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Discussion Starter · #1 ·
I'd like to say hi and thank everyone for all the good info on these forums, I've been reading them for several years but haven't posted much since I had no room for a theater.


I've been in the new house long enough to get a few projects done for the wife and now hope to start on a theater this fall. I had a theater in mind when I built the house, so had a room in the basement set aside just for me. The room is approx. 24'3" by 18'3" with 9 foot ceilings. According to the "Room Dimension Calculators" I'd be better off with a 17 foot width, others say don't put too much faith in the calculators. I'd have to build a false wall to take up the extra foot, would this be worth it or am I ok to just leave it at 18 feet wide. Thanks for any opinions.


Phil
 

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Hi Phil,


Determine your seating requirements, screen size/distance from the screen, rows of seats, speaker placement before deciding what the ideal size should be.


I don't think there necessarily is an ideal size until you determine some of these things.


Your room sounds very much similar to the size of my future theater. I was going to use a specific brand of theater seats that would have allowed for 2 rows of 5 seats. Then decided to save up for some nice Berklines. The downside is that the seats will be much larger than I ever expected. So I'll only get 2 rows of 3 seats. For me it's not a big deal since I watch most movies alone or with my wife. The times I do have people over for movie night, there aren't enough seats anyways and they are usually nieces and nephews who don't mind a floor seat.


That extra foot could be used to build your speakers into the side walls or add decor.


Hope this helps a little.
 

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Discussion Starter · #4 ·
Thanks for the replies,,


Playing with the calculators a bit more looks like a lower ceiling may help too. Now I don't want to get rid of the 9 foot ceiling, but I like the ceiling on page 20 of the last Home Theater Builder magazine. It has sofits around the edges and also two more down the center, so about half the ceiling would be 9 foot and the other half 8.5 foot. Should I use 8.5 or 9 in the calculators. If I have to build the extra wall I can use the space to build in some DVD storage shelves and the other part is my equipment rack anyways.


Phil
 

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Quote:
Those "others" are very wrong.
...and, indeed they may not.


Here are general issues with the spreadsheets, Phil.

1. They are only reasonably accurate on perfectly rectangular rooms;

2. They are only reasonably accurate for rooms with 100% reflective wall services (at the frequencies under examination);

3. They will not predict modal amplitude;

4. They do not address modal interaction;

5. Too many think once they have the best room dimensions they'll have good sound...not true at all. The issue really is that most (other than acousticians specializing in small rooms) have difficulty interpreting the results, don't understand that twisting this dial will have an effect elsewhere, and, in the end, often find the predicted doesn't match the as built.


In your case, if I put a constraint on the room size of between 23' and 24.2' in length, 17.5' and 18.2 feet in width, and 8.5 to 9' in height, the "ideal" size becomes 24' x 28' x 8.5'. Note that in the model just a few inches can make a "sizeable" difference. While my internal scoring would predict this to be 'twice' as good as your suggested size, let's look at some details:


2 axial coincident modes rather than 3,

No "retros" in either,

The preferred "dimensions" has 290 modes whilst the current size has 309 (axial). Generally more modes are better; however, more even spacing is even better than more modes, etc.


We're not dealing, in small rooms, with simply looking at a modal analysis and tweaking the dimensions an inch or two here until we get the result we want. There's much more to it than that and that is why I wish the spreadsheets would go away.


If you have a ceiling with both 9' and 8.5' ceilings, you'll have two sets of height modes, not height modes based on an average 9' and 8.5'. Equally to the point, height modes are generally much less problematic in small rooms...particularily if you're seated in a big ol' recliner.
 

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I have a basement HT project that is shaping up to be 16x12 with a 7'3" ceiling (mostly). I say mostly because my ducts will hang down to about 6'6", but that is only on about a 2 foot section the length of the room. I want maximum headroom in the actual room because I am 6'7" tall and will have to slouch a little when entering the room.....


The calculators say I need a 8.26 ft wide room! That's terribly narrow isn't it? I mean, my 61" Sony and the entertainment center and the speakers are over 11 feet wide. I guess what I am asking is, how bad will my room sound if it's 12 x 16 with this low ceiling? Is there any design I can do to try to minimize the size issue?


Also, this is making me have to stick with a double sheetrock ceiling, with only single sheetrock around the bottom of the ducts...will this be a large problem?


P.S. - this calculator says my room will sound fine...hmmm

http://www.componentacoustics.com/Ro...alculator.html
 

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this calculator says my room will sound fine...hmmm
Yes, there are a fair number of room ratios that a fair number of individuals have 'determined' ought to have fewer bass response problems than other ratios. Even with the best of ratios, or the worst of ratios, work must be done to smooth bass response in the room.
 

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Thanks, guys ;) Looks like I have hours and hours of more reading to do, heh. Oh, and I will be sheetrocking the ceiling, the dimension I gave for ceiling height was with 2 pieces of 1/2" sheetrock below it. Due to my mutant height however, I am unable to do the "room within a room" technique.
 

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Where do you buy this resilient channel? Can you get it at Home Depot or a construction supply? Also, how do you finish joints between walls and ceilings with resilient walls and ceilings? I know you would caulk the spaces, but wouldn't that require perfect joints in every corner because you can't get too creative with caulk....but spackling you can. How much better is resilient channel than double sheetrock? I do need to insulate the sound reasonably well, but I am afraid my HVAC will be the weakest link so I don't want to spend thousands trying to soundproof only to find out my HVAC ducting is a giant sound tube.
 
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