Here are the pictures of progress last Friday and over the weekend.
My rudimentary plan for the soffit face. I've ensured that there is at least 20% difference in the distance from acoustic centre of speaker to each edge of the face, according to Stuart's general rules for soffit design.
Power and signal cables clipped to frame.
All hangers in underneath, spaced apart to coincide with equal divisions of the room width.
Bottom of 18mm MDF speaker box screwed to the shelf (which is 2 layers of 18mm OSB). Four hemispheres sat on there calculated to deflect by around 20% with the weight of the speaker. Calculations done in collaboration with hemisphere supplier.
Speaker being positioned with a spirit level so that the acoustic centre (according to the manual) lines up with the mark on the framing measured according to my design. The speaker location is determined by a list of things to avoid, like avoid a line 45 degrees from the corner of the room, avoid placing it on a quarter of the width etc. This was designed in sketchup.
Smaller hemispheres used on the box sides: the box had been designed to account for 20% deflection of these hemispheres. The box side panels were screwed to a piece of 3x2 and the 3x2 then screwed to the shelf, as I couldn't screw up from underneath.
Second side added, as above.
Top of box with hemispheres same as the sides. Something had gone wrong in the measurements meaning I had to add a layer of 9mm ply on the inside of the MDF to get the hemispheres to touch the top of the speaker.
Looking down from above to show the speaker's amp heatsink and through to the cavity below with the hangers in.
List of the hemispheres I bought, if it's useful for someone!
Spirit level and clamps used to get the framing level before screwing the top shelf above in, which held it all in place and true.
Framing for one side finished. Hopefully its strong enough!
Chicken wire metal to create a path for the warm air from the back of the speaker to exit. Managed to fix to the box with a few staples and twist it to itself.
The chicken wire wrapped in felt like fabric (left over from the window gap), held in place with cable ties around the outside.
Lots of insulation cut to fill the cavity around the speaker box.
Insulation in cavity.
Second side box complete and 3x2 screwed to shelf to attach upright supports to.
Plastic packers used to fill gaps between wood to ensure front uprights level. This one is particularly bad just because I didn't give any thought to where I was attaching the 3x2 to the speaker box sides. This has been a bit of design as you go!