Axiom Home Page Forums General Discussion Home Theater HT in-progress

The HT is in the base basement and concrete on three sides. The last side is an interior wall. The rest of the basement is a walk out to the back. The concrete walls are 10 feet high and about 7 to 8 ft of that is below grade. It varies a bit front to back.

Sounds like you are built into a bit of a slope or hillside if I’m envisioning that correctly being a walkout.

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? L R channel facing the interior wall or the opposite?

I guess what I’m wondering is what were your considerations with the concrete in terms of how it will sound? Concrete gets a bit of a poor reputation overall in terms of sound quality and yet it has redeeming qualities and some great benefits too. Zero criticism at all , I just simply don’t know what to think when it comes to concrete and sound reproduction. Or is it all moot as you’ve built a purpose built room with in the concrete with its own surfaces for the sound to interact with? I guess it’s more about the bass and the concrete’s relationship…

Yes there is about an 8' drop in grade from front to back

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.


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.

Sounds like it will be a wonderful home theater!

I'm putting up all the ceiling layers first (before the walls). With only a 1/4" between the top of the wall and the ceiling I think this is the best/only order I can do it in. So, today most of the ceiling OSB is up.


Tomorrow we will start on the next 2 layers: floorMuffler and first layer of wall board. They will be installed as a unit. The floorMuffler has some adhesive on one side (covered by the white strip in the pic below). Since it is 4' wide I can just lay it over each 4'x12' wallboard panel and adhere it in place.


BTW: Getting these large panels up is greatly simplified with the wallboard lift. It was well worth the $179 I paid Harbor Freight. A single person could hang all the board with this and with two it's a piece of cake. Actually I don't think I could have done the job without it. After I'm done I bet I'll have no trouble selling it on craigslist.

Not much to say except great attention to detail. Worth the wait to do it right!

Once drywall is on you should consider getting carpet ordered. Not sure what lead times are in your area, but here its all over the map. Might be a few weeks away.

In the first phase, the platform will be rectangular and stop just behind where the main seating is to start. Since the seating drawn in the plan is custom and still unknown I've delayed it till phase II. Since the platform hugs and warps around the seating this last part of the platform will have to wait till then ... so,

In phase 1, I'll have a temporary couch and depending on what the carpet guys tell me I'll either put in some cheap temporary carpeting or carpeting I can extend later.

Anyway there is time ... After all the ceiling wallboard is up I'm gonna have to add shims for most of the clips on the walls as the studs are not lined up perfectly and some are bowed. Some of these shim will need to be as much as 3/4" thick ... that's pretty bad. It's an extreme example of the first guy in causing next big headaches ... and the owner (your's truly) a lot of money.

The theater is designed for flexibility in expansion of future channels and a possible Hail Mary on future formats. The current plan is for 7.4.6 for phase 1 (see below). If prepros with over 16 channels ever come down in price it would be interesting to see how much of an improvement say 11.4.8 would make. But for now we will live on earth

Note: the plan below is a bit out of date with probably the biggest change being that the top and bottom center speakers are now planed to be just one VP180ow behind the screen and a M3ow for center height. Most other things are little changes like adding alternate rear speaker wires at approx +/- 160.

The grey areas are the angle ranges for the bed speakers (angles in red outside of walls)
A red + indicates a speaker wire in the ceiling and a red T indicates a speaker wire in the wall. The 7 inner +'s are for tops and the rest are for heights. The blue line indicates as step down into the front of the room. The main seating is on this level. Bed speakers are red and heights and tops are purple.

What brand of residual channel did you use? I've been looking at the PAC international sound isolation clips and hat channel.

The channel is from Home Depot ... It was the least expensive I found and was conveinently 15-20min from my house.

The brand of clip is Whisper Clip ... lots of places on the web carry them
I pick them up from Trademark Soundproofing