You might be confused if you had to place your sound diffuser without any technical knowledge. Some of the locations where you can place them, keeping in mind that you can put them just about anywhere reflections are expected to be. Every room is different and has to be treated accordingly, but what I suggest is to try and place your sound diffuser in different position until the desired effect is achieved.
Rear Wall of Your Control Room
If you might have noticed, this is by far the best location in control room where the diffuser can be placed. I would choose to place it in the same location as I have seen them placed in many other professional recording studios that I have been to. This does not mean that other design concepts will not work, but you can be rest assured that countless sound engineers have chosen the rear wall as prime location for diffusion.
Diffuser placed on the rear wall will make sure that the sound coming out of your monitors will be redirected in a number of directions around the room. As a result, you will experience better sound quality. Just to remind you that many control rooms are designed with heavy absorption at the front, hence it is recommended to place the diffuser at the rear wall for better sound.
Ceiling Acoustic Treatment
Sometimes we forget about the ceilings which is an open space right above our head. At the time of mixing or tracking we forget that our ceiling has the capacity to produce flutter echos, keeping in mind that the ceiling is often the closest surface and fastest reflection that you will experience as compared with the rest of your walls. As this is the only surface left untreated, it can blur the stereo field and create all kinds of other issues, especially in the higher frequencies.
Make sure that the ceiling has been treated well and there is no flutter echo in the listening position. Once everything is in place, you will notice the difference immediately.
Spaced Around Side Walls
In most cases you will find live rooms or performance spaces that are large in area but yet untreated. It is not practical to have tons of absorption on these walls as the natural liveliness should be preserved. Even in smaller spaces, placing diffusion around side walls periodically can help add to the complexity of reverb and reflections bouncing around the room, yielding a natural sound with more balanced decay.
It is very important to have a sound diffuser that will improve the quality of sound in your recording studio and performance hall.