Only a little bit of progress today:-
first off, here's a pic of the notch filter for Pilbarabass:-
Today I braced the cab. As mentioned, Most commercial cabs use 15 or 18mm ply but no bracing. I use 12mm ply to save weight, but brace it for strength and to eliminate unwanted panel vibrations. I’ve seen bracing jobs that add more weight than was saved by using thinner timber. I’ve settled on what I call “Crucifix Bracing” i.e. bracing that’s basically a cross in the middle of the cab or as in this case, at the weakest point of the front baffle. Not only does this link the opposing panels together as normal bracing would, the point where the cross intersects is glued and screwed so as to create a link to both adjacent panels as well. In other words, the front baffle draws on the stiffness 4 panels at the same time: itself, the back panel, and BOTH side panels. This in effect gives my 12mm ply the same strength characteristics as 48mm ply would have, more if you factor in the strength of the brace itself and the direction of the forces being applied to the adjacent panels. As you can see that’s far superior to 15 or 18mm ply with no bracing. I intend to brace the composite cab the same way, even though Zac deemed it unnecessary. And the best part is the bracing adds so little weight my scales could barely tell it was there. The glue, bracing and screws added a mere 200grams in total.
Next I used a router to round off the edges, once again using a bit designed specifically for this with a roller guide and a 6mm radius. I did take a pic at the time but the camera didn't seem to save them properly and those pics are corrupted files. Sorry about that. But you can see the rounded edges in the pic below.
I got so excited I forgot to add screws to strengthen the joints (I'll do that tomorrow) and rushed straight to wiring the cab up for some preliminary testing. Turns out I made a mistake wiring up the crossover and wasted some time fault-finding, then re-wiring it. The tweeter sounds excellent, but to my surprise it will need to be attenuated. The 2.5K mid hump will definitely need to be smoothed out. I tried both notch filters briefly and they both did a good job - I'll need to do more testing to decide which I'll use.
I put the cab on the scales as you see it in the last pic. On top I placed a metal grill I've got lying around from an old Trace Elliot 2x10 I not longer have, the carpet I plan to use, and the corners I plan to use. The whole lot weighed in at 12.1kg.