New HT Construction -- Starting From Scratch

[dtmille2]

We are going to turn a room in our basement into a dedicated home theater. (I can't even begin to tell you how excited I am about this ) After looking around the Internet, this forum seems to be the perfect place to get advice on all aspects of the design and construction. Right now the room is just framed in, so this is an opportunity to do it right from the ground up.

First, here are the basics:

-- Room is 12' x 18', with two walls block, two walls framed 2x6's
-- Room height is 9' (plan to install drop ceiling though)
-- Door location can be moved anywhere along the wall (see image below)
-- Plan to go with overhead projector, 720p, DLP, ~ $800 - $900, upconvert DVD
-- Looking at 7.1 HTIB system, possibly the HT-SR800 $420 on amazon
-- Fixed projector screen, maybe with speakers behind the screen? (seen these on amazon for ~ $100)
-- Hope to have 2 rows of seats, possibly couches with recliners built in, maybe rows of recliners?

All of these are subject to change, but these are some basics I have been leaning towards. Also, looking at viewing angles and projector capabilities, I was hoping to end up with a screen in the 8' to 9' diagonal size range.

We hope to keep this entire project in the $4000 range. I'm looking right now at $1500 for projector, HTIB, and screen. The sheetrock, dropped ceiling, and flooring (carpet) should come in around $700, then we will probably spend another $1000 or so for some seating (possibly using one couch we already have). Basically, I think I have about $800 or so to dedicate to the walls etc. to improve the acoustics in the room. I feel like the acoustical treatments on the walls/ceiling and the placement of the speakers and sub are things that should be focused on during the initial construction. The components themselves can be upgraded later (1080p projector, better receiver/speakers, etc.). I'm open to feedback on this "design philosophy" as well.

Here's my question/challenge -- What should I do to get the most bang for my buck in the area of room acoustics? Curtains on the walls? Panels? Bass traps? Acoustical foam in certain/all places? Packing the walls/ceiling with insulation?

I do have access to tools and a can build things if DIY is the way to go (I plan to build the rear seating platform, drop ceiling, electrical wiring, and can frame, etc. if needed to move the door), so please keep that in mind. I don't mind putting in some sweat equity on such a sweet project (beats building window boxes and hanging drapes )

So please give me your best shot and let me know how you would go about it. And thank you thank you thank you for all of the posts that are already available in these forums. This is such an awesome resource!

Here is an image showing the basic layout of the room that I have in my mind so far. The yellow walls are framed with 2x6's, and the gray walls are cement block exterior walls of the basement (they're below grade, dirt on the outside):

Thanks in advance,
Daniel

[Tony G]

This is a picture of our Drop Ceiling which we got from Home Depot(Acoustic Tile)

[dtmille2]

Thanks for the pic. Did these tiles have any acoustic properties that would make you recommend them for a dedicated theater room? We haven't decided on a certain tile to use, but we do hope to either buy or (gulp) paint them black.

Thanks.

[bpape]

As nice as they can look, for best HT performance, I'd recommend not doing a drop ceiling. You'll get basically zero isolation value from it which will impact the ambient noise level and max dynamic range available. Also budget for a solid core door for the room.

As for treatments, the things that always need to be addressed are:

- Broadband bass control
- Early reflection points on the side walls
- Deadening of the front wall to eliminate reflections from the surround mucking up (technical term there) the front image clarity and lock to the screen.

The key is to get the decay time in the room correct across the entire spectrum. Curtains and foam aren't it - they're high frequency only absorbers, and you already have a LOT of that with carpeting. Consider 2" fiberglass/mineral wool/acoustical cotton on the front wall, minimum 4" (6" or chunk is better) panels straddling the front corners, 2" panels on the side walls for reflections and decay time as required, etc.

Another place to consider is the rear wall with a treatment that will deal with midbass through lower mids but be somewhat reduced in high frequency absorbtion content to deal with the most prominent bass issues in the room from the length dimension.

Bryan

[Tony G]

I'm fairly certain they were marketed as acoustic tile. I think we tend to over think some aspects of acoustics.

I had the CEO of AV 123 over along with a bunch of HT geeks and audiophiles and they all commented on the fact that this tile made all the difference in the world. I really didn't get into the specifics when purchasing but the angles in the tile act as a sound deadener if that makes any sense... That's what you want, no echo when you clap your hands...

Mark told me it was the best he had ever heard his speakers in a theater set up!


TG

[dtmille2]

Thanks Bryan. That gives me some pointers on things to investigate further.

What is the best way to go about the design and construction then -- start with some basic panels etc. and then use some of the software tools to evaluate the acoustics, and then modify the layout?

I will look around the forum and elsewhere for info on decay time and try to get a better handle on the concept. Anyone have some good samples panel images or construction info to look at?

Thanks again!!

[dtmille2]

Tony G wrote:

I'm fairly certain they were marketed as . . .

. . . Mark told me it was the best he had ever heard his speakers in a theater set up!

TG

Thanks Tony, sounds like a good point about the angles.

[Prof.]

Your basic plan looks ok..but I would move that door away from the centre line between the two rows..
That is where you will need to mount your RH side surround, which would place it high up over the door frame..

You may also need to include a cavity on the RH side wall (if you have space behind the wall) for an equipment rack..

[bpape]

In that size room, you're probably looking for a decay time (pure HT) of around .25 seconds in the mids. Below that it could go up to maybe .4, above that, maybe .20 Those are RT60 times so address it accordingly. You can find absorbant coefficients for materials at www.bobgolds.com. In addition you need to account for the coefficients of:

- wood doors
- single or double drywall walls
- carpet (and if it's over wood or concrete
- glass for any windows
- type and number of seats
- number of people

If you model your room first with the basics (walls, doors, furniture, people), it will become painfully clear what needs to be addressed. Add in an acoustic ceiling instead of a drywall ceiling and see what happens - try to get the curve to fit then without having the high frequencies too dead before you get the bottom end under control.

As for the clap test, sorry, but that's not really something to hang your hat on. First of all, it's using a source at the same place where the listener is - which doesn't happen. Also, it's upper mid and high frequency only and tells you nothing about vocal range and bottom end control - nor does it tell you if the room is TOO dead in the highs because the bulk of the frequencies are where our hearing is very efficient and it's a very short, dynamic sound - very much unlike most of what you'll be listening to in a home theater.

Sorry - it's one of those logic things. All dogs are mammals but not all mammals are dogs. If the room is right, the clap won't give you an echo - but - just because you don't get an echo, doesn't mean the room is right.

Seriously, I can put curtains on every surface of a room, ceiling included and you'll pass the clap test - but it will sound like do-do when watching a movie. It's WAY too dead in the highs and has basically zero addressing the bottom except chairs, people, and drywall wall cavities.

Do your homework. Figure out what your target range should be, look at what the basic structure and furnishings will give you, then adjust and treat from there.

Bryan

[dtmille2]

Ok, ok, getting there . . . or getting more involved, anyway

Moving the door is not a problem, and if that's where a speaker needs to be, then sounds like it should be done.

I'll look at what you're saying again Bryan--thanks again!!

I did come across another posting talking about the tanner ridge thread, and that room was a foot or two wider and longer than mine, but hopefully I will pick up a lot of good tips there, too.

[bpape]

Just a little help....

In Sabines at 125, 250, 500, 1k, 2k, 4k. All are per square foot except seating and people which are each:

Single drywall over 16" OC studs, insulated cavities:
29 10 5 4 6 4

Suspended acoustic tile ceiling (assuming 16" space above and minimum 6" insulation)
40 50 65 70 80 75


Double drywall over 16" OC studs, insulated cavities:
2 2 3 4 4 3 (but this centers around 50Hz)

Person in stuffed recliner - each
350 450 500 550 550 450

Stuffed recliner - no person
150 340 400 450 475 450 (people are great bass absorbers...)

Air per 1000 cu ft
0 0 0 90 230 720

Moderate weight curtains hung to half fullness
7 31 49 75 70 60

5/16 carpet with foam pad
5 15 30 40 50 60

Bryan

[John Simpson]

dtmille2 wrote:

I did come across another posting talking about the tanner ridge thread, and that room was a foot or two wider and longer than mine, but hopefully I will pick up a lot of good tips there, too.

No doubt, DT. That thread is one of the best we have for DIY home theatre. Combined with Bryan's ideas you'll end up with a terrific room.

[jaxvon]

bpape wrote:

- Early reflection points on the side walls
- Deadening of the front wall to eliminate reflections from the surround mucking up (technical term there) the front image clarity and lock to the screen.

While I agree with most of your post, I have to take issue with these two points. If you end up selecting speakers with controlled, smooth off-axis dispersion, absorption on the sidewall may not be warranted. Depending on the treatment scheme in the room, and the dispersion of the speakers (best case omnipolar, but these are available), these reflections help enhance the realism of the presentation. As for deadening the front wall, I would use treatments to prevent cross-channel interference behind and between the speakers, and bass traps in the corners. Though, this could be what you mean by the whole front wall, lol.

To the OP, $4000 gets a bit slim when you step up to the dedicated HT level. If you can't afford more, then don't do it. But if you could, you would find some great benefits. Still, with what you have budgeted, I think you can create a great space with some usable equipment that will be upgraded to its full potential later. I think you should be dumping as much money into the room as you can.

-Get a good door, or make a mini airlock like this guy. Of course, I think his room treatment scheme is way off.
-Where do you want to keep the equipment?
-Cabling, conduit, connectors, wall plates
-How much potential do you need?
-Run a ton of circuits. If you want to be future-proofed for addiction, run 4 20A lines. Yes, really.
-Frame out the block walls, insulate behind them and behind the already framed walls with 8# mineral wool.
-Media storage?
-How much wow factor do you want?

[bpape]

I'll respectfully disagree.

The front wall needs to be deadened and proper speakers should be selected accordingly. The front wall has to stop reflections from the surrounds from coming back off the front and smearing the front soundstage. Selecting a speaker that limits your ability to do this, is a mistake IMO.

As for the side walls, you're speaking of things that are a 2 channel goal (and a definitely hotly debated topic). If you want a proper presentation for 6-8 people over 2 different rows, an omni is far from the best choice.

Even if we could do it, it would require a TRUE omnipole - something like the old Ohm F with the Walsh driver and couple that with OB bass. I'm not aware of anything like that available today that's suitablefor the power, extension, and dynamic requirements of HT and that has voice matched center and surround speakers.

Bryan

[dtmille2]

From what I've gathered from the replies here (THANK YOU!!) and reading the Tanner Ridge forum, one place where I feel I can't skimp on the cost is in the walls/structure. That's an area that will be incredibly expensive to upgrade later, and seems to be a definite limiting factor if not done properly.

It also appears that the mineral wool insulation is the way to go in between the studs and joists of the floor above. I will scan the forums for more information on that.

I also hope to future-proof the room using conduit wherever possible (it looks like it will be cheaper per ft^3 to stick a conduit in the wall than fill up the volume with mineral wool insulation anyway )

The $4000 mark isn't set in stone, but I do hope to keep it near that level. I could definitely see making the structure of the HT as good as possible, then upgrading panels on the walls, bass traps, and of course all of the system components later. I'll just have to see how it goes . . .

Thanks again for all the posts--I'm learning as fast as I can!

[gullfo]

i think you have the right idea - get your structure correct - proper isolation, conduits for wiring, hvac (soffits if necessary), and then work on the basic treatments first (corner traps and key reflection points) and then build up from there.

[dtmille2]

Glenn,

Thanks for the comments and the pics--are those scaled to my room size and layout, or just general views? Either way, thanks!

I've found a few sites for buying mineral wool type insulation, which is what I've decided to go with in the walls between the studs. ATS Acoustics (http://www.atsacoustics.com/) has 2-inch thick, 2.5 pcf, 24" x 48" Roxul AFB Mineral Wool. A case of 6 pieces of the bats is $36.00, and 6 pieces of the boards is $54.

Two of the walls are framed in 2x6's, so I am thinking about putting 1 layer of the 2" rock wool directly behind the sheetrock, then filling the rest of the void with fiberglass insulation. How much would I gain by going with 2 layers of the 2" rock wool and some smaller amount of filler material instead?

Also, on the sides of the room that are block walls, how are these going to compare with the 2x6 walls? Would framing out walls with 2x4's and placing rock wool in between them be the way to go? Could I even rip boards down to 2" width to make it a cavity in between the studs just deep enough to put 1 layer of 2" rock wool in there? Or would I need more on those block walls than I do on the framed walls?

Thanks again everyone!

[gullfo]

its scaled on your room size.

[dtmille2]

Excellent.

[dtmille2]

Ok, I've broke ground on the HT construction. So far I've just put down the plates for 2 new walls that I will need to frame out in front of the current block walls. I also put Tuff-R insulation board on the face of the block walls, to give a little vapor barier and warmth.

Here are some basic ideas I have for the construction:

-- 3" mineral wool in the 2 x 4 framed walls I'm constructing
-- 3" mineral wool with fiberglass insulation behind it in the existing 2 x 6 walls
-- Superseal under carpet and padding (www.superseal.ca, $88 for 166 ft^2 roll plus ~ $11 per roll for 2-day ground FedEx)
-- Sheetrock walls with DIY panels at first reflection points
-- two rows of couches (the kind with a reclining seat on each end)
-- drop ceiling (I really wanted to avoid this, but because of the need for future access, I don't think I can)

I will also be building a stage and soffit similar to the Tanner Ridge build, and my equipment will be housed in the right rear corner in a cabinet I will build. I hope to pack all voids full of mineral wool insulation.

I found a local source for mineral wool insulation that seems to be a good price: 3" x 24" -- 68 ft^2 of coverage for $16.64 a pack

I don't have an actual part # but it's made by Roxul. I will try to get more info and post it so that I can get some feedback on whether I'm buying crap or not.

Thanks again for all the advice so far--any further comments? Maybe pics will follow over the weekend . . .

[jaxvon]

What density of mineral wool are you buying? I find 6lb-8lb/cubic foot is good for audio applications.

[dtmille2]

I'm not sure what the density is, I'm having trouble getting information from the place where I plan to buy it. I hope to swing by there tomorrow and I'll get better info. If it's really light weight, it may not be suitable. The range you're talking about is what I want to use, also. Thanks.