Yes, sorry typo - should have been "Squares vibrate, but triangles do not?" (But I think that you knew what I meant.)
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Gedlee, If you have a PhD in Acoustics, and I have no doubt that you do, then you must have done high school science classes. I can not believe that a man so learned does not understand the special nature of the triangular form. I can only conclude that you are being delibrately obtuse. (I love puns!)
If you have to win each and every argument by any means, then I have little respect for you.
Terry
Just trying to keep up with the recent conclusions 
There are some Triangles in here , some cross bracing ...
On a side note : Gedlee , I've noticed that your speakers , while having big 8' - 15' woofers , the boxes have only 1 simple cross brace in the middle , how is that optimal ?
There are some Triangles in here , some cross bracing ...
An externally hosted image should be here but it was not working when we last tested it.
On a side note : Gedlee , I've noticed that your speakers , while having big 8' - 15' woofers , the boxes have only 1 simple cross brace in the middle , how is that optimal ?
Hi
This is my take on trying to make a stiff but light cabinet .Using ply with alloy rods for the dowelling and an alloy baffle .On the internal walls I'll bond more alloy rodding to break up the size of the walls so they apear to be smaller panels.Whether it all works ,who knows .The outer & internal walls will be wrapped in 1.6mm alloy sheet .
Cheers
This is my take on trying to make a stiff but light cabinet .Using ply with alloy rods for the dowelling and an alloy baffle .On the internal walls I'll bond more alloy rodding to break up the size of the walls so they apear to be smaller panels.Whether it all works ,who knows .The outer & internal walls will be wrapped in 1.6mm alloy sheet .
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Cheers
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Just trying to keep up with the recent conclusions
There are some Triangles in here , some cross bracing ...
On a side note : Gedlee , I've noticed that your speakers , while having big 8' - 15' woofers , the boxes have only 1 simple cross brace in the middle , how is that optimal ?
Move the points of the triangles fully into the corners and you have it. As thick as you have drawn it, it makes little difference in a practicle sense but the triangles formed add extreme rigidness to the structure of the bracing. The bracing can not flex.
Terry
Phoenix , That's what I did in the past few pages until I was told that corners are the strongest points in the box , Thus I redesigned it and moved it away from the corners ( I cannot put them in the middle of the baffle because that would interfere with the holes as you can see from the picture ).
There is an explanation in some pages back that triangles , while wonderful mathematically correct rigid structures , do not handle panel resonance too well ... or somthing like that
56oval , I thought about making an aluminium baffle , How did you glued it to the birch ?
edit: phoenix , how can I put front to back brace in the middle ? the hole kinda ruins any chances I dont have any room ... I dont see anywhere else I could put the braces ( notice how the upper brace is a double brace ) lack of room ... or it would interfere with chamfering the holes or somthing ...
There is an explanation in some pages back that triangles , while wonderful mathematically correct rigid structures , do not handle panel resonance too well ... or somthing like that
56oval , I thought about making an aluminium baffle , How did you glued it to the birch ?
edit: phoenix , how can I put front to back brace in the middle ? the hole kinda ruins any chances
I dont have any room ... I dont see anywhere else I could put the braces ( notice how the upper brace is a double brace ) lack of room ... or it would interfere with chamfering the holes or somthing ...
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Phoenix , That's what I did in the past few pages until I was told that corners are the strongest points in the box , Thus I redesigned it and moved it away from the corners ( I cannot put them in the middle of the baffle because that would interfere with the holes as you can see from the picture ).
There is an explanation in some pages back that triangles , while wonderful mathematically correct rigid structures , do not handle panel resonance too well ... or somthing like that
56oval , I thought about making an aluminium baffle , How did you glued it to the birch ?
edit: phoenix , how can I put front to back brace in the middle ? the hole kinda ruins any chances
The weakest point on any baffle is the point between the drivers. Put your braces between the woofer and mid and between the mid and tweeter. Braces do not need to be as thick as you have shown them. The x part of the brace is to provide an unmovable point that the true brace pieces can connect to. Doing it this way will also assist to dampen driver vibrations that occur at this weakest point of any baffle in a multiway system.
Dr. Gedlee is quite correct in that a top to bottom brace can further solidify the structure but in general terms the top and bottom of most speakers is the smallest panel and as such requires little in the way of bracing.
What do you guys think causes most problems: acoustic coupling of the sound in the box to the panels of the enclosure, or the mechanical coupling of the driver basket to the enclosure? I reckon both need to be dealt with differently. In my experience the latter is hard to get rid of.
Art Ludwig has done some very simple, yet illustrative experiments: Loudspeaker construction
It appears - probably nothing new to most people here - the problem of sound within the box can be remedied quite well with a dampening material.
Art Ludwig has done some very simple, yet illustrative experiments: Loudspeaker construction
It appears - probably nothing new to most people here - the problem of sound within the box can be remedied quite well with a dampening material.
Yes, this is technically correct and I have done this on some speakers that were being flown because in that configuration the loads are all in tension and the glue joints are far less strong. Putting them in compression adds a lot to the strength (but not all that much to the stiffness). But doing this bows the sides and this is readily apparent when you look at the box.
As to "optimal bracing", "optimal" is the minimum it takes to get the job done and hence, YES, my configuration is "optimal". Overkill is NOT optimal, and doing things that are not audible is overkill.
As I said before - I have been way down this road before and I'm just trying to correct some big misconceptions that are being propagated regarding enclosure rigidity. But obviously people want to believe what they already believe so I guess there is not much point.
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Thanks for your answer.
Oh, don't worry. There's still those of us here, who appreciate being educated.
Oh, don't worry. There's still those of us here, who appreciate being educated.
In his work Art uses fiberglass as the sound absorbent material. In a sealed enclosure I have no problems with this. In a vented enclosure I do. This type of material is a carcinogenic and having the fibres ejected into the room at port velocities is justed plain dangerouse. If you need convincing just read the label!
The best material I have found is LDF. The type of board made into pin up boards. It MUST be completley waterproofed first, including edges, in a way that does not cause a hard surface. Add to this any of the materials sold as speaker lining. It is far better to absorb the energy before it impacts the walls of the enclosure than to try to deal with it once it has. Bracing is still required, but less is now needed.
Terry
Terry
At first view I agree...except perhaps with your conclusion...
Triangular (corner to corner) braces will enhance the global structure rigidity because they strenghten their already most rigid areas. OK, this will also strenghten each of the parts of this structure (panels). But they will be less effective stoping the vibrations in the middle of the panels than cross braces, no? so the best of both worlds seems to be star bracing, no?
If i'm wrong in this statement, could you explain? thanks.
At first view I agree...except perhaps with your conclusion...
Triangular (corner to corner) braces will enhance the global structure rigidity because they strenghten their already most rigid areas. OK, this will also strenghten each of the parts of this structure (panels). But they will be less effective stoping the vibrations in the middle of the panels than cross braces, no? so the best of both worlds seems to be star bracing, no?
If i'm wrong in this statement, could you explain? thanks.
You go from two corners to the middle of the opposing panel. Thus the panel can not move at that point, not even a little bit. A star brace is simply more convenient but the same thing.
Terry
Not Just a Brace Issue
First:
Most effective means of reducing the deleterious effects of the enclosure on the quality of sound reproduced by a speaker system, is to avoid the parallelepiped enclosure shape and common dimension values that reinforce standing wave frequencies within the enclosure.
Second:
The purpose of bracing is to increase panel stiffness and raise the resonance frequency beyond the operating range of the drivers mounted therein. If the internal volume of the cabinet is to be fixed, then adding bracing will increase its size. For most cost effective results, place cross-braces only at the nodes of the first mode of un-braced panel resonance. It is clear from the forgoing observations, that there are diminished returns in any extreme bracing solution.
Third:
For every action, in this case, movement of the driver cone and surrounding air, there is an opposite and equal reaction, in that case the movement of the speaker motor, basket, the attached enclosure , and the all the air that surrounds it as well. The more massive the cabinet the less it will move its much larger radiating surface. Thus, avoid lightweight cabinets.
First:
Most effective means of reducing the deleterious effects of the enclosure on the quality of sound reproduced by a speaker system, is to avoid the parallelepiped enclosure shape and common dimension values that reinforce standing wave frequencies within the enclosure.
Second:
The purpose of bracing is to increase panel stiffness and raise the resonance frequency beyond the operating range of the drivers mounted therein. If the internal volume of the cabinet is to be fixed, then adding bracing will increase its size. For most cost effective results, place cross-braces only at the nodes of the first mode of un-braced panel resonance. It is clear from the forgoing observations, that there are diminished returns in any extreme bracing solution.
Third:
For every action, in this case, movement of the driver cone and surrounding air, there is an opposite and equal reaction, in that case the movement of the speaker motor, basket, the attached enclosure , and the all the air that surrounds it as well. The more massive the cabinet the less it will move its much larger radiating surface. Thus, avoid lightweight cabinets.
Hi Diforce
The baffle will be bolted to the ply with a layer of green goo or a SikaFlex product in between the too.
Cheers
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