O-Top 12 build issue, I just can't get it.

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DK1968
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Joined: Fri Aug 27, 2021 9:44 pm
Location: Soddy Daisy TN

O-Top 12 build issue, I just can't get it.

#1 Post by DK1968 » Thu Nov 25, 2021 6:10 pm

Building my O-Top 12 cabs and everything was going good until I got to the throat reflectors. I know it can't be difficult but I can't get my head around it. I have tried to cut it 4 different times and every time it winds up either short at the top or bottom. I guess I need someone to explain where to start and then walk me through it, because right now I just can't understand it.

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Strange Kevin
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Location: Scottsdale AZ

Re: O-Top 12 build issue, I just can't get it.

#2 Post by Strange Kevin » Thu Nov 25, 2021 7:10 pm

I'll give it a shot.
I just cut some out the other day.
Talking about page 8 in the Otop 12 plans, right?
Without knowing exactly what's triping you up, I'll just walk you through how I usually do it.

I started with a blank around 4-1/2" by 12-1/2. (Slightly bigger than final dimensions)

Cut the 45° angles at the top and bottom. 4-1/4" apart measured on the "long side" or outer face, so if using a tablet saw, your fence will be set to less than 4-1/4" to compensate for the angle of the blade.

Mark the center of your piece.
Then measure out from the center to get the top and bottom lengths.

In my experience, a compound miter saw makes quick work of the final step of cutting off the sides. But a jigsaw is fine too, just a little trickier to hold onto.

Just make sure all the angled cuts (45°/26°) are cut "into" the piece so the outer face matches the dimensions listed in the plans.

Hope this helps!
Authorized Builder - Phoenix AZ.
Main Rig - 6 DR200s - 6 T48s (30")
SLA Pros for the smaller stuff.

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DK1968
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Location: Soddy Daisy TN

Re: O-Top 12 build issue, I just can't get it.

#3 Post by DK1968 » Thu Nov 25, 2021 7:28 pm

Yes page 8 is what I am referring to. I think I just need someone to tell me where to start, I would lay it out and it would look right until I cut it. Thanks for the tip, I will let you know how it turns out.

jimbo7
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Joined: Fri Dec 28, 2012 10:45 am
Location: St. Louis

Re: O-Top 12 build issue, I just can't get it.

#4 Post by jimbo7 » Thu Nov 25, 2021 7:35 pm

I guess I'll say it: Look at the Sketchup model!

It should answer most questions you'll have from the pdf. You can get measurements from the individual pieces, too. I just looked at it and remembered why I went with a flat array. The model has the wiring for crossover and driver(s), along with any other version you might wanna build. The sketchup file help me tremendously when I wired up my SLA's.
BFM builds:
XF212
T24 BP102 24"
2x SLA's 6-5" mids, 9- gt-302's
2x AT 14" MCM 55-2421
TrT 5" MCM 55-2421
AT 18" JBL GTO804
2x OT12 flat array
2x SLA Pro 2-Alpha 6's 2-Goldwoods
2x T39 24" 3012lf
Simplex 10 BP102

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DK1968
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Re: O-Top 12 build issue, I just can't get it.

#5 Post by DK1968 » Thu Nov 25, 2021 9:23 pm

Thanks for the suggestion on the Sketchup model, I have many times and still I had trouble with it. The first horn panels almost tripped me up because on the Sketchup model, when you isolate it, it shows to be beveled on both ends. I had to go back to plans and look and it showed a bevel on both ends. Then when you jump ahead to the trimming part it shows it as square. I was skeptical to reach out for help on something I could not understand because I knew I would get a response that said I guess I'll say it: Look at the Sketchup model or something like that. I am sorry I asked for help on something I did not understand. 👍

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Tom Smit
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Re: O-Top 12 build issue, I just can't get it.

#6 Post by Tom Smit » Thu Nov 25, 2021 11:08 pm

DK1968 wrote:
Thu Nov 25, 2021 6:10 pm
Building my O-Top 12 cabs and everything was going good until I got to the throat reflectors. I know it can't be difficult but I can't get my head around it. I have tried to cut it 4 different times and every time it winds up either short at the top or bottom. I guess I need someone to explain where to start and then walk me through it, because right now I just can't understand it.
If you were to cut a section of plywood that is wider than the panel that you need, make a 45 degree cut along one edge. Then, rotate that piece to make the next cut on the opposite face. You should have a mark on the top side that indicates the final width needed. Nudge the fence over until the mark almost lines up with the blade, lock the fence, and tease the panel into the blade to see where it comes through (hopefully too wide). Adjust the fence in again if needed, and test a smidge again. Do this until you cut on the mark, and then make the final through cut.
After this, you will have to figure out the sides.
TomS

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Bill Fitzmaurice
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Re: O-Top 12 build issue, I just can't get it.

#7 Post by Bill Fitzmaurice » Fri Nov 26, 2021 10:23 am

We can't tell you what the problem is without seeing what you're doing. Post pictures.

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