bee_dub

Huh, I'm surprised that Birch ply is the same weight as MDF.. I'm always surprised by how heavy 18mm MDF feels. So for a sub that needs to be as light as possible, but not at the expensive of functionality, should it be all 18mm Birch ply? Or could bracing be lightweight ply?

Sure, thanks.. weight is the main consideration, so I would definitely not use MDF. When you say it's like a musical instrument though, instruments like a cello for instance are made to resonate, whereas here we're aiming to prevent it, yes? Also, if one theoretically was to attempt a lighter weight version, would it be possible to include some extra bracing, or would this interfere with the properties of the design?

While I'm at it, what are the important considerations for the type of plywood? Is it just stiffness? I used some lightweight plywood a little while ago, and from memory it was something like 40% lighter than the usual stuff. The seller claimed it was as strong as a standard type of plywood, but I don't know by what metric. I don't know if this is a foolish aim, but I'd love to be able to throw one of these around by myself if necessary..

At the risk of becoming a @h3idrun Reply Guy, here's some Melbourne plywood info: Plyco in Fairfield have 18mm Birch BB for $160/sheet and Hardwood Exterior Plywood for $100. I think they'll chop it up for a relatively modest fee if transport is an issue. Here's another supplier - don't ask me what all the terms on that page mean though! Also, Upton's in Epping sell some really cheap, VERY light plywood that I reckon I'll use at least for bracing, once I get around to building something. I can't find it on their website, but give them a call if you're interested.

G'day! First up, hello, and let me add my thanks to @Ricci for the generous provision of your plans and knowledge. I've gotten interested in live sound recently after long absence, but this time have carpentry/joinery skills in my back pocket! I can't wait to build my first Skram once the appropriate number of pennies have been saved for a driver. For @h3idrun, I know your pain as a fellow payer of the Australia Tax! I've spent quite a bit of time researching buying drivers, so for what it's worth, here are some observations that may help: - I've found TLHP in France to be by far the cheapest supplier of drivers to Australia. I haven't used them, but they claim to be the EU's biggest stockist of speakers. I'm surprised you don't hear about them more, but I guess in the US at least pretty much everything would be distributed there.. - Ordering from TLHP, the sweet spot for 21" driver prices is up to 400 euros. Once you add shipping and convert to AUD, it gets you just under $AUD1000, which means not involving customs (assuming you're happy buying one at a time). By the way, if you make an account with them, you'll see ex. VAT prices and be able to calculate shipping. Drivers under that amount include B&C 21SW115-4, Lavoce SAN214.50, and others by RCF, Beyma, etc. - In terms of Australian stock, there's obviously very little.. Here's a link to an SB Audio 21" from Wagner Online (no idea about its suitablity); The Speaker Factory stock Eminence drivers, but only seem to have 18" max; then you can also obviously buy through eBay, but you'll have to pay GST and I've only seen prices a fair bit higher than THLP anyway.