1. Why build a stage for a screen? Why fill it with sand?
2. I see some soffits with hvac flexible ducts. Are these used to heat/cool the room? If so why don't I see where the outlets are?
3. Why have a drywall ceiling in a basement theater? I thought a suspended ceiling would be better as far as accoustics are concerned. It would also be easier to feed wires across the ceiling. Presently I use 2x2 commercial grade ceiling tiles and have never had ratteling issues.
4.If you put the speakers behind the screen doesn't that ruin the sound? I have Def. Tech. speakers and could never see putting them behind the screen, or any other speaker for that matter.
5. I see some very nice and expensives theaters built, but then small monitor speakers being used. Why not go bigger & better?

TIA,
Ken

4.If you put the speakers behind the screen doesn't that ruin the sound? I have Def. Tech. speakers and could never see putting them behind the screen, or any other speaker for that matter.
5. I see some very nice and expensives theaters built, but then small monitor speakers being used. Why not go bigger & better?

I can answer 4 and 5....

4. As long as people use acoustically transparent material there is no effect on the speaker sound also speakers that are behind the screen are not rear ported generally

5. Bigger does not mean better whatsoever. Front speakers are for mid and high range (80hz and above) in my opinon and the Sub(s) handles the low freq. stuff. Monitor and bookshelf speakers are very popular for HT.

1. Why build a stage for a screen? Why fill it with sand?

You can search on this question to find a lot of answers. Basically, a lot of people like the look. Some prefer the look without a stage. Filling with sand is to decouple speakers or subs that are placed on the stage.

2. I see some soffits with hvac flexible ducts. Are these used to heat/cool the room? If so why don't I see where the outlets are?

Just becasue the duct runs through the soffit doesn't mean the outlet is in the soffit. They might be going other places int he house, as well.

3. Why have a drywall ceiling in a basement theater? I thought a suspended ceiling would be better as far as accoustics are concerned. It would also be easier to feed wires across the ceiling. Presently I use 2x2 commercial grade ceiling tiles and have never had ratteling issues.

Drywall looks better than a suspended ceiling, IMO. And if you care about sound isolation (different than in-room acoustics), drywall is infinitely superior.

4.If you put the speakers behind the screen doesn't that ruin the sound? I have Def. Tech. speakers and could never see putting them behind the screen, or any other speaker for that matter.

Those that put there speakers behind screens use acoustically tranparent screens that are designed to let the sound come through unaltered. However, some would agree with you and say that there is no such thing as acoutcially transparent. There is only "more transparent than others".

5. I see some very nice and expensives theaters built, but then small monitor speakers being used. Why not go bigger & better?

Simple - bigger isn't necessarily better, There are some very, very nice monitor speakers on the market. Larger speakers will usually be more efficient at bass reproduction, but with a proper subwoofer, that might not be an issue.

Hope this helps.

1. Aesthetics - the front wall can sometimes look a bit bare without one. Practicality - it can help steer people away from your screen and speaker setup. Acoustic isolation - if built and isolated properly, speakers and especially subs are sitting on a heavy damped platform and not directly on your floor, where it's coupled to the room. Some fill with sand, others with insulation. It's for reducing cavity resonance and/or damping.

2. Quite often the soffits are there to hide ducts carrying air to other parts of the home. The flexible acoustic ducts do a better job at isolating noise from the HVAC system than regular rigid duct.

3. Aesthetics - drywall just looks more finished. It has much better acoustic isolation if techniques such as double drywall, RSIC and/or green glue are used. Ceilings are often not treated for internal acoustics depending on the room, or else treated in other ways, like with a cloud panel. But utilities are easier to manage with a drop ceiling. It's a tradeoff.

4. Screens with speakers behind them are designed to be acoustically transparent. Fabric panels with speakers behind them are too. Testing on GOM and many AT screens show a typical high-frequency rolloff of about 1-2db at 10,000hz+ - tough to detect in a blind test with the very best materials, although some have reported a difference with lesser fabrics.

5. Sometimes it's space limitations (often depth behind screen), other times it's because of already owning equipment or simply preference. At any given price point, bigger doesn't necessarily mean better, especially in HT where subwoofers for LFE are such a priority. I would personally rather take an exceptional minimonitor and superb pair of subwoofers over an equivalently priced tower.

Try searching and reading the various threads on all those questions and you will gain a fuller understanding. By the way, NOTHING beats good speakers behind an SMX At screen for a great movie experience, with the sound coming from the screen and the characters as it should.
My Speakers are REVEL Performa Series, and they are fantastic behind my SMX screen.

Thanks for all the info.
McCall, I still don't think Bi-Polar Def. Tech's are meant to go behind a screen. Defeats the purpose of rear-radiating section.