Another small update... Warm weather is here so it's getting harder to find free time to plug away at these.
ANYHOW... My original plan was to build all 4 SLAs at once, but I decided to assemble one completely to work out any kinks/bad habits and apply what I've learned sequentially to the next boxes. This first one was a pain... Originally when I was ripping the wood I discovered that I somehow had the angle on the blade offset by about 3 or 4 degrees. I thought I had corrected/weeded out all the pieces with angled cuts, but apparently I missed one. Mounting the side to the back revealed that they certainly did not form a right angle. Even though the cut was only off by 3 degrees, the alignment with the top/bottom piece was off by about 1/4 inch, which meant I had to forcibly bend the two connected pieces back into shape. The only way to accomplish that (as far as I knew) was to temporarily mount the top/bottom pieces to hold everything square, and then mount the main brace. Even after removing the top/bottom, the brace wasn't enough on it's own to hold everything square, so I had to cheat a bit and mount the top, then the baffle, then the other side and lastly the bottom. There was still some twisting at the bottom, so I did my best to force it square and then secured the last piece. I think it turned out ok overall, but the next boxes should go more smoothly.
I decided on screws for fasteners. It's what I'm accustomed to from my car audio sub box building days, and I like that the screws forcibly hold the butt joints together. I few misguided pre-drills left some extra holes in the box, but that's nothing a little wood filler can't fix.
The plan is to fill all the holes, sand the boxes down, stain them with a light-colored stain and then cover the baffles with grille cloth rather than expanded metal. It's a cosmetic choice, as I'm sick of looking at the big, black looming EV speakers that stick out like a sore thumb.
I was, of course, eager to hear what these sound like, so I went ahead and mounted the crossover, wired everything up and did some listening. For reference, I had the SLA running off my Great American Sound GAS-3200 in bridged mode, which puts out about 800 watts into 8 ohms. Don't worry, I went easy on the levels.
Not that this speaker was mounted in anything resembling what it's final habitat will be, but I was excited to hear what it can do. My first impressions are that the response of the SLA is extremely natural and smooth. Our current setup, which is a pair of EV Sx100+ tend to be unnaturally bright and lack good midrange response, specifically around vocals. We've had complaints of vocalists being lost in the mix, and I can already hear that the SLAs will rectify much of that. I did a sine sweep just for kicks, and just from listening by ear I can tell that the overall response is indeed pretty flat as Bill suggests. There a few peaks here and there, but nothing a little EQ can't fix. One thing that surprised me was the low-end extension. I wasn't expecting much below 100Hz, but from what I was hearing they do reasonably well down to about 80Hz before rolling off significantly. I've never personally been a fan of how piezos sound, but then I've never listened to one connected to a properly-designed crossover. The piezos blend extremely well with the Alpha 6a, and although not as "crisp" as some of the compression drivers I've heard, they sound more natural and complement the midbass quite well. I did notice that 10k peak in response, so once they're all build and mounted I'll so some EQ-ing to flatten things out. Horizontal off-axis response seems good, and it almost seems like the further you get away from the speaker the better it sounds. I'm limited in distance I can put myself from the speaker in my basement, but as I said I just wanted to hook it up for kicks and get some first impressions.
Anyways, will keep plugging away. I doubt I will post anymore build progress pics until all 4 are completely finished with stain and grille cloth, so that could take a while.
Stay tuned!