to wall or not to wall?

Personally, I would leave the wall open. Anything that creates parallel relecting surfaces is generally a bad thing acoustically as it supports standing waves. The more odd shaped the room, the better it is in preventing standing waves.

However, there is something you could do as an experiment at no real cost. Start out with the wall open. Don't trim the edges of the opening for now. See how your system sounds. Now, take a piece of drywall and stand it up to block the opening totally or partially. Just tack it into place. Now see how the room sounds. If you don't like it, you can finish the trim on the opening. If you do like it with the blockage, you can now finish the wall/door as you originally thought of doing.

By the way, this may or may not be an issue to you. But, many speaker wires cannot be buried in a wall or ceiling unless it's approved for such a use by government regulation. If you don't have approved wire, and you bury it, you will not pass an electrical code inspection. Also, if your insurance company finds out about it, they will not pay any insurance claim. It might also be an issue upon selling the house. I'm not preaching, but if you're going to do what you're going to do, at least be aware of the implications.

I wouldn't get too freaked out about the 'to wall or not to wall' question. The more important question, imho, is if you want the room secluded or not? You will not have an authentic HT if it's an open-air affair where room noise can intrude. Same with two channel listening. Will you be bothered by outside influences if you keep the wall open? does that matter to you? What's the purpose of the room, for you alone, mostly or entertaining? If you want seclusion, then build for seclusion. If it doesn't matter, then it's cheaper to build a three wall room than four wall...

I can discern a difference in sound in my HT just when the rear door is open! I prefer the sound of the enclosed room with the door closed.

A lot of sound issues can be worked with by room tuning after the walls are up. Markphd has a pretty good idea about putting up a piece of drywall as an experimental back wall. However, it won't sound anything like that in the end, least of all due to the additional drywall to be added at later date. Moreso, it won't sound great, I'm guessing, if there's no carpet down yet, no furniture, etc. It will probably have more of an echo effect with the back experimental wall in place, and that could throw off your perception in an unrealistic simulation of the finished product.

Regarding the wire, I put the wiring for all surround and the video above the dropped ceiling so that it could be accessed for later replacement if so desired. I made the access from the ceiling into the side walls such that new cables could be pulled. It's not very likely you'll change that wiring often, but you may want to think twice before burying it under drywall ceiling. Your call...

Since you do not have the walls done, you still can save yourself... by finishing your walls in exceptionally soundproof style. I used hat channel (2 leg) on the exterior walls of the room facing the inside of basement. Then I used Homasote (from Home Depot; a sheet compressed paper product for soundproofing) as a first layer prior to drywall. I used 5/8 sheetrock over that. Works fabulously! I ran the screws from the outer later drywall into both the Homasote and the hat channel. The room is like a vault! No sense of hearing room resonance, and that with twin subs!

I would also, if you have the space overhead, consider running the hat channel above on ceiling of room; then use the Homasote as first barrier, especially if there are bedrooms above. In order to have entirely soundproof ceiling (zero gaps) you will need to build recessed sound proof boxes into the joists where the can lights (in order to make this work, you must use mini cans - about 4") will go. make them big enough to have room to maneuver them when you later put up grid and ceiling tile.

Order the hat channel at local Lowes or similar home improvement store at fraction of cost of an audio sound supplier.

Calk very seam and hole. Caulk outlets, etc. Use cable holders to screw the A/V cables to the solid underceiling, so they won't potentially rattle on the grid of the dropped ceiling.

Screw down everything conceivable in the walls when you do drywall. I used approx. 3x the normal amount of drywall screws and screwed into such things as A/C supply duct inside the wall next to the drywall so as to remove any possibility of rattling due to subwoofers.

You have to keep your brain in gear on this project...do not rush it, or you'll potentially regret it.

Yes, this seems excessive, or overkill, but I have an EXCEPTIONALLY quiet room which makes the audio/video experience all the sweeter! WELL worth the extra effort! Cost-wise, it may add another $500-$600 ball park to the project. Most worth it for the super quiet environment in the finished product. If you do it well enough, the room will almost seem like an acoustically separate building.

Remember, going to this extreme will not only save your loved ones from noise (they won't tell you to turn it down!) it will also save YOU from their noise like wallking on the floors above you!

One last thing; if you decide to go this route, with the solid soundproof ceiling under the dropped ceiling, draw out both your electric and A/V cabling schematic a few times to make absolutley sure you're covering everything, and consider upgrading and adding extra cables to future-proof your system as much as possible.

There is plenty more to consider, but this'll get you thinking.

Thanks for the quik posts , I went to home depot last night and bought the biggest solid door I could find
my deciding factor was a new baby is due in 4 months and I don't want him getting near all those tubes from the monoblocks(Safty factor).My ceiling is only 7 feet, so wouldn't a drop down make it too low? I have been using the poly they make bass traps with all around and plan to put it in the new wall as well then in between the rafters on the ceiling i had planned to put pink insulation over the r-30 but it is very difficult and time comsuming but i dont want to lower the ceiling another inch. I am trying to decided where to put the rack its a brightstar sandfilled horizontal and i had it to the side but I am not sure now? What is Hat?
Thanks

The carpenter came but the electrician no showed so I can make some adjustments like douglas suggested maybe returning the 5 inch cans for some 4inch , my rafters are 9 inches deep what do you make the soundproof boxes out of? I went to the electric whare house today and bought lutron smart dimmers and leviton hospital grade recepticals I wasn't sure what kind of wire would be best for the dedicated lines. So I called VTL and I spoke Luke Manly the man who designed the equipment I just bought (5.5 pre ,TP2.5 phono ,St150,and the mb450) He said to use the 30 amp wire and it would be better if it was sheilded,to keep out rf but most important he said was to make sure all the components where on the same phase in the electrical fuse box,to keep out ground noise...
The door I bought last night was to big .There is a structural beam making it only 75 inches tall and the door is a six panel so it couldn't be cut .I have to go back and get a solid flat that he can cut. I have the option of putting the door in the middle of the left side or at the front closer to my left front channel speaker.Thanks

Tis a dilemma I too have faced. In my case the room is about 14x13 with a eight foot ceiling. From the sound perspective, the folks from the speaker maker susgested the smaller space.As the amp, a tube one, would not have to work as hard. The big issue is really one of family lifestyle. Do you want a room dedicated to music and movies alone or one that will bring in the future pool table and such. You mentioned a former remodel job,consider moving such things as water heaters etc that may be in the wrong location for your needs. Douglas puts some very good points for anyone looking to do this project. Main thing is try to get it right the first time no matter how long it takes, once done you may have little chance to go back and change the configuration. Good Luck

Glen