To a greater extent the quality of the sound of low frequencies depends on the size of the mixing vocals over instrumentals and the arrangement of monitors. It’s explained by a large length of LF-waves on which materials of walls, the floor and most ambient objects are almost out of power to have influence. When LF-wave hits an obstacle, it is almost all reflected back.
If you use a subwoofer along with monitors, you should place it at an equal distance from the three nearest side surfaces of the room as some low frequencies are enhanced by the reflecting surface which is the nearest to the subwoofer.
When reflecting surfaces are at an equal distance from the subwoofer, the enhancement of some low frequencies will be excessive what can bring on a powerful rambling at these frequencies.
With the help of proper arrangement of monitors in your studio you can regulate LF-reflections and resonances to a great extent. With proper position set you'll be able to achieve sound quality like in the following demos of music mixing and mastering.
You should pay special attention to the distance between monitors, the front and back door. The more nonparallel and geometrically different the front and back door will be, the less undesirable resonances will be from emerging standing waves that cause unacceptably gross distortion of FRF.
5. To define the best possible distance between monitors, the audio engineer should play and listen to recording distinguished by good focusing of the central image. Set monitors at the distance of nearly 1–1.2 m from each other and point them at your head.
You should give it a listen whether the sound has been focused properly. Increase the distance between monitors by 10–15 cm and listen out again. Keep repeating these manipulations until the center of the stereo picture starts getting fuzzy.