Unless you’re sitting in an air raid shelter, I assume that your room has at least one pane of glass. Unfortunately, these tend to make the sound “clink”. Especially if the monitors are placed directly in front of the window, this can lead to unwanted effects, such as overemphasis of certain frequencies and distortion of the stereo image.
That’s why I recommend hanging a thick curtain in front of each window, which also works as an absorber. Not beautiful, but practical are thick velvet curtains. With this, there should be no more problems as soon as they are drawn.
Just like the window pane, the floor and ceiling reflect very strongly. That is precisely why you should not disregard them in any case. Especially broadband absorbers on the ceiling have an enormous effect on the sound of the room.
If you don’t already have carpeting, for example, in larger rooms you can pimp the sound with individual carpet elements.
Furniture also absorbs a variety of frequencies. A large couch in particular likes to absorb bass. However, these are mostly random products.
To obtain a reliable result as to whether the current setup produces good surround sound, you can use a measurement microphone. The measured values can then be used for targeted optimization. The measurement microphone should definitely be placed in the position of your listening position (in the sweet spot).
This is especially true of those people who like to do a little too much of everything. A room should sound and not be dead. The ideal value is the so-called RT60 value at 0.3 seconds. This value describes the decay of a sound source of 60dB.
If you completely wallpaper the room with absorbers, it sounds too dry. This is definitely more of a disadvantage than an advantage. A room that is too dry also puts pressure on the ears and is perceived as unpleasant.
To minimize the mid- to high-pitched flutter echoes in the room, so-called diffusers are used. As a rule, several of these elements are mounted at eye level in the room.
The frequencies want to spread out in the room. Unfortunately, this is even more difficult, especially in small rooms. The listening position is ideally ⅓ of the room away from the wall.
If this is not possible, every meter that the boxes are away from the wall counts.
Often it is small optimizations that solve big problems. Bass absorbers alone will improve the sound of the room on guarantee.