Mark Audio Alpair 10.3 full range curved birch ply cabinets. Inspired by the Pensil speakers, with dimensions loosely taken from them, these were and experiment to see how easy it is to make curved cabinets with the help of a CNC and a few festool power tools. Each cabinet can be made from 1/2 sheet of 18mm birch ply. These are surprisingly light weight, for a Mk2, I wish to change the overall height by a few inches, and increase the strength, mass, weight of the bracing and curved walls. The bendy ply was painted rather quickly with chalk paint, to hide any blemishes, which has sadly done the opposite...
Very happy with the overall results, only had 20hrs run playing Naim's high-def radio at low levels, in but sounding great, previously had Alpair 7.3's in small bookshelf design. These are making me re-think if the fast approach is needed!?
Very happy with the overall results, only had 20hrs run playing Naim's high-def radio at low levels, in but sounding great, previously had Alpair 7.3's in small bookshelf design. These are making me re-think if the fast approach is needed!?
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I'm not. I shall register now.
Had a headless pinner that I hoped would make it easy to form the curve, but they simply pulled out, ended up using a stapler (air powered) which left lots of holes to fill and destroyed a bit of the edge by the baffle.
Tried with bessey band clamps but could get the pressure.
Wondering how best to reproduce these especially if I start to make a few to sell, perhaps big Cnc cut formers and a couple of screw clamps? Can't fit a big pneumatic ram in the shop...
Had a headless pinner that I hoped would make it easy to form the curve, but they simply pulled out, ended up using a stapler (air powered) which left lots of holes to fill and destroyed a bit of the edge by the baffle.
Tried with bessey band clamps but could get the pressure.
Wondering how best to reproduce these especially if I start to make a few to sell, perhaps big Cnc cut formers and a couple of screw clamps? Can't fit a big pneumatic ram in the shop...
Have you researched with local fabricators regarding thermo-forming of curved designs with Solid Surface materials?
We work with a few different brands in our little millwork business, and not all of them are particularly amenable to that tight a radius, and certainly not in a single piece.
In theory, all you need to do is heat the material to plastic state, then transfer to at least a set of passive positive / negative forms - or even better a vacuum bagging process such as seen here.
Corian Thermoforming - YouTube.
Then of course there's the matter of adhering to the carcass / substrate.
I think to do justice to the material and your project so far would probably be beyond most DIYers skill set and/or equipment.
You'd most likely have far better success with adding another layer of substrate (try contact cement and "rubber ply"), and wrapping with either a 2 ply wood veneer, or a post form grade of plastic laminate. (hint - high gloss finishes telegraph and amplify irregularities in underlaying surface)
edit: actually, as has been seen elsewhere, fabrications of such shapes consumes a lot of time and materials - whichever type of fabrication techniques are employed - e.g. stacked lamination in the line arrays
CCM - curves cost money
We work with a few different brands in our little millwork business, and not all of them are particularly amenable to that tight a radius, and certainly not in a single piece.
In theory, all you need to do is heat the material to plastic state, then transfer to at least a set of passive positive / negative forms - or even better a vacuum bagging process such as seen here.
Corian Thermoforming - YouTube.
Then of course there's the matter of adhering to the carcass / substrate.
I think to do justice to the material and your project so far would probably be beyond most DIYers skill set and/or equipment.
You'd most likely have far better success with adding another layer of substrate (try contact cement and "rubber ply"), and wrapping with either a 2 ply wood veneer, or a post form grade of plastic laminate. (hint - high gloss finishes telegraph and amplify irregularities in underlaying surface)
edit: actually, as has been seen elsewhere, fabrications of such shapes consumes a lot of time and materials - whichever type of fabrication techniques are employed - e.g. stacked lamination in the line arrays
CCM - curves cost money
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I developed these as they seem to use less materials than building square cabinets, and far quicker (with the CNC). The Hi-Macs, although expensive (cost price is £170 a sheet 6mm 2400mm x 800mm) it doesn't require anything to finish other than sanding. Considering a good high build spray finish would cost upwards of £100 the material costs of the solid surface seem better value. The radius was rather tight for the ply, this may be tweaked, but I'm hoping to take them along to the thermoformers and see what they say, as all I need is the shape formed, I can CNC the top and bottom and flush cut to fit.
The quotes for thermoforming were around £400+ per cabinet, a little too much at this stage...Idea was to do a basic veneered form, and a hi-end corian/hi-macs version. Idea is to eventually commercialise a design, hence the prototyping now, but is still quite far off.
Next step is a couple of those new Mark Audio woofers with the Alpair in a sealed section on top.
The quotes for thermoforming were around £400+ per cabinet, a little too much at this stage...Idea was to do a basic veneered form, and a hi-end corian/hi-macs version. Idea is to eventually commercialise a design, hence the prototyping now, but is still quite far off.
Next step is a couple of those new Mark Audio woofers with the Alpair in a sealed section on top.
Honestly, if you're looking for a different aesthetic than wood veneer finish, I think paint is a better approach for a commercial product of this particular type than the Solid Surface.
There must be far more auto body painters easily accessible than thermo-forming solid surface fabricators, and and once all factors are considered, I'd be surprised if the former didn't have a ultimate lower cost.
I'd also be surprised if the thermoformers didn't advise that regardless of radius, an elliptical curve of this shape would require 2 pieces joined at the rear.
There must be far more auto body painters easily accessible than thermo-forming solid surface fabricators, and and once all factors are considered, I'd be surprised if the former didn't have a ultimate lower cost.
I'd also be surprised if the thermoformers didn't advise that regardless of radius, an elliptical curve of this shape would require 2 pieces joined at the rear.
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I'd have everything glued up solid by this point, including the front baffle - as this gives you more to clamp / band round - supporting the edge of the ply your forming etc.
I'd be tempted to add a few vertical stringers as well, they would aid bonding and reduce any possible 'starved horse' effects that might creep in over time.
Nice looking speakers for prototypes though
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@ Sippy,
A few of the problems occurred as I glued up the whole thing with the baffle in place, but not glued, and had to remove loads of the stapeles to firstly get it out, was done so I could but in acoustic dampening.
I'm thinking making a big former would be a good option, would just need a negative to press down over the internal frame. I have a vacuum bag but at 800x1200 it would barely fit lengthwise flat let alone with the rather large horseshoe shape.
A few of the problems occurred as I glued up the whole thing with the baffle in place, but not glued, and had to remove loads of the stapeles to firstly get it out, was done so I could but in acoustic dampening.
I'm thinking making a big former would be a good option, would just need a negative to press down over the internal frame. I have a vacuum bag but at 800x1200 it would barely fit lengthwise flat let alone with the rather large horseshoe shape.
Don't forget that with vacuum bagging, you need very sturdy and perfectly shaped forms to withstand the literally tons of pressure on a larger panel surface, and to ensure uniformity of finished profile.
This in an ideal application for both CNC routing of the support ribs, and use of MDF. We space the 3/4" ribs in our forms on 2" centres, with at least 3 layers of 1/8" tempered hardboard glued and stapled to the ribs. It should go without saying, but ensure that you've allowed for the total build up of those layers when programing for the support ribs, otherwise the radii on the the vacuum formed panels won't match that of the enclosure's skeleton frame, and that would be a major bummer.
This in an ideal application for both CNC routing of the support ribs, and use of MDF. We space the 3/4" ribs in our forms on 2" centres, with at least 3 layers of 1/8" tempered hardboard glued and stapled to the ribs. It should go without saying, but ensure that you've allowed for the total build up of those layers when programing for the support ribs, otherwise the radii on the the vacuum formed panels won't match that of the enclosure's skeleton frame, and that would be a major bummer.
Beautiful they are indeed. Fantastic project. Before sinking into MA nirvana I had a pair of Audio Pro Bravo speakers which had very close shape I am missing sometimes. They had narrow flat back though which probably makes build simpler while keeping overall look nearly the same - maybe you'll find it useful.
Thanks, I have been designing some ply laminated smaller versions, and due to the waste can't have complete U shapes, so have designed them with a solid wood spine down the back, allowing to shallower C shapes to join.
I think If I can adjust the curve and make it more subtle it will bend with more east, problem wasn't flexing the ply, but holding it there (3 or 4 hands needed) with large moulds/presses would make light work.
Mockup of the laminated one to come...
I think If I can adjust the curve and make it more subtle it will bend with more east, problem wasn't flexing the ply, but holding it there (3 or 4 hands needed) with large moulds/presses would make light work.
Mockup of the laminated one to come...
Yes, the mould / die could make for "lighter work" , but you'd need high precision on those.
I'm thinking the required investment in tooling is probably why this shape is not so common amongst commercial products.
You've probably seen the animation about half way down this page?
800 Series Diamond | Technology - Bowers & Wilkins | B&W Speakers
What I'd really like to see is the removal of formed shell from the die/mould - maybe a perfect episode for "How's that made"?
edit: don't take my comments negatively - I admire your goal, and have even tried something like this myself a few years back - the results were too embarrassing to display, and the closest I've tried since is the much simpler wide baffle Ellipsas
I'm thinking the required investment in tooling is probably why this shape is not so common amongst commercial products.
You've probably seen the animation about half way down this page?
800 Series Diamond | Technology - Bowers & Wilkins | B&W Speakers
What I'd really like to see is the removal of formed shell from the die/mould - maybe a perfect episode for "How's that made"?
edit: don't take my comments negatively - I admire your goal, and have even tried something like this myself a few years back - the results were too embarrassing to display, and the closest I've tried since is the much simpler wide baffle Ellipsas
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