Studio Monitors Part 3: The Feng Shui of Monitors
By Glen Stephan on September 27 2008 01:00 PM | Permalink | Author Info
The ancient Chinese may have been on to more than they realized when they developed their concept of "feng shui"; the idea that one can cultivate positive energy through the proper physical placement and alignment of our living spaces. That may not have been that far off. It turns out that the performance of our nearfield monitors is inextricably connected to their location within the room and the condition of the room itself.
ACOUSTIC FENG SHUI
OK, so after reading parts 1 and 2 of this series, we’ve picked out our favorite nearfield monitors.
We’re only halfway home. Just as important as monitor selection is the room in which we put them and how we place them within that room. There’s nothing like bad speaker placement in the wrong room to cause us to make bad mixes on even the best studio monitors.
There are a few simple rules and guidelines on speaker and workstation placement we can follow along with some basic and inexpensive room treatments to ensure that we are getting the most out of our monitor investment and that our mixes come out clean and true:
If we are converting an existing room of our house or garage to a small project studio, and if we are lucky enough to have a choice between rooms, generally speaking, the larger the room, the better it will sound and perform acoustically. Unfortunately, the more likely the wife will be to want a divorce. At least I hope that’s unfortunate news to you.
Note that room size means all three dimensions of length; width and height need to be considered. When building a new control room from scratch, acoustic engineers usually recommend a total room volume (L x W x H) of 2500 cubic feet or more. This is a pretty large room, and one that most of us who have to work with existing conditions in our home or garage don’t have as an option. But we do know that we can try to pick as large as possible.
Note that we’re talking all three dimensions. This also means that if we have a choice between rooms of similar length and width, but one has a 7ft. ceiling and the other a 10ft, ceiling, that the taller ceiling will usually be better for our purposes.
THE SHAPE I’M IN
The shape of the room is also important. A perfect square or cube is not good; this tends to cause an unnatural buildup of sound towards the middle of the room. We should instead try choosing a room that has differing dimensions for length, width and height. At the same time, though, we do not want one dimension so narrow so as it will be hard for us to put our monitors in a position where they are not too near the side or front walls (more on this in a moment.) A shoebox-shaped room is no good if the sides of the shoebox are too close together.
So we should ideally go for high ceiling, if possible, and non-identical length and width, but not so narrow in either dimension as to cramp our style.
At the beginning, most of us are tempted to set up our desks in the corner of the room in order to maximize space. This is perhaps the very last place we should set up our workstations. Sound waves tend to get reflected, bounced around and amplified in all sorts of bad ways in the corners of rooms.
This means that ideally we want to place our monitors symmetrically in the room, away from the walls and corners. In general, we’d like to place the monitors centered L-to-R along the shortest wall, facing into the longest dimension of the room. This is because the ugliest frequency build-ups tend to happen closest to the rear wall. Therefore the farther we can push the rear wall back away from us, the better off we will theoretically be.
In order to have an accurate stereo image from our monitors, we should set up our workstation so that the distance from each monitor to the back of our head is the same and the distance between our monitors L-R is somewhere between 3/4ths and 1.5 times distance from each monitor to the back of our head with our monitors forming the base of the triangle parallel to the front wall and our head just inside the apex of the triangle.*
Note, however, that we do not want our nearfield monitors pushed back against the front wall or set up in the corners of that wall, as that has a tendency to unnaturally boost bass and muddiness. A minimum distance of 1.5-2 feet from walls and corners is often cited.
Ideally, if we can set things up so that our listening position – the position of our ears - is 38% of the distance from the front wall to the back wall, that is the area where acousticians tell us we often should encounter the least acoustic problems. If the room is large enough, we can use that as the measurement to the point of the triangle, and then just place the monitors at the base corners of that triangle, leaving any excess room behind the monitors.
Note also that this triangle should lie parallel to the floor; i.e. the centers of monitors should be at about the same height as your ears.
A LA MODE
Rooms share something in common with things like guitar strings and drums, they all have a tendency to want to vibrate at certain preferred frequencies determined by its dimensions. These are called their resonant frequencies. Any sounds coming out of our monitors at the resonant frequencies (or their harmonics) of your room will be strongly affected by the very presence of the room itself. It’s like playing music inside of a drum.
These resonances form a wave-like pattern in the room, a patchwork quilt of peaks and valleys called “modes”, where the affected frequencies are alternately boosted and attenuated. Bass frequencies are those most affected, because those frequencies are the ones with wavelengths on the scale of the size of a typical room.
Perhaps the biggest problem many home recordists have with their setups is they just can’t get the bass in their mixes to translate properly to the outside world. Their mixes wind up either too muddy or too anemic in the bass region. I’d bet that nine times out of ten this is because of their room setup and because they are sitting right in the middle of a positive or negative bass mode when they mix.
This is why seasoned engineers almost always recommend that one of the first things that the new home studio builder should do is invest in what are called “bass traps”. These are specially designed acoustic panels or tubes that are placed in the corners and wall edges of the room (starting with the rear walls mostly) and serve to tame the severity and effect of bass modality in the room.
There are many excellent manufactured bass traps available via the Internet. The better of these providers also provide instructions on how to build your own traps on the cheap from materials that can be bought or ordered from your local building supply store. Go with what your budget will allow.
ON FIRST REFLECTION
Unlike bass frequencies, which fill the room with a patchwork of peaks and valleys, high frequencies tend to shoot in straight lines and bounce off of smooth, hard surfaces. This can cause problems with first reflections – the initial bounce of high frequency sound off of a wall or ceiling back to the engineer’s ears. Such reflections can cause problems with esoteric names such as comb filtering and flutter echo, which can affect our mixes just as badly as bass modality can.
For this reason, broadband absorption panels (or, at least very thick drapes) are usually recommended at each point on the walls, ceiling and floor where the mid and high frequencies coming out of each monitor can bounce once and come back to our ears. The first reflection points are those points on the wall where if you put a mirror there, you could see the source monitor in it from your listening position. See the yellow paths in Fig, 1 for typical first-reflection paths for all four walls in a typical room (ceiling and floor paths are not indicated in this diagram.)
GETTING MORE DETAILED
This article and diagram discuss in broad strokes just some of the basics regarding the Feng Shui of mixing room and monitor setup. This topic will be covered in more specific detail, including some interactive design and calculation tools, in a new online applet coming to the IRN website Real Soon Now. Keep your eyes on the IRN main page and the website’s RSS feeds for further information.
In the meantime, I suggest you head over to Ethan Winer’s RealTrapsTM website (www.realtraps.com) for a treasure trove of information on acoustics, acoustic design and products both professional and DIY.
In our fourth and final installment on nearfield monitor selection and setup, we talk about subwoofer selection.
*Controversy abounds regarding the exact relative lengths - and corresponding angles of incidence - of the monitor/listener triangle. Depending upon your source of information and belief, the angle between the two speakers at the apex where the listener sits should be somewhere between 45° and 120°.
In reality there is no definitive "optimal" configuration, the experts disagree on this issue. But if one gets something roughly approximate to an equilateral triangle (all sides the roughly the same length and all angles somewhere around 60°) without getting too close to the corners or walls, that's doing pretty good.