The subwoofer box bracing task is needed to illiminate standing waves in the box and also brings strenth to the subwoofer enclosure constraction.
The first thing we will do is to make two frames from "STD" and "L1" braces.
Put carefuly some wood glue at the joints and use long throat clamps for fastening.
Important : pay attention joints are smooth and there are no bumps between the braces!
On all steps ahead, wipe carefully the glue before drying for the same purpose.
Left and Right Boards
Now, take the left and right boards and attach to the frames from the previous step.
You may put the the clamps on the centers of the boards as shown here.
Front and Back
Now, take the front and back boards and attach to the previous construction.
Pay attention everything is smooth because there you may put the slices afterwards.
Bottom board and its braces
This step has to be VERY precise!
Take two of the "L2" braces and attach them PRECISELY on the correct distances.
Here it is with some of my tools for the box building.
Now the bottomless box wil get its bottom :)
Put nice amout of glue and insert the box on its bottom.
No regular clamping at this stage.
Justt put the TOP board on, and some weight on it and remove it on the next day.
Now it is a good time to start sealing the subwoofer box from the inside to ereas that will be hard to reach afterwords.
Sealing in closed box is very important and need to prevent powerful Helmholts resonator effect.
The TR Braces
Now will we put the upper box TR braces:
Take the TR braces and put them from BACK to FRONT on the pencil signs you made.
Exact 45 angle is not so important.
The holly moment arrived, now we can bring woofer to the subwoofer :)
Insert the woofer with its screws.
you can dip the screws in some glue to make it stringer and seaedl.
Instead of using a regular rubber gasket I molded a 5mm thick silicon gasket.
I left it to dry and then add more before attached to the box with the screws.
One of the secrets of this subwoofer box design is the woofer bracing.
A british loudspeaker builder taught me this important trick he is now a sales man that became my friend (maybe because I bought a lot of audio equipment).
Put a ~10mm silicone layer on the braces and let it dry, like you did with the woofer.
Glue the braces from sign to sign LEFT to RIGHT tightly to the woofer.
After the glue of the braces will dry,
put another silicone layer between the new braces and the woofer.
The Long round braces
Place the long round braces on the marks of the bottom board.
Strength here is not so critical.
Here is the technique I used in order to hold them in place while drying:
Now the woofer cannot escape..
Continue seal with RTV silicone also from the outside.
Wipe carefully with dry cloth! You will have to color the MDF and silicone layer will not let you.
Closing the box
Take the TOP board and do the same thing as done with the BOTTOM with the "L2" braces.
Put glue on connection, the top board and heavy weight on the top of everything.
Here is the closed and bare subwoofer box ready for the subwoofer amplifier.
Put the 635mm MDF slices as described here - to cover sides-front/back connections.
Before finally weld the amplifier connectors pad the box inside with foam.
Rock wool is the most efficient but VERY uncomfortable to work with and without safety mask, google glasses and clothes it can be even dangerous. The best technique for the fine tuning is trail and eror.
My box was filled with foam to about 75% of volume in the upper room of the box.
After messing with the rock wool I couldnt satnd it and moved to the acousta stuff.
Connect and insert your amplifier to the subwoofer.
If you chose to completely stick it to the box with silicon it will be almost irreversible.
Here is a picture from the first trail error sessions.
If you want to learn from scratch you can go to this wonderful site that will give you the start: The Subwoofer DIY Page