Designing a cabinet for Mark Audio Alpair 7.3 - Page 2

chrisb · 31st October 2011, 10:12 PM

Quote:

Originally Posted by chrisb

Issues of material "waste" aside (or do the latest drawings imply a vertical "seam" that would allow for nested pattern layout that would substantially improve yield?), also keep in mind that the very high aspect ratio of the port slots is an important part of the overall tuning of bass performance of this archetype.

To my eye the width of slot in the central figure of the three looks to be wider than the 7mm spec on both rectangular and trapezoidal tapered versions of the "marken7" that I've built or currently have underway.

as to the requirement for bracing, since we've not used the stacked lamination method ourselves, who knows for sure?- I have some vague ideas on the subject that would be and exercise in very wooly logic if I attempted to expressed them, and could be completely booooh-gus, so I'll refrain

BTW, these could look silly gorgeous

errata: should read as above - operate word being "NOT"

planet10 · 31st October 2011, 11:06 PM

Quote:

Originally Posted by Studio Au

Is the brace needed in such a rigid and strong cabinet?

To be as stiff as the sheet material used in a convential manner, wall thickness will need to be higher, and all bets are off if you use MDF.

When you cut up the ply like this, you are reducing its strength and the curved shape is not increasing its stiffness. The way to do that is like B&W do in their 800-series.

The brace's prime purpose is to draw energy away from the driver so that it is shared with the back of the box and not all dissipated by the baffle.

dave

doubtingthomas · 1st November 2011, 11:02 AM

Cutting so much material with a CNC machine, with all the associated wastage seems an incredibly brutal approach, surely flexi ply or mdf would form the basis of a more elegant solution, it would certainly be cheaper and I suspect stronger. Unless one was getting the material and facilities gratis of course.

planet10 · 1st November 2011, 07:03 PM

Quote:

Originally Posted by doubtingthomas

Cutting so much material with a CNC machine, with all the associated wastage seems an incredibly brutal approach, surely flexi ply or mdf would form the basis of a more elegant solution, it would certainly be cheaper and I suspect stronger. Unless one was getting the material and facilities gratis of course.

This is true... it may well not be as easy thou to get a pretty box.

dave

chrisb · 1st November 2011, 08:06 PM

no matter the methodology - CCM - curves cost (time and) money

Studio Au · 2nd November 2011, 11:51 PM

Facilities are free, material is not........did a rough cost, came in at more than i hoped. Using 18mm Birch Ply.

Perhaps a design utilising single ribs, as opposed to a complete hemisphere would allow for a lot less wastage....cost.

The miniOnken Sketchup picture has this as it was easier to flip one half than make both sides the same, perhaps this is the way to go? Insert a piece of solid wood matching the baffle to hide the seam?

Colin · 4th November 2011, 11:30 AM

Nice design but it would be a shame to use this construction method with birch ply - too much waste and you wouldn't be getting the best performance out of the material. It makes more sense with MDF, which is cheaper and could do with some stiffening.

Otherwise go for the laminated, thin ply approach or bendy / kerfed MDF. Best of all, make 'em out of metal.

j.michael droke · 17th November 2011, 03:33 AM

Quote:

Originally Posted by Studio Au

Here was the initial idea, using the Pensil design as a starting point for internal volume, port size, overall height and positioning. I am by no means set on this design, but do want to keep the aesthetic, curved walls, solid wooded baffle. And Ideally as small as practical or visually small.Can anything more radical be done? ......[/IMG]

Hi there SAu: Have you considered cast concrete? Someone else on this forum recently cast boxes, his thread might be able to give you some ideas. You would build one reusable form and make several enclosures for your system, making your hardwood front plate removable for internal dampening changes. ....regards, Michael

chrisb · 17th November 2011, 04:48 PM

SAu just to revisit the question, and with a little context. I've worked in a commercial millwork shop for 18yrs - we build a lot of curved reception walls, bulkheads, cabinet doors, etc. A few years back I built something very much along the lines of your design, but with the ribbed skeleton/ multiple layers of rubber ply approach. Not a huge success, and ultimately binned.

For the average DIYer, I'd concur with Colin's earlier suggestion of Kerf-core / Timber-flex etc. You can still use the CNC to route the top, bottom and one or two intermediate braces. Fabrication of the external shell for a Pensil style would be relatively straightforward, but curving of side mounted slot ports shown on the smaller enlcosure would be a bit trickier. It might be easier to build in two sections and join at the back with a full length spine. This would allow you to work on the inside of the curved panels before final assembly. .

Studio Au · 19th January 2012, 05:01 PM

Update...

The original aim was to try and achieve a teardrop shape, I started designing some speakers to replicate great design products, this one using the same materials as the Eames Lounge chair, with plywood and some solid rosewood.

I have recently been sketching out a version based on Ron Arads 'Well tempered Chair'

This was the very quick sketch up model. Utilising a plywood, or possibly hardwood skeleton with bent aluminium or stainless steel wrapped around.

Im hoping it will form a organic and rigid shape simply by bending metal, riveted to hold it all taught.

Any thoughts?

1st November 2011, 08:06 PM	#15
chrisb diyAudio Member Join Date: Aug 2002 Location: victoria BC	no matter the methodology - CCM - curves cost (time and) money __________________ you don't really believe everything you think, do you? community sites t-linespeakers.org, frugal-horn.com commercial site planet10-HiFi

17th November 2011, 04:48 PM	#19
chrisb diyAudio Member Join Date: Aug 2002 Location: victoria BC	SAu just to revisit the question, and with a little context. I've worked in a commercial millwork shop for 18yrs - we build a lot of curved reception walls, bulkheads, cabinet doors, etc. A few years back I built something very much along the lines of your design, but with the ribbed skeleton/ multiple layers of rubber ply approach. Not a huge success, and ultimately binned. For the average DIYer, I'd concur with Colin's earlier suggestion of Kerf-core / Timber-flex etc. You can still use the CNC to route the top, bottom and one or two intermediate braces. Fabrication of the external shell for a Pensil style would be relatively straightforward, but curving of side mounted slot ports shown on the smaller enlcosure would be a bit trickier. It might be easier to build in two sections and join at the back with a full length spine. This would allow you to work on the inside of the curved panels before final assembly. . __________________ you don't really believe everything you think, do you? community sites t-linespeakers.org, frugal-horn.com commercial site planet10-HiFi

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1st November 2011, 11:02 AM	#13
doubtingthomas diyAudio Member Join Date: Aug 2011	Cutting so much material with a CNC machine, with all the associated wastage seems an incredibly brutal approach, surely flexi ply or mdf would form the basis of a more elegant solution, it would certainly be cheaper and I suspect stronger. Unless one was getting the material and facilities gratis of course.

2nd November 2011, 11:51 PM	#16
Studio Au diyAudio Member Join Date: Sep 2008 Location: Bristol	Facilities are free, material is not........did a rough cost, came in at more than i hoped. Using 18mm Birch Ply. Perhaps a design utilising single ribs, as opposed to a complete hemisphere would allow for a lot less wastage....cost. The miniOnken Sketchup picture has this as it was easier to flip one half than make both sides the same, perhaps this is the way to go? Insert a piece of solid wood matching the baffle to hide the seam?

4th November 2011, 11:30 AM	#17
Colin diyAudio Member Join Date: Aug 2003	Nice design but it would be a shame to use this construction method with birch ply - too much waste and you wouldn't be getting the best performance out of the material. It makes more sense with MDF, which is cheaper and could do with some stiffening. Otherwise go for the laminated, thin ply approach or bendy / kerfed MDF. Best of all, make 'em out of metal.

19th January 2012, 05:01 PM	#20
Studio Au diyAudio Member Join Date: Sep 2008 Location: Bristol	Update... The original aim was to try and achieve a teardrop shape, I started designing some speakers to replicate great design products, this one using the same materials as the Eames Lounge chair, with plywood and some solid rosewood. I have recently been sketching out a version based on Ron Arads 'Well tempered Chair' This was the very quick sketch up model. Utilising a plywood, or possibly hardwood skeleton with bent aluminium or stainless steel wrapped around. Im hoping it will form a organic and rigid shape simply by bending metal, riveted to hold it all taught. Any thoughts?