There are basically two
fields here that are donating methodology, one is musical
instruments, with which I was familiar if not awfully
knowledgeable. Experience, however, was there : in music
projects I've had several electric guitars and a full acoustic
piano taken down to small parts in my travels, and had the
occasional expoded view --literally-- of an overtuned acoustic
guitar. Ribs, fan-braces, struts, corner & cross-braces were at
least things I'd known in several contexts. The other field is
aeronautics, about which, of course, I know nothing at all.
The original plan
---discarded in this present version-- the idea of doing real
cabinetry around the form of assembled winecrates, and
then knocking them apart from within and removing the
evidence... was what gave rise to the Torsion Box
concept. Which arose from the thought that maybe some parts of
the winecrates, spines, corners, etc that had subsequently been
perfed for mass relief ... could stay on in the finished
product. What would be added would be a rigid exoskeleton of
plywood to strengthen and stiffen the enclosures.
So if there were to
be an outer layer or skin of veneer-ply to be added to the
outsides of the winecrate assembly, why not utilize a specific
structural approach that was known for it's strength, low mass,
and resistance to vibration ..?
Well, you can check the
links below for a start, but the idea of a Torsion Box is simple
: adhere outer skin materials above and below an inner grid or
framework. With the resulting structure being considerably
stronger than the sum of the parts in a straight stack or
layered construction. And of course being lighter than solid
materials of the same dimension. In acoustic terms, I reasoned
that the grid-core would be much less inclined to resonate at
any one fixed rate, and present a complex target for vibration.
This general idea of
the Torsion Box is honed to an excrutiating, nano-precise extent
in Airframe Technology for aircraft, but is also in universal
usage in nearly every "solid" element in furniture from Ikea and other
low-cost manufacturers. Ever notice those thick, sturdy
looking tables and furniture that don't weigh anything at all as
compared to what they look like ? Ever wonder how hollow doors
stand up to repeated use ?
Torsion boxing. Think
internal I-Beam, but taken further, in both length and width
directions, like a chessboard of sorts.... the grid of crossed
beams becomes its own plane. In addition to forming flat
panels, any wavy or complex curve can be accomodated
with torsion-box strategies, given appropriate core design and
flexible enough outer skin materials.
So, a wonder of modern
engineering, a sleight-of-hand trick with light materials doing
heavy-duty service. Right up my alley, maybe. Does it suit
speaker cabinetry ?
On this particular
point, I really have no idea. Hence, Sound & Torsion.
And make no mistake,
what we learn here will forever influence the way sound is heard
in ... my living room. Or at least until exotic & beautiful
cabinets from real speaker builders appear ...