If you are considering the addition of a home theater, you need to pay close attention to the room's acoustics. A room with the proper acoustical treatments and only average gear will easily outperform a room with great gear and poor acoustics. Typically the weakest link in your system's playback chain will be your acoustical environment. This is because when you are more than a few feet away from the source, the majority of sound comes to you indirectly from the room and not directly from the speakers.
Because speakers spread sound in many directions, the room and its contents filter your systems audio output, exaggerating some frequencies and softening others. The goal of a home theater is to re-create the same sound that that was heard in the studio when the soundtrack was recorded. The problem is that every room and their surroundings and contents have different characteristics that will affect the performance of your speakers.
The first issue you should address is sound transmission, in other words external noise leaking into the room or visa versa. One of the greatest misconceptions in sound control is that absorptive materials such as acoustic ceiling tiles will block sound waves. While absorptive treatments such as fiberglass panels greatly enhance the quality of sound by controlling such unwanted effects as reverberation, they do not act as a sound barrier. In order to stop the transmission of sound you need to add mass and air space. There are many in-wall acoustical materials and techniques to control sound transmission and can be as simple as using multiple layers of drywall, adding mass loaded vinyl, or decoupling walls, floors, and ceilings with isolation clips and resilient channel. When it is not practical to decouple the floor, you can use isolation risers to decouple the loudspeakers from the floors. Another place sound will escape is through doors and framing. Although acoustically rated doors are not inexpensive by any means, if your surrounding environment is noisy and it is within your budget, they are well worth the investment. If you already have a good solid core door, another option is to add an acoustical door seal kit to seal the air gaps at the perimeter and bottom of the door.
Another issue can be intrusive noises from HVAC and plumbing. The steady noise of air blowing through ductwork, or the occasional whooshing of water through plumbing can be enough to distract from the subtleties of the soundtrack, making it difficult to discern dialog. These noises can be controlled by simply applying pipe and duct lagging materials. HVAC Silencers can be placed inline with your existing exhaust and return ducts to quiet blower noise and prevent sound from leaking into other areas of the house that share the same ductwork.
Once you've dealt with the sounds you don't want, you need to enhance or "tune" the room's acoustics utilizing absorptive panels and/or diffusor arrays. Low frequency waves are the strongest and hardest to control, so the best place to start is with bass trapping. To identify where bass trapping is needed, you need to identify room modes based on the relationship between length, width, and height using a room mode calculator. You can also simply play a music sample that is familiar, and walk around the room listening for a buildup of base. This will often occur in corners which are a good location for adding bass traps. To deal with the higher frequencies, as a rule of thumb, a well treated home theater will have approximately 40 to 50 percent of the wall and ceiling surfaces treated with absorption, and the remainder with diffusion or reflection. The most widely used treatment technique is to absorb reflections along the front and side walls, and diffuse reflections toward the rear of the room. The objective is to create a well balanced room that is not too"boomy" on the low end, and not too "dry" on the high end.
While it is always best to seek professional consultation to address acoustical problems at the beginning of construction, there are always ways to improve an existing room's acoustics. Remember that everything in the room has acoustical properties, and in many cases can be used to your advantage. For instance, lining up a bookcase with the spines of the books staggered will offer some degree of lateral diffusion, and a carpeted floor is more desirable than hardwood, since bare surfaces in a room will reflect sound waves, distorting sounds and causing fuzzy dialog. The bottom line is that regardless of your budget, there are always ways to enhance the performance of your home theater system, resulting in a more pleasurable and realistic sensory experience.