"It's amazing how well sealed you can make your cabs using this method."
Are you sure about that?
I would never use that method, paint is too brittle and will crack under a torsional load.
Any open angles in portable cabinets should have full-length splines, or enormous contact area and/or glue blocks. Joinery should be so tight that when screws are used in construction they are only needed to clamp the joint until the glue dries, and could even be removed after it cures.
A TH can be built with a minimum of angles, or none at all. Old designs from RCA and Frazier had complex folding schemes with only 90° cuts, a TH can be made with the same techniques.
Taper can be induced by angled boards between parallel walls, the angles needing to have little structural strength.
A folding scheme with only one angle (cut on the glue block), all others can have 90° cuts. The driver fires into the 'V' throat as above.
With a little thought, it is possible to cut every piece that needs to be the same width all at the same time, and not need to move the rip-fence. This leads to better fitting joints, and no real need for caulking.
I recognize all the skill and effort that went into Marcello's work of art, but I don't think it's needed below 100hz.
Are you sure about that?
I would never use that method, paint is too brittle and will crack under a torsional load.
Any open angles in portable cabinets should have full-length splines, or enormous contact area and/or glue blocks. Joinery should be so tight that when screws are used in construction they are only needed to clamp the joint until the glue dries, and could even be removed after it cures.
A TH can be built with a minimum of angles, or none at all. Old designs from RCA and Frazier had complex folding schemes with only 90° cuts, a TH can be made with the same techniques.
Taper can be induced by angled boards between parallel walls, the angles needing to have little structural strength.
A folding scheme with only one angle (cut on the glue block), all others can have 90° cuts. The driver fires into the 'V' throat as above.
With a little thought, it is possible to cut every piece that needs to be the same width all at the same time, and not need to move the rip-fence. This leads to better fitting joints, and no real need for caulking.
I recognize all the skill and effort that went into Marcello's work of art, but I don't think it's needed below 100hz.
I'm not talking about using paint as a substitute for good carpentry. I use dado joints whenever possible, and generally will use the method of cutting outer panels oversized and trimming them flush with a router. I am about 90 percent sure that my joints are airtight before sealant goes in. The latex paint is used as a substitute for latex caulk, silicone, or blu-tak. None of these substances are fit for holding the cab together. That's what glue, screws, and nails are for.
Also, I think that latex based paint is quite durable. It stays flexible and it's also fairly water resistant when cured. Besides, if I do my job right of building the cab, there won't be a torsional load on the joints.
Also, I think that latex based paint is quite durable. It stays flexible and it's also fairly water resistant when cured. Besides, if I do my job right of building the cab, there won't be a torsional load on the joints.
djk said:
I once read a post from Tom, where he said that you cant measure a significant difference, as long as the longest dimension is smaller than 1/4 WL of the highest in band frequency. Still, the lab sub has curved/angled bends. What i want to say is... it depends on the frequency, if you can build it without smoothed bends. For tapped horns which reach into the midbass, maybe smoother bends are a benefit.
I googled but found nothing... what is a glue block?
In this context, a "glue block" or "glue batten" is a thin strip of wood (it could be rectangular or triangular in cross section) that is added to a joint to increase surface area to increase strength for the glue joint.
http://www.expertvillage.com/video/...oo&utm_medium=yssp&utm_campaign=yssp_mainvids
See figures Q and S:
http://www.diynetwork.com/diy/ww_chests/article/0,2049,DIY_14440_2270140,00.html
See page 9 (dual 8 TH):
http://www.wipo.int/pctdb/en/wads.j...075&WEEK=39/2007&TYPE=A2&DOC_TYPE=PDOC&PAGE=1
http://www.expertvillage.com/video/...oo&utm_medium=yssp&utm_campaign=yssp_mainvids
See figures Q and S:
http://www.diynetwork.com/diy/ww_chests/article/0,2049,DIY_14440_2270140,00.html
See page 9 (dual 8 TH):
http://www.wipo.int/pctdb/en/wads.j...075&WEEK=39/2007&TYPE=A2&DOC_TYPE=PDOC&PAGE=1
Strong or Stiff?
If you're building "Roadie Proof" boxes the following doesn't apply!
I don't use 18mm or 3/4 inch stock because it is strong ... I use it because it's stiff, and because it provides some damping against vibration. Biscuits, Dados and rabbet joints add NO stiffness and no damping, only strength. Glue blocks, likewise, add no stiffness, only strength. Expanding glue fills badly fitted joints, but does not increase the stiffness or the strength. Screws every 6 inches add no stiffness, and very little strength.
If you have good glue lines (0.010 inch, max), butt joints are almost always strong enough, and 2 or 3 screws will prevent a panel from moving while the glue dries.
Rog Mogale knows how to do it right ...
http://speakerplans.com/index.php?id=guide
Make your Tapped Horn as strong as you'd like, I'll make mine stiff!
~Don
If you're building "Roadie Proof" boxes the following doesn't apply!
I don't use 18mm or 3/4 inch stock because it is strong ... I use it because it's stiff, and because it provides some damping against vibration. Biscuits, Dados and rabbet joints add NO stiffness and no damping, only strength. Glue blocks, likewise, add no stiffness, only strength. Expanding glue fills badly fitted joints, but does not increase the stiffness or the strength. Screws every 6 inches add no stiffness, and very little strength.
If you have good glue lines (0.010 inch, max), butt joints are almost always strong enough, and 2 or 3 screws will prevent a panel from moving while the glue dries.
Rog Mogale knows how to do it right ...
http://speakerplans.com/index.php?id=guide
Make your Tapped Horn as strong as you'd like, I'll make mine stiff!
~Don
adding glue blocks or battens to the corners makes the joint stiffer. This in turn makes the panel between the joints stiffer. Result, adding glue blocks makes for a stiffer box.
It's what structural and civil engineers do every day to make their buildings stand up.
And I agree with the Mogale construction guide - glue and screw.
But, I would add a big condition. Don't use end grain screws for a roadie type speaker box.
It's what structural and civil engineers do every day to make their buildings stand up.
And I agree with the Mogale construction guide - glue and screw.
But, I would add a big condition. Don't use end grain screws for a roadie type speaker box.
Hi Andrew,
If we're considering only acoustic loads, the box needs only to be as strong as the speaker cone, but it must be MUCH stiffer than a speaker cone. The cone should flex, the box shouldn't.
The corners are already the stiffest part, reinforcing them adds little to the stiffness of the panels.
~Don
If we're considering only acoustic loads, the box needs only to be as strong as the speaker cone, but it must be MUCH stiffer than a speaker cone. The cone should flex, the box shouldn't.
The corners are already the stiffest part, reinforcing them adds little to the stiffness of the panels.
~Don
agreed, adds little. But, it does stiffen the panels.Don Snyder said:
Although one would need to take account of the ratio of panel width to corner stiffening batten width to see where the stiffness becomes optimum vs total volume. i.e if panel to batten ratio~=2 then the panel is virtually infinitely stiff. The only flexibility is the stiffness (Young's Modulus) of the batten brace running from mid panel to mid panel of adjacent panels. But, the internal volume has been reduced considerably.