New t39 Build - 1st

[dswpro]

Got the plans. Couldn't find the 5 ply Baltic birch around here, so I got some wood that didn't look too bad with as few voids as possible. Figured out I'd mess something up anyway on the first one, so no big loss. Build was easier than I thought, with a few jigs and some patience. Drilled shallow reliefs for the T-nuts on the speaker ring. Sealed them up with silicone.
About to seal it up and paint. Asked my kids for a Gallon of Duratex for Christmas. this winter I'll build 1, possibly three more.
Can't wait to hear it.

[bassmonster]

Good looking build! Hehe, with the flashlight you find some shining examples of too little glue.

[subharmonic]

You dog looks kinda pissed. Is he a camera shy?

[AntonZ]

I would have drilled holes for the T-nuts through ring and baffle, rather than ring only. Pulling the driver tight is going to make the ring separate from the baffle where the T-nuts are. It will try pulling the plies of your baffle apart, if you will. Here's hoping you got good ply , rest of the build looks solid to me. Nice work.

[Gregory East]

There is no prying force between ply layers.

The t-nuts are being drawn to the spacer ring, the driver pushes back against the spacer ring, There is shearing stress along ply layers from the bending induced in the spacer ring being resisted by the spacer/baffle unit. It's very strong in shearing.

The "free body potatoe" learning of a long time ago.

[Rune Bivrin]

There is no prying force between ply layers.

The t-nuts are being drawn to the spacer ring, the driver pushes back against the spacer ring, There is shearing stress along ply layers from the bending induced in the spacer ring being resisted by the spacer/baffle unit. It's very strong in shearing.

The "free body potatoe" learning of a long time ago.

There is always the risk that the compression of the spacer introduces leaks between spacer and baffle. Moreover, in the event of a T-nut failure it will be a right pain to remove it, but then again that's pretty much always the case with Bill's designs, They have a preference for T-nuts in one-shot places...

What's most important is that there's really no good reason for putting the T-nuts like that. Follow the plans...

[dswpro]

I don't recall any specific mention about the t-Nuts being behind the baffle in the plans. Makes sense, I guess. I checked my screw lengths, however against the spacer ring, + speaker frame and I know I have enough room drilled into the baffle that the screws won't hit anything. Thanks everyone for the advice!

[Rune Bivrin]

I don't recall any specific mention about the t-Nuts being behind the baffle in the plans. Makes sense, I guess. I checked my screw lengths, however against the spacer ring, + speaker frame and I know I have enough room drilled into the baffle that the screws won't hit anything. Thanks everyone for the advice!

The plans say to attach the driver spacer to the baffle, then drill the holes. Now, my plans are not the newest, but I doubt this has changed.

[Michael Ewald Hansen]

Using a flashlight to find leaks is not optimal, as air can easily leak out of holes that does not leak light.. Make sure you are generous with the PL and run a bead of PL down the seam and run your finger down the seam to make sure its completely sealed.. I tried first hand whats its like to find a leak inside the cab even though i was confident there was no leaks - it sucks big time

[dswpro]

I see the error of my ways, Thanks, everyone. I read the instructions many times but I guess I'm not a careful reader. So, my choices are now:
A) Drill new mounting holes through the ring and baffle, reach through and mount T-Nuts or find threaded inserts for the holes.
B) Counter the shear stress the on the ring by adding screws through the ring into the baffle, counter-sinking them into the ring.
C) Pray the generous PL I used to attach the ring to the baffle holds through the shear stress and low frequency vibrations.

How does the court vote?

[Jon Barnhardt]

choice A.

Rotate the hole pattern about 2 inches and drill through both pieces. Use PL glue to fill the old holes (if they present an air leak situation)

[subharmonic]

I have to disagree about using light not being a good method. I have foud it to be the best. I bright light in a dark room make airleaks stick out like a sore thumb. The best is to use a blanket over you head to keep the light from bouncing back into the adjacent panel.

[Gregory East]

Resisting sheer is PL's reason for life. It's meant for replacing nails in attaching flooring to the joists.

[Tom Smit]

How does the court vote?

I think that if you use a bit that will just fit in the T-nut threads, and just drill completely through the baffle, you'll be fine. The machine screw then will thread through nut and then through the baffle while cutting it's own threads in the baffle...sort of like a pre-drill before screws. If there is a solid track of PL on the spacer when it was installed on the baffle, there should be no problem.

[88h88]

I have to disagree about using light not being a good method. I have foud it to be the best. I bright light in a dark room make airleaks stick out like a sore thumb. The best is to use a blanket over you head to keep the light from bouncing back into the adjacent panel.

We tried this to great success too. Completely pitch black with odd bits of ply blocking the light from making it around the folds of the Titan and it works very well, I'm not going to say it's perfect and foolproof but it made finding places where there was less than an ideal amount of PL far easier.