There are two main aspects when it comes to control room troubles. Reflections of mid range and high frequencies from hard surfaces and peaks and troughs in the room's low end response caused by the rooms dimensions and the reflectivity of the walls at low frequencies. Both of these will effect what you are hearing from the monitor speakers and have to be dealt with in different ways. Here is a picture of a typical home studio recording and mixing environment:
In professional studios there are a lot of techniques you can do with wall angles to divert reflections. As most home studios are rectangular there are many potential reflections in a room, these should ideally be absorbed or diverted. Reflections from the desk and other equipments can be a big issue so it is important to set up the monitors in the correct position. The monitors should also be stood up not lying on its side as this will compromise the stereo image significantly. The speaker should also be on a stand at head height with drivers pointing towards your head. You should ideally avoid putting monitors to far in the corners and they should be placed symmetrically in the room. hardware computer screens or racks come in the way of you and your monitors Unwanted reflections meed to also be considered as mid range and high range frequencies can reflect from hard surfaces such as plasterboard walls. This results in the sound energy being scattered, having the speaker next to a hard wall will result in the same effect.
Most home studios will have have rectangular rooms. Once the main reflection points have been identified then you can place treatment there to absorb the sound and kill the reflections. Absorber panels will need to be fairly large so they can cover all of the reflection points. Understanding the limitations of the materials such as foam is an important factor. A thick black cloth can be placed over a mirror to absorb visible light of its reflection. A piece of acoustic foam will only be acoustically black at high frequencies and transparent at lower frequencies. For example four inch thick foam stuck directly onto the wall is only mainly effective at frequencies above 200-300Hz. A two inch foam is only effective above 400-600Hz. If you halve the thickness of the foam the frequency above will move up by an octave.
The diagram below gives an indication of best position of monitors. Note the points on an equilateral triangle give best positions for the speakers and the listener.
In most home studios dealing with reflections correctly can help improve the stereo imaging and focus of the sound. Bass treatment will be needed as bass problems are linked with room modes which depend on a room's dimensions.The smaller the room then the wider spaced the modal frequencies will be. This means that bass response will be more uneven. Depending on the room dimensions some of the bass frequencies will be cancelled due to reflections coming back of the wall. Small room have problems that are in a cuboid shape. Low frequencies are normally treated with foam or rockwool. The treatment needs to also be relatively thick and also carefully positioned. If there is a deep ceiling void you can utilise this by cutting large holes in the ceiling and putting Rockwool, after this the holes can be covered with acoustically transparent fabric. The same applies for fireplaces, alcoves and other unused places. Once you have correctly addressed the acoustic problems with your room you will find that your mixes translate much more evenly on different speakers.
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