Dedicated listening room design

There is a difference between Acoustic Treatment, and Acoustic Isolation/Sound Proofing.

There are also differnces in Acoustic Treatments to 1) Listening/Reproduction Rooms for Audio 2) HT rooms 3)Live performance Rooms/Venues.

And lastly, there are different treatments for 1) Sonic Accuracy and 2) Sonic Preferences.

The solutions you use need to take these paths into consideration. Quite often the goals get homogenized and you don't get the desired results.

Summit, well said. Sound proofing only keeps the sound inside a room, nothing about making the sound inside the room any good!

The basics are to avoid parallel walls, hard (reflective) surfaces where the speakers project sound (usually the side walls). Using commercial grade absorption from any of the major companies on the sides and behind the speakers can really help. Many companies offer room kits, which is perhaps the ideal starting point for most of us, really simple and a huge improvement.

Being from the pro side, I cannot help but chuckle a bit when I see folks with these extremely expensive systems, hi end power cables, CD vibration isolation etc, speakers near side walls, all in an untreated room. That's like $10,000 in tires on a 1971 ford pinto!

Thanks for all your input -- most helpful as usual. I've decided to use Dietrich RC Deluxe resilient channels on the walls and ceilings, double 5/8" drywall w/ Green Glue between the sheets on the walls and double 1/2" drywall & Green Glue on the ceiling, wall-to-wall carpeting, and LED lights (contractor says they're the quietest w/ dimmer) if budget permits. R30 insulation or maybe special insulation, again if budget permits. Not sure about absorbers/diffusors yet, but I'll fight that battle another day after the room's done.

Thanks again, and I'll follow up with results after it's done in case anybody's interested.

Soix - I was in your shoes about 5 years ago. Exciting times and certainly enought to learn that will take some time to digest and internalize.

Using my basement 2-channel room as an example, here are some of my learnings:
* use a solid core exterior door to keep sound inside the room
* HVAC: I used a round flexible tube with sound insulation on the inside. You want to install it in such a way that there are several near-90 degree bends in it to prevent sound from traveling back to the furnace and up through the rest of the house. Also, baseboard heaters are dead quiet as another option.
* Lighting: don't use dimmers! They hum and your stereo system will pick it up. Instead use lights that work on 120volts (assuming you're in North America) and that don't use a transformer which can introduce humm.
* use J-molding and an acoustic sealant between the ceiling and walls so that if the walls move they don't transfer energy to the ceiling and vice versa.
* your wall-to-wall carpet will absorb much high end energy so you will need to pay attention to how you treat your room's surfaces so as not to create a dead sounding room with low reverb time for middle and high frequencies. Try using reflection (i.e. bare wall) and diffusion for middle and upper frequencies and absorption for bass frequencies.
* get a Dayton Audio Omnimic or XTZ or similar product to take in room measurements so you can do before and after measurements to gauge how effective your treatments are.
* buy Toole's book.
* not all reflections are created equally. Address reflections from the back and front wall as they are the least beneficial.
* experiment with reflection vs absorption vs diffusion at the side wall's 1st reflection points. Reflection provides the widest apparent sound source and maintains the mid/high freq energy whereas absorption narrows the sound source and attenuates the mid/high freq energy but usually allows for the best retrival of musical details. Diffusion is like the best of both - it widens the apparent sound source to something more akin to a live performance while preserving the mid/high freq energy and allows nearly as much musical detail retrival as absorption. Personal taste prevails.
* If you're considering diffusion within your room and if the sitting distance to the side and rear walls is short, then use diffusion that either is two dimensional (e.g. RPG Skylines) so that only about 50% of the sound is scattered back to you latterally, or a diffuser that doesn't provide temporal effects (e.g. phase) such as geometrical shapes like round surfaces.

Pictures in my 'System' will show what I speak of.

And have fun as it's an itterative trial and error kind of experience.

Kevinzoe,
I have absorption on the side walls. I also have wall to wall carpeting, and think i may be overdamped. Would you recommend trying a pair of the GIK d1's at the 1st reflection points?