Many scientific calculations can indicate the position where is a best for placing loudspeaker in room based on the principle and calculation via three-dimensional space. However, it is difficult for players to arrange position of loudspeaker at most reasonable place in normal condition.

Listening room. Photo: Tiscali

In order to understand supportable instructions, you should clearly understand some basic issues about how to transmit sound when they go out of loudspeaker at first. All surfaces of room and objects in this room are all sound reflects and the thought that sound just goes straight from loudspeaker to listener’s ear is not accurate. In fact, there are numerous sound waves to your ears through reflections with object, wall or floor in listening room. Stereo images are also created from phase; however, the exactly positioning of images can drop by reflections. Factors such as sound or color of sound, the nature of musical instrument, and the clearance of singing voice will also be affected by many combinations of straight and echo sound.

To avoid echo sounds, many experts advocate placing loudspeaker at "death" area in the listening room where sound reflections will be at a smallest level; for example, placing loudspeaker near walls hanging thick blind. The handling of sound in listening room is to cancel a part of these reflective sounds. If you want loudspeaker to play exact sounds according to technical analysis of frequency that the manufacturer has indicated, you have to put it in areas without sound refection, or "death" region of listening room. However, in this case, your ampli must have greater power than there is no sound-proof.

Behind and side walls also help multiply the capacity of sound. Photos: Diginteriors

So, how about the sound when a room usually does not have sound-proof is? Thanks to sound reflection from behind and side walls, the sound will be "multiplied capacity" and entirely larger compared at the time there is sound-proof. Just a little more size, you will have a sense of being confused, being sonorous with bass, etc. It doesn’t entirely have any magic here. You can try to put a loudspeaker outside the garden, the sound will be very small and lacking vitality compared with placing it in a standard room.

One of the sound-proof matters for loudspeaker is that all devices absorb sound as blind or carpet  used in room will restrict mid and high sound reflection (from 500 to 20,000 Hz) very well, but badly or completely does not work when experiencing low frequency (less than 200 Hz). And low frequencies are always most amplified by room, in many cases, to 12 dB at below 100 Hz. Placing loudspeaker at "death" area will only achieve an effect on mid and high range, the rest will make low frequency more serious.

A corner placing loudspeaker. Photo: Acoustics.

To evaluate the effect of walls and floors for low frequency signal (under 200 Hz) of loudspeaker, people made an example of placing a loudspeaker in many different locations in the room. Put loudspeaker on the floor (or put back to the wall on a high platform or rest), the sound compression level increases at tolerance of 6 dB. If put the loudspeaker on the floor and back to the wall later, the sound compression level increases approximately 12 dB. But if you put it into the right corner, the sound compression level will increase to 18 dB. With most of us, if your loudspeaker lacks bass, the easiest way to use low frequency amplification factors is to place the loudspeaker near behind wall (Bookshelf loudspeaker still must have the loudspeaker’s base).

Result, if we move the loudspeaker closer to behind wall, the bass signal of output will be increased and also very good to combine it with listening room based on the room’s size placing loudspeaker.

On the contrast, if you move the loudspeaker away from walls, the bass signal of output will be reduced and also very bad to combine it with the listening room. This is the first method that you can adjust the bass mode for loudspeaker due to most loudspeakers can be balanced between bass and treble by moving the loudspeaker closer or farther to behind wall.

You can also avoid listening room mode does not like by adjusting sitting position. Let's consider what happens if you put loudspeaker back to wall at the end of room while you sit on chair at an opposite position in the room. In this case, not only a loudspeaker with listening room mode at a point of increasing bass but you are also sitting at the right point that has a high sound pressure. According to the calculations and practical experiences, with low frequency ranges under 50 Hz and an increased slightly intensity, the majority of listener is not affected and in fact, players who are keen on sweet sound will still feel comfortable. But with the level of different frequency range from 70 Hz to 120 Hz, the listener will feel very tired. In this case, let's move sitting position in room to place of loudspeaker.
 
(To be continued)
(According to Audio-Visual)