OTop12 Build Thread

[Tom Smit]

Not sure if I'm going to build one cab at a time to completion before starting the next, or use the assembly line method. Probably the former, as I'm limited on table space....unless I put all my cut-with-love cab pieces on the floor. I'll figure it out.

+1 on building just one first. From there you know what's needed for building the rest. That should result in less mistakes.

[miked]

Thanks, Tom. I will do just that; build one first, from start to finish. That way I'll have all the "lessons learned" in my hip pocket for the next three.

Life got in the way today. All I got done was gluing/cutting more 1" square strips for the rear panel braces. But, by tomorrow morning the glue will be dry and I'll slice'em up and that 'll be DONE. At that point the only wooden cab parts not cut will be the two strips that the array mounts to and the grill mounts. Both, very easy and fast to cut. On a related note, I can clearly see how someone who builds cabs of any kind for a living, would be wise to invest in a CNC machine. Seems to me that 75% of the total time spent building this cab is just cutting the parts! I will never again wonder why any cab builder charges x dollars when "it's only xyz dollars worth of parts."

Building will commence tomorrow. Copious pics to follow.

[miked]

I'm not too pleased with my progress. I spent ALL DAY in the garage yesterday. I thought I'd be halfway done. I spent HOURS and HOURS trying to get the $!#$$%(#!!! horn braces attached to the blasted baffles. In all the build threads I've read, I can't recall anyone complaining about this step, so it must be me. Even using a guideboard it was a royal PITA and I'm still not sure they are on securely. We'll find out tonight when I try to attach the horn panels.

Allright, a small, but necessary step. Predrillng/aligning the screw holes for the back panel. Much easier to do this now than after the Duratex is on.

I set up the fence on my drill press for a 1/2" space b/t the bit and fence. Marked my holes and voila, matched panels.





Back panels are completed. One thing down, 400 more to go.


OK, now, what has been the most frustrating part of this entire build so far. Cutting out the baffles was extremely tedious but not "difficult" per se. THESE THINGS? I haven't been so ticked off in a looong time.

Guide board. Yeah, yeah. Guide board. Keeps the thing straight. Doesn't do much else.



The problem is that no matter how hard you try and hold the panel in place, clamps, whatever, when you try to brad nail it from below, the panel "pops up" and doesn't stay flush. Then, you finally get the brace to stay still, but then you have to remove the guide board before the PL cements it to your baffle....and you remove the guide board and the brace moves. ARGH!

I tried driving a screw...and didn't predrill. Split the brace clean in two. I wind up setting up my tablesaw again to cut one new panel. I was not a happy camper.

I smeared a bead of PL along both side/edges of the braces. Hopefully it just cements them in place. I'm sure there's some fancy jig I could've built...but I just couldn't figure out how to do this easily. I did the best I could.

So anyway, here are my completed baffles. No closeups...I already know how lousy they are...you don't need to see that.



Finally, I marked the bottom panels, "top and bottom" where the baffle and horn panels go. This will make it much easier to screw them in place. I also predrilled for the cab feet. You can see that in the corners of the panel. Doing as much of this small stuff up front as I can. Will make final assembly that much faster.



On a related note, after my "fastening fiasco" with the horn braces yesterday, I'm inclined to go the screw-together route for fastening the baffle to the bottom, the horn panels and the sides/top. The reflectors would be diffcult to get screws in there, so they'll get brad nailed...they aren't load-bearing anyway. It will be a PITA to predrill the tops/bottoms, but build once, cry once, right?

Need to mark the top panels too. Tonight, building proper will commence. Heres' hoping my horn braces don't snap clean off.

[DJPhatman]

miked, step away from the build for a day or 2. Go do something that you really enjoy, and that relieves stress for you. Don't think about the build, talk about it, or come on here. Clear your mind and come back to it all with a fresh perspective. I sense you are putting undue pressure on yourself to get your build done, and it is ruining the joy of building for you. This should be fun, not freaking you out!

Also, here's a hint you may have missed... wrap some wax paper or clear plastic cling wrap on your guide boards so they don't stick to your work.

The problem is that no matter how hard you try and hold the panel in place, clamps, whatever, when you try to brad nail it from below, the panel "pops up" and doesn't stay flush. Then, you finally get the brace to stay still, but then you have to remove the guide board before the PL cements it to your baffle....and you remove the guide board and the brace moves. ARGH!

I tried driving a screw...and didn't predrill. Split the brace clean in two. I wind up setting up my tablesaw again to cut one new panel. I was not a happy camper.

I smeared a bead of PL along both side/edges of the braces. Hopefully it just cements them in place. I'm sure there's some fancy jig I could've built...but I just couldn't figure out how to do this easily. I did the best I could.

So anyway, here are my completed baffles. No closeups...I already know how lousy they are...you don't need to see that.

Relax, man! Think about each step before you actually do it. There are other ways of doing thing, if you think them out first.

A simple solution for doing the braces would be to attach the guide board to your work surface edge, clamp your woofer baffle to the guide board, lay a small bead of PL on the edge of the brace, position it, clamp it to the guide board, shoot a couple of brads into it at 45 degree angles ( like this \ / ) just so it holds everything while the PL cures. The PL holds everything together, the brads and screws just hold the pieces against the PL expansion until the PL cures. If your pieces are still moving, use better clamps. Those spring loaded clamps are not enough to hold parts while you shoot brads. Get a 8 of these clamps from Harbor Freight Tools. Get a bunch of the 36" long ones, too. They will come in handy on your sub build.

[miked]

Thanks, DJ-P. I have some of those HF clamps. As you know though, you cannot clamp the brace from the top, b/c where the parallel edge of the brace begins, it hangs over the end of the baffle. IOW, nothing to clamp it to.

I did forget about the wax paper...and I have a roll in my shop.

I did not want to toenail the braces for fear of driving a brad through the spacer ring directly on the other side. I've been doing this stuff long enough to look on the other side of the workpiece for potential bad side effects...I've learned the hard way. If I could toenail them in, that would've made things a lot easier. We'll see what the end result is tonight. Depending on the fit, I might not actually nail the horn panels to the braces; just plenty of PL and clamp in place. I don't have a lot of faith in the structural integrity of the joint b/t the brace and baffle at this point. Thanks for the tips.

I'm hoping that the baffle/brace assembly is strong enough that I can just get the cab together. Once all the panels are PL'd/screwed in place, it'll be solid as a rock. As I said, thankfully the horn braces really aren't structural...they really are only there to aid in alignment, which the miter cut on the horn panel (if done correctly) and your pencil lines on the bottom panel really take care of. The horn panels are secured to the top/bottom/baffle; they aren't going anywhere. They do brace the baffle though...hmm. Well, here's hoping I don't have to redo the entire baffles! That's another week.

[ncgrove]

As I said, thankfully the horn braces really aren't structural...they really are only there to aid in alignment, which the miter cut on the horn panel (if done correctly) and your pencil lines on the bottom panel really take care of. The horn panels are secured to the top/bottom/baffle; they aren't going anywhere. They do brace the baffle though...hmm. Well, here's hoping I don't have to redo the entire baffles! That's another week.

The braces are structural in that they tie the baffle, horn panels, and sides together. That's why they are called braces. You might want to read that bit at the beginning of the plans about not being worried if things are a little off. My first Jack was tilted about a quarter inch, as well as twisted. I'm the only one who knows. The best part about these builds is that if you screw up anything, it can all be fixed with bondo.

Also, another thing that I started doing for my Jacks (and I'm pretty sure it would work on the Omni Tops) is to install the horn panels to the top, bottom, and baffle, and add the horn braces after. That way you can trim them to fit perfectly and not have problems with the brace getting in the way of the horn panel being true. You'd might want to make sure you'll have room to install the brace first.

[zefrenm]

I changed the Assembly on my omnis'; I first cut the top, bottom and side panel; then use bills jigs to keep that shape square (90 degree corners) and dry fit them with screws (note:always pre-drill) , no glue. Then cut the baffle panel and finish it with driver spacers, screen, tee nuts for the driver then square it to the top and bottom panels with more jigs, then screw into place, and making sure all the 90 degree corners jigs are secure (90 degrees at the box corners and the top and bottom panels to the baffle). Then the baffle side brace cut to fit from the baffle to the sides (glue the baffle side brace to the baffle only here), and finally fit the the side horn panels (remove only one side at a time to make the flush cut of the horn panels) ; each step secure with screws only. Keep thee jigs tight. Then remove screws & glue in the reverse order of the dry assembly one step at a time, horn panels to battle, Top & Bottom panels (notch out the wire for tweeters) and then sides.

[miked]

Funny you guys should mention changing the order of panel assembly. When I finished gluing up the horn braces (6 hours later) I stood there staring at the complete baffles and thought "You know, I wonder if I could have slipped these braces in later somehow?" But obviously it was too late at that point.

I will ensure that my cabs are square. That much, I'm good at. I will sand the braces if need be on the angle cuts and ends. Thankfully, PL has such great expansion/fill capabilities that anything about to about 1/4" gap can be filled in. I know the angle of the horn panels is very important; I'll make sure to keep them correct.

My only real worry at this point is securing the horn panels to the braces. How did you guys to that? If you shoot a nail into the braces, they split. Ask me how I know that. I guess a good predrill and a #6 screw would work?

[zefrenm]

Funny you guys should mention changing the order of panel assembly. When I finished gluing up the horn braces (6 hours later) I stood there staring at the complete baffles and thought "You know, I wonder if I could have slipped these braces in later somehow?" But obviously it was too late at that point.

I will ensure that my cabs are square. That much, I'm good at. I will sand the braces if need be on the angle cuts and ends. Thankfully, PL has such great expansion/fill capabilities that anything about to about 1/4" gap can be filled in. I know the angle of the horn panels is very important; I'll make sure to keep them correct.

My only real worry at this point is securing the horn panels to the braces. How did you guys to that? If you shoot a nail into the braces, they split. Ask me how I know that. I guess a good predrill and a #6 screw would work?

When i remove the the sides to cut the horn panels flush, I mark the Baffle Brace to from an outline on the horn panel, drill that out and when your gluing the panels back later use the hole to drill back into the baffle brace. and i use #6 1" screws and the occasion 1 1/2 #6 with a 3/32 drill bit (not sure all i know it's tiny)

[Grant Bunter]

All you need to remember is that it's the PL that is the adhesive, and nails or screws or clamps or a guide board only hold things in place until the PL is set.

So when it comes to the side to brace (or brace to side) pre drill and screw if you find the nails are splitting your ply.
Or if you're eyeballing the spot and miss, when you're done, fill the hole with PL.

It sank in for me very early, the cabs don't have to look great inside, the requirements are purely that the cabs are structurally sound and leak free.

The outside of the cab can be totally sorted with PL and bondo and finish.

Chin up! So far, your builds look great

[miked]

Thanks, zefrenm. I'll have more to report tonight. Despite the fact that it's a lot more work, I'm going to go with the screw-together method of assembly for most of the panels. Shooting brads just doesn't work unless you can really clamp the two panels together (guide board isn't enough) before shooting the nail in, else the panel moves up, vertically, preventing a secure clamp/glue joint. The reflector panels, I'll PL and nail in b/c they aren't structural at all.

Thanks, Grant. I'm not worried about how it looks inside, only that it is structurally sound. I'm thinking I'm going to be OK. Yesterday was just a nerve-wracking day, that's all. I've taken several deep breaths since then. LOL! If it turns out that the horn braces are not "on there real good" I'll pull them off, scrape the PL and start over. Don't think I'll have to do that though.

[Bruce Weldy]

If it turns out that the horn braces are not "on there real good" I'll pull them off, scrape the PL and start over. Don't think I'll have to do that though.

If there is enough PL on there to scrape - you won't be getting them off.

I used very few screws in my OT12s...brad nailer is enough to hold it together while the glue cures.

[miked]

Yeah, I forgot that stuff dries like concrete...remember it from when I built my bass cab. And if they're on there too good to come off, then I'm home free! I'm probably worrying over nothing. Back to it tonight!

[Bruce Weldy]

I'm probably worrying over nothing.

Cut probably and insert absolutely.

Your build looks great.

[miked]

Long day at work. Came home, ate dinner and I'm shot. Well, I've got good news and "meh" news.

Good: I was worried about the strength of the horn braces for nothing. The PL dried really well and the braces aren't moving anywhere. Glad I'm building 4 OTops up front b/c I don't want to construct a baffle again...ever. Or at least in the distant future.

Not So Good: (But not BAD, per se) While the braces are at a perfect 90-degree angle to the baffle, and level horizontally, some of them aren't where they are supposed to be side-to-side. IOW, with the baffle centered on the bottom panel, in it's proper mounting position, the left brace is too far to the left, so it prevents the left side panel from sitting flush and the left horn panel isn't touching it. Some braces will need to be sanded down anywhere from 1/16" to almost 1/4", while I'll be putting in big old globs of PL on others. Good thing PL expands a lot! I have a love/hate relationship with the stuff...as I'm sure most of us do. I am thinking it's much more important for the baffle to be centered where it's supposed to be, and the horn panels to fit correctly like they are supposed to be, than for the horn panels to solidly mount to the braces. For the bigger gaps I plan on cutting shims and gluing them in there...I have lots of off-cuts laying around and who cares what the inside looks like, right? Square and air-tight is all that matters.

Being that I'm shot and don't want to do any heavy thinking (or lifting) in this state, I finished up some assembly squares that I glued up last night. They are 12" x 12" and made from two laminated pieces of 1/2" BB, in case anyone cares. These will come in handy for the OTops and mighty handy for the Titans.



More tomorrow. Thanks for looking.