Yet Another (3rd!) Way to Construct a 28" Spherical Shell...

Yeah..."someday", Gary...NOT! But due to the number of hours spent veneering, I was toying around with the idea of making a pair from solid HW (like walnut, etc.). The extra cost is offset by the ~20 hours of labor needed to do the veneering... Anyone know where I can get a "plank" of solid walnut that is 1" thick (and another 3/4" thick) and 14" wide?

But yes, that's a bitch'in looking wood stove: very creative and all that metal would retain a bunch of heat with maximum firebox volumn vs surface area... Cool! I see he's also using brass/glass ship portals: wonder if he had to add special heat resistant glass or they came with glass strong enough already??

It's alive! AOS-III #2 is assembled with driver holes cut and routered. Just need to do a bit of rough sanding/filling to get each "facet" flat and smooth and ready for veneer. Surface is MUCH more uniform this time and requiring a lot less sanding/filling then #1. After glueing/assembling the 1st two quarters of #2, I still had just a tad bit of gapping in some of the seams around the area of the "equator". Determined that the sum of my two taper jig angles was ~11.0 degrees which is a tad off (should be 11.25 degrees). I determined that I needed 0.039" more height in the taper jig block for the side two tapers. So I got out my set of feeler gauges and cut the 0.039" one into four pieces and used them to shim the taper jig block to the proper height. Ran the remaining 16 "slices" thru the planer one last time and vola!: the remaining hemisphere of the sphere had very tight seams with no gapping whatsoever. Now that the taper jigs are "dialed in", SOMEDAY, I may build a pair of these round speakers from some hardwood. Would be expensive, but would also save the ~20 hours of labor needed for veneering and the ~$100 cost of the veneer. So at $30 an hour (what a good carpenter/wood craftsman might work for??), that would allow for ~$700 to $800 for the purchase of hardwood. I'd need enough 1" thick and 3/4" thick by however wide boards to assembly into two 20" wide by 1" thick by 8' long "planks" and three 16.75" by 3/4" thick by 4' long planks and three 14" by 3/4" thick by 4' long planks (for two speakers). The grain would need to run // to the width of these planks (so it would be along the the vertical axis of the sphere when using the "arc cutter" to slice off the arc pieces from these HW planks). That's a lot of HW board feet...but I have not priced out what it would cost for any hardwood (maple or walnut or teak or cherry, etc.). Due to the MUCH higher modulus of elasticity of HW vs. MDF, the shell thickness could drop to 1" (from current 1.25") and still be as stiff (or stiffer) then currently and that might save a bit of board-ft as well. I think they'd be beautiful and definitely have a different "sound" then the MDF one's I'm currently building and which I'll soon get to hear what a matched pair sound like. Currently I have one AOS-II with 6.5" woofers and one AOS-III with 8" woofers playing in my LR system...which some people who've heard them (with the 300x2) prefer to the EPI 1000's (with the TFM-42) in my FR system. Mahalo! - Ed

add: Mbskeam wrote (and TNRabbit agreeded): "instead of a steel band. why not use a ratchet type web strap."
That thought must have stuck in my consciousness 'cause I DID use one of those nylon strap with ratchet for cinching (up to 900 lbs of tension!) for build #2. Worked great; however, at a certain tension level no amount of additional tension will EVER 100% close the gaps unless/until the taper angle of each "slice" is very close to the required 11.25 degree value.... I DID learn that for this build #2!

Lookin' good, Ed!

Ok! All ready for drivers and finishing...probably could have pushed it and installed the drivers today/tonight, but why push it (at ~9 months in total to build/"birth" both speakers - at ~3/4 hour per day on average, one thing this project has taught me is patience...)? Haste makes waste, etc. Can easily install the drivers evenings this week and then do the ~3 coats of shellac on Saturday and Sunday. That will leave me ~9 days "behind schedule" on this project which is pretty good considering I laid out the schedule several months ago (highly recommend making a schedule for ANY project you work: it really helps a lot to keep one motivated and "on track" to finish... Can't wait to finally hear what a balanced pair of these new speakers sound like...:

"fit and finish" better on #2 than #1....lessons learned, etc.:

Here's what wiring for 14 drivers looks likes :

Lookin good!

Ed, are you using polyfil in these?

Ed, you do awesome work.

Gary wrote: "Ed, are you using polyfil in these?"

What's polyfil, Gary? I've always used simple fiberglass (pink) insulation batting for "fill". Already bought a roll from HD for this one, and if I switched I'd probably have to pull the fill from AOS-III #1 and re-fill it with this stuff...so it would have to be a lot better... The 1.25" thick MDF spherical shells of these speakers are so "inert" and stiff (the ol "arch effect") that I can almost get away with no fill at all, but it does seem to make a small difference/improvement in the sound to pack some "fill" inside...Thanks, Ed

Gary wrote: "Ed, are you using polyfil in these?"

What's polyfil, Gary? I've always used simple fiberglass (pink) insulation batting for "fill". Already bought a roll from HD for this one, and if I switched I'd probably have to pull the fill from AOS-III #1 and re-fill it with this stuff...so it would have to be a lot better... The 1.25" thick MDF spherical shells of these speakers are so "inert" and stiff (the ol "arch effect") that I can almost get away with no fill at all, but it does seem to make a small difference/improvement in the sound to pack some "fill" inside...Thanks, Ed

http://www.walmart.com/ip/Poly-Fil-Prem ... z/17808670
http://www.walmart.com/catalog/product. ... gMethod=rr

That's hilarious, Gary! I've literally picked up TONS of that stuff all over my house. Our new dog chews everything so wife has bought him probably several dozen stuffed toys that all use this crap. He tears them to pieces and the stuff/stuffing ends up everywhere. I pick it up and throw it into the fireplace. If I knew it was $10 per 32 oz (and could be used for speaker "fill"), I would have saved it, ! Oh well: fiberglass fill works just as good...?

Poly-fill sounds better than pink fiber glass and yellow fiber glass sounds better than them all!

Oops, there it is! Only took 9 months and ~180 hours (for both)...but was great fun! Sound is fantastic and of course now "balanced" with both speaks the same... Was cool to watch the identical twin to #1 "materilize" right before my eyes today as I installed the drivers.. The grill seen on the top woofer of the one in the foreground is just temp, but I'll probably add them to all of the "front" and top/bottom woofers... May do some response curves and post later, but not much point at this stage...all about "ears" now; room acoustic treatments is 'bout all I can do with the measured frequency response curves...:
AOS-III #2:

Both in my living room (300x2 is in the corner). 'scuse the poor lighting of the background one...I'm not much on taking pics:

Looks great!!!!!

Wow.... I've done some DIY speakers so I know the amount of planning and work that went
into these....Congratulations on a spectacular build...

They look fantastic; much better than your previous pair!