Techshop closes

Things are now at a dead stop. Techshop declared bankruptcy today and closed its doors. 

I should have been clear, in hind sight that this was going to happen - for the last few months the equipment hasn't been repaired or well maintained. The dust extraction was dismantled a few months ago and never replaced. 

It's not clear how I can proceed since the design depends on the precision cutting of the braces, frankly not very easy (and not intended to be done) by hand.

That's half the $1,000 membership down the drain. By the time I'm finished I could have bought a pair of speakers for less.

 

Second iteration for the matrix bracing

Each horizontal brace is now made from two sheets of 1/4 inch ply. The slots for the vertical spacers are cut completely through so that each spacer sits directly on top of the one below. This idea is to make sure that the drawing's dimensions are absolutely adhered to and don't depend on the thickness of the plywood which is quite variable.  Moving to this two layer brace sandwich also afforded the opportunity to add additional vertical spacers at the front.
 



The spacers are rather 'bendy' when the vertical axis lies across the grain, but stiffer when it is with the grain. Although the spacers are not load-bearing, I think for the remaining cuts I will ensure that they are all vertical.

This build is turning out to be much more complicated and time-consuming than the Phase-IVs. Partly that's a function of getting to grips with the Shopbot, and one false start, but Phase-IVs had very little assembly. These by contrast have orders of magnitude more; and I'm not even close to starting on the cabinet walls yet. 

Matrix-like interior bracing

The matrix-like interior bracing takes shape. Only as I was assembling it did I realize who I could have built this in half the cutting time. Dam!

The cutting begins!

After weeks of practicing turning the Sketchup designs into tool paths using the trial version ov VCarve pro, I finally started cutting the wood. Although the design may have to be tweaked as I learn more about using the Shopbot, the first session was more productive than I expected. I cut all the matrix bracing stays (vertical separators) and did an experimental cut (one that after a few minutes was clearly wasn't going to work).

The laminate panel (chipboard and 1/4" finished plywood looks like it worked  much better than I had anticipated. The rolling on the the glow and lots of clamps seems to have done the trick. The only issue is a gentle warp which makes cutting difficult as the sheet has to be very firmly secured to the sacrificial  board. And there is a tendency to break though the tabs if there aren't enough of them.

These two videos show the Shopbot in action. It is remarkable to see the finished pieces taking shape. It's as if, after staring at them for months on the screen in the CAD program, they were being slowly beamed¹ down from the virtual world of Sketchup.

What was also gratifying was that the toolpaths worked exactly as envisioned. Of course that was perhaps a little less surprising since VCarve has a very sophisticated preview for exactly that purpose. 

(Note the passage of time - the first was show at about 3pm, the second at about 6pm. Some of that was testing and altering tool paths, but the cutting does take some time).

The only remaining question is the 45 degree cut at the top of each panel. Since they are still fairly firmly attached to each other, I might try using the router here....

¹ Gratuitous Star Trek reference

Waming up

Thais may be a trick of the mind but the bass response seems to get better after about an hour's continuous use.  I wonder whether the rubber suspension is cold and stiff but as the bass driver imparts energy to it, it warns up and becomes more supple?

If so, I need to ensure that I calibrate all the drivers after playing music through them for a significant period at the kind of volume I intend to listen at.

Pick up the thread

August 10, 2011 - that's when I finished building the Phase IVs - was 1690 days (or 4 year 7 months) ago. But today I took the first concrete steps in the next phase; I bought some of the wood I need for the Phase Vs.

The woofers AC 250F1s I've had for 4 years. I was going to use Hiquphon OW1 tweeters but at $250 a pair I decided instead to go with the Vifa D27TG-45-06s, the same ones I used in the Phase IVs since I bought 6 of them during the last build (not sure why).

I had been thinking about the AC 130F1 for the mid driver but they didn't seem, on paper anyway, much better than the Scan Speak 15m-4624 I already have (from the MkIII project). First, it's cheaper to get a second Scan Speak than two AC130s and the Scan Speak has a circular chassis which makes routing it into the baffle much easier. 

So what was once going to be a no-compromise final build has turned into a more incremental evolution (though I know it will probably be the last iteration).

I'm experimenting with panels made of plywood glued to fiberboard.  I need to figure out how not to damage the veneer on the panels while I'm building the enclosures. Other than that next weekend it's off to the races.      

About time

It's about time I started work on the Phase Vs. I have an all-wood design completed, and an idea for how I will build them; I just need to buy the wood (and the tweeters) and make a start...