It doesn't really matter if its laminated (like this) of one big board - it moves with moisture. Moisture as in humidity and its changes throughout the year. As long as you understand that, and build accordingly you can selectively use it. Would I use it for a front or rear baffle? Not typically. You could use it for sides, top and bottom with the grain all running in the same direction - as in around the cabinet - so that any movement is consistent (it'll be front to back). That also means no cross bracing to restrict the movement. If in doubt, use your library (or Google) regarding proper ways to make solid wood furniture (a chest of drawers is a good example) to understand the pitfalls.
Ah - I see you are calling the wood I pictured "butcher block" which I suppose is another term for it. I bought it as "kitchen worktop". Looks like the same thing. As far as I can see the joints have remained solid. It's 26mm thick. I have enough for the sides and back. Not sure about the top and bottom which might have to be something else. I would make a window frame brace around 2/3 down.
My intention is to put the tweeter on top, like B&W designs. Then make a removable front which could be changed for different bass units I might want to try. The tweeter could go on that as an alternative. My plan is to attach the front with 19" rack parts - some compact 90* angle frame and the M6 inserts which means I can use M6 screws to fit and remove the front easily. I was thinking about 16 litres which would work for 165mm or 150mm mid-bass units.
I haven't seen any comments about using 90* steel angle to attach top and bottom. All the interior joinery traditionally seems to be wood. Any reason why L shape steel would not work for attaching parts at right angles like top and bottom?
The wood pictured has been indoors in my flat for several years and would remain so, so I imagine it's pretty settled in a fairly uniform environment. How careful do I need to be about putting a window brace in it? Are cross braces a better alternative? Or no braces, which would be a shame?
The crux seems to be that the shrinkage is different in each dimension, and with a glued box it's very hard to avoid any joints with unequal shrinkage rates.
One idea that comes to mind: 1) align the grain vertically all around the sides. 2) instead of gluing the top and bottom, use a tensioning rod to pull them together. A sealant, maybe with some kind of slot for stability, provides air tightness, while still allowing for seasonal movement.
One idea that comes to mind: 1) align the grain vertically all around the sides. 2) instead of gluing the top and bottom, use a tensioning rod to pull them together. A sealant, maybe with some kind of slot for stability, provides air tightness, while still allowing for seasonal movement.
I've thought about a tensioning rod and may do that. The problem I had when I did that before was that the rod vibrated to its natural frequency when towards the middle of the cabinet. It wasn't inert. Maybe 4x rods right in each corner might be better. Anyone know? I also presume the rod should be thicker rather than thinner, both for structural strength and resistance to vibration.
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Those worktops are made of laminated hardwood staves, and the staves themselves will probably be finger-jointed. It's often referred to as butcher's block, but that's using the term loosely. (Strictly speaking butcher's chopping blocks have normally been made with vertical grain staves, so the end grain is exposed on the top.)
I wouldn't think angle steel would work too well. As is mentioned earlier in the thread, there's an issue with ferrous metals causing staining. Also it's not going to move along with the movement of the wood - laminated hardwood will still contract and expand a bit, just like any other hardwood.
For a similar reason, I'd suggest using the worktop for sides, top and bottom, if there's enough, because then the grain can run the same way on all the pieces, and any shrinkage or expansion will be in the same plane, and is less likely to cause failure. I'd also be wary of a horizontal window-frame type brace - at least, you'd want to use the same material, with the grain running in the same orientation, or it would be in conflict with the movement of the hardwood. Maybe a vertical frame-type brace would be safer? And I've never been a fan of tensioning rods, I'm afraid. Normally my instinct would be to use bituminous damping pads, but to be honest the worktop is so think that they probably won't do much.
@andyjevans
Yep. I'm in a similar boat. I had this ambitious idea to make the horizontal cross-section of the box a swept-back teardrop shape, but no good plan on how to attach the flat lid and base. The sides and front are made from 60 cm lengths of assorted 20x60 mm + 20x80 mm + 20x120 mm larch wood (a conifer that loses its needles?! So I guess that makes it a medium wood?). I actually wanted to go thinner, about 12 mm for a more lively cello-like sound and multi-phase output, but was worried about excessive warping. The overall shape is based on a hand-drawn sketch on engineering paper, from which I got some rough coordinates transferred to Excel, followed by tinkering and equations to get 70-75 L of volume and to find out the exact cutting angles.
It's all very nice on paper, but making the mitred edges straight enough for leak-free glue lines will be a miracle. Most of the wood looks quarter-sawn, except for some of the more prominent pieces that have resinous swirls and knots.
Now that I'm thinking out loud about it, I think a tensioning rod (x4, or x3 for that sort-of heart shape) seems very promising. Once it's all built, I'll have to play around with gasket options to hear what works best. 1mm nitrile rubber may have too much movement and muddy up the sound, so maybe beeswax or something similar? A thin 4-5mm rod thickness seems about right. A friend has a 20mm+ drill bit for making candle holders, which will be perfect for making it nice and flush with big washers. I may do a separate thread on it once I have some more progress.
Yep. I'm in a similar boat. I had this ambitious idea to make the horizontal cross-section of the box a swept-back teardrop shape, but no good plan on how to attach the flat lid and base. The sides and front are made from 60 cm lengths of assorted 20x60 mm + 20x80 mm + 20x120 mm larch wood (a conifer that loses its needles?! So I guess that makes it a medium wood?). I actually wanted to go thinner, about 12 mm for a more lively cello-like sound and multi-phase output, but was worried about excessive warping. The overall shape is based on a hand-drawn sketch on engineering paper, from which I got some rough coordinates transferred to Excel, followed by tinkering and equations to get 70-75 L of volume and to find out the exact cutting angles.
It's all very nice on paper, but making the mitred edges straight enough for leak-free glue lines will be a miracle. Most of the wood looks quarter-sawn, except for some of the more prominent pieces that have resinous swirls and knots.
Now that I'm thinking out loud about it, I think a tensioning rod (x4, or x3 for that sort-of heart shape) seems very promising. Once it's all built, I'll have to play around with gasket options to hear what works best. 1mm nitrile rubber may have too much movement and muddy up the sound, so maybe beeswax or something similar? A thin 4-5mm rod thickness seems about right. A friend has a 20mm+ drill bit for making candle holders, which will be perfect for making it nice and flush with big washers. I may do a separate thread on it once I have some more progress.
Using the photo of his laminated board as an example there will be no movement along the board's length, which is why it could be used for sides, top & bottom with the grain running 'up' the sides and 'across' the top and bottom. There will be marginal movement in the thickness dimension of the board. The greatest movement will be across the board's width which is why it shouldn't be used for a front or rear baffle. That's also why you shouldn't use a window frame style brace fixed in place across solid (which his board effectively is) sides.
You may discount the movement, thinking a finish will prevent it, but you'd be wrong - it just slows the moisture absorption and release down.
I make 'designer' jewelry and display boxes and chests (well, it ain't a living so it must be for fun) and am a juried craftsperson and I am always fighting a lid, or drawer, that fits perfectly until the season changes. Even a small lid, say 5" across, that fits flush in one season will protrude slightly in the next.
It's wood, it moves.
I have enough kitchen worktop for the cabinet shown, just the 4 sides with grain front to back. I have a bit left over but it would only do a top or a bottom, not both. So seems to me I should use something like 25mm MDF for the top, bottom and back. Does that look OK? I doubt if I can get any similar offcuts but anyway they'd be fresher and mine are years old.
This breaks my first rule of bracing: the aspect ratio of the subpanels created by the brace should have a higher aspect ratio than the panel being braced.
dave
Potential issues with leaking. We did this (Al angle iron) in the original Frugel-Horn Mk3 (successful) prototype.
dave
I'd be a little anxious about orienting the board that way. If it moves, it's the height that will be most likely to change, and that would surely stress the joins to the other boards. Maybe, though, you could build complete boxes of mdf/ply and then attach the worktop as cheeks, using a compliant fixing of some sort? It could be almost Sonus Faberish, if you wanted. If you used viscoelastic adhesive, such as some of the 3M tapes, you'd even get a CLD effect, maybe.
In my experience with wood, acrosss many builds by Scott or Bernie, only 3 have failed, and 2 of those were fixed so they are just fine now.
Quick changes in humidity are the great killer, given that teh wood has lived in the same place and that will not change he will unlikely have issues. One of Bernies boxes that failed was purposely tortured by leaving it downstairs where it is unheated thru an entire year. ie had to work to break them.
dave
Quick changes in humidity are the great killer, given that teh wood has lived in the same place and that will not change he will unlikely have issues. One of Bernies boxes that failed was purposely tortured by leaving it downstairs where it is unheated thru an entire year. ie had to work to break them.
dave
I worried about it, used cedar which was for me the lowest cost / lowest movement option (well, mahogany was but other issues diverted me), then, because I was making small boxes for 2.5" drivers, I just rode it out. If it breaks, I'll make them new ones.
Your application may be different.
But there are calculators available to let you know how much you can expect the wood to move:
https://kmtools.com/pages/wood-movement-calculator
That's based on: "Wood Handbook, Wood as an Engineering Material"
https://www.fpl.fs.usda.gov/documnts/fplgtr/fpl_gtr190.pdf
Data on Larch.
https://www.wood-database.com/european-larch/
https://www.wood-database.com/wood-articles/dimensional-shrinkage/
Your application may be different.
But there are calculators available to let you know how much you can expect the wood to move:
https://kmtools.com/pages/wood-movement-calculator
That's based on: "Wood Handbook, Wood as an Engineering Material"
https://www.fpl.fs.usda.gov/documnts/fplgtr/fpl_gtr190.pdf
Data on Larch.
https://www.wood-database.com/european-larch/
https://www.wood-database.com/wood-articles/dimensional-shrinkage/
We did a batch of solid Westren Red Cedar (old growth) and it is a surprisingly good material for loudspeakers. Just have to figure out how to make them less prone to “bruising”.
dave
In the case of a box taller than wide and deep the brace(s) should run vertically.
dave
A veil of light glass and epoxy layup under the polyurethane will sort out the bruising concerns. As done on wood look marine parts like old school runabouts and light timber canoes. Once under the finish, the veil will be invisible
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