MJL21193 said:I'm just going to go ahead and give it a name - "The triangular Six-pack" and call it the official brace of this thread.
call it by its real name. a "truss".
incidentally, I wouldn't worry about skew in a 6-sided enclosure. there are shear walls for every joint.
i still wonder about in-phase (absolute direction, not pressure) opposing wall vibration.
pooge said:
No brace stops panel resonance, they move them up in frequency -- the higher the better ... in the case here the diagonal moves the 1st resonance from 60 Hz up to (oops, misread that as 215 Hz earlier -- thanx for making me look at that again) to 115 Hz -- so it isn't as effective as the vertical brace, but better than the horizontal and the point brace.
dave
planet10 said:
So "stop" was a poor choice of word. However, the diagonal brace is not placed at an anti-node where the vibration amplitude is at the max, i.e., at the middle of the panel between clamping points. It is placed at panel nodes where the panels are clamped by adjacent panels. Therefore, it should do very little, if anything, to the panel resonance.
A vertical brace in the form of a dowel will clamp the antinodes and divide the panel in half in two directions.
A means of damping panel resonances is this thingie:
http://www.korff.ch/E/hawaphon.htm
It converts motion into heat by the use of friction.
One manufacturer using it is:
http://www.duevel.com/
Regards
Charles
http://www.korff.ch/E/hawaphon.htm
It converts motion into heat by the use of friction.
One manufacturer using it is:
http://www.duevel.com/
Regards
Charles
Here's a recipe for a good cabinet:
Brace everything and keep the spacing between each to 15-20cm.
Use composite panel construction ie. 9 + 18mm MDF for walls or better still mix different materials and thickness's.
Line the walls with 2mm lead flashing sheet (roofing material). Affix using contact adhesive and hammer down with mallet. Over this place 2mm bitumen sheet.
These are things I follow and I always end up with nice dead cabinets. Downsides are the weight, added construction time and extra material costs.
An interesting tool is a stethoscope. Place it in various places on the cabinet and lightly tap a panel. You'll probably be shocked with most commercial cabinets, they're quite disappointing. The recipe I mentioned above fares very well in comparison to the average.
Brace everything and keep the spacing between each to 15-20cm.
Use composite panel construction ie. 9 + 18mm MDF for walls or better still mix different materials and thickness's.
An externally hosted image should be here but it was not working when we last tested it.
Line the walls with 2mm lead flashing sheet (roofing material). Affix using contact adhesive and hammer down with mallet. Over this place 2mm bitumen sheet.
An externally hosted image should be here but it was not working when we last tested it.
These are things I follow and I always end up with nice dead cabinets. Downsides are the weight, added construction time and extra material costs.
An interesting tool is a stethoscope. Place it in various places on the cabinet and lightly tap a panel. You'll probably be shocked with most commercial cabinets, they're quite disappointing. The recipe I mentioned above fares very well in comparison to the average.
y8s said:
I think Dr. Geddes' cross posts are, by far. the most cost effective bracing approach. I make my panels with two layers, sometimes different materials, with a flexible adhesive between for a constrained layer approach. But this is DIY so a little excess is fine. If you need more deadening , first thing I'd do is just add a couple more cross braces. I don't think that in-phase panel movement will be significant, but it's easy to add a couple of diagonal braces - you only need two in opposing corners. Doing all four corners adds very little.
Sheldon
pooge said:
The measured experimental data speaks for itself. The diagonal passes thru the centre of the panel -- where the end of the dowel is in the adjacent drawing -- so prevents deflection and is certainly more effective than the dowel -- dowel pushes resonance from 60 to 85 Hz, the diagonal from 60 to 115 Hz
I think you may also be looking at the pictures without understanding what it represents. You are looking at the cross-section of the bracing, down onto the panel that sits on top of those braces.
dave
phase_accurate said:
That is interesting. It could be very effective and bonded to the panel would provide damping for both means of transmission. From the sketchy tech data (did you find any more?) it is less effective at low frequencies, so would not eliminate the need for braces.
And the added mass with no additional stiffness will push panel resonance in a direction opposite of what is desired (also an issue with lead & bituminum pads). Some of the illustrations seem to show it as part of a sandwich -- ie a high tech version of the sand in Brigg's panels.
dave
MJL21193 said:
A sense of humour? Got one?
Believe me, I know what a truss is.
So what happens to the corners when the panels flex in and out? Those angles don't change? Geometry.
believe me, i know what a sense of humor is. i'm just trained not to react.
just to clarify for myself, corners are points of intersection of 3 planes. edges are lines of intersection of 2 planes (glue joints). surfaces are planes (sheets of wood).
anyway, the corners are, by definition, supported in three dimensions right? you have an "L" shaped intersection with a flat wall perpendicular to both legs of the L. Essentially that triangulates the L. integrity of the 90 degree angle goes from "strength of the joint" to something much higher.
unless the third dimension of your L (think extruded L) is very large, the adjacent walls are going to support the angle of the L quite well. This is why I dont stand on my subwoofer enclosures when two opposing sides are missing but I can when all 6 walls are installed.
Here's the question for the day though:
How do you install your panel support pole on a dipole panel? (no pun answers please!)
y8s said:
Think of it like this: What would be stronger, one big box or two smaller boxes that when put together take up the same amount of space as the bigger one? Which would control vibration better?
This is what you are doing when you add a full panel brace - the box is effectively cut in two, and this forms 8 more 3 plane corners.
Its quite funny, but you have denied any difference between plywood and MDF...makes me wonder if you really think you can hear any difference between different types of bracing, rods or whatever...hell, some people even deny any difference between amps
You were very eager to do measurements on ply vs MDF, and I must say did good work, but probably inconclusive...when do we see some vibration measurements on bracings
You were very eager to do measurements on ply vs MDF, and I must say did good work, but probably inconclusive...when do we see some vibration measurements on bracings
tinitus said:Its quite funny, but you have denied any difference between plywood and MDF...makes me wonder if you really think you can hear any difference between different types of bracing, rods or whatever...hell, some people even deny any difference between amps
I don't want to be rude, but have you actually read any of my posts in this thread?
You said I claimed "expert" status. I did no such thing.
At no point did I say that effective bracing will make an audible difference. My focus here has been entirely on strengthening the box to reduce vibration.
Explain to me the reasons for ignoring excellent design strategies and going with a less than ideal solution? Pride? Obstinance?
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