Project Studios
The most common recording environment is the project studio. This ‘all in one’ environment generally combines the control room with sufficient space to record guitars, bass, keyboards and manipulate the tracks in the digital domain. These multi-purpose environments can range from basic acoustic treatment using a London 12 ‘studio in a box’ and be augmented with high performance bass traps, ceiling clouds and diffusers.
Acoustically treating a recording studio comes down to creating a neutral listening environment that will allow one to record, mix and produce music with confidence so that when the music is played on other audio systems, it will sound balanced – both with respect to spatial placement and frequency response.
Spatial balance
Spatial balance in the studio begins by locating the listening position where acoustic wall treatment and distance to the walls is a balanced as possible on both left and right sides. For instance, sitting with a reflective surface like a window on the left and then having a bass traps and acoustic panels on the right will certainly distract from creating a balanced recording. The brain will have a difficult time attempting to balance the auditory clues in such an extreme environment. And although it is preferable to eliminate parallel walls, most recording spaces are in fact built in rectangular rooms as these are the most common and economical to construct.
Start by sketching a plan drawing to the scale of your room showing the doors, windows, cupboards and anything else that you cannot move or change. Then place your work surface and chair in the room in such a way that you can create a balanced stereo field. This means you should try to have the left side and right side balanced. If at all possible, stay away from the middle of the room as this tends to be the worst place to sit. This is also a good opportunity to look at natural diffusers such as corners, columns and stair cases to see if you can take advantage of them.
If you have a room that is lopsided, such as an L shape, sometimes placing the ‘mix position’ in a corner can present a viable alternative. And even if your room is not perfectly balanced, your brain is a lot more powerful than you may realize; it will automatically ‘fill in’ or ‘remove’ the auditory cues as you get used to your room.
Balancing the Frequency Response
Probably the single biggest misconception with acoustics is that if you put some type of treatment up on your walls, you will improve the sound of your room. Truth is; bad acoustic treatment can just as easily do as much harm to your room as no treatment at all. In many ways, one should think of acoustic treatment exactly like you would a microphone, preamplifier or speaker system. Your room treatment should be ‘linear’ or ‘flat’. In other words, just as you would never use a microphone that cannot capture bass, or a speaker with a blown tweeter, you should not treat high frequencies without also considering what to do about the mids and lows.
As a general rule, the longer the wavelength you wish to absorb (bass), the thicker (and denser) the absorptive material must be. So if you put a thin piece of carpet on the wall, you may remove some high frequency ‘ring’ from the room, but this will have no effect on the bass and your room will end up being bass heavy. It will not be balanced. And when you record, because the bass will be more prevalent, you will likely reduce the bass content when you are mixing. When you play your recording on another system, the bass will be lacking.
The good news is that just like audio equipment that is specified with a frequency response curve, acoustic panels are specified in a very similar manner. The curve that is used is called the absorption coefficient. It is basically a graph that shows how well the acoustic panel will work at a given frequency.
Sound Absorption Coefficient
This graph compares two acoustic panels. One is made from low density urethane foam while the other, a high density 6lb Broadway glass wool. As you will note, even though both panels are 2" (5.08cm) thick, the performance of the panels vary immensely in the bass region. This is due to the density of the panel. This is the primary reason Broadway panels are made from high density glass wool… it provides better balance across the full audio spectrum.
2 " (25mm) Broadway
2" (50mm) Auralex Managing Bass
The most challenging aspect to achieving a good sounding room is managing the bass. Most small studios suffer because the size of the room is incapable of handling the pressure that the bass will develop; the low frequencies extend beyond the room's physical size; and room modes cause inconsistencies. Depending on where you sit two frequencies can combine and cause a peak when in phase or a valley when out of phase as they cancel each other out. Bass traps are used to attenuate the bass and reduce the effect of modal interference.
With acoustics, corners are your best friend. The walls and ceilings act as wave guides that cause sound to migrate into the corners where energy builds up. It therefore makes sense that we target the corner as the first place to position our acoustic panels. Primacoustic offers a variety of corner solutions including the Cumulus tri-corner trap, the Australis, the MaxTrap and the FullTrap. The London 12 comes with two Broadband Absorbers and corner mounting hardware that create a deep air cavity behind the panel. This effectively increases the bass performance by trapping sound behind the panel.
A good rule of thumb is to apply 25% of your panels to managing bass. This generally results in a fairly well balanced room and you can always add more if you find your mixes to be ‘bass light'.
How much absorption do I need?
Creating a comfortable recording space is a matter of taste. Some engineers prefer a more controlled environment while others prefer a more natural feel. More controlled spaces are achieved by adding more acoustical panels. Darker rooms tend to allow you to better pinpoint issues such as spectral balance, depth of field and instrument placement. Livelier rooms tend to sound more natural. There is no ‘right or wrong’ when it comes to creating a recording space… it comes down to personal preference.
To get you started, we have created a selector chart that will help guide you to achieving a comfortable working environment. Start by determining the size of your floor area and then go to the table that coincides with your ceiling height. You can then choose the level of absorption that you feel will meet your preferred working environment and budget. If you are not sure… start with less. You can always add more!
Example:
Say your room is 14' x 15' with an 8' ceiling (4.27m x 4.57m with a 2.44m ceiling) Total square footage: 210 sq-ft (19.51 sq-meters) Go to the table with 8ft (2.44m) ceiling and choose between minimum (budget), light, medium or dark coverage.
For light treatment, we would need to apply about 90 sq-ft (8.36 sq-meters) of surface area. You could start with a London 12 room kit. This comes with 70 sq-ft of coverage (6.50 sq-meters). Then add another 3 or 4 Control Columns to tighten things up. Keep in mind that it takes some time to get used to your room and to make the adjustments to make your room sound right for the way you work.
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Radial Engineering Ltd. Copyright 2010. All rights reserved.