Sound insulation advice for home theater room in middle of the house?

Google soundproofing a room.  Seriously. 

We designed and sound proofed rev runs home theater for the show rev runs renovation

Season 2 Secreat cinema

Most sound proofing doesn’t work as it won’t block bass frequencies so you need a solution with mass. Only mass can block bass.

WE came up with a quiet rock clone for a fraction of the price using durarock green glue and sheet rock.

Dave and troy

Audio intellect Nj.

An alternative to the above, try these people

Generally speaking, however, you will have a hard time taming bass resonances in that smallish room! Mass behind the couch is one way -- but you don;t seem to have much room there either

Agree with the above.  Solid heavy sealed MDF doors, double staggered studs, double sheet rock, all would go to waste with the removable partition.  That's a deal breaker.

This book has a lot of great info.  Chapters 6, 10, and 11 in particular would be helpful for tips on room design with instructions any competent contractor could follow. 

http://www.gedlee.com/downloads/HT/Home_theater.pdf

In answer to your question whether the doors make mass loaded vinyl impracticable, it may depend on how they are hung,

I have successfully used MLV with large melamine sheets. The combo is a sound deadener.- This isn’t acoustic treatment, it is sound proofing. And in combo, extremely effective. MLV is very reflective on its own.

Wireless headphones for all of the movie watcher's will save a bundle on the soundproofing, electronics, speakers and acoustical room treatment.

You could even add bass "vibrators" to the seating if desired.

Make the most out of a flawed from the beginning layout which is further limited by budget.

DeKay

Go onto the Acoustic Sciences Corp. (ASC) website. Owner Art Noxon has designed a complete systems approach and product line for soundproofing a room, named IsoWall Soundproofing. Robert Harley of The Absolute Sound built his room using the ASC products, here's the video he made detailing the build.

https://youtu.be/OtUcfiaN6CY?si=fHzwvqSpAL11VSNd

I've done two rooms in my own house. In the home theatre, I built a wall on each side of 2x4 frames and filled the interstices with playground sand. Same for the ceiling. It was highly successful.

For the purpose built music room I used Quietrock 545, which is a 5 layer drywall with a sheet metal core. Far easier to build, but not as effective. Still, good enough for the purpose and my usual listening levels.

You want two things: first, you want the walls to be stiff so that they do not flex and interfere with the music. Second, you want to prevent sound from escaping. The two goals can both be met, but they require considerations like my solutions.

As for a terrible room, you can always change the dimensions. The scientific work has been done by the famous acoustician Cox, who published the results about 20 years ago. The research is on the website of the School of Acoustics at the University of Salford, UK. As for construction, the people at Quietrock are very, very helpful. Also, there was a reasonably good article published about 6 years ago in Stereophile or Absolute Sound, can't remember which.

Good luck - glad your client had the good sense to hire someone like yourself.

You will have to do a lot of research on google by looking at people's dedicated listening rooms to pick and choose the methods that would best apply to their layout. You are welcome to start with the construction of my house of stereo under my system details. The double sheetrock with green glue sandwich for walls and ceiling plus offset studs construction would be a good start. Then thick outdoor solid wood doors are also a must. Finish it up with quite a bit of absorbing material to tame the low frequencies that are so prevalent in a home theater. Like 4 corner bass traps and decorative wall mounted absorbers panels. Then add some diffusers at first reflection points to liven the room back up to improve the high frequencies for better dialog deciphering. It won't be an easy overnight design but if those folks are serious about getting satisfactory results they will have to likely spend a lot more money than you all thought. 

You are welcome to start with the construction of my house of stereo under my system details. The double sheetrock with green glue sandwich for walls and ceiling plus offset studs construction would be a good start.

That’s a good start, but resilient channels go much further toward not only preventing vibrations/sound from being transferred through studs to the rest of the house, they also greatly improve the sound within the room.  Refer to my prior post to learn more about resilient channels. 

@soix 

Resilient channels slid onto soundproof mounts screwed into the joists is how I did the ceiling as shown in pics and described in my system. Both methods accomplish the same goal, isolating inner wall from outer wall.