Do any of you have experience with speakers whose cabinets are tuned to sympathetically resonate in a controlled manner through relatively thin “tone wood”?
Apparently this would give some additional efficiency if the wood material and its thickness and proportions are such that a rather wide spectrum of the driver’s output is sympathetically radiated by the cabinet, even some omni-directional aspects to the sound. Of course, this is véry much “coloring the sound” so this is definitely not for a “monitor speaker” but something that loans a bit of idea from how instruments are constructed and a special case of a design with its compromises.
The common approach is inert cabinets as we know. They have their downfalls apparently, this is not my own subjective experience but there’s this Youtube channel dealing with these type of tuned wooden high-efficiency speakers and it is said that by utilizing the right wood and construction (even brass screws making a big difference compared to steel!), string instruments for example gain that often missed natural wooden “body” sound of the instrument and that inert, lower efficiency speakers in comparison often present “just the strings”
I do believe that wood can be tuned for an overall more natural, if not as pristinely precise, presentation, “musical” as they’d say. It’s not heresy to build a speaker akin to an acoustic instrument.
“It’s not heresy to build a speaker akin to an acoustic instrument.” There’s a difference between the two to consider. A musical instrument is expected to have distinctive timbre and resonant character. It’s what distinguishes a Les Paul from a Telecaster or a Bosendorfer from a Steinway. On the other hand, most of us want a speaker to accurately reproduce the recording without undue imposition of obvious resonances that weren’t part of the original recording. I’m familiar with the theory behind those designs and I’d like to hear a realization of the concept that’s successful to my sensibilities. I’ve only heard a few such resonance tuned, thin walled speakers as you mention in audio shows. None of them were my cup of tea so to speak. Obviously some do enjoy them, as they’ve been on the market for many years. I’ve not had occasion to hear Devore speakers and they enjoy a reputation for successfully spreading their resonant frequencies successfully to good effect.
ah, the aged question: transparent or colored
Most likely, the nature of materials, construction, visual aesthetics, and snake oil will inevitably lead to choices of color
A selection of acoustic guitars on stands around the room with the strings tuned “sympathetically” might be fun to play with 
Sonus Faber Maxima Amator 2-way solid wood acoustic speakers Maxima Amator | Sonus faber uses solid walnut for the cabinet. Its tweeter uses solid spruce. Built similar to a Stradivarius in concept. This might address your concerns
The basis of the BBC constrained thin-wall concept that resulted in the LS3/5A and its many variants is a cabinet that resonates in a controlled manner with the drivers. Harbeth, Rogers, Stirling Broadcast, Spendor, Falcon Acoustics (and other brands I’ve probably forgotten) have all produced monitors based on the resonant constrained thin-wall cabinet design. From the BBC engineering effort to generate specifications for a speaker better voiced for the broadcast booth.
Is 12mm birch solid wood (“solid” as in glue block panel with 160mm plank width) a “thin” wall by these standards?
I’m contemplating a tetrahedral speaker with maximum efficiency and room-filling acoustic power factor by virtue of a tuned solid wood cabinet. Unsure how thin it’s feasible to go for which wood panel of which construction - 12mm for birch ply would be stronger but I don’t think ply is feasible for purism in “tonality”, it’s artificially rigid.
Speaking of overall materials that can comprise a proper speaker cabinet, hard to see a proper solid wood board being beaten in natural timbre. Again, when used right.
Would be even better to have each face of a cabinet from a single continuous cut from a single tree but that could require some large trees for big cabinets.
The less seams the better for a cabinet that’s meant to resonate in tuned unison. More whole the better, to me seems the best way here.
It is easy to machine and while could be termed “acoustically neutral” loosely speaking, I don’t trust it quite is. MDF will not give a natural resonance, while of course when implemented properly its resonance should be low in amplitude. But not natural. Then again a natural resonance spectrum from a cabinet could be deemed “not acoustically neutral”, more an emphasis on natural timbre.
I think for prototypes I might consider fairly thin birch ply but I trust solid wood would give the best result. 160mm hand-picked uniform birch plank glued to board, then cut to shape…
In your initial post you referred to the use of thin walled “tone wood” used to build speakers akin to a musical instrument. Laminated plywood layers make for very different resonant qualities vs. solid wood. Plywood, no matter how thin, does not really behave like tone wood used for building musical instruments. Quality guitars, violins, cellos, etc. all use solid wood. Drums use plywood of course. Some piano manufacturers are using plywood and mdf these days, but it’s not anything you’re going to see Steinway doing I suspect. In the case of the speaker you contemplate, the cabinet maker had to consider construction stability and resistance to warping, etc. Plywood has advantages over solid wood in that regard. It’s always about picking the best set of compromises.
Couple of things to keep in mind about plywood is that even the best furniture or cabinet grade birch or oak will still likely have some kind of ‘filler’ wood as the center. Usually poplar, as it’s a quality hard wood but cheap and abundant. The other thing about plywood is that even the best made plywood will have some gaps and parts that the glue might have not completely set and the vibrations of the speaker could exploit that weakness.
I would suggest trying to work with Baltic Birch plywood, if you can find it (seems like it’s all but impossible to find right now) the manufacturing tolerances are a lot higher and it’s has more ply’s per thickness that other ‘furniture’ grade ply. Additionally if I remember correctly Baltic Birch ply is 100% birch and it uses no ‘softer’ filler woods. Baltic Birch is often 100% free of blemish’s (or footballs) on one side meaning it can be stained or polished.
However, I suspect that there is a reason that most speaker manufactures work with MDF and I don’t think it has to do with price. MDF has doubled/tripled in price in the last 5 years and is as expensive as most hardwood plywoods now. I suspect that part of the reason most manufactures use MDF is that it is ultra stable, acoustically neutral and can have strong joints with glue and biscuits alone. MDF comes in various densities which I’m sure speaker manufactures take advantage of when developing speakers. Unlike plywood, MDF is also a completely uniform product with no gaps or soft spots. While it is kinda ugly it can be easily painted and accepts veneer beautifully.
Those appear pleasant.