Home Studio Practitioner
Time proper planning and small investments in acoustic absorption materials can pay big dividends in the effectiveness of your home studio space.
by Luka Sraka, May 2016
Acoustics for Bedroom Producers
We live in a time when music can be produced anywhere with little investment, and indeed, a lot of great music production nowadays is done in small home studios or even rooms that are not just used for this purpose i.e. bedrooms, living rooms, etc. I recently moved into a bigger house where I have enough space to have the luxury of a room that is solely used as a music room or a home studio, but there are many of producers and musicians who just don’t have this option.
Working in a room that wasn’t designed with music production in mind can be frustrating and demotivating, but there are a few tricks which can help us to make the room or rooms we are working in more suitable for the task. And it doesn’t have to cost a fortune.
Geometry and Speakers
I don’t want to get too technical, but the geometry of the room and the placement of the workstation (i.e. computer desk) and speakers is one of the first things to consider when trying to get the best out of the available space.
Room dimensions and ratios are the first things that are considered by studio designers when designing a studio, there are many reasons for that, one of them being room modes. Room modes are the collection of resonances that exist in a room when the room is excited by an acoustic source such as a loudspeaker. These resonances affect the low-frequency and low-mid-frequency responses of a sound system in the room. These are one of the biggest obstacles to accurate sound reproduction.
If you ever had a chance of visiting or working in a professional studio you will have noticed that most of the walls weren’t parallel to each other. This in fact prevents sound waves from traveling to one wall reflecting and traveling to the parallel wall, reflecting again, and so traveling back and forth from one wall to another which causes the room modes. Room modes are calculated from the distance between two walls and the speed of sound (speed of sound divided by twice the distance), but there is no need to start looking for your calculator because there are free online room mode calculators which can calculate the modal response of a room for us. Since most of rooms we live and work in are rectangular, the room modes can cause quite a big problem when working with loudspeakers.
In general cubes are bad, since the ratio between all of the walls is the same the modal response – problematic to say the least. You should avoid room ratios that are multiples of one to another too (i.e. length 4meters, width 2 meters and height 2 meters). The stranger the ratio the better the modal response will be. To hear what a room does to your sound just put some white noise through your speakers and move around the room. You will notice that in some areas the bass frequencies are much more present than others; those are the areas of room modes. Even if your room dimensions are not perfect there is a lot you can do with positioning your speakers and your listening spot.
In small rooms positioning the speakers so that you face the shorter wall is always best (the speakers should be projecting sound the long way down the room). You also have to consider the geometry. Both speakers should be at the same distance from their adjacent walls, so that the early reflections of the walls hit your ear at the same time (failing to do so would result in bad stereo imaging), and your listening position and speakers should form an equilateral triangle (the distance between your ears and the speakers and the distance between the speakers themselves should be the same). There are different theories about the speaker placement too. Some say that positioning your speaker close to the front walls is good (that may be the case for front ported speakers). But some say this is bad in theory and you should avoid positioning your speakers or your listening position at 25%, 50% or 75% of the length of the room, being at 50% of the length (the middle) would result in frequencies of the fist room mode to be too loud, or in the case of 25% and 75% too quiet. Many acoustic designers say that the 38% point of the room length is the perfect listening position, but this may vary from room to room, I think it is a good starting point, but let your ears be the judge.
One last thing to point out before we move along is the size of your speakers themselves. We all like to spend a great deal of money for our gear and want to have the best speakers possible, but working in an imperfect, untreated room, big speakers having a large frequency range can be our enemy. Working on smaller speakers would mean fewer problems with the problematic frequencies, and you could always use a pair of good quality headphones to check the low end of your mix and the stereo imaging of your music.
Soundproofing and Absorption
If you have noisy neighbours, or your neighbours complain about the noise that is coming from your bedroom studio, I’m afraid that sound absorbers won’t be of much help. To sound proof your room you need mass (i.e. the more mass your walls have, less sound will escape or enter the room). Your room should also be as air tight as possible, since sound waves can travel through any hole even if it’s a tiny one. Vibrations are a problem too, those are caused by low frequencies especially, and to deal with those you might consider building a room inside a room with floating floor (the construction for the floor should lay on neoprene or other suitable material) and detached walls. Since soundproofing a room can be very expansive most of us try to work around the issues by working, when we are not bothering anyone, etc. Sound absorption on the other hand is used to tame the problematic frequencies that arise in our room. In small rooms we deal with great bass frequency build up, and flutter echo (early reflections) can be a problem as well.
There are many companies that make absorption panels out of open cell foam or other materials, but those can be very expensive and the cheap stuff does not work as well. With a bit of handyman know-how you can build your own absorption panels and bass traps and do that quite cheaply. Rock wool or glass fibber panels are great for that purpose and they are used for sound treatment in professional studios too. You can build a frame out of wood and insert a panel of rock wool into it, covering it with breathable fabric – all for a very reasonable price. You should be careful that the material used for absorption is dense enough, and that the fabric is not too reflective (burlap is used often). The absorption panels will not work for low frequencies, below 250Hz (unless they are really thick). For bass frequencies, super chunk corner bass traps are effective and you can find how-to tutorials for building absorption panels and bass traps online. Placement of the absorption is crucial too. The first task should be eliminating the early reflections which can be done with placing absorption panels on the walls left and right from your listening position and also on the ceiling. The first reflection points can be calculated or you could use the trick with a small mirror, again search for the help online. By treating the early reflection points you will hear the direct sound coming from your speakers more accurately. The second task is to treat the low frequencies, starting with corner bass traps. Keep in mind that the goal is not to make a dead room (absorption on all walls) but to address the problematic areas in the frequency range.
In the last few years reflection filters that are mounted on a mic stand became popular. Although they can be a life saver in very reverberant (reflective) rooms, they have an inherent design flaw. Usually when we record a vocalist the mic is in a cardioid polar pattern. That means that the capsule is picking up the sound in front of it, but not behind where a mountable reflection filter would be. All though there is nothing wrong with using such devices, you should have some form of absorption behind the singer as well, and absorption which would take care of low frequencies that are not affected by the mentioned reflection filters. And since I’ve mentioned the microphone polar patterns one last word of advice: when working with a cardioid polar pattern you can position the mic and the source (singer, guitar, etc.) so that the source faces the noisiest place in the room (the computer, a window that is facing a road with cars driving on it, etc.) the mic will pick up the source but not what is happening behind the mic.
Even small changes can have an effect on the sound of your room, what is written above are just some simple guidelines, that may help you achieve good results, but remember to experiment and try different things.