Home Recording
SO YOU'VE GOT YOUR SPACE SORTED OUT. NOW LET'S MAKE IT SOUND LIKE A WORLD-CLASS STUDIO!
Last issue, we looked at the highly challenging issue of soundproofing a room for general recording and music production. It’s tricky enough if you own the property and have carte blanche on what you can do with it, but it's far more difficult if you're renting and need to keep alterations (and damage!) to a minimum.
This time, we'll take a brief look at the (only slightly) less daunting subject of acoustic treatment. This deals with the behaviour of soundwaves within the room – not with sound isolation from the outside world.
The average domestic dwelling is not designed to ‘sound good’ in any considerable way, so usually you’re faced with some fairly daunting and often immovable obstacles – low ceilings, square rooms, windows and doors placed in challenging positions, rooms next to bathrooms and laundries...
Most studios are designed and built from the ground up, obviously. However, most people delving into the world of recording begin with a basic setup, which slowly grows and improves over time as things get serious and budgets expand. The gear is often capable of producing great results, however the room is often overlooked, until such time as issues and limitations begin to arise. Thus, acoustic treatment often becomes a perpetual ‘work in progress’.
Basically, the better your ears, mics, preamps and converters are, the more the issues will be apparent. It’s a wake-up call capturing sound sources with pristine equipment in a less-than-pristine environment – not unlike zooming in on a low-quality image on a large screen.
TIME TO REFLECT
A portion of the soundwaves within the room are termed ‘direct sound’, which travels in a straight line between the source and the microphone. This is obviously the ‘meat’ of the tone you’re attempting to capture in its purest form.
However, thrown into the bargain are soundwaves reflected off all surfaces (including the floor and ceiling) and can bounce around in a myriad of directions – often back into the mic. This can enhance your recording, but it can also totally mutate what you capture – there are infinite possibilities. The biggest issue here is the difference in time it takes all of these different reflections to reach the single mic.
The louder the sound's source is, the more it will interact with the room. While high frequencies are very directional and highly reflective, lower frequencies become unidirectional and actually penetrate structures beyond the walls, doors and windows.
The harder and ‘shinier’ your surfaces are, the more they will reflect soundwaves. Achieving the delicate balance between reflection and absorption is a tricky business – and not everyone seeks the same result. Obviously, there are ‘live’ rooms and ‘quiet booths’ – but we're focusing here on those folks who essentially have one general-purpose room for tracking and mixing. Your setup has to be useful in a multitude of situations.
Reflections are not your arch enemy. It’s natural to hear reflected sound – we do it all day long. However, reflections can seriously complicate and dilute things in a recording environment if the factors causing them are left completely unchecked.
Generally, for the home studio projects, it's most sensible to record things as tightly and cleanly as possible, with predominantly close micing techniques – then use digital means later to create space around the sounds during the mixing phase. This makes every element more malleable and controllable, and of course less random.
LAYOUT
If you have the luxury to choose which room you want to make your studio, obviously you want to pick the largest one you can get a hold of. Not because you can fit more gear into it, but because the further your walls and ceilings are from your sound sources, the less impact their reflections will have on things.
As much as possible, you want to make your setup symmetrical. Soundwaves from your stereo speakers need to travel identical routes to your ears, if possible –
otherwise you’ll have an impaired impression of the stereo field (kind of like one dirty lens on your glasses).
Try to give as much space as possible between the speakers and the back wall of the room. If you’re mixing and getting heavy reflections back into your listening position, you can easily find yourself pushing and pulling things all over the place and tearing your hair out. Often you’ll see a fair bit of work put into the rear wall of a studio (bass trapping, absorption, diffusion), as the length of the room will often coincide with the ‘peak’ of a low frequency wave.
An interesting way to approach the placement of acoustic treatment is to have someone move a mirror around the walls and ceiling. Any place you see a reflection of your speakers in the mirror is an ideal candidate for absorption or diffusion.
THE THREE AMIGOS
There are three main types of commercially available acoustic treatment devices, which are found in virtually any professional recording space. They all have their uses, and work together to achieve the final result.
SET SOME BASS TRAPS
Corners are generally not your friend. Soundwaves – particularly in low frequencies – tend to build up in corners, as the two surfaces reflect waves back and forth. Of course, a typical room has twelve corners – four around the walls, four from floor to wall, and four from ceiling to wall.
Think about those dark, smelly rehearsal rooms which sound like oversized boomboxes. Look around, and you’ll find a whole lot of high-to-mid frequency absorption (often stuff you’d find on a council clean up) – and absolutely no work put into absorbing low frequencies. The result is a room that sounds like a subwoofer, where there’s absolutely no clarity in anything above 800 hertz.
The bass trap is really a great starting point for acoustic treatment. Tame those low frequencies early on, and the rest of the room will (usually) be much easier to deal with.
REACH FOR THE CEILING
Most studios have a mix of hard and soft surfaces. The general approach is to have a soft ceiling, a hard floor, and a mix for the walls. If you think about it, there’s a wide variation in ceiling height from room to room and building to building, so the distance from the ceiling to your ears is always changing. On the other hand, the distance from your ears to the floor is always the same – that's just dependent on your height. So this becomes an important source of orientation.
Low ceilings really mess with overhead mics on drums, and can create all kinds of phasing issues. The average adult’s head is well above the halfway point between the ceiling and floor in the standard dwelling. Thus, if they are singing, or holding an instrument above the shoulders (violins, violas, most brass and woodwind instruments, etcetera), the reflections will hit the ceiling before they hit the floor.
You can minimise ceiling reflections in various ways, and don’t necessarily need to treat the entire ceiling. I’ve seen people hang an old parachute upside down from the ceiling – looks great! More conventional methods might involve using a mixture of absorbers and diffusers. These can be fixed directly to the ceiling, or sometimes more strategically ‘hung’ on panels which are floated from the ceiling like a ‘soundcloud’.
Absorbers reduce a portion of the incidental acoustic energy in order to minimise the amount being reflected back into the room. They actually convert the sound energy into heat; they deal with a specific frequency range – usually upper mids to highs. They are often the first thing people grab for, and thus when used alone, or excessively, can completely suck out the very frequencies that make many instruments and the human voice coherent.
Diffusers, on the other hand, scatter the sound energy over a wide range of angles, rather than allowing a coherent reflection to bounce back as it would on a flat, solid surface.
It’s important to ensure that the soundwaves remain in the room.
For this reason, diffusers tend to work better in larger rooms. These devices look amazing, but can be quite expensive as they are usually labour-intensive to build. Think of them more as ‘icing on the cake’ rather than fundamental essentials.
SOFTWARE
It’s common to use software to aid in ‘tuning’ your room from the inside out. This often involves generating frequencies from you studio speakers into a mic which captures information and analyses it, giving important feedback on your setup.
Acoustic treatment is a deep and complex subject, which involves years of dedicated study to fully understand. Hopefully this article will help kickstart some thoughts about how you can work to improve your current setup.
You may wish to take things further by doing some more serious research, visiting professional studios, asking questions or talking to a professional acoustic engineer. Or you may decide that you’d rather just record in the box with samples and loops and mix with a good set of headphones, and bypass the whole issue! Whichever route you choose to head down, remember – the most important piece of equipment in the studio is your ears… Oh, and the coffee machine!
Rob Long is a multi-instrumentalist and producer working @FunkyLizardStudios in Newcastle.