[bob53]

Hi all,


I am the the stages of designing a home... I am looking forward to having my HT in a dedicated room! The limitations are few except perhaps dimensions. It will either go above the garage or in the basement. The home will be a rambler with a main level and a basement and staircase leading to the room above the garage where the theater may go.


1. Dimensions - Given the roof pitch - I anticipate the room can be ~ 16 feet wide with an 8 foot ceiling. The room length can be large - 25 feet if needed. I will try to follow the golden ratio's for these dimensions. If the HT is placed in the basement, I will probably need to have a smaller room size. If above the garage, I will try to use green glue and perhaps a strap wall system to decouple the room from the rest of the house.


- I worry that there will be less acoustical dampening if placed above the garage and more acoustic energy loss due to the absence of concrete walls. Is this a valid concern?


- Is it acceptable to cheat with respect to ceiling height via use of a soffit on the sides of the room? I could probably get 9' ceilings if there was a soffit in the ceiling corners due to the roof pitch. Does this adversely affect room acoustics?


2. Layout. I have a few questions:


- If placed above the garage, I'd like to build a window into the room in the event the room is converted into a play room or party room. I'd prefer to not have the window interefere with the acoustics of the room and so I'd like to find a way to hide the window. Has anyone found a clever solution to hide a window or part of a room via use of a semi-permanent wall or something along those lines? I do not need the window when the room is used as a HT room now. Another through was some sort of pocket door system or hidden door in the wall that reveals the window. Has anyone done this before me?


- Stage - is it best to fill a stage with sand after construction to eliminate resonance?


- Speaker placement - I have an Anthony Gallo Reference 3.1/Center/AV Surrounds setup and may upgrade to the Reference 5LS. In either case, I was not thinking of hiding the L/R speakers in the stage. Aside from asthetics, is there any reason to hide the speakers behind grille cloth? Can I get the same 2-channel performance if I hid them?


In general - is there a good set of books or online webpages that would be considered required reading? I have the basics down but I want to educate myself further before finalizing the plans. I'll probably finish the theater after building but I want the dimensions and windows done properly before proceeding. Here are the general ideas/items I plan to do:


- Conduit in all walls to run cabling at cieling height and ground height.

- 20 Amp dedicated circuits

- 2+ rows of seating

- Thinking of a cool celiing treatment like a starry sky (I now, that isn't too novel

). If I do it it will be done properly following the night sky with (somehow) nebulae and galaxies (M31) showing up properly (I'll cheat and give them more color than we can percieve with our eyes

)


Thanks for your help.


Bob

 

[tlllava]

I'd go over the garage as this is likely more isolated from the rest of the house than the basement. This will make the job of isolating the theater easier. Also, concrete does not vibrate and so is less fun with a good sub than a raised floor. ButtKickers can help but I still wish that I had a bonus room rather than a basement for my theater.


The bonus room is certainly big enough. However, there are many golden ratios and all are approximates. Russ Herschelmann wrote many articles for Stereo Guide to Home Theater years ago which stressed room diamentions, seating possition and speaker placement. From this, David Henderson created an Excel spread sheet that can calulate the peaks (bad) and nulls (worse) you will have at your seating position. Naturally, the calulations assume a perfect rectangle which few people have but the calculations are still probably better than a golden ratio.


If you PM me, I can send you the spread sheet & directions which I can no longer find on the web. I can either send you the original or a modified version where I added macros to more quickly experiment with changing diamentions. It makes the graphs almost animated as you can quickly scroll to make things bigger or smaller. Here is a screen shot from the spread sheet...

 

[tlllava]

I found the new link on the web to the original spread sheet...

http://www.ultimateavmag.com/news/10388/index.html

 

[Dennis Erskine]

Here are some of your more interesting considerations:


Above the garage:

This space will be much harder to sound isolate from the remainder of the house.

This is also one of the few, if not the only, space in the house which is over non-conditioned space, below non-conditioned space, and with three walls exposed to the exterior...net out. Space will require considerably more A/C than the basement option.

You can install, and hide, a window, if you plan for it now. Do not even think of using a "pocket door". They rattle big time.

It is not likely you're going to get sand into a stage in this space. The static load of the sand will require rather significant foundation and structural changes. Sand in the stage is a good thing, not a bad thing, if you can do it.

You can "cheat" the ceiling with soffits...been there, done that, and you may find pictures of those who've done exactly that.

Most people, when they entertain, have their entertainment spaces in the basement and main floor avoid guest traffic into what many consider the "private" spaces on the second floor.

You do not want your sub bouncing the floor under your feet. All that means is the sub is using it's abilities to move the house, not move air. If you want some tactile energy...there are better ways that don't involve moving the whole house (or a large portion of it).


Basement

The fact that it is a basement does not mean you can skip floor isolation.

Unless you have a comprehensive set of plans for the builder PRIOR to construction of the house, you'll likely find a high level of disregard for clear ceiling spaces. You'll have plumbing and HVAC almost randomly placed below the joists.

The theater walls adjacent to concrete walls still need to be constructed with isolation techniques. Concrete is a wonderful transmitter of sound (as are steel beams).

Due to structural support, you may find steel columns or support posts in places most inconvenient for a clear area for the theater/music space.


Modes in General.

The nice thing about golden ratios is there are so many of them...pick one that will give you the answer you want ... it will be wrong anyway. That being said, in residential spaces you will have modal response regardless of what you do with seating and room dimensions. There are other and far more effective ways of dealing with room modal response issues (and you're going to need to do this in any case). So design the space to fit your functional requirements. BTW, the soft flexible wall thing is a certain amount of non-sense. Your walls become speakers and what is really happening is your walls are more transparent to low frequencies meaning the reduction is bass modal excitement is really as a result of a reduction in low frequency energy in the room. Solution? Bigger subs. Oops, now I have real modal (and other problems).

Modal spreadsheets seldom, if ever, are accurate predictors of room modal response. They fail to take wall impedance and a long list of other factors into account. You may be sweating a dimension to reduce a mode which, when the room is finished, wasn't a problem to begin with.

You would get the same two-channel response from your speakers whether they were hidden or not. With the speakers you have, you'd get a better result from baffle mounting in any case. As well, you need to decide your primary use for the space - two channel or multi-channel (I didn't say music vs movies, btw). The acoustic treatments for each are very much different. You can compromise two-channel, or you can compromise multi-channel, or you can compromise both. Your choice.

You didn't mention which surround speakers you have; but, if they are monopole, plan on keeping your seating distance about 15' from the speakers ... alternatively plan on three pair of sides and one pair of rears.


What did I miss?

 

[indygreg]

i keep hearing the thing about pocket doors being so bad but mine doesnt make a peep and i think it is fair to say that i have higher than average subwoofer output. i really think the key is getting a good door system. i really liked the flexibility it gave me in design.


maybe i just got lucky.

greg

 

[Dennis Erskine]

A big heavy door on a solid track system can work. If it doesn't, making it work is expensive. The flexibility is nice, but; the flanking isn't.

 

[bob53]

Dennis, Thank you for your very comprehensive reply. Since I have a clean slate (and I'm picky) I have some freedom here with regard to construction.


Due to the fact that I'm a car nut, the garage will have micro-lam beams below the heavy-duty roof trussing so that an engine could be hoisted out if needed. I think it should support a fair amount of weight in a room above it

so sand could work to fill a stage if needed.


The basement will use micro-lam beams in addition to engineered floor joyces with no posts interfering in the potential space in the basement that could be used as a HT room.


Thanks for the heads up re: HVAC. I'll have as much as possible sunk below ground in the concrete floor.


I was planning on paying attention to improved insulation in the room above the garage. In addition, I was going to look into decoupling the floor of this room with a floating floor or something along those lines.


Just to clarify - I take it subwoofers above a garage space are more difficult to tame with respect to room interactions and leakage than a basement room???

 

[bob53]

Greg - I love that door and door frame combo - very classy...

 

[bob53]

TLLLAVA - thanks for the spreadsheet.

 

[bob53]

Thanks so far, keep the suggestions coming!

 

[Dennis Erskine]

Bob...interactions between speakers (subs or otherwise) and rooms occur regardless of where the room is located. The speakers don't know where they are at (well, that's true of me from time to time.) If there's a boundary, you have an interaction. The only more significant challenge in an upper floor room is in the mechanics associated with sound isolation. Upper floors typically have much less mass than the lowest floor. (We have a MN contractors license, btw).


Speak to your architect ... we're speaking of 3 to 6 thousand pounds of static load. A tad more than the 312 block from a 67 Ferrari (for example).