Tutorial Tuesday 5: Broadband Absorber Build (Part 1)
When it comes to mixing the sad reality is that you're not only as good as your ears.
It's common to invest so much money into monitoring systems, plugins, instruments, DAWs, yet rarely do project studios spend anything on acoustic treatment (a rule of thumb I've heard repeated as mantra is 'spend as much money on treatment as you do on your monitors').
Your mix can only be as good as your room - that is to say that if your room is impeding you and your ear's ability to accurately interpret what's coming out of your monitors, you'll never have a truly good mix that will translate well over any playback system.
Obviously each room will be different - perhaps you suffer from lots of reflections, or maybe you'd benefit from some bass traps?
In the following few posts we'll be building some broadband absorbers which, as the name suggests, will help absorb some errant frequencies.
There's a lot of science behind acoustic treatment (which I might go into in another post, as there's a heck of a lot to consider!) that we don't really have space for in this tutorial, but if you'd like to learn more I've attached a further reading section at the bottom of the post.
A plan! Obviously the size of your absorbers will be dependent on the size of your studio (or perhaps more accurately, how much free space you have to accommodate some potentially large wooden frames!), and your budget. You may choose to wall mount the frames, but do bear in mind that they might be quite heavy (and that opens up a whole can of 'will I find the wall strut hidden beneath the plaster and will it all stay up and not topple onto several grand's worth of studio kit). I've gone down the freestanding route (to maximise portability to a new studio in the not too distant future, and to bypass any DIY mishaps) and have chosen to build two 1800 x 600 x 100mm absorbers and have bought the following supplies accordingly:
Timber - six lengths of 1800 x 100 x 22mm bits of wood. Four lengths make up the long side of the frame, and the remaining two are cut into equal thirds, giving six 600mm widths - two for the end of the frame and one for a reinforcing crossbar.
Rockwool - is a dense insulation material used in lofts (or attics...). It's also very good at acoustic insulation. Ideally, for it to do anything beneficial it needs to be 100mm thick. It's available in a variety of sizes, and can be bought from most DIY stores, online or even ebay.
N.B. It's nasty stuff to handle, smells horrible and can be an irritant, so wear gloves, long sleeves and a mask when you get to the rockwool stage! You can cut it with a stanley knife or similar quite easily, but it will dull lesser blades.
Fabric - which must be acoustically transparent! The acid test is can you blow air through it easily. If the answer is yes, then you're good to go. Common choices are burlap, or hessian weaves, both of which come in a variety of colours, so you can match your studio's decor. I'm using two layers of fabric for my absorbers - one is a very loose gauze which is attached first. This is to ensure no rockwool fibres escape, and also will help prevent things from sagging over time.
Tools and Fixings - Nails, a hammer (or screwdriver and drill, if that's how you live your life), probably a saw if your timber vender of choice (like mine) can't cut it to length, a glue gun (if you're going down the nail route) and a staple gun to attach the fabric.
I think that's about it! On with the build!
Saw your timber to length if necessary and start assembling your frames. It's easier if you have a studio pal or someone well versed in the dark art of DIY to give you a hand. I used a glue gun to make the initial bonds between the wood, waited for it to dry (which doesn't take too long with hot glue), and then drove in some heavy duty nails. I don't have a drill, but I imagine the screw route would be an equally good (if not better) way to fix everything together.
Upholstery Part 1. When the frames are nice and stable, and resemble some sort of rudimentary door or window stand back and admire your work (I know I did in a state of sheer disbelief!). The next step is to attach the gauze or fabric (as mentioned I'm fixing the gauze first).
Start with the front of your panel so you have something to lay the rockwool on later. Using the staple gun pull everything nice and tight to make sure you don't have any aesthetically and acoustically displeasing fabric ripples.
And that's about enough for this post! Next time I'll be laying the rockwool and finishing up the upholstery.
Further reading. If you want to know more about acoustic treatment I recommend browsing the following links:
There's a wealth of good information, often with examples, over on the gearslutz forum - http://www.gearslutz.com/board/studio-building-acoustics/
A good introduction to acoustics - http://gikacoustics.com/acoustic-primer/
A great guide to broadband absorbers - http://www.ethanwiner.com/acoustics.html#mhf%20absorbers
The BBC's guide to acoustic practice - http://downloads.bbc.co.uk/rd/pubs/archive/pdffiles/architectural-acoustics/bbc_guideacousticpractice.pdf
