Your room has significant impact on the audio that you hear from the audio system. The walls, furniture, mirrors will have effect on the sound quality. These room factors causes harm to the bass frequencies generated by the subwoofer. Where you place the subwoofer in the room is extremely important.
Unless you are a guru in acoustics and have deep understanding of the audio video equipments it is always a trial and error method that you apply to get the optimal performance from your subwoofer and enjoy the music to its fullest. However this is not a rocket science and anyone who follows some of the tips mentioned here would be able to get the optimal performance of the subwoofer.
Subwoofers are normally heavy and bulky and lifting them from one place to another may not be possible all the time. Their biggest enemies are the parallel walls in your living room. The bass waves the subwoofer generates are Omni directional. The waves bounces all over the room, they bounces back from into one another either nullifying the bass or creates standing waves.
You have option of changing the room acoustics by giving some acoustical treatment and also placing the subwoofer in an ideal place or get a high end equalizer and buy some sound correction software. We will talk about the first option as it is the ideal and cheapest option.
Which is the ideal place?
The usual place of the subwoofer is normally the corner of the room but remember it is not always the ideal place. It will generate more bass, but may not generate the best bass. Subwoofers will give good performance if they are placed closer to your front loudspeakers. This helps in reducing the time delays and phase cancellation.
If you have enough space in the room and can keep subwoofer anywhere, you can place the subwoofer at one location and check where the bass is even. You can play some heavy bass music to check the same. You generally will get couple of spots from which you can choose the most convenient place.
By placing the subwoofer at the front will also reduce the standing waves and chances of getting good bass are high.
If corner is the only option, then put some cushions like tennis balls or rolled up socks surrounding the subwoofer and place it at least 6 to 8 inches away from the all corners.
One should avoid placing the subwoofer in a cabinet. The low frequency waves get killed inside the cabinet and you will defeat the purpose of having a subwoofer.
Now-a-days there are options where the subwoofers can be placed on the walls. However you need sturdy stands fitted into the wall and need some expert advice in installing them. If done correctly, this is an effective solution.
One must think about the crossover settings also while setting up the subwoofer. The point at which a speaker stops producing bass and the subwoofer takes control is called crossover. Crossover setting is very important in getting the best possible bass. Determine the best crossover settings for your system by yourself. General recommendation is to keep all speaker frequency at 80Hz.
You also need to remember that concrete floors reflect sounds much so get a carpet or rug. Getting a permanent subwoofer stand would also help in improving the sound quality.
One can try combination of the options mentioned above to get the subwoofer work with optimal performance.