Sounds like you are built into a bit of a slope
Yes there is about an 8' drop in grade from front to back
That’s a great ceiling height to work with. Very nice. I’m assuming your floor is slab concrete…are you building up a subfloor? Which orientation are you using?
In opposite order ...
You walk in from the back of the theater onto a raised platform which is ends directly behind and warps around the sides of the main seating (I'll have to post the drawings). The main seating is one step down and is on a carpeted floor (build: carpet | carpet pad OSB | floor muffler | concrete ). The platform is also carpet.
The 10' height was a compromise as originally I was aiming for a basement height of 11'
Some of the trade-offs considered:
House, comfort, and zoning:
- How high do you want your house relative to the street
- How much grade do you have to work with
- How deep is the water table
- What does the town consider a basement v.s. a floor (usually some % of wall below grade)
- How many steps do you want form 1st floor to basement
- Garage height (steepness of drive way, steps to 1st foot, steps to basement)
- Landscape grading
On the theater
- how big of a screen are you planning
- eye level of viewers
- how thick is the floor and ceiling (i.e. what's the finish dimensions)
- how much room do you need for speakers above and/or below the screen
- any furniture below the screen to account for.
- projection angle: if you stand up do you block the movie (depending on the projector might not be avoidable)
One solution to some of these limitations would have been to sink the theater floor down a bit from the rest of the house ... that is if you are not worried about the water table.
I guess what I’m wondering is what were your considerations with the concrete in terms of how it will sound?
Concrete is interesting. It has lots of mass and if naked will reflect most of the sound energy. That said it can conduct sound. My dorm in college was made of concrete. Someone was playing his stereo pretty loud below me and in my room all I could hear was boom, boom, boom. Went to the dorm room below me to complain and it was pretty quiet. The stereo that was playing was two floors down. Think it was hitting the resonant frequency of the concrete wall. So, the dorm room below me was at a null. Mine unfortunately was not.
I suspect that with all the isolation I have in the HT that it will not have problems with that type of transmission. As far as bass energy reflecting off the concrete and back into the room ... it has to get though all that material twice. I think the walls themselves will have more impact than the concrete. My plan to control the low-end modal energy is to use 4 subwoofer to even it. We will see, nothing is guaranteed at this point.
