Studio acoustics is a large and rather complicated subject but you don’t need to be an expert to do a good job of your mixing or mastering.
I’m going to go through the main points and show you how to easily and quickly achieve a professional listening environment.
When mastering, it is vital that we are able to accurately monitor the sounds that we are working on. A major part of this is the build quality of the speakers and how flat – and therefore accurate – their frequency response is.
However, an occasionally overlooked yet vital element is the design of the room within which we’re working.
A fantastic monitor speaker response would be practically wasted in a room which unduly colored the sound they produced. As an extreme example, imagine setting up your speakers at one end of a tunnel, then trying to produce an accurate mix from the other. As you can imagine, the physical manipulations of the tunnel will warp the direct speaker sound, completely changing the way we perceive it.
Although less obvious, an unsuitable mastering environment can also be quite harmful to the end result.
Depending on its size, shape and reflective characteristics, certain frequencies – or bands of frequencies – can be perceived at different levels from others. If the room happens to reflect more higher frequencies than others, then the sound you are hearing may appear brighter than it really is. If the room exaggerates the low end, then the speaker sound will appear to have more bass than is actually in the mix. Similar to how the speakers have a ‘frequency response’, the room’s response to different frequencies will vary also. The more ‘neutral’ our room’s response, the more accurate the sound reaching our ears will be.
So before we discuss factors like monitor placement and acoustic treatment, let’s first look at one of the most fundamental aspects which influence the way we perceive sound within the room – the size, shape and raw surface materials of the room.
Size and Shape
The worst-case scenario for a room would be a perfect cube with flat walls, floor and ceiling.
Apart from the walls, floor and ceiling allowing the sound waves to reflect around the room, changing the way we perceive the sound (which will be discussed shortly), the major problem is the cube shape itself as it causes a specific set of frequencies to appear to be louder compared to the speaker sound, particularly in the lower frequencies. This is due to a phenomenon known as ‘standing waves’ – sound waves that literally become trapped between parallel surfaces such as walls, bouncing back and forth, overlapping with each other perfectly, reinforcing themselves every time.
Rooms with parallel walls will ‘resonate’ at certain frequencies. The frequency at which resonance occurs is referred to as the room’s ‘mode’ and is directly related to the distance between the walls (a sound wave’s frequency is directly related to its physical length in meters).
No matter what distance the parallel walls are apart, a sound wave of some frequency will be able to fit exactly into that space, then flip over when it hits a wall and go back the other way, perfectly in time with its immediate following sound wave (at that same frequency). Theory states that when you allow two identical sound waves to add together, they double in size.
Interestingly, half that frequency can do the same thing – it hits the wall, flips, then goes back, meaning it fits itself in between the walls after two trips. This adding also occurs when the frequency is doubled, quadrupled, octupled and so on, as they all still fit perfectly into that space.
When this reinforcement happens, a doubling of sound pressure will occur for that particular frequency, which can work out to a 3dB rise in audible level in the main area of the room. Quite a dramatic difference where audio accuracy is concerned.
What you will also find is that depending on where you are sat, you will experience differences in the way the room resonates. Two identical waves overlapping will increase the audible level of that frequency. However when two waves overlap whose wave cycles are opposite (anti-phase), a cancelation will occur giving the perception of a reduction in that particular frequency. The overlapping of identical waves is known as ‘constructive interference’, whereas the overlapping of anti-phase waves is known as ‘destructive interference’. Some areas of the room may cause constructive interference, while other areas may cause destructive interference.
Where possible, choose a room that deviates from a cube, ideally one that is fairly symmetrical, with slopes, uneven features and details that help to redirect and diffuse reflections and lessen the impact of resonances. If this is not possible, don’t worry as I’ll be showing you how to lessen the impact of resonances using other methods.