Go to the Cardas Website, George has some good, sound info on this. I believe www.cardas.com.
This is actually a complex subject. You could read the Master Handbook of Acoustics and use the required room optimizer software and then hope you get it right or you could hire Richard Rives who is an experienced acoustic engineer specializing in home audio. When and if I build a new home, that is what I will do. Your room has a lot to do with the quality of the sound. My recollection of the handbook is that it gave a range of desirable ratios and suggested a minimum volume.
well it's a basement and the ceiling height is about 7-9ft.
I can do some stuff since I am finishing the basement from scratch, but I'm not planing to hire somebody or spend "a lot" of money just for the room. I would rather spend the money in equipments. I'm trying to make the most out of what I have to get the biggest, bang for the buck. thanks. I should probably check out the libratry, too...
Per F. Alton Everest's book (Sound Studio Construction on a Budget), there are three recommended ratios of room dimensions: 1) width=1.14 times height and length=1.39 times height, 2) width=1.28 times height and length=1.54 times height, and 3) width=1.6 times height and length=2.33 times height. Alternatively, the "golden ratio" rule is width=1.618 times height and length=2.618 times height. This assumes that height is the smallest dimension -- as long as these ratios are maintained, things are fine so if width is the smallest distance, calculate the height and length ratios based on the width (e.g., height=1.14 times width and length=1.39 times width).
Without getting into all the details, distances between parallel surfaces tend to reinforce certain frequencies (those frequencies which fit neatly into that distance). One likes to avoid too much of a gap between these frequencies and too little gap between these frequencies. A cube is an awful shape since the same frequencies are reinforced by each parallel surface since the distance is the same. Direct multiples (e.g., an 8x12x16 room -- all multiples of 4) are usually also a bad idea for the same general reason.
My rule of thumb is to keep the length of the room as long as possible since the longer the room, the lower the bass frequency that can be accommodated. An 18.33 foot room can handle a 30 Hz wave and up without the introduction of acoustic problems of one kind or another.
If you have an 8 foot ceiling, an approximately 13 foot width and 18.33 foot length works out pretty well. There will be a coloration (gap in response or weaker perception of the signal) between 90 and 123 Hz, between 185 and 212 Hz and between 217 and 246 Hz. The 217 Hz signal will seem a bit colored in the opposite direction (reinforced frequency or stronger perception of the signal). This is a pretty darned good result since there is no room dimension that will be perfect in all respects.
If you have a 9 foot ceiling, you can move more to the 13.5 to 14 foot range in width keeping the 18.33 foot length. You'll notice a slight peak in sound at about 61 Hz, 125 Hz and 251 Hz. You'll notice a dip in sound between 92 and 123 Hz, between 125 and 154 Hz and between 215 and 246 Hz. This is also pretty darned good.
All kinds of other factors also influence your overall listening experience from an acoustic point of view: The materials you use for the room surfaces, the position of the speakers relative to the listening spot and the use of absorption/diffusion materials are all important. Experiment with different materials and/or talk to an acoustic engineer/expert for help. Picking up the Everest books is also handy. The one I referenced is a reasonably easy read. Everest also wrote the Master Handbook of Acoustics (as referenced by Holzhauer above), which is a tougher book to get through.
Starting with the right dimensions is important. Acoustic drop ceilings may not provide you as good a result as a more solid ceiling. Non-parallel walls can also help since that helps to dissipate the reinforcement phenomenon. Unfortunately, I don't know enough to calculate the optimums here. I suspect that the walls are still relatively parallel in your sweet spot (sort of a calculus slope thing) so you may wish to apply the recommended ratios at that point. Acoustics is very complex and I don't want to get in over my head, so the advice about an expert is good if you think it's worth the bucks. On a rough basis though, the aforementioned ratios should work reasonably well. Good luck.
I invite any acoustic engineers or gurus to add their expertise to this.
Wow Ozfly - nice post and I think it's exactly what Eandeely needed. Room acoustics as you point out are so important. They however get way too little attention. In my case, I know some RPG Skylines on the ceiling would help my system a lot. Unfortunately, my wife steadfastly refuses to let me get them. She insists they are too ugly for our living room. But darling I say- whats worse ugly sound or ugly looks. She says looks. See the problem.
By the way- the pictures in the Master Handbook of Acoustics of various acoustically treated rooms and studios are way cool and inspiring.
These days I am doing nothing but reading on room acoustics as I am having sleepless nights thinking about my new abode where I intend to move into and from the present room size of roughly 12x12.25 feet (pidgeon hole)ideal for near field listening. I will be setting up my system in room 22 feet long, 14.5 feet wide and approx 11 feet ceiling (will need to reconfirm the exact height). Few years back when I was putting up in another place, my system was setup in a room 12x16x8.75 which was the best room musically for my Maggies. My current room did not favour Maggies so had to sell them and get the Paradigm Studio 40.
Now I am again moving to a larger room (rather much larger) and I wish I had the Maggies. I am not sure if my current system will sing or cry, just hoping for the former :) I do not intend to upgrade anything or change anything until I have settled down and I give a good listen to the system I have now. In the last 10 years I moved three times and I always ended up either upgrading or downgrading. This time I will not be in a hurry.
Will know the result in the first week of January.