New Demo Home Cinema Room Week 1
The Demo Room Buildout Starts
We will be putting up a full write-up of our new home cinema demo room when it’s all complete. For now I will be posting regular updates on the progress and talk about some of the design and engineering considerations as we build it out.
Stage 1 of the plan involves building out an 8mx4m room within a room. Our workshop was far too large and irregular for us to be able to control the sound as we liked, besides it was so cold and damp. The decision was made to build an entire building inside. Our workshop is what would have been Stables for the local Inn, just off St Mary’s Road in Market Harborough.
Concept
Conceptual plans were drawn up showing the basics of what we wanted the room to accomplish, we know we wanted a starfield ceiling, an office area, big double doors and solid, isolated and soundproofed as much as possible.
These aren’t detailed home cinema plans but sketches, ideas - a bit like a fashion designers initial scribblings. Further, more technical CAD drawings and calculations for speaker locations, acoustic control and projection system will come at a later stage. Once the room is built we will feed in all of the “as-built” sizes into our engineering process to design and engineer the interior fit-out. At this stage we are building a box for it all to fit in.
Floor Joists
It starts with a base, we used 6x2 boards to frame out an 8mx4m floor, with a gap of 40cm between joists. Noggins were spaced every metre to give the floor rigidity.
Once the base had been built the next step, and probably the most important part of the entire process was to make sure it was flat. If the room isn’t completely even it would make life very difficult in taming knocks, vibrations and rattles.
Laser measurements were taken across the floor and piers were measured and put in every metre or so, the floor has over 240 piers holding it up, flat. Each piece of timber is screwed in, there are to be no nails in the entire structure - Nails squeak and creek, not good for a home cinema.
Sound Isolation
Rockwool was placed between the joists, Rockwool is a wool made from molten rock that’s spun into fibres (similar to fibre glass insulation) that trap sound waves and deadens vibrations, it also helps insulate so will keep the room from sucking up the cold from the concrete floor.
Padding out the floor with Rockwool and the small gap between joists, extra noggins and piers help to make the base more solid and less hollow. In terms of sound and acoustics it will ring less and be more inert, warmer and let less sound out or in.
Bitumen & Floorboards
Next up we stretched a bitumen layer between the joists and our floorboards, this acts as another layer of sound isolation but additionally decouples the laid floor from the joists, being sandwiched between the two.
For the floor itself we went with a 22mm chipboard, tongue and groove glued with expanding polyurethane.
The stage is set (and it literally looks like a stage at this point) for the next step, which is the walls.
Walls studs are 4x2 timber and initially we built a 3m walls for the office portion of the demo room, these were framed internally with MDF over the same bitumen layer we used for the floor. This part of the room is 2.4m high, the cinema section will be 3m high.
The Walls Go Up
Next up was the cinema wall, this was a much larger wall (took 3 of us to lift it) at over 4mx3m and was framed with OSB 18mm over a partial bitumen layer.
Of note each wall in the building will have either different materials and/or different thickness of wood on each side, the aim is to tame resonance and get the walls behaving acoustically as we would like them to (or as near as we can get it).
Screw It All Together
Once the cinema wall was up the remaining 4 walls were built and moved into place, the 8x2 timber joists were connected to the office walls and everything was screwed in and together. At this point in the project we have used over 3 tons of wood, 3,200 screws and 0 nails. This was the end of week 1.
