Home theatre in-wall acoustic design?

Well the room dimensions itsself are important. Use an online calculator to see whether your room dimensions are ok... well worth checking because if you have standing waves it will cost more to treat the room. As brettbert says, soundcheck is a good start but you need to decide how far you take it. you can double skin the walls and have the second skin isolated using green glue etc but this start to become expensive.

I think look at avsforum build threads for a similar sized theatre and see what they did and how the approach was taken. This will allow an overall plan of attack. Regarding the walls you could use rockwool or something like acoustic batts but not sure what the goal is whether it is to stop sound bleed out of the room or to improve the internal sound.

More info pls....

What you meant by online calculator?

Dimensions are critical, and reduce the treatment for good acoustics later. There's a number of proven tested Ratios.
Have a read of this and the Next & Next+1 pages. Note that ratios also depend on the total room volume.
http://www.acoustics.salford.ac.uk/acoustics_info/room_sizing/?content=index

In the end, the Acoustics of the room is what really matters, so consider your needs for budget in case you overspend on isolation.

For isolation between rooms, a different subject altogether, using thick or double sheets of Fire Rated Plasterboard and low-density insulation, eg Earthwool 10 kg/m3 is very commonly used in Studios.
I have not known an Acoustic Architect who has specified Soundcheck or batts. If you really need isolation use 2x13mm FR Plasterboard, maybe Resilient Clips and 16mm Furring Channel on the inside walls, and use the money you save on Green Glue between sheets.

There are Home Theatre Forums with more details, but you can also check Recording Forums, like Gearslu-tz (remove that hyphen) and John L Sayers recording forum. Both have threads with heaps of detail.

The main question is what do you mean by accoustics? Are you trying to prevent leakage of sound to other parts of the home, or are you looking to treat the rooms accoustics to ensure your nice audio gears sound is not being coloured by standing waves and reflections?

The answer to these is different.

wow this HT thing is getting more and more technical the more you read about it. You know what, I'm just gonna do black thick curtain around the wall. This should help heaps according to some. cbb putting batts or panels here and there..

Yes, you're right. The more I read about acoustic is home theatre, the more lost I am lol

Actually I think I just want to keep the sound, and not have too much sound "bouncing" in the room like my precious uni small room. Not sure what I need, but I'll just work on thick curtains and some acoustic panels on ceiling & batts in wall. Gonna be too much to ask to get my builder to use a different plasterboard I thnk.

to be honest, some drapes will be fine and they will look good. Acoustic treatment is generally ugly (subjective) and used in studios where they are mixing down audio professionally so that you, the consumer, can get the most pleasing sound through an array of audio equipment. If you are an Audiophile, you should look into learning about sound and its properties if you want to get the best out of your equipment.

However I get the impression that you will be will be using a standard $2k audio set up from a retailer for your HT. If so, I wouldn't bother too much about all the various technicalities of treating the acoustics of a room and just make it nice and comfortable. The likelihood you will notice any major sound/reflection issues is probably zilch if you're the type of person who cant tell the difference between an MP3 and a 24bit 96khz recording. Not a bad thing, just highlighting that you might benefit more from saving your coin for more desirable things in your home than treating a room for an issue you will likely never perceive.

/cue audiophiles who disagree (but before you do, as a fellow audiophile, how many times have you seen DJs mixing 128 bit MP3s through sound systems that cost in excess of 100k and not even realise themselves that it sounds like poo?)