What is ideal dimension size for a home listening room?

Is it a cozy size, large living room, 10 x 15, 20 x 30, some where in between?  I guess it shouldn’t be square.  Let’s assume ceiling is 7 1/2.  Heard ceiling height means a lot.
20' x' 24' x 9'.  Textured ceiling, wall to wall carpet, one end opens to a dining room with a vaulted ceiling, lots of upholstered furniture.
You could use the Golden Ratio of 1:1.62 to get an idea of the "ideal" dimensions.
So for 15' wide: 24' long.
Dudes, I just measured my room. My ratio is 1:1.63. 14 Karat gold? Or 24 Karat tin?
I would be solving for reverb time and at least a 9’ ceiling before I got too worked up over  ratios....
Magic, numbers I don't know.  The best I've heard was not a room.  It was an ampa style indoor theater, in Aspen, Colorado. Back wall retracted.  That was a wonderful, setup.. Krell.

The worst 8x8x8, 9x9x9, 10x10x10. 

If you have the opportunity to build a room, and you have the space, make the room as big as your budgeT and physical constraints will allow. I am in a dual purpose custom built listening room that is used mainly for audio. But, wife wanted movies in the cavern, so I had to accommodate the home theater for the wife. I learned noise mitigation techniques in the Army and incorporated that knowledge into the design. If your building out a room, then adding acoustical elements such as Roxul Safe and Sound sound insulation in the walls, and perhaps increasing drywall width, by doubling up, or buying Quietrock Sheetrock will aid in reducing noise from escaping the room. You can also get a company to spray foam the joists in the ceiling of your room to further reduce noise leakage. Generally speaking,  it’s easier to tame a large rooms acoustical anomalies than a small room. It can be done, but the audio presentation will be vastly different in a smaller space. If your room is a dual purpose room like mine, move the AV rack out of the room to free up space and reduce heat.  
I just watched a Dennis Foley Acoustic Fields video, in which he makes his case against the claims made for Green Glue. I can’t speak to that product, but can to another wall damping material: Wall Damp, made by ASC, Acoustic Sciences Corp., the Tube Trap company. It is a viscoelastic material made to be installed between double layers of sheetrock. I heard a room so constructed employing Wall Damp, that of Audiogon member folkfreak. I rapped my knuckles on the walls of his room, and it was like stone: very close to absolutely non-resonant.
I wonder how cost effective Wall Damp is to Quietrock and if it compares to the performance parameters of Quietrock Sheetrock. I think on the low end, Quietrock double layer 5/8 EZ snap is roughly $60 per 4x8 sheet. Using Quietrock 530 is about $110 per sheet average. How much does Wall Damp cost per sheet or roll? Wall Damp is certainly a viable solution to sound mitigation if it is not too cost prohibitive and less than the cost of using Quietrock.
There are no "ideal" room dimensions with a 7.5 ft ceiling.  Ceiling height does mean a lot, and the higher the ceiling the better up to about 12 ft.  Since you are stipulating a 7.5 ft ceiling, my guess is that you might be thinking about finishing an existing basement space.  If so, recognize that the ceiling is going to limit what you are going to be able to accomplish.  I couldn't find a favorable Bolt Area using a 7.5 ft height without making the room too small to be practical.  So you are going to have a real challenge dealing with room modes.

If (or hopefully when) I have the opportunity to add on a custom built room, I would start with a carpeted concrete floor and a ceiling over 10 ft.  I'd like the room to be fairly wide, something approaching 20 ft.  I'd like the room to be deep, approaching 30 ft.  If you start getting much smaller than these dimensions, you can have your work cut out for you and face limitations in selecting a speaker that will mate well with the room. I'd select dimensions that allow the room to fall within the Bolt Area and which exhibit a favorable Bonello distribution.  26.5 ft x 17.5 ft x 12 ft dimensions fall within the desirable Bolt Area, would provide a favorable Bonello distribution of modes, and have a relatively low Schroeder frequency.  Most of the calculated low frequency modes resulting from those dimensions are do not coincide well with the frequency of notes resulting from standard A = 440 Hz tuning of instruments.   As far as I can determine, this is about as good a scenario in a real world room as you can get. 

Such a room would offer the following additional advantages.  The  concrete flooring would greatly reduce problems associated with resonance being transferred back into the speakers and electronics as compared to plywood or OSB over 16" joists. Carpeting over concrete in conjunction with a high ceiling will substantially reduce problems with floor to ceiling slap echo and permits more flexibility in dialing in speaker to listening room position without having the room become too reverberant. 

My current room is 14 ft wide and 20 ft deep.  It is too narrow to accommodate more than one critical listener.   Another 3.5 ft would make a world of difference and reduce the intensity of side wall to side wall slap echo.   My speakers are full range and don't do all that well in near field listening.  So my listening position is only about 4 ft off the back wall, which creates an unfortunate low frequency null at the listening position due to out of phase cancelation coming from reflection off of the rear wall.  A deeper room allows one to move the listening position forward enough to push that rear wall cancelation to a low enough frequency that it becomes less important. 

+1. Great way describing the complexities of room modes associated with room size. I guess, in this sense, more is better. However, there is nothing wrong with intimate close distance listening either, it’s just going to be a different experience....but music is music, and enjoy it anyway you can. 
@audioquest4life , thanks for your kind words. Music is music indeed, and I enjoy music through my car stereo enough to know that sometimes you just need to turn off the audiophilia nervosa.  We all live in a real world and deal with compromises.  But a post like this invites dreaming, so dream I did.  It is akin to someone asking "What is the ideal 2 channel system?"  

I agree that near field listening can be wonderful.  In fact, I'd love to be able to build a system around that paradigm.  But if I were designing a new room, I would not want to get locked into a particular paradigm.  I'd want a room that would likely be as friendly to a near field paradigm using a monitor/dba approach as a more traditional full range system with the listening position further back.  I'd want a room that could work with panels, line arrays, point source, and horns.  

For the last 6 years, I've been "enjoying" my first dedicated listening room in which I'm using my first set of full range speakers.  It has been a challenge making it work, and I'm not completely there yet.  I've got the main issues addressed, so I'm getting close.  What remains is fine tuning, and it is not easy.  It takes a lot of critical listening to a lot of different recordings and an equal measure of critical thinking about what I am hearing. 

Most of the issues I've had to deal with were baked into the cake with room dimensions and construction choices that I had no control over since we bought an existing house.  Next time will be different.  I will either be going new construction or buying with the intent of building a music room as an add on.  

Right on Brownsfan, I think Rettinger sure appreciated Bolt and summaries as most of the Magic ratios as falling outside his unity adjusted ideal area. Hence my paraphrase to work reverberation time.. too bad about that cancellation node you have. I can move my chair just enough to get out of it. You might actually be a great candidate for swarm or some analog EQ down low, although based on the deep knowledge you show in your post I suspect you already know this


Like all things, labor and importantly expertise needed to install these products in a systematic way to achieve best results per $. What a lovely thread :-)
Considering  people doing "near field Listening " , having speakers a few feet from you , I doubt size matters .
Just make sure  you've taken care of  bouncing sound
brownsfan made many good points. I suggest that you find a good on-line Room Mode Calculator which speaks of Schroeder Frequency,  Bolt Area, Bonello, etc. to help you better understand the consequences of room dimensions. You might consider consulting with a professional because once the walls are up you are stuck with the design.

You might also consider non-parallel walls. Our purpose built room was designed with non-parallel walls and the results are well worth the effort. The calculations are more complicated but worth it. They help minimize the need for absorption and diffusion. The end result is a lively (not bright) well balanced room. The next time you are at an indoor live venue check out the enclosure you are sitting in.

If possible, consider which family of speaker design (mono-pole, dipole, point source, line source, omni-directional) you will likely end up with. This consideration doesn't necessarily influence the optimal room dimensions which is more about distributed room modes and a smooth bass response but it will influence the interior room design and treatment needed.

Consider built in or free standing corner bass traps. There are real reasons why qualified professionals recommend corner and soffit bass traps. Don't believe the general statement that too many bass traps will absorb all the mids and highs and make a room sound over damped. Not all bass traps are created equal. For example, DIY "bass traps" that are basically a 4" thick block of Corning fiberglass wrapped in fabric are marginally effective as bass traps and are really broad band absorbers that can, if overly used, over dampen a room. A REAL bass trap (bass attenuation only) typically has a membrane covering the fiberglass which reflects the mids and highs back into the room and does not over dampen the room.
@tomic601 ,  I ordered a swarm system about 6-8 weeks ago.  I'm hoping delivery will be soon.  The dba approach is, at least conceptually, a game changer.  We will see.

@arion,  Good comments.  I've been intrigued by the use of non-parallel walls.  Conceptually, it solves a lot of problems if it is properly executed. I'm not aware of any commonly available mathematical models that provides predictions of modes in non-rectangular rooms, which would give me pause in committing to that approach.  
Google says a 20Hz wave is 17m, or 55.8 feet. Wouldn't the ideal room have to have one dimension (diagonal) of at least that length?

You are welcome. Looking forward to your results with the swarm system. I have been using the Velodyne SMS1 bass eq for years with two subs and it has been fantastic. Note, I stated years, subs and velodyne are over 15 years old. They are classics now:) 
@docknow  55.8 ft in one dimension buys you the ability to sustain a 20Hz standing wave in one direction.  I'm not sure that would be on my top 10 list of goals for a good listening room.  Most of us are looking for what can be done with small rooms, that is, rooms that can reasonably be accommodated in a single family residential dwelling.  50-60 feet is about 2 times the length that most of us could reasonably execute.  

It is a tall order trying to get great low frequency reproduction outside of a concert hall.  Fortunately, there is not an enormous about of musical information at 20 Hz.  So we can do pretty well with most music in rooms that most homes can accommodate. 
brownsfan, I am not aware of any room mode calculators or  mathematical model for rooms with non-parallel walls. We started with a rectangle shape for a base line. Then we did some calcs and made some assumptions to come up with which walls to skew. About 60% of the room is made up of non-parallel walls. About another 20% of the walls are covered with diffusers and broadband absorption. About half of the skewed walls are actually built-in bass traps with reflective surfaces and tuned sections. I can't be absolutely positive we did it 100% correct, but it works great.

I started using non-parallel walls after a learning experience while exhibiting at an audio show in Los Vegas about fifteen years ago. A pair of very large and flat shipping crates placed staggered and skewed along the side wall saved the day.
Non parallel sides, rounded California corners. You probably will settle for less than "ideal."
What’s a California corner?
”ideal” is somewhat subjective and relevant to the objectives.
Please share your experiences with non-parallel walls as used in a dedicated room. I’m always eager to learn.

Anybody live in a geodesic dome?How would a dedicated room work in that circumstance I wonder.
arion, thanks for the reply.  Your approach makes sense.  

I'm grateful for the online calculators we have, but we could certainly use some that are a bit more sophisticated.  It has been 48.5 years since I finished my last quarter of calculus, and I didn't use it enough professionally to maintain competence.  But I would think a physics graduate student could make quick work of generating a  calculator for non parallel walls at least for calculating axial modes.  The most difficult part might be figuring out how to present the output visually in a clear fashion.  

In some respects, I like the REW room calculator, because it allows you to introduce speaker and listening position into the model as well as room dimensions.  Unfortunately, my speakers have side firing woofers, so the model doesn't make the best predictions in my case. 
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Awfully great comments herein.

i believe great amp power would be essential especially in a smaller room to allow great control over lower volumes.

Curious on thoughts of an ideal size for a b&w 803 d3 or their very dominant 802 in a residence.  My belief is that anything below 15 x 20 would be on the edge of being comfortable for an 803. Great Danes are unable to thrive in a nyc apartment.