TransLam Alpha
Goal: Create a cool looking loudspeaker enclosure using a somewhat novel construction technique I call transverse lamination or "TransLam". (not to be confused with coronal or sagittal.)
Drivers: Woofer: 5.25" MCM 55-2205; Tweeter: GR Research GR-T1 1" soft dome.
Configuration: Vented MTM
Crossover: Passive. 2nd order electrical. 2.8k
Intro: For some time I've wanted to create an enclosure using the TransLam technique. In addition to interesting aesthetics, this technique lends itself to the creation enclosures with non-parallel walls, large radius front baffle roundovers, and the ability to layer many materials with dissimilar resonance characteristics. In this case I chose to use 11 ply 1/2" Baltic Birch for all layers. Since there is an odd number of plys, every other layer would have to be rotated and cut 90 degrees from the others. This would allow me to alternate the layers of face grain and edge grain to give an illusion of continuous odd/even/odd/even laminations with no hint that is was made from 1/2" sheets. Extra damping materials would be attached to the interior to control the higher frequency resonance of the stiff Baltic Birch plywood.
The project began in early September with sketches of truncated ellipses in TurboCad. The candidate "ring" shape was saved as a .dxf file. From there it was taken to a local CNC router facility here in Albuquerque, NM, USA where all of the "rings" were cut from the 1/2" Baltic Birch. I could have cut all the shapes myself with a template and my router, but I didn't. I may be mentally disturbed, but I'm not crazy!
Just returned from the CNC Router facility. What the
heck am I thinking! Hmmm.. I think it would be prudent for me to consider
this project a prototype - Alpha.
The three basic elements for the TransLam Alpha.
From top to bottom: Ring, Brace, End Cap. Wall thickness varies from
1" to 1.25".
Dry fit. Two end caps on either end
making a 1" thick top and bottom wall. I used only two braces per
enclosure, I could have used more. It's hard to see here but the
router bits used left a lot splinters and fuzz on the edges of each piece that
had to be carefully sanded off by hand.
The glue-up process. I had planned
all along to add 1/4 alignment holes that would allow me to use a rod to align
all the pieces, but I didn't. I honestly don't know why. It just
slipped my mind. So.... I
had to use carpenter's squares to help keep the stack on track. A 4"
foam roller was used to apply yellow wood glue to two mating pieces. Lots
of hand pressure was used to make sure all the glue was evenly distributed and
flowing from around the entire seam. Once the piece was carefully aligned
it was pinned down with up to 8 1" 18 gauge brads. This process was
repeated for each layer... and repeated... and repeated...
One enclosure all glued up with no end
caps.
Application of the enclosure damping
material.
This door mat material was purchased at my local Home Depot
for $10. It is a 3/8" thick semi visco-elastic closed-cell foam that
is very pliable with a shiny textured skin on either side.
Acrylic Laytex caulk was used to adhere the
door mat material.
Sanding!
And sanding!
And sanding!
Sanding was about a 12 hour ordeal. I started out with 50-80 grit working against the grain with a belt sander. Then 80-220 with a random orbit sander. Then 220-400 by hand. Every other layer (approx 1mm) is end grain and is a total pain to sand cleanly and completely.
I really had to take a deep breath before I
cut the woofer though holes. This is one of those situations that you
don't want to mess up. Measure 50 times, cut once. The front baffle
is 1" thick (the thinnest part of the box). I cut though the
enclosure with my router a quarter inch at a time (as seen by the lines on the
inside of the through hole).
I used a saber saw to create a "back
chamfer" for the woofer to breathe.
Cutting the 2.5" port hole.
Cowabunga!
Cowabunghole!
The enclosure gets pretty thick towards the back.
Driver test fit. Hey this just might
work!
I did not take any pics of the woofer flush cut process. It was WAY too
frustrating and I forgot about any photo documentation.
Dave Elledge "dBe" turned me on
to natural cotton batting for stuffing.
The port tube is 2" aluminum polished within an inch of it's
life. Came out looking like chrome.
