Square but not cube shaped room, will it hurt the acoustics??

RCduck7 · « **on:** 8 Nov 2011, 10:15 pm »

I'm going to make myself a dedicated listening room in the attic and it will be about 17 feet by 17 feet. I know, i have read that a square room is a no go for low frequencies as it will generate it's problems. But the sides of the room will have sloped ceilings starting at about 5 feet up measured from the ground. The back of the room will have no sloped ceiling and at the front the sloped ceiling will start at 3 feet high. I wonder if they mean with a square room being bad, being a cube shaped room? My room with sloped ceilings will only be square at a certaing heighth with the sloped ceilings. Any ideas? Will it still not be a good idea and should i avoid having a square room when i can??

bpape · « **Reply #1 on:** 8 Nov 2011, 11:01 pm »

It's still essentially square at ear level and regardless, you'll still have the room modes in exactly the same places making them much more intense.

Bryan

JohnR · « **Reply #2 on:** 8 Nov 2011, 11:36 pm »

The frequency of modes isn't dependent on where your ear is, though Bryan...

The construction method you use will likely have a larger effect - some starting points here: http://www.hifizine.com/2011/09/bass-integration-guide-part-2/

bpape · « **Reply #3 on:** 8 Nov 2011, 11:47 pm »

I agree John - not totally dependent.... If for instance though a room had slanted ceilings down to 1' from the floor, the squareness would not be as big an issue. It's still there, just not as prominent. The less of the room that is square, the less of a problem it becomes.

That's why I prefaced the second part of my statement with 'regardless'. It's still square and the problems will still pile up.

Bryan

ebag4 · « **Reply #4 on:** 9 Nov 2011, 12:03 am »

If you are building walls why not narrow the room but leave the length in tact? The Golden Ratio gives you a width of about 10.5 feet but you wouldn't necessarily have to go to that extreme. BTW, you can get good sound out of poor rooms with the proper treatments, some speaker types work better in small rooms IMO (especially in bass reproduction) as well. My room is 10.5'x12.5' but I am getting great sound now.

Good luck!
Ed

JohnR · « **Reply #5 on:** 9 Nov 2011, 02:07 pm »

So a hypothetical then. Given the max dimensions are 17 ft, is it better to

a. Reduce the room dimensions to say 10.5x17, or
b. Use the max dimensions of 17x17 but use 3 feet of bass traps on either side of the room.

?

ebag4 · « **Reply #6 on:** 9 Nov 2011, 02:22 pm »

Quote from: JohnR on 9 Nov 2011, 02:07 pm

So a hypothetical then. Given the max dimensions are 17 ft, is it better to

a. Reduce the room dimensions to say 10.5x17, or
b. Use the max dimensions of 17x17 but use 3 feet of bass traps on either side of the room.

?

Interesting question, I look forward to reading the response of some of our resident acoustic experts. Perhaps somewhere in the middle, a foot of absorption on each side in conjunction with making the room less square.

Best,
Ed

bpape · « **Reply #7 on:** 9 Nov 2011, 02:45 pm »

Not sure I'd do either one honestly. Taking a little out of the room width would be helpful but I don't think I'd cut it all the way down to 10.5'.

3' thick bass control behind you can certainly help tame things though not sure how practical it is.

In the small studio world, in square rooms, we'd just set them up diagonally facing into a corner. You can get pretty good results that way and the reflections are naturally more pushed behind you. It also gives you more play in seating in relation to the 'length' of the room.

Bryan

JohnR · « **Reply #8 on:** 9 Nov 2011, 03:29 pm »

Why is 3' of fiberglass not practical? Bearing in mind that the room is being constructed at the time.

bpape · « **Reply #9 on:** 9 Nov 2011, 03:34 pm »

Just purely looking at the additional cost of building the larger space and then losing 3' of it and the additional cost of an entire wall of 3' thick fiberglass. I'd think that just making the room a couple of feet narrower would avoid the problem and cost less rather than spending more money, creating a problem, then paying to fix it.

Bryan

JohnR · « **Reply #10 on:** 9 Nov 2011, 04:17 pm »

But the narrower room will still require damping. Right?

Hipper · « **Reply #11 on:** 9 Nov 2011, 06:55 pm »

As I understand it, you will get room modes based on the dimensions of the room.

A typical room will have three different dimensions, hence three different frequencies will be affected, but if you have a square room a particular frequency will be doubly affected.

The problem frequency will have a wavelength twice that of the room dimension. In your case the wavelength is 2 x 17' = 34'. To calculate the frequency divide this into the speed of sound - roughly 1130 feet/second) - that makes 33.2Hz. I had a room 13 x 8 x 8, so had a particular problem around 70Hz.

That's why a square room is not ideal.

In part you can deal with these problems by moving speakers or listening position, and/or absorbing the nuisance frequency with acoustic treatment. I would suggest that this is the better approach as you can take that material to another room if ever you move your listening room.

I use a combination of acoustic treatment and a digital equaliser.

I don't use this equipment but there's some useful info here:

http://www.rivesaudio.com/PARC/basic%20function.html

bpape · « **Reply #12 on:** 9 Nov 2011, 06:57 pm »

Quote from: JohnR on 9 Nov 2011, 04:17 pm

But the narrower room will still require damping. Right?

Sure. There will still be some treatment most likely. Just not near anything of that magnitude.

Bryan

RCduck7 · « **Reply #13 on:** 9 Nov 2011, 10:39 pm »

Thanks for all the replies. It seems the best solution is to change the shape of the room instead of finding a cure to counter it. The length of the room is 17 feet and will stay that way but i can make the room wider or narrow, i can go as wide as 24 feet! I agree making the room narrower will prevent the problems that come with a square room but i think with the pretty big speakers i am using (Hyperion 938's), going much wider will give the speakers more room to breath at both their sides and give the sound a more relaxing and open presentation. First reflections will be less of a problem with going wider also i guess. Also with going wider, the sloping ceiling on the sides will start at 3 feet high instead of 5 feet high. This room (17' x 24') in the attic will give me less space to put the stuff that supposed to be in the attic, my stuff will have to be in a crawling space then at the sides of the attic.

Tell me what do you think, in the meantime i will see when i find some time to make some pics of the room. I just moved house and i have other priorities but once one have been bitten by the virus... it's even there in more bussy times.

brj · « **Reply #14 on:** 9 Nov 2011, 10:43 pm »

If you have that much freedom to alter the room shape within your max dimensions, you don't have to limit yourself to orthogonal (90 deg) walls either...

http://www.cardas.com/content.php?area=insights&content_id=36

JohnR · « **Reply #15 on:** 10 Nov 2011, 01:56 am »

Quote from: RCduck7 on 9 Nov 2011, 10:39 pm

i can go as wide as 24 feet!

!!

Well, that's easy then, do that

There are some charts showing optimum range of ratios somewhere, I'll find them later on.

bpape · « **Reply #16 on:** 10 Nov 2011, 01:13 pm »

Just from personal experience, if you have that kind of flexibility - 17x21 is a nice dimensional blend. I have it in my room and have done that size in other rooms and it propogates bass very well and very smoothly. That would be a good compromise to get you out of the square situation, give you a bit more room width, and still leave you with some storage that you wouldn't have to crawl into...

Bryan

usp1 · « **Reply #17 on:** 10 Nov 2011, 02:58 pm »

A rookie question and I hope it does not derail the thread. I hear a lot of talk about using the Golden ratio for room dimensions. WHy is the golden ratio preferred? Can some one point me to material I can read which explains why the golden ratio reduces slap echoes and other audio gremlins? Is this an empirical observation or is this something that come from wave mechanics? Thanks.

rofo · « **Reply #18 on:** 10 Nov 2011, 03:09 pm »

Grab a copy of this book http://www.amazon.ca/Master-Handbook-Acoustics-Alton-Everest/dp/0071603328/ref=sr_1_1?ie=UTF8&qid=1320937565&sr=8-1

It will help you out with your project(s)

bpape · « **Reply #19 on:** 10 Nov 2011, 03:15 pm »

Quote from: usp1 on 10 Nov 2011, 02:58 pm

A rookie question and I hope it does not derail the thread. I hear a lot of talk about using the Golden ratio for room dimensions. WHy is the golden ratio preferred? Can some one point me to material I can read which explains why the golden ratio reduces slap echoes and other audio gremlins? Is this an empirical observation or is this something that come from wave mechanics? Thanks.

Slap echo isn't going to be solved by a room ratio. That's just a matter of addressing large, flat, hard, parallel surfaces. This can be done with absorption or diffusion.

What good room ratios so is to help spread room modes farther apart and distribute them more evenly through the spectrum so they don't pile up and reinforce each other making them more difficult to address - especially in the lower frequencies.

ALL rooms, regardless of the ratios will have modes and modal problems. Some are just less bad than others.

Bryan