Tech \ Technique \ Gear Tips

DIY room acoustics

Studio sound treatment on a budget

2017 May 01     
2 Bit Thugs

Chris Jackson shows how you can improve your mixing environment without breaking the bank

The sales pitch given to us by the audio industry is that you are just this one more product from your perfect mix. Those rounded lows, airy transparent mids and lush stereo field are just a plugin away, but the truth is a lot more complicated than that. What many producers leave untouched is room acoustics. 

Room acoustics play an important part in the way we perceive the various elements in our music, and ultimately how others hear it on their own music-playing equipment. The goal of mixing is to get our musical vision across to the public, so we have to make sure our mixes sound good on home stereos, nightclub PAs, paint-splattered kitchen radios from 1974, iPod earphones and so on. But how can we accurately judge (for instance) the correct level of bass in our tracks, if we can’t hear it properly because our room is completely unsuitable for mixing?

Most aspiring producers work in a less than ideal acoustic environment. Often we work in small, square-ish rooms which make accurate monitoring nigh-on impossible, as every decision we make will be coloured by the room’s uneven frequency response. Bass frequencies cause the biggest problems in small rooms. They take several metres to fully resolve and so will bounce around the room like a pool ball off the side cushions, creating what are known as “standing waves”. The result of this is that some frequencies will boom out much louder than others, while others may be barely audible. 

Just by doing a quick test of standing in the corner of your room while playing a track, you will notice how bass-heavy it is compared to the middle. The only way to get rid of these peaks and troughs is to use targeted absorption that soaks up the problematic frequencies where they gather, so they won’t bounce back into your room. A treated room is a much more pleasant environment to work in: your midrange will be better defined, the low frequencies will be tighter, and your high-end will be more detailed. So you can see there are clearly many benefits to treating a room. 

Balance is everything
Getting your mixing environment right starts with room symmetry. Even if you ignore the rest of the article and just implement this, your mixes will improve greatly for it. To start with, have your monitor speakers pointing down the long side of the room. It’s also important to have your speakers placed symmetrically, so the stereo image is correctly balanced. If possible, try to have the speakers placed a few feet away from the wall, especially if they are rear ported. To find where is the best mixing position in your room: 

1. Get a tape measure and face your speakers
2. Measure the length of the room from front to back
3. Work out where 38% of the length of the room is as you face your speakers
4. Mix from there  

Home (studio) improvements)
Often studio owners cover the walls with foam, in the belief that this is enough. It’s easy to see why, as when the walls are lined with this kind of material it deadens the high-frequency flutter echoes that you get with the hand-clap test. Unfortunately this material is of virtually no use for low frequency control, which is a major problem when mixing music intended for playback on large systems. 

So, let’s go to work! You can quite easily buy a complete room treatment kit that will provide excellent results with little effort on your part. You can even get it tailored to the exact size and shape of your room, but this does come at a price. The much cheaper DIY approach thankfully is also very effective, but it’s a lot more time-consuming and it can make you itch in strange places.

To treat your room, you will need to make two kinds of absorbers:

1. Bass traps to keep our problem low frequencies under control
2. Mid/high frequency absorbers to dampen down early reflections and flutter echoes.

The big build
The material that we will be using for this is compressed fibreglass sheets. This material’s as ugly as a Jeremy Kyle Show participant after a run-in with a bear, but is much cheaper and more effective than standard foam.

The general consensus is that Rockwool RW3 or Rocksilk RS60 is a good all-purpose material to use, as it provides very useful broadband sound absorption. It comes in handy 1200x600mm sheets (varying in thickness) which is an ideal size for one absorber, and it can be bought from most builders’ merchants. Whichever type you choose to buy, make sure the density is at least 60kg/m3. Please do wear gloves, and a mask is vital if you are cutting this material. You may also want to get the local fire brigade to hose you down afterwards as it makes for an uncomfortable bedfellow…

To make the bass traps, place a 4-6 inch thickness of compressed fibreglass (Rockwool/ Rocksilk) onto a rectangular wooden frame measured to the size of your compressed fibreglass, and cover with cloth. Then turn it over, pulling the fabric tight and staple gun it to the wooden frame all the way round. This will hold the fibreglass nicely in place. Use an acoustically transparent cloth: that means anything that you can breathe through, but ideally opt for something with a tight weave to stop loose fibres escaping. Bed sheets will do nicely! If your studio is in a shared space such as a living room, it may be an idea to involve your partner or flatmate in helping choose a cloth that is aesthetically pleasing to the eye, as this will help with the longevity of the shared studio living room situation. You can put small wooden feet on the traps and have them as portable units if leaving them in place is not an option.   

The mid/high frequency absorbers will be made of 2-4 inch thick compressed fibreglass and covered and mounted in the same way as the bass traps. Small rooms ironically need more treatment than larger ones, so if your room is less than say 10ft x 10ft always go for the thicker option. The mid/high absorbers are generally best hung on the wall by attaching a rope or chain to the back so you can hang them like a picture frame.

Placing your new traps
The corners of the room are the first places to treat, as this is where bass gathers and reflects back around the room. Ideally, all four corners of the room should be straddled crossways with the 4-6 inch thick bass traps.

Then some 2-4 inch thick mid/high frequency absorbers should be placed in each of your reflection points. Your reflection points (as numbered in the diagram above) are:

1. The walls either side of your listening position.
2. The back wall behind your listening position.
3. The front wall directly facing you. If you're facing a window, mixing with the curtains shut is a decent workaround.
4. The ceiling directly above your listening position. A thick duvet above your listening position will do just fine.  

With all of this done, your room will now be a far more accurate environment to mix in. Depending on where you get this material from, you should be able to treat an average size room for no more than £200. It will maybe take a day or so to build the frames - and a mate who’s good with joinery will come in handy if you're not exactly Noah in the woodwork department - but in fairness it’s not that demanding. 

Acoustics is a vast and complicated topic and many books have been written on the subject of studio design, but what I’ve tried to do here is suggest simple, affordable ideas that will make a huge difference to the quality of your mixes, and that will continue to pay off, long after that shiny new plugin has been replaced by The Emperor's New Clothes. 

Words: Chris Jackson Pic: David J/Creative Commons, via Flickr

 

 

 

 

 

Tags: room acoustics, studio acoustics, DIY studio, home studio, mixing, mixdown, acoustic treatment