You're a movie-and-music maniac with the latest, greatest home theater gear. You've just popped for a bright new plasma display, high-powered multichannel receiver, five (or seven!) speakers, and an earthshaking subwoofer. All you have to do is plug everything in, and it's time to rock, right?

Wrong. Unless you've prepared your room for the high-tech thrills to come, you could be disappointed. Electronics makers would like you to believe that an open checkbook is all you need for great pictures and sound — just move that fancy equipment into an expansive loft and you are there.

It's a compelling fantasy, but the truth is that no home theater system can be separated from the room it's in. Hardwood floors, huge windows, vast stretches of flat white plaster — the bare, spare spaces beloved by ad designers — look incredible as the backdrop for Gen Y sitcoms. They're also the stuff echo chambers are made of. Hard surfaces bounce sound around the room, destroying all the localization cues that movie sound engineers worked so hard to record. View a Hollywood blockbuster in a room like this, and it's Excedrin time.

Lesson One: Build it right
Luckily, there are cheap cures for the acoustical nightmares that are most modern architecture. If you're in the pre-construction planning stages, consider "staggered wall" construction. A simple but obscure building technique, it can substantially reduce transmission of sound from room to room, or house to house — especially bass signals, the bane of neighbors everywhere. Use two rows of studs instead of one, with those on one row offset from those on the opposite row (see illustration). Stuff the bays between the studs and the ceiling joists with standard fiberglass insulation, or acoustical-grade insulation if it's within your budget.

The air gap and lack of mechanical coupling between walls reduces sound transmission between rooms.

Stronger is better: Sheetrock is an egregious sonic offender. It's reflective through the midrange and high frequencies, and transparent to bass frequencies, like a drumhead — exactly the opposite of what you want in a home theater. "Sheer-wall" construction can help tremendously. Required by law in earthquake country, it means screwing plywood to the studs before applying the sheetrock. The result: stiffer, stronger walls that keep the bass in the room where you want it, rather than sending it down the hall and out the door.

You can exploit these two techniques — insulation and sheer-wall — even if you aren't doing new construction. Stripping a room down to the studs, insulating, sheer-walling, and re-sheetrocking are messy, time-consuming jobs, but the materials are cheap and the results rewarding. If you want to go this route, consider the services of a home theater installer to help you run all your cabling while the walls are open. Use flexible conduit with "pull wires" in it for future upgrades.

Lesson Two: Randomize reflections
If you live in a rental where you really can't make structural changes, there are still plenty of cheap tweaks to improve your system's sound. The home theater guru's prime directive: break up those reflections. Great theaters and concert halls don't have flat surfaces — they have uneven, non-parallel surfaces that randomize reflections so that most of what you hear comes from the performers and not from the room.

Bookshelves provide an uneven surface which helps randomize acoustic reflections; they're great for improving your room's overall sonic performance.

You can emulate this with rugs, draperies, furniture, and the all-time best acoustic treatment — loaded bookshelves. Have you ever noticed how quiet libraries are? It's not just because of the "No Talking" rule — it's because books absorb sound and randomize reflections, just like the high-tech "abfuser" (absorber/diffuser) acoustic treatment used in recording studios.

Bookshelves are the classic solution for storage and display. I sometimes recommend IKEA's modular "Billy" units — they are inexpensive, good-looking, easy to assemble, and can fit almost any space. Install your bookshelves across the back wall in your home theater, and load them up with books, DVDs, CDs, and art objects. Your rear/surround speakers can go on an upper shelf, toward the outside. There's even space behind them to hide your speaker wires.

Lesson Three: Defeat the glass ceiling
Glass is another problem — windows, framed art, and coffee tables all need some treatment to break up acoustic reflections. Drapes or curtains are the obvious fix for windows — you also need to block external light to see movies as they were meant to be seen. Hard-surfaced coffee tables are seldom recognized as acoustic problems, but they are. Think about it. There's a large acoustic reflector a few feet from your face. Covering it with fabric, like a small rug or tapestry, will help immensely. So will throwing a few magazines or small pillows on it. Even better: replace it with wicker. Import stores have a huge selection.

Avoid sound-muddying reflections by using drapes over larger windows, and hanging paintings instead of glass-framed prints.

Another common problem: framed art covered with glass or acrylic. The glass bounces sound back into the room rather than diffusing it. Try moving such pieces to other places in your home, and hang actual paintings instead. Sound expensive? Maybe you can't afford an original Picasso, but art schools in every city have sales of student work, much of it excellent and quite affordable.

The sonic advantage to real paintings, as opposed to prints, is that the surfaces are rough ("impasto" in art parlance) and the canvas breathes. There's also an inch or two behind the painting to mount acoustic treatment — a rectangle of corrugated foam rubber or pressed fiberglass panel, or even a piece of styrofoam covered in fabric. Support the arts! Not only will you be upgrading and personalizing your décor, but you'll be making your theater look and sound great.