Acoustics
As promised, here is my little bit on the room and what we’re doing to treat it as best we can.
Background
I did a year on acoustics whilst studying music technology, wherein all the principles were laid out, and we ended up having to do a full work up on a room (sound proofing, acoustic paneling, designing traps and QRDs).
That was over 10 years ago though, so I did a little bit of researching and online reading to refresh my memory on some formula and things. Ethan Winer’s Acoustics was pretty good reading as was just googling “Studio Acoustics”, “Bass Traps”, “Acoustic Treatments” and so on.
With acoustics there’s so many different ways you can treat a room so I would suggest spending a bit of time reading as widely as you can before dropping money on any products - you may not need them or those products may be pretty ineffectual in your situation. And sometimes you can solve the problem by just moving your kit around the room.
What acoustic treatment ISN’T is just sticking egg cartons to every wall in your drum - you do that, you might as well be creating an anechoic chamber. And if you’ve ever been locked inside one, and heard the blood pumping through your veins and your eyes scratching around inside your skull you’ll appreciate why we don’t want to spend hours in a completely ‘dead’ room.
We need to do something about the sonic character of the room, so that we produce and mix a tune accurately so that it sounds the same on properly tuned systems wherever we take them, either to a club, a hall, a car, another studio or (hopefully) the A&R department of some mega-huge label.
The Problem
How to improve the sound in small room in a rented apartment in a concrete building, without affixing anything to the walls. The sound needs to be improved for production purposes, rather than for DJing. Sound proofing is not so much a concern as three of the four walls face outside and the other wall backs onto my kitchen.
Measuring Up
Here’s the room - 4 walls. One has a built-in wardrobe and the door in it, one has a nice large window in it and the other two (the longest ones) are bare apart from an airconditioning unit up high in one of them.
First things first - we know there’s some funny high-end crap going on in the empty room because when we “excite the room” (clap our hands) we can hear about 500-800ms of ringing going on. Kind of metallic sounding, so we know there’s a bunch of harmonics going too.
Secondly, because it’s a small room with nice 90-degree corners and hard walls we know there’s going to be an issue with bass. Small Room Syndrome it’s called. You can get the same thing singing in your shower - sing in the middle, then bring yourself closer and closer to the corners and see how the bass kicks up.
That being done, we whip out the tape measure and measure up.
4m long
3.3m wide
2.55m high
Now we plug those into Bob Gold’s excellent Room Modes Calculator.
Luckily we pass the comparison to recommended Room Ratios - these are ratios of L:W:H that are recognised as being the basis for sounding “good” or having the potential to sound good.
Next we find that we have Room Modes dominating from 43Hz to 135Hz, which would be the sub and bass end of the spectrum. This is where the room size matches the physical wavelengths of sounds that allow standing waves to build up and resonate off these tones.
Diffraction and diffusion dominate from 135Hz to 540Hz - something we can do something about. These are the frequencies that the room is really resonant at, where parallel surfaces allow standing waves to develop.
Upwards of 540Hz we have ringy, bouncy echoes with sound bouncing off every bare surface in the room.
Our solution
First of all, we have decided to go with a Live End/Dead End room. This means that we will treat the room around where our monitors are but leave the back of the room live. Plus, because we are using near-fields we want to make sure that the only sound we get in our ears is directly coming from the monitors.
To that end, the first thing we do is make sure that the monitors are pointing at our mix position, with the tweeters going straight into our ears. We juggle this by using our awesome milk-crate speaker stands and angling the monitors with something like Auralex foam wedges or similar.
Second thing we are going to do is try to kill off any “flutter echo” stimulated by our near fields. This will be 135Hz and upwards. For that we have one person sit in the mix position whilst the other holds a mirror against the wall. They move the mirror along the wall and we mark where we can begin to see the monitor and again when we can’t see it. We do this horizontally and vertically. Then add a little extra around for good measure
These areas will be treated with something to absorb the sound and to stop the sound from echoing off the walls in these areas. This means that we should only be getting the direct sound from the monitors and not the combination of the direct sound and the sound reflecting of the walls either side of the mix position.
In the image below (although this is for home theatre, the principles are the same) you can see the idea: Green is the direct sound, red is the indirect sound coming from the monitors. Without treating those points to absorb that indirect sound, we would get a variety of reflections that would cause a “smeared” stereo image and usually a bump in the mid-range frequencies.
The blue is other indirect sound, but we won’t be cranking our monitors that loudly so we hopefully won’t have too much issue there.
Third thing we’re going to do is deal with the corners a little. The room is too small to benefit from anything other than a full sealed bass trap (which needs to be affixed to the wall with no gaps). Plus, the HS80Ms are ported at the rear and will be angled towards our mix position pushing the bass straight into the corners (which are already bass hotspots thanks to proximity effect). We need to do something to soften those corners a bit.
What we’ve decided to do at this point, is to get 4 single foam mattresses (cheap and nasty at about $50 each) and lean them against the walls either side of the mix position to kill flutter and across the two walls meeting in each corner in front of the mix position in order to lower the amount sound entering those bassy corners.
There’s not much we can do about small room syndrome with the low, low bass but the HS80Ms roll off quite significantly around there so we hopefully won’t have too many problems.
Anyways, that’s what we be doing about the sounding. Thoughts?
I used to have a Xone:22 and I loved it - plus the blue A&H LEDs will match those on the Virus Indigo sitting next to it.
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