Building a Golden Cuboid Listening Room garage

For along time I wanted to build such a room. Hopefully within a year or so I will. But first I am needing to know everything about materials and the best construction ideas before I procede.

This room will be outside of my home (garage type) and it will have room dimensions of 10ft(9ft) x 16ft x 26ft. I might even have the ceiling climbing from 9ft to 10ft to rear of room.(depending if this is beneficial or not)..

I am not overly concerned about sound getting out of the building , but more concerned of making it sound best inside:)

It will be on a concrete slab of 6 inches reinforced with steel (rebar). A 1 foot high knee wall will be built into the slab around the perimeter.

The walls will be 2x6 or 2x8.

Questions I have are:
1) Should I insulate under concrete slab with high density foam board. Any advantage for bass control ?

2) Should I build a subfloor over the concrete, or is it ok to just put down carpet etc..Any advantage for bass with or withought subfloor?

3) What type of wall insulation is best?, paneling gyprock?

4) Is it better to have thicker walls, 6 or 8 inch? what advantages?

5) Would it be better to have tapered walls and ceiling from front to back (smaller to bigger) or is the 10ft x 16ft x 26ft good enough.

Any other suggestions or ideas about building this would be appreciated. Hopefully some of you have a building like this with success.

I also have a number of DIY bass traps, acoustical foam and room lenses to help control some of the sound once it is built,if needed.

Check this system out. Mike gives a link to an article relating his experience building his room. It should prove informative.
What is the plan? Do a short or long wall setup? Will you be using this for 2ch listening or HT use as well?
If 'all new' construction, investigate audio oriented building materials and techniques. Staggering studs is a good idea to decouple inner and outer walls. Weaving a hi-density acoustic material BETWEEN the studs helps lots.
Pre wire? absolutely! 1 or 2 exclusive circuits and maybe even a sub panel for power. Cable TV? Pre wire that, too. Between the new listening room and the rest of the house, consider an Exterior door. Non-parellel walls/floor/ceiling are certainly a good idea to reduce standing wave propagation. Taper all walls differently. I have seen a recording studio made with this in mind.

Windows? Double glazed vinyl probably. Low -E-. If designing for HT, place appropriately and consider where the sun would come in.

Think about where you intend to sit and HOW MANY people. It is a bad idea to sit mid-way of any dimension. I Personally don't like sitting up against walls, but I have seen some advocates of that position.

The dimensions you have chosen are 'perfect' golden section numbers. My plans are similiar except I added a 2'deep by 7' wide by 5'high 'alcove' for the placement of a RPTV since I intend to ultimately have a 5.1 HT oriented system. I was planning a long-wall setup, with the listeners about 3 feet or so from the BACK wall, leaving an isle and providing some ambient space.

Also, please consider BOOK SHELVES as both a design and acoustic element.
Thanks Timrhu and Magfan,
I will be using this room as a dedicated 2ch listening only.. I already have a dedicated movie room, happy with that:). Listening position will be facing short side, unless long side proves better. Have to wait and see:)

I already have two listening rooms in my home, one in basement and one in dining room. Each room has its benefits and bad qualities. But would love to experience the best possible room dimensions.

I've used the same equipment in about 6 different rooms in different homes, and for sure the rooms and speaker placement make such a difference, way more than any component I ever tried.