OTop12 Build Thread

[Bruce Weldy]

Ahhhh....those are beautiful things!

One mod though -- cut the corner up a little higher. You could end up gluing it in when the PL expands. Just take off another 1/4".

Now I guess I have to make some new ones - mine were old 3/4" scrap pieces - yours put mine to shame.

[Tom Smit]

Sometimes it's small steps, sometimes it's big steps. Regardless, progress is still being made!

+1 on putting shims in the gaps.

[miked]

Thanks Bruce, I'll do that. With my luck, they would wind up PL'd AND brad nailed in somehow. Of course, these things are yet another idea shamelessly stolen from your workshop! I've been meaning to build them for...well, since I visited you. After gluing up the horn braces the other night, I really couldn't do anything else w/the build, so I figured I'd finally build some assembly squares.

@Tom: Yep, small steps. Being that these are already a year in the making, why rush at this point? With the tweet arrays yet to be built, it's not like I'm "that close" anyway. LOL!

[miked]

Progress made today. These OTops are the most complicted woodworking project I've yet to do. I gotta laugh...on the main BFM page where all the different box designs are listed, they have a degree of build difficulty; the OTops are rated a "3." Only a 3? If I tried to build DRs, I'd have put my shotgun in my mouth already. Luckily for me, I'm a "second-best is just fine!" kinda guy. LOL! Besides, 4 OTops with Deltas at 400 clean watts per pair will be nothing to sneeze at.

This is quite a learning process. EVERYTHING you do must be absolutely perfect, else the panels don't line up. E.G. your panels may be cut at exactly, to a 32nd, the correct length and the miter angle could be perfect. But if you glue the baffle just a bit crooked, the horn panel won't line up perfectly. I know; these DIY speakers aren't about perfect, but "good enough and airtight." I just like jigsaw-puzzle perfection when I build things. But as usual, PL saves the day. Love the stuff, hate the stuff. I did the "PL fillet thing" with my gloved finger on every joint. You can see it in the pics. Probably didn't need to do it, but in the interest of ensuring air-tightness, it was an easy decision.

I will also add that if are thinking about building these and you don't have an assembly square like I show a few posts up, build one. Heck, build 4. They are PERFECT for holding the baffle at 90-degrees while you nail/screw it from below. I will also add that as you get to the 3rd and 4th sub-assembly it goes much quicker and easier b/c you know where to hold/how much/what angle to hold the brad nailer, etc. I'd imagine guys like Leland put one of these together in one shot, in 10 minutes flat...and the PL magically dries for them in 20 minutes to boot. :p

The next big step is adding the top and cutting off the protruding horn panels. I'm a bit concerned about getting the top on perfectly square. Is there a trick for that? Guide boards brad-nailed to the bottom, extending up to the top, maybe?

I've gotten "this far" today, and I'm done. 24 hours to let the PL cure as two of these sub-assemblies have quite a bit of the stuff on there where the horn panel meets the brace. Tomorrow I'll glue in the the throat reflectors...that will be interesting as some of my horn panels are not exactly at the angle in the plans. Plenty of tomorrow for sure.

Pics or no progress!

[Jon Barnhardt]

I'd imagine guys like Leland put one of these together in one shot, in 10 minutes flat...and the PL magically dries for them in 20 minutes to boot. :p

My record is 12 minutes once all the pieces are cut

But I have a custom jig and I reverse the order a little bit on assembly. The assembly goes smoking fast once everything is in order (which takes hours).

You are doing fine. Everything looks great. Get a few more builds under your belt and you will be surprised how fast they go together.

[miked]

Thanks, Jon. I'm pleased with the build so far. I know I've got some time-consuming steps ahead of me as I continue the build. For instance, I already know that some sanding of the outer edges of the horn braces will be required in order to correctly fit the sides, b/c I did a lousy job gluing them to the baffles. That was the MOST frustrating thing I've done in years. I haven't built the tweeter arrays yet, but I will be building the cutting and gluing jigs for them, and taking off the actual tweeter element before cutting so I don't have to mess with cutting screws.

Tell me more about this custom jig of yours...feel free to share pics, unless you dont' want to give away your trade secrets or something.

[subharmonic]

Tell me more about this custom jig of yours...feel free to share pics, unless you dont' want to give away your trade secrets or something.

Slip me a $20 and I will sneak some shots next time I am over at his shop. Prolly tomorrow for a SLA Pro listen. But don't tell Jon!

[Jon Barnhardt]

Lol. Unless you are building lots of them it's prolly not worth the time to build the jig and re-engineer the plans.. But I might share a pic tomorrow when I get over the shop

[miked]

Please do share a pic or two; I really enjoy seeing any type of "how-to" pics.

And subharmonic...they have those eyeglasses with the HD videocam embedded in the frame. Just sayin'...

[LelandCrooks]

The only part for me on an Otop that gives me trouble is the brace. Every time it's a bit off. I'm not as fast as Jon, haven't built a jig for these. But my son Sam is, without a jig. He's become a cab assembly machine. But it only runs on weekends. School takes priority.

[miked]

So I stood around scratching my head trying to figure out how to put the top on dead-square. Don't know about anyone else, but in this case, guideboards didn't work worth a darn for me in this application. You can't lay the cab on it's side b/c there is no side at this point. Can't lay it on the front b/c the horn panels stick out. Stood there for at least an hour, flipping the cab end-for-end-sideways-upside-down. Nothing.

Then, it happened. The light shone down from above (GE Daylight Flourescent bulbs...excellent bulbs.) I remember reading a thread where someone used guide pins or dowels to get the final side aligned on their Tubas or Titans. GENIUS! If it worked there, it would work here too!

Being that I already had the baffle/horn panel pattern drawn out on the top (IITP!), it was a simple matter to:

Mark and countersink for a #6 screw dead center


Another two holes 3" to either side


Measured off, from center, the same hole spacing on the top of the baffle and drilled pilots. On a few holes, I drilled them too deep and the some screws didn't bite, but no matter, they were for alignment. I nailed those suckers down but good with the brad nailer.


Here's a shot with one screw slightly protruding through, so those still trying to figure this out have a better idea. The only thing better than pics is more pics, right?


PL'd, gently dropped the lid in place, squished the lid left-right-left a bit until all three screws dropped into their respective holes, screwed down and brad nailed the horn panels and baffle.


Topped OTops!



I'm waiting a few hours for the PL to set a little before gluing the reflectors in and trimming the horn panels. That'll be tonight. I also hope to start on the side panels, which is going to be a PITA b/c I know my horn panel braces are off and some stick out too far. More to come.

[Bruce Weldy]

They are looking great!

If I remember correctly, I lined up the top by using the W braces to hold the sides in place then put the top on accordingly - lined em up an shot 'em.

[miked]

I guess that would've worked too. Oh well, it's done.

BTW, Bruce: What size mattress topper did you buy to line the two OTops you built? I'm wondering if one Queen size topper will be enough for 4 cabs? I'm off to Walmart in a few...

[Bruce Weldy]

I guess that would've worked too. Oh well, it's done.

BTW, Bruce: What size mattress topper did you buy to line the two OTops you built? I'm wondering if one Queen size topper will be enough for 4 cabs? I'm off to Walmart in a few...

I bought enough for two OT12s and three WH10s.....about the same as four OT12s. I might have bought either two twins or two fulls....I just can't remember....sorry.

Buy the biggest one you can get, then go back for more if you need it.

[miked]

Got it. Thanks for the fast reply; I was just walking out the door.