appreciate everything you wrote here...
I guess I do care about external design as much as the engineering part - and the combination of two.
I want to go with the floor-rubber-stand option - what do you mean by monitor solidly attached to the stand? How much attached exactly? Hope you don't mean I should bolt them together
What about the overall weight of stand+monitor - for something like 0.5cm thick butyl rubber? or maybe it should be thinner? I suppose that if in practice it'll compress thikness by 9%, it'll work fine too... I just don't know how to measure something like this.
thanks alot for the info!
very much appreciated
I appreciate everything you wrote here...
I guess I do care about external design as much as the engineering part - and the combination of two.
I want to go with the floor-rubber-stand option - what do you mean by monitor solidly attached to the stand? How much attached exactly? Hope you don't mean I should bolt them together
What about the overall weight of stand+monitor - for something like 0.5cm thick butyl rubber? or maybe it should be thinner? I suppose that if in practice it'll compress thikness by 9%, it'll work fine too... I just don't know how to measure something like this.
thanks alot for the info!
very much appreciated
If you build it, it will...
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knightfly
- Senior Member
- Posts: 6976
- Joined: Sun Mar 16, 2003 11:11 am
- Location: West Coast, USA
For one way to figure out loading, check out my first post on this page
http://www.johnlsayers.com/phpBB2/viewt ... 39&start=0
By choosing to place your "spring" below the stand, you gain the advantage of more weight in the upper mass; by "solidly attached" I meant that the speaker should not be able to move independently of the stand - if the speaker is very light, this might be difficult because the woofer movement can cause lighter speakers to move on their resting place - in that scenario, bolting the stand and speaker together would be preferable.
IN any case, when placing the "spring" material below the stand you do NOT want ANOTHER elastic material between the speaker and the stand, because this will cause an unpredictable (and almost always undesirable) second spring and third mass, forming a m-s-m-s-m assembly. This will raise the individual resonance frequencies more into the audible range.
If you can find some sort of relatively thin "anti-skid" type of material that does NOT compress (or at least, not easily) to place between speaker and stand, it will keep things from shifting but shouldn't cause a second spring effect. Speakers that are heavy enough to help keep the interface between speaker and stand from moving around would be a plus here.
If you check out the post I linked to above, it should help with the basic concept of "dialing in" the cross-sectional area of the "spring" material - keep in mind that the wider the gap between masses (with any given spring material) the lower the resonance frequency - so generally thicker elastomer is better. The downside is that if you get it TOO soft then the stands will tend to rock around.
IF you already know the weight your proposed materials will add up to, you can calculate the total weight that will be "sprung" by adding the weight of a speaker and the weight of dry sand the tubes will hold - dry sand weighs approx. 100 PCF. So take the inside diameter of your tubes, divide by 2, square that, multiply by 3.1415926 (3.14 is close enough) to get the area in square inches, multiply that by the length of the tube (in inches), then multiply that by the number of tubes - finally, divide by 1728 to get cubic feet, and multiply THAT # by 100 to get the total weight of sand in pounds.
Use that figure to do the experiment on the linked page, and adjust the size of your rubber pucks under the speaker stand until you have just enough total surface contact to achieve 10-15% compression - hopefully your floor is solid enough to handle the type of point-loading this will cause - if not, you could maybe place a thick piece of MDF on the floor UNDER the bottom plate of the speaker stand, with the rubber pucks between them. That would spread the weight around better on a weak floor. Keep in mind though, that if your floor is that weak it'll probably add to the resonance problems whether your speakers are there or not... Steve
http://www.johnlsayers.com/phpBB2/viewt ... 39&start=0
By choosing to place your "spring" below the stand, you gain the advantage of more weight in the upper mass; by "solidly attached" I meant that the speaker should not be able to move independently of the stand - if the speaker is very light, this might be difficult because the woofer movement can cause lighter speakers to move on their resting place - in that scenario, bolting the stand and speaker together would be preferable.
IN any case, when placing the "spring" material below the stand you do NOT want ANOTHER elastic material between the speaker and the stand, because this will cause an unpredictable (and almost always undesirable) second spring and third mass, forming a m-s-m-s-m assembly. This will raise the individual resonance frequencies more into the audible range.
If you can find some sort of relatively thin "anti-skid" type of material that does NOT compress (or at least, not easily) to place between speaker and stand, it will keep things from shifting but shouldn't cause a second spring effect. Speakers that are heavy enough to help keep the interface between speaker and stand from moving around would be a plus here.
If you check out the post I linked to above, it should help with the basic concept of "dialing in" the cross-sectional area of the "spring" material - keep in mind that the wider the gap between masses (with any given spring material) the lower the resonance frequency - so generally thicker elastomer is better. The downside is that if you get it TOO soft then the stands will tend to rock around.
IF you already know the weight your proposed materials will add up to, you can calculate the total weight that will be "sprung" by adding the weight of a speaker and the weight of dry sand the tubes will hold - dry sand weighs approx. 100 PCF. So take the inside diameter of your tubes, divide by 2, square that, multiply by 3.1415926 (3.14 is close enough) to get the area in square inches, multiply that by the length of the tube (in inches), then multiply that by the number of tubes - finally, divide by 1728 to get cubic feet, and multiply THAT # by 100 to get the total weight of sand in pounds.
Use that figure to do the experiment on the linked page, and adjust the size of your rubber pucks under the speaker stand until you have just enough total surface contact to achieve 10-15% compression - hopefully your floor is solid enough to handle the type of point-loading this will cause - if not, you could maybe place a thick piece of MDF on the floor UNDER the bottom plate of the speaker stand, with the rubber pucks between them. That would spread the weight around better on a weak floor. Keep in mind though, that if your floor is that weak it'll probably add to the resonance problems whether your speakers are there or not... Steve
Soooo, when a Musician dies, do they hear the white noise at the end of the tunnel??!? Hmmmm...
-
Trip-
- Posts: 21
- Joined: Tue Nov 28, 2006 6:39 pm
- Location: Israel
knightfly thanks alot for this info!
It took me time to reply - but I was waiting to make this sketch into reality...
And now it's ready!
Anyone who wants to check out the results the whole process is posted here:
http://forum.studiotips.com/viewtopic.p ... 0&start=40
Thank you very much!
It took me time to reply - but I was waiting to make this sketch into reality...
And now it's ready!
Anyone who wants to check out the results the whole process is posted here:
http://forum.studiotips.com/viewtopic.p ... 0&start=40
Thank you very much!
If you build it, it will...