Panel flexing even with cross bracing in a sealed sub - Page 2

Not getting at anything. I just think there is a better way to do it. It's really simple, not complicated. Wide braces. I just need some figures/diagrams to explain why it works better. Maybe your braces already do what I'm thinking about.

The image is just a diagram I was able to find on the internet about slender column design.

Here is a better one I managed to find: http://www.ejsong.com/mdme/modules/fea/Buckling.GIF

Because the panel is "fixed" at the corners, we have the second from the left case.

Now look at this: http://1.bp.blogspot.com/_721bPXg5FDs/TVA9Q1RzCQI/AAAAAAAAAME/BN0Zp1e11oM/s1600/fig.jpg

By adding a cross brace you add 1 or 2 or nth nodes to the panel thus reducing the effective L that can vibrate. That's because a dowel or a 1" wide brace acts like a node. If you use braces that are say 3 or 4" wide (even if you want it light, just cut out the middle portion) then you aren't adding a node, you add a fixed brace which reduces L again by 0.5. I just can't find the last diagram I need to explain that part.

It's why holey braces are so effective. But I'm proposing something smaller than holey braces, yet close to the same effect. Nothing new, many have done it I'm sure. Possibly everyone does it. I just don't see many pictures of it. I usually only see 1" strips, dowels, or holey window braces. The best brace for the weight is a 4" wide stip, imo.

I'd be more worried about your room flex, you lose more SPL there because of the greater surface area. Go Go Gadget Green Glue

I have an idea to visualize flex/vibration if anyone wants to try it. Lemme know if it sounds like a sane thing to try.

Put some sticky dots on a surface of the sub box in a grid pattern or whatever, turn the lights out and play some test tones. Use an adjustable strobe light to look at the dots using the aliasing effect (x < f < 2x the frequency of the vibration/flexing).

My theory is it will appear in slow motion and you can see the dots moving up and down and back and forth and be able to tell the difference between flexing and vibration. It's the same idea as using a strobe light on a fan or timing belt.

Similar to this video:

I believe the SPL inside the enclosure will be much higher.

Or just do the simple gas law calculation: % volume change of box from cone excursion x 14.7 psi.

I just did for my abovementioned sub and got .25 psi.

Not sure what you're getting at either, but maybe it's stress stiffening, like tightening a guitar string to increase its resonant freq.

You could do that by using crossbracing slightly too long, or too short and screwing into it from outside to pull the panels up to it.

Using simple beam theory, deflection is related to span ^ 4. So 1/2 span gives 1/16 deflection. Very approximate for 2D bending only.

Cheers,

Bending stiffness varies with the cube (^3) of length, same for section height.

It would be ^4 if increasing the dimension in 2 dimensions, as for a round or square section.

No that wasn't it either, but once I drew up the diagrams I was thinking about, I realized where I went wrong. The concept of buckling doesn't apply. Well, it does, but not how I was thinking. Major disconnect. Oh well.

How so?

Buckling, also called elastic instability, only occurs in compression loading of thin members, which is not the situation here.

It applies to the brace if it's suffeciently slender (a dowel), but as I already said, what I originally was thinking doesn't work how I thought.

I've never heard it called elastic instability. That phrase sounds like it can be applied to much more than just column buckling.