Ideal design for a new music room

fwiw. Don’t try to reinvent the wheel. Rectangular rooms work and I can’t imagine why you say the Golden Ratios are hard to apply- but- you are wrong. Someone suggested 3/8 inch walls- I can’t think of a kind comment about them. Along with the Cardas site look into the construction features of the Rockport Technologies listening room. The best advice you will get is to decide the size room you want and build it solidly and symmetrically. Allow 5 -6 ft behind your speakers and at least 4.5 feet from speakers to side walls. 8 ft behind your head. Plan a vibration isolated area with a door to the side of your speakers for electronics and vibration isolation for your amplifier. Organ music right?  Assuming you’d like your speakers 6-7 ft apart you need 16-17 ft width, about 19 length. 9 ft is contemporary minimum height for a classy space. Get yourself graph paper and draw to scale-precisely. Use 2-3x5/8 drywall on walls. I’d use a base of 5/8 mdf as the first layer behind the speakers if your speakers can drive organ music down to about 30cps. I did these with my 17x27 rm and got positive comment.  Floor shd not flex. Symmetry helps to kiss. Helps resale value and decorating as well :) Enjoy and best wishes. 

I am no expert but in my there are advantages to having a dedicated listening room in the basement. 

Advantages:

1) No large windows, if any at all.
2) Concrete floor.
3) More design flexibility than if the room was in a more public area of the home. This includes the addition of acoustic treatments that only look attractive to the eyes of the audio enthusiast.
4) Easier to design such that music can be listened at high volume without disturbing other family members, especially in the late evening when the audio “magic” often occurs.
5) The option to have an adjacent equipment room to house a turntable that is well-isolated from the listening area.

Disadvantages:

1) Part of the enjoyment of the hobby is sharing music. Not many folks like to spend hours in a windowless basement listening to sonic perfection other than audiophiles.
2) If your system will include very large speakers betting them down into the listening room can be a pain.
3) Basements rarely have ceilings more than 8 feet high. This may partially be related to cost but also, the deeper the basement, the more concerns there may be with water inflow. Our neighbors rebuilt their home and deepened their basement. Their sump pump runs continuously. Our basement, less than 20 feet away but not as deep, is bone dry and our sump pump has never kicked in over the 14 years we have been in the house. 

Your idea is amazing. I have long dreamed of owning a stereo room. Wish you soon complete your ideal.
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Thanks for everyone's comments. I've had experience with 7 different listening rooms. I agree with many of the suggestions. Each room came with dimensions that I could not change. Each one sounded different. For sure room characteristics are big contributors to the sound you experience. So I wondered what characteristics an ideal room would have. So far there are excellent ideas but no one has come forward to say they've built a listening room (not a recording room) that is close to perfect in being able to create a satisfying sound stage. Even better, no one has suggested that an inexpensive system, say under $5,000, in a great room will deliver a better audio experience than systems costing multiples more in a poor room. Is it possible that fortunes are being spent on equipment that is fighting rooms with poor acoustics?

Hello encore, I can personally relate to your post and find it refreshing to see someone seriously identifying / questioning the elephant in the room. 
 You have hit the nail on the head and I will repeat your quote with an answer: 
 “...no one has suggested that an inexpensive system, say under $5000, in a great room will deliver a better audio experience than systems costing multiples more in a poor room. Is it possible that fortunes are being spent on equipment that is fighting rooms with poor acoustics?”
   And the answer is absolutely YES! 
And that’s exactly what’s going on in probably a major percentage of the rooms we see on our audio sights and hear in our visits to our audio friends and acquaintances. 
   An ‘excellent room’ for listening is almost always at odds with a room designed for anything else... 
    A dedicated listening toom will have the speakers placed EXACTLY in THE 2 spots where they will sound optimum in that specific room. 
    A dedicated listening room will have the listening chair ( or perhaps ‘love seat’ but you’d be pushing your luck a bit to try and use a couch)... in EXACTLY THE correct location for the speakers to sound their optimum....
    A dedicated listening room contains the requisite audio rack(s) necessary to properly serve the components and should be strategically positioned to have minimum influence on the acoustics of the environment.
    A dedicated listening room will be seriously addressed with corresponding acoustic room treatments placed where they ideally benefit the system’s prime directive of replicating the musical performance as realistically as possible. 
   With that said... most homes have a chosen room which can be deemed ‘the one’ where the system tries to do its best while still remaining a somewhat socially integrated venue. 
     In my humble opinion a properly set up $4000 system in a dedicated listening room utilizing $1000 in select room acoustic treatments and the available open space void of unnecessary furnishings will be very very tough to beat. 
    Commit to a room first.. work it all from there. 
    Lots more to talk about but just wanted to get started. 
     Happy Lissn’n.     Lissnr