Another OT12 build

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ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Another OT12 build

#1 Post by ctmullins »

With the T39s almost done, I'm starting work on four OT12s. I'm making four based on recommendations from other, senior forumites; seems having a pair on each side smooths out response. Sounds good to me! I have enough electronics on hand for two currently, so the other two might be shells for a short time. Melded piezo arrays, 2512 drivers, Arauco ply. I'll use standard top hats, with the bottom cab having them in both bottom and top, so I can join the top cab securely.

All major panels got cut out last weekend. Today I'm beginning the markup on tops and bottoms!

Image

It would be great to have these up and running (at least the first pair) by our March 5 gig, but that may be too ambitious.... :noob:
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Another OT12 build

#2 Post by Bruce Weldy »

ctmullins wrote:having them in both bottom and top, so I can join the top cab securely.
That really isn't necessary. Put the locking chevron corners on 'em and they aren't going anywhere.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#3 Post by ctmullins »

Baffles are cut. I remember this maddening step from my W8s. Only this time I have four of them to do! :wall:

So I decided to do two at a time, by stacking, clamping and cutting. Good idea or foolhardy? Inquiring minds...

After each section I tidy up the blade wander with the fearsome Shinto Saw Rasp. :twisted: It's one of my favorite tools!

Image

First pair nearly done....

Image

And then there were four!

Image

We'll soon find out if this little shortcut causes any problems.... :D
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

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Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: Another OT12 build

#4 Post by Tom Smit »

Your process is fine if you don't have a router....cuts the work load in half.

If you have a router (and pattern bit), you could make just one of which you could use as a template for the rest.
TomS

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#5 Post by ctmullins »

ctmullins wrote: It would be great to have these up and running (at least the first pair) by our March 5 gig, but that may be too ambitious.... :noob:
Humph. That's definitely not happening. Too much life stuff lately. Tonight's the first night of progress since writing that...

Putting the shells together. I deviated from the plans again.... :fruit: But a big "thanks!" to whomever invented those W clamp thingies!

Image

Image

Image
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

User avatar
Tom Smit
Posts: 7457
Joined: Sat Jan 05, 2008 1:24 pm
Location: Sarnia, Ont. Canada

Re: Another OT12 build

#6 Post by Tom Smit »

But a big "thanks!" to whomever invented those W clamp thingies!
Bruce Welby posted a few times about them.
TomS

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Another OT12 build

#7 Post by Bruce Weldy »

Tom Smit wrote:
But a big "thanks!" to whomever invented those W clamp thingies!
Bruce Welby posted a few times about them.

Just something I found in an old woodworking magazine......I've used 'em for tons of stuff outside of speaker building over the years.

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#8 Post by ctmullins »

Small progress today - got eight throat reflectors cut out, with their angle cuts. The long side 45 degree cuts were easy, then I used this makeshift sled on the small tablesaw for the other cuts. First one side:

Image

Then I rotated the sled over to the other side of the blade, flipped the piece over, and did the second side:

Image

I don't think I have the energy to actually glue them tonight, though...
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

David Raehn
Posts: 676
Joined: Tue Apr 30, 2013 5:56 pm
Location: Colonial Beach VA

Re: Another OT12 build

#9 Post by David Raehn »

http://billfitzmaurice.info/forum/downl ... &mode=view

I've found this to be the best and easiest way to clamp those buggers.....
BFM rig:
6 OT12
4 T48
4 WH8
Other:
56 box Electrotec LabQ rig
Way too many cables
:noob:

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#10 Post by ctmullins »

Thanks David, that's easier than what I was going to try! Makes perfect sense!
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#11 Post by ctmullins »

Throat reflectors installed, lots of excess PL trimmed (tedious), and holes cut for top hats. I clamped my little "portable drill press" to the cab and used a 1 9/16" Forstner bit. This way the holes line up just right.

Image

Image

The top hats (the steel Penn-Elcom ones that Leland sells) are a very snug fit. I won't need to use any sealant here.

Image

On the very last one, however, the final layer of ply gave way and separated completely. I'll have to patch that up. I suppose I should have used a sacrificial backer board...

Image
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Another OT12 build

#12 Post by Bruce Weldy »

ctmullins wrote:Throat reflectors installed, lots of excess PL trimmed (tedious), and holes cut for top hats. I clamped my little "portable drill press" to the cab and used a 1 9/16" Forstner bit. This way the holes line up just right.

Image

Image

The top hats (the steel Penn-Elcom ones that Leland sells) are a very snug fit. I won't need to use any sealant here.

Image

On the very last one, however, the final layer of ply gave way and separated completely. I'll have to patch that up. I suppose I should have used a sacrificial backer board...

Image

Just put a doghouse on all of 'em....you have to seal 'em anyway....
OT12 Build 028 small.JPG
OT12 Build 030 small.JPG

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

ctmullins
Posts: 195
Joined: Thu May 13, 2010 9:05 am
Location: MS Coast

Re: Another OT12 build

#13 Post by ctmullins »

Bruce Weldy wrote: Just put a doghouse on all of 'em....you have to seal 'em anyway....
You know, I need to understand this part of the design a little better.

Unlike the Jacks, the space under the throat reflectors is completely isolated from the main chamber. This means that it must not play a part in cabinet tuning, other than serving as part of the horn path.

So why exactly does it need to be sealed off?
-todd

5 and 8 string bass | SansAmp | Crown | 2 x J110
2 x W8 panel-mount
2 x T39 24" 3012LF
4 x OT12 2512 melded (finally done!)

Bruce Weldy
Posts: 8301
Joined: Fri Nov 27, 2009 11:37 am
Location: New Braunfels, TX

Re: Another OT12 build

#14 Post by Bruce Weldy »

ctmullins wrote:
Bruce Weldy wrote: Just put a doghouse on all of 'em....you have to seal 'em anyway....
You know, I need to understand this part of the design a little better.

Unlike the Jacks, the space under the throat reflectors is completely isolated from the main chamber. This means that it must not play a part in cabinet tuning, other than serving as part of the horn path.

So why exactly does it need to be sealed off?

Well, you made me do some research. I built mine under an older set of plans where the baffle had slots in the top and bottom - only the baffle for the 3012HO was solid. Looks like the newest plans don't show a different baffle for the 3012HO and the other drivers as far as the slots.

I guess you don't need to seal 'em.

Mea Culpa....

6 - T39 3012LF
4 - OT12 2512
1 - T24
1 - SLA Pro
2 - XF210


"A system with a few knobs set up by someone who knows what they are doing is always better than one with a lot of knobs set up by someone who doesn't."

User avatar
Chris_Allen
Posts: 3355
Joined: Wed Jul 11, 2007 2:43 pm
Location: Huddersfield, UK

Re: Another OT12 build

#15 Post by Chris_Allen »

Bruce Weldy wrote:Looks like the newest plans don't show a different baffle for the 3012HO and the other drivers as far as the slots.
Yep, they disappeared in the 2011 set of the plans and aren't present in the JArray version either.
Built:
6xDR200, 2xT39, 2xT48, 2xJack110, 1xOmni10.5, 1xAutotuba, 1xT18, 1xSLA Pro, 1xW8, 1xW10

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