[JohnR]

Both lighter, and stiffer push the panel resonance up. As does panel thickness, and shorter panel spans.

Just tapping on a 600x1200mm sheet of 18mm marine ply, it's loudest resonance frequency appears to be around 580 Hz. The 9mm ply is around 350 Hz. (This is not very scientific, just using a tuner in my phone and guessing at the correct octave...)

[jules]

I like jules' idea of external bracing - could get quite creative that way (fins?)

Yes exactly, fins! Easy to do and it's possible to make them convex [if that makes sense] so the bit in the middle of any section is the strong where it's needed most. It could be designed to use less material while giving more strength. It's hard to do that internally.

I used a couple of 100mm X 50mm circumferential "girths" on my sub [in addition to Rythmik's internal bracing] but I've been thinking of using a series of them on the unicorn project, maybe 75mm apart and approx 12 parallel, across the short side of the box.

As an afterthought, it would be easy to clad them with thin ply to give the much desired curved look but I think the ribbed look would be much more interesting.

Marine ply sounds like a good choice. I wonder if it uses our Aus. hardwood? What sort of price can you get it for John?


jules

[JohnR]

Hi Jules - the 600x1200 piece of 18mm thick was $50 - I'd be happy to hear of ways to get it cheaper

They had bending ply as well, which leads to some interesting ideas as well altho I have more than enough to think about right now!