Build Thread: The Bombers (SR71's become 3-ways)

[rvsixer]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Remember that these are sealed and will never see anything above 200 hz....

Unless I am reading the sims incorrectly, these are crossed over at ~400Hz (with extended output to 800-1000Hz ) .

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Unless I am reading the sims incorrectly, these are crossed over at ~400Hz (with extended output to 800-1000Hz ) .

You are correct sir...

Well that makes it even more interesting, because now you're getting up into freq's where nice thick rigid fiberglass really starts to shine...

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

ARRRRGH!!!

So the cheap POS dado cutting blade turned out to be...

...wait for it...

...a cheap POS dado cutting blade.

After testing a "1/2" setting on the blade, which turned out to be significantly under, I readjusted to "9/16", which ended up being even smaller... when I went to then readjust th-

-oh screw it. It was a piece of crap, broken now. Whatever. And I lost the receipt... $17 down the tubes.

Every build must have at least one moment like this one... hopefully just one in this case.

[greywarden]

Re: Build Thread: The Bombers (SR71's become 3-ways)

At least it's just $17

I have a tablesaw that I "recieved" (back when I was married and I was the only one that worked) for xmas (it's the thought that counts, right?) that couldn't cut a straight line if the fence were calibrated by a lab and bolted down, haha. That was a tad over $100 and I've only used about 3 or 4 times. :eek:

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Time for the front corners...

Started with 4"x4" douglas fir (amazingly cheap at home depot, $13 for 8 feet!), which I cut down to 3.25" octagons on the table saw...




Then I screwed an adapter to the end, which allowed me to chuck it up on the 3-jaw chuck...






Then the fun part, turning it down to 3"... took about .06" off the radius per pass, the final pass about .02" to get it nice and clean... then some 180 grit sandpaper while the piece is still on the lathe...



Next I need to create the flats into which the side panels will glue... haven't decided the best approach yet... I could machine them on the mill, or I could just cut it into a 1/4 round and glue strips on... probably the mill...

On a side note, if I ever use the word "lathe" as a verb again, the old school machinist shop manager will have my head... "turn" is the verb

[davepellegrene]

Re: Build Thread: The Bombers (SR71's become 3-ways)



Lunch I have to ask since I didn't see any explanation. How did you ensure that the braces properly align with each other. It's hard to tell from the photo's if it's as simple as laying them face down and they self align. I've got to assume this is very important when you apply the outer box.

Looks good so far!
Dave

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Lunch I have to ask since I didn't see any explanation. How did you ensure that the braces properly align with each other. It's hard to tell from the photo's if it's as simple as laying them face down and they self align. I've got to assume this is very important when you apply the outer box.

Looks good so far!
Dave

Well, the scraps between the layers were precisely the same length, and the holes for the dowel were very tight, so all I had to do was lay one flat edge against the table to make sure they were aligned rotationally, and that was enough, believe it or not. I layed a straight edge across the layers to check as I went, but it wasn't actually necessary.

[davepellegrene]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Well, the scraps between the layers were precisely the same length, and the holes for the dowel were very tight, so all I had to do was lay one flat edge against the table to make sure they were aligned rotationally, and that was enough, believe it or not. I layed a straight edge across the layers to check as I went, but it wasn't actually necessary.

The rotational alignment is what I was talking about. With the clamps on the sides you can't lay it on the side. The third brace from the top doesn't appear to come out all the way to the front making laying it on the front not work. Putting a straight edge on the side would align the pieces with each other but would not insure that the the box would be square. In other words if you stand the bracing up right and put a square on the side it might not be square.
Not giving you a hard time just being curious. I know from experience if you don't get this right you will fight it the rest of the build.

Dave

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

The rotational alignment is what I was talking about. With the clamps on the sides you can't lay it on the side. The third brace from the top doesn't appear to come out all the way to the front making laying it on the front not work. Putting a straight edge on the side would align the pieces with each other but would not insure that the the box would be square. In other words if you stand the bracing up right and put a square on the side it might not be square.
Not giving you a hard time just being curious. I know from experience if you don't get this right you will fight it the rest of the build.

Dave

What you're not seeing is that I glued up only two layers at a time, and didn't put the long clamps on (as you see them in this picture) until I had already used smaller clamps to-

-oh never mind, too complicated to explain.

Trust me, I got it right

[BeerParty]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Lunch - thanks for posting up this build. This cabinet has given me some new ideas, I may steal this shape for my next build. I'm looking forward to seeing how you wrap the backs of these cabinets.

Sorry to hear about your el-cheapo dado blade.

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Jeez, downgraded to 3 stars...

Detailed build thread not good enough for you?

What's the critique?

[lunchmoney]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Lunch - thanks for posting up this build. This cabinet has given me some new ideas, I may steal this shape for my next build. I'm looking forward to seeing how you wrap the backs of these cabinets.

Sorry to hear about your el-cheapo dado blade.

I've actually run into some problems getting the kerf cut plywood to behave... keeps cracking on me, despite the generous radius.

Might have to use 1/2" mdf instead, which I know will work... but that would be a bummer. I was really looking forward to these being all plywood.

Or I might glue 1" wide strips vertically around the rear corners, but again this would be a serious punt.

The answer might be that the kerfs need to be quite deep, leaving only about 1/16" left (tried leaving 1/8", CRACK!)

[greywarden]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Try steaming it before you try to bend it?

[GTB]

Re: Build Thread: The Bombers (SR71's become 3-ways)

Not quite like a "Bomber", but same idea. I have SR71's with a "Blackbird" center.

I have small stands now for the SR71's, about 8 inches.

The subs each have a RSS370HF-8 driven by a Dayton SA1000 hooked in parallel. They are tuned to 22Hz.

I continue to be amazed by this setup. I have the bug to build again, but I am so happy with this that it will be for my daughter, not for me.

Lunchmoney helped with me with this build, and I am grateful to him.

Greg

[djkest]

Re: Build Thread: The Bombers (SR71's become 3-ways)

[hijack]
That's a nice looking LCR setup you have there!
[/hijack]

This is a cool project. I like how you stuck to your guns (or bombs, as it was).