RichardH Posted January 4, 2021 Share Posted January 4, 2021 I juts played with that very nifty ply weight calculator: An area of 1.57m2 using 18mm MDF gives 20.76kg (plus the 8kg of the driver and allow some for hardware etc gives the quoted weight of the current cab). Here are the weights for various materials 18mm MDF: 20.76kg 18mm Birch: 17.55kg 18mm spruce/poplar: 12.42kg 12mm birch: 11.7kg I wouldn't use 12mm poplar unless you really know what you're doing with bracing etc. So if you can get hold of 18mm poplar then you'd be nearly as light as a 12mm birch cab - though the cab will still weigh 21kg once the driver etc is added. 1 Quote Link to comment Share on other sites More sharing options...
lowrentdiscographer Posted January 4, 2021 Author Share Posted January 4, 2021 1 hour ago, RichardH said: I juts played with that very nifty ply weight calculator: An area of 1.57m2 using 18mm MDF gives 20.76kg (plus the 8kg of the driver and allow some for hardware etc gives the quoted weight of the current cab). Here are the weights for various materials 18mm MDF: 20.76kg 18mm Birch: 17.55kg 18mm spruce/poplar: 12.42kg 12mm birch: 11.7kg I wouldn't use 12mm poplar unless you really know what you're doing with bracing etc. So if you can get hold of 18mm poplar then you'd be nearly as light as a 12mm birch cab - though the cab will still weigh 21kg once the driver etc is added. I got very similar numbers, and I think represent significant weight savings? Quote Link to comment Share on other sites More sharing options...
RichardH Posted January 4, 2021 Share Posted January 4, 2021 Yes - but if you can build in 18mm poplar it will be an easier build - though poplar isn't the easiest to get hold of. Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted January 4, 2021 Share Posted January 4, 2021 You'll find it is difficult to source small amounts of sheet material, generally the smallest amount is an 8x4 sheet or 1220x2440mm in new money. Even that can be problematic from local suppliers or the big chains and this adds to the cost. Jewsons however were offering Birch ply with a poplar core recently at a good price. Fortunately a lot of fast growing poplar was planted in Europe a few decades ago so expect some of it to replace dwindling tropical hardwoods used in making ply. A 20kg single cab solution is not ridiculously heavy (12mm birch+ driver) The only way to get much below this is to reduce the size of the cab but this sacrifices bass response as I've mentioned, as Bill pointed out the EV design already sacrifices some bass for portability. I wouldn't have started with the Kappa for bass, it has limited excursion for bass, a far too strong mid peak and needs a big cab to get the best out of it but that doesn't mean Steve needs to go out and spend, he already knows what this speaker sounds like in the EV design. 8kg is a lot of weight saving. I use the 20Kg bar for exercise with lots of reps but can barely get 30kg above my head. Designing any cab is a bit of balloon squeezing, as you tighten your grip in one area something else pops up elsewhere and in the end you have to compromise. For me that is half the fun Quote Link to comment Share on other sites More sharing options...
Phil Starr Posted January 4, 2021 Share Posted January 4, 2021 Here you go Hardwood Plywood Poplar Core FSC 2440 x 1220 x 12mm (jewson.co.uk) Quote Link to comment Share on other sites More sharing options...
lowrentdiscographer Posted January 4, 2021 Author Share Posted January 4, 2021 5 hours ago, Phil Starr said: You'll find it is difficult to source small amounts of sheet material, generally the smallest amount is an 8x4 sheet or 1220x2440mm in new money. Even that can be problematic from local suppliers or the big chains and this adds to the cost. Jewsons however were offering Birch ply with a poplar core recently at a good price. Fortunately a lot of fast growing poplar was planted in Europe a few decades ago so expect some of it to replace dwindling tropical hardwoods used in making ply. A 20kg single cab solution is not ridiculously heavy (12mm birch+ driver) The only way to get much below this is to reduce the size of the cab but this sacrifices bass response as I've mentioned, as Bill pointed out the EV design already sacrifices some bass for portability. I wouldn't have started with the Kappa for bass, it has limited excursion for bass, a far too strong mid peak and needs a big cab to get the best out of it but that doesn't mean Steve needs to go out and spend, he already knows what this speaker sounds like in the EV design. 8kg is a lot of weight saving. I use the 20Kg bar for exercise with lots of reps but can barely get 30kg above my head. Designing any cab is a bit of balloon squeezing, as you tighten your grip in one area something else pops up elsewhere and in the end you have to compromise. For me that is half the fun Pretty much this. IF I were doing the full new setup thing, I'd still be tempted to self build. But I would probably go for a pair of higher grade 1x12's, for more options of volume and portability. Maybe next year? Quote Link to comment Share on other sites More sharing options...
lowrentdiscographer Posted February 10, 2021 Author Share Posted February 10, 2021 Resurrection! Some ply arrived yesterday. Before I start cutting... I want to make a shallow sacrifice to aesthetics, and it's something I did on the last build without thinking, but I thought I'd run it by the wisdom of the BC crowd this time. I want to extend the front edge of the port top so that it runs flush with all the other front edges of the cab, and ideally the same with the fore-aft port "runners". This deviates from the EV plan, where the port top plate doesn't extend beyond the baffle. Is it the overall port length that is important or the depth it reaches into the box? To achieve what I want, can I extend the port top's front edge, or do I leave it at it's original dims and move the whole port forward. Or do I stop being silly and just leave it as-plan? Thanks, Steve. Quote Link to comment Share on other sites More sharing options...
RichardH Posted February 10, 2021 Share Posted February 10, 2021 Overall port length - so keep the original dims and bring it forward. 1 1 Quote Link to comment Share on other sites More sharing options...
lowrentdiscographer Posted February 10, 2021 Author Share Posted February 10, 2021 2 hours ago, RichardH said: Overall port length - so keep the original dims and bring it forward. Thanks Richard. I've just been in the back garden, made a saw fence and cut up a sheet of ply into the major pieces. I was hoping to do a bit of a noddy-spec how-to, but it was just too cold to be messing about and the ply needed getting out of the way. Quote Link to comment Share on other sites More sharing options...
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