OTop12 Build Thread

[miked]

Last night I got the rear panesl predrilled for the mounting holes. I erred on the side of caution and put 9 screws across and 6 on the sides; every 2 inches, basically. There will be no air leakage from the back panel, no way.

Yeah, the ironic thing? A few posts up I poked fun at those guys who are all paranoid and have 30 screws holding the backs on their OTops. And I wound up with how many? Exactly 30 screws. I have a little surprise, if you will, for the backs. It's a secret and you'll have to wait until the cabs are done before you see it. Something to look forward to.

[Michael Murphy]

miked, all I can say is WOW, very very interesting, enlighting and entertaining. Now I know why I paid leyland to build 2 for me and dont tell any one but my first T39 is 3/4 shorter on 1 side and the second 3/8 maybe nos 3 and 4 ill get it right
Again great thread

[miked]

The past two days have been pretty educational for me. I've learned quite a bit. In no particular order:

15 years after buying my compressor, I'm still thrilled every time I use an air tool of any kind. It's the only way to go.
If you don't own one of the HF 6" Air Palm Sanders yet, you NEED TO get one ($30 on sale/with coupon...you can't go wrong). I sanded down 4 cabs in 30 minutes. Would've taken an entire DAY by hand or hours with the electric orbital sander.
When sanding down Bondo or Spackle, sand the cabs OUTDOORS if at all possible. Massive clouds of the finest dust imaginable are created and it gets EVERYWHERE. Even inside jeans pockets.
A 3/8" roundover fits the small plastic corners perfectly.
Thank goodness for plastic corners; they hide (will hide) how badly you suck at building cabs.
Rounding over 4 cabs creates 4 gallons of sawdust.
If fastening the cabs with brads, keep them away from the edges of the boards if possible b/c hitting them w/the roundover bit causes tearout.
Roundover your cab edges BEFORE you go patching nail holes and dings b/c rounding over will cause massive tearout on the edges and you'll have to PATCH AGAIN.

Yeah, that last one was a hard lesson learned. I got massive tearout on half the edges of my cabs from the BRAND NEW 3/8" roundover bit I bought today. All the nailholes on the sides/top/bottom are nice and patched and perfectly flat. But I had to go back and re-spackle many of the rounded edges due to tearout. It will be tedious work "re-rounding" those edges with the air sander, but I think it's safer (much less chance of tearout) than going over it with the roundover bit again.

No pics of the tearout, but here's the rounded over cabs, RE-spackled.






Oh, and before I started the rounding over/respackling, I got around to predrilling the rear panel braces for all the mounting screws. Cutting out all the parts with a CNC would take care of all this tedious work.



So tomorrow I'll resand the cabs and HOPEFULLY be able to call them "done." I still have to line the cabs with mattress topper, wire the arrays, build and mount the crossovers, mount the drivers/arrays and of course, Duratex the cabs.

Cleaning the cabs of all the sawdust and spackle dust will be a real chore, even with 100-PSI compressed air. It's just so hard to get it all off. I bought some tack cloths today. They work reasonably well, but they don't get everything either. I wish we'd have a real windy day soon; I'd just put the cabs outside and let Mother Nature handle it.

[Bruce Weldy]

Cleaning the cabs of all the sawdust and spackle dust will be a real chore, even with 100-PSI compressed air. It's just so hard to get it all off.

Don't bother. You aren't going to do a smooth, gloss finish. The duratex will cover any dust or fine particles left over. Blow it off, then start painting.

[miked]

Thanks, Bruce. That's good to know. One less thing for my OCD to get all tied up about. LOL!

[DJPhatman]

Just an FYI, miked. The tear out you are experiencing may be because you were running the router the wrong direction, too low powered motor or moving it too fast. Practice on some scrap wood to get a "feel" for the movement. And the 16-18 gauge brads used during construction are no match for a router round-over bit.

[miked]

Come to think of it, I was running the router in both directions around the cab...which way am I supposed to run it? Against the rotation of the bit, so I thought....not that I was paying attention to it. So maybe half of this is my fault. But as I remember it (being pelted with high-speed toothpicks of death) stuff was flying off the cabs no matter which way I was going. But still, being that i wasn't paying attention to the direction I was routing in, I'll take half the blame.

Weather is totally crappy here today; thunder boomers. I will not sand these cabs in my garage...at least that's my initial inclination. The sander comes with this bag thing that fits over a hose that attaches to the dust port on the router; no idea how well it works, but I really don't want to get "talcum powder" all over my shop and garage. Plus, a fair amount of that dust would just hang in the air and I'd be breathing it in. I'd much rather sand outside.

[DJPhatman]

Take the bag off and attach your vac to the dust port. Build a "sanding box" with the plethora of free plans on the internet. Add a dust collection system to your garage, workshop, wherever you do sanding. I have pulmonary disease attributed to inhalation of fine industrial dust, including sawdust.

[miked]

Thanks for the advice and it's GREAT advice. I have a 2HP dust collector and a Thein baffle (garbage can separator) that I use with my TS, BS and spindle sander. The HF palm sander has a 1-inch port and I don't have the right adapter/hoses for it. The health impact of the dust is one of the reasons I want to sand outside.

[AntonZ]

Do the sanding outside, and if at all possible do not bring your dusty cloths in the house. You will bring the dust through your entire house, it will stay there. Undress in the garage or whatever if you don't want to upset the neighbors, but keep it away from your house and family. It will stay there forever. Good thing you built the thien separator, love mine. One of the best diy tools I ever made.

[miked]

I installed the mattress protector tonight. This is probably my least favorite thing to do. The big cab manufacturers get their damping material die-cut. They grab a "left side" and a "right side" and just lay it in. Easy. Cutting the foam to shape and using spray glue is like root canal with a hangover for me. I used a combination of the electric staple gun (where it would fit in the cab) and 3M 77 spray glue (hate the stuff).

I purposely left the area above the handles/ports free of foam b/c I don't want to be grabbing it and pulling on it (and ripping it off) every time I pick up the cabs. They're not all "identically damped" but I did the best I could. Tomorrow I'll spray through the port holes and hopefully get the white foam at least a dark gray. The crossover will mount in the lower right-hand corner, hence the 5"x5" empty square in that area.

Various shots of the lined cabs. You can see I sprayed the rear cover area black to hide any "wood color" that might be visible around the rear cover. The mouths are also sprayed flat black, but no pics of them. They'll be hidden by a blacked-out grill anyway, so the flat black treatment is just insurance against being able to see through the grills.





Got the rear panels done too; they were dead-easy. All staples, no glue. They all look like this.


Oh, and the second coat of spackle and sanding went pretty well. Time will tell how well the spackle in the deeper gouges holds up...I'm starting to think I should've used wood putty. But Duratex specifically said "we recommend plain spackle" so that's what I went with.

Tomorrow is spray paint through the ports time and maybe the begining of Duratexing. We'll see.

[Tom Smit]

You're making steady progress. Good for you!

BTW, may I suggest getting rid of the push stick and getting a Microjig instead? It would be incredibly safer. (Leland at SpeakerHardware sells them).

[miked]

We've had some torrential rain and hail here in south Texas and with it, the temperature has dropped a whole lot. It's 54 degrees right now and not much warmer in my garage. So Duratexing tonight is out. I am sure I could if I HAD TO to do it tonight, but I don't. So I'll wait for warmer temps...like tomorrow when it's in the 70's.

I did, however, make some progress. I ran the wires for the array and spray painted through the port holes and on the back panels.

Ran the wires out through the lower left horn panel. The crossover will be on the right side of the cab (looking in from the back) so this keeps the wire run short.



Sealed the hole with a healthy dose of hot-melt glue. Hole was drilled with a 1/4" bit...I could've used a smaller bit for this 16-gauge wire, but this made it easier to fish the wires through. Yes; I did shoot the glue with flat black spray paint after the glue dried. Don't want anything shiny behind the grill.


Gave the rear covers a dusting with the black paint. The goal here was not to turn the white foam black, but to knock down the bright white foam to a much less visible shade...like grayish. Most of the view of the rear cover through the port holes will be blocked by the driver anyway.


Looking in through the ports you don't see much...and that's the idea. The white foam to left was painted black after this pic was taken.


Upper sections visible through the ports sprayed nice and dark.



Also cut and painted the diffusers for the melded arrays.


I'm running 16-gauge wire from the crossover to the arrays and I will wire the arrays themselves with 18-gauge wire, which will be more than sufficient. I am planning on 12-gauge wire from the back panel jacks to the crossover and 12-gauge from the xover to the woofer. Nothing like overkill, right? Besides, I have about 150 feet of oxygen-free, copper 12-gauge speaker wire and only about 15 feet or so of 16 gauge hookup wire. IMO, 14-gauge would be the best to use for wiring the jacks and woofer but I don't have any and I'm not spending any more money on "incidentals." The incidentals for these cabs cost almost as much as the drivers, crossovers and wood! I used 5 cans of cheap flat black spray paint just to paint the mouths and the insides...and as you can see, I didn't cover every square inch of the inside.

Tonight I'll probably cut eight, 5-inch squares for the crossover boards and the backing board for the crossover. Screwing a 1/2" piece of ply to the 1/2" cabinet would mean I'm limited to a 3/4" screw and 1/4" of "bite" is not good enough for me. The crossover will be fairly heavy with the two coils on it...don't need it coming loose, ever. Will probably get the mounting board PL'd in there tonight too. The paint is probably dry to the touch by now anyway.

Thanks for looking!

[Tom Smit]

Did you that you can use the 16 gauge from Speakon to x-over to woofer with absolutely no problems (because the cable run is short). Then you could use the 12 gauge for the much longer runs.

[miked]

Thanks Tom. I'll see how it all works out once I'm ready to wire the parts together. Got a few steps before that such as Duratexing (2 coats) and wiring the arrays. Rotating all those elements will be a PITA but it's got to get done.

I was laying out crossover parts on my 5x5" board and decided it was too small. So the backing board will still be 5x5", but the crossover board will be 5x6". That will give me a little more room to fit the components on there. I'm no pro at crossovers so it may take me awhile to figure out just how I want to lay it all out. I can solder pretty well, so that's not an issue.

Theoretically, (notice the disclaimer...) I could have these all wrapped up this weekend! I can't Duratex the entire cab at once; it has to sit on one side, afterall! So I'm limited as to how much I can do at once. I'd imagine the curing time for Duratex is 24 hours; I know how temperature-dependent that is, so I"ll have to gauge my time b/t coats. It should be about 70F in my garage tonight, which is a little on the cool side. I have a space heater in there...I may use it...we'll see.

Tonight I'll definitely get the first coat of Duratex on the cabs....5 sides, anyway. Pics later.