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.
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 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.
SPL = 20 Log(p/p ref)
p ref = reference pressure in pascals = 2 x 10^-5 Pa (pascals)
1 Pa (Pascal) = 0.000145037738 Psi (Pound Per Square Inch)
I made the assumption his sub's output was under 130dB and did the math.
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.
so i take it that nobody else is having panel flexing and/or vibration with their build?
my second pair which is also built with 18mm MDF also exhibit the same vibration albeit at a much reduced manner. probably because of the less capable 15" driver used (dayton dvc15).
i doubt the vibrations/flexing are caused by panel resonance as the side panels are of difference length (slanted build) and they still exhibit vibration when only one driver are mounted (the other woofer mount sealed with MDF).
i'm not able to mount the ixl15 in this enclosure for testing as the drivers won't clear the side panel. too bad.
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.