Getting beautiful and balanced sounding mixes from speakers can only happen if your studio room is treated properly. Read our practical step-by-step guide for acoustically treating your home studio for better mixes.
By Omer Karni
Most musicians, producers and mixing engineers tend to be a little insecure when it comes to “acoustic treatment,” especially in their home studio. Gaining a proper understanding of the physics of sound waves is like a bomb; completely overwhelming and ready to explode into millions of elements that alter the behavior of the frequency response, reverberation time (RT60), stereo imaging, clarity, punch, and so on.
Home studio freaks, today is your lucky day! Without getting into too much of that physics, you’re in for a step-by-step guide to fixing your room and making it mix-worthy. I hope you’re excited because this is gold!
For this session, you’re going to need an omnidirectional measurement mic ($100 on eBay) and Room EQ Wizard (free utility software for download).
1. Find the right room for your studio space
On our quest to find the right room for your studio, we’re looking for a rectangular room. The minimum recommended size would be, let’s say: 3.2x2.7 meters, but hey, if you must compromise, compromise. Winning is doing the best with what we have.
2. Correctly place your speakers
Place your monitors on stands, as close as possible up against the narrow wall of the room about 1.1–1.3 meters apart, with equal distance from the side walls. And don’t worry about a window if there is one. Fresh air and daylight are usually more essential to your studio than the acoustic benefit of covering them.
Run your first measurement, placing the microphone in a perfect equilateral triangle distance from the speakers.
In a small room, the mic would be placed around the 35% - 40% point of the room (just in front of the midpoint of the room). In larger rooms, you might have to extend the distance between the speakers a bit to place the mic past the quarter point of the room (both quarter and midpoints are usually bad placements for the mic and your future ears’ listening position).
This measurement will indicate the room modes present in your studio space. Room modes are the resonant frequencies in your room caused by the 3 sets of parallel surfaces and are calculated by the speed of sound (343 meters per second) divided by twice the distance between the parallel walls.
For example: if your room is 3.8m length / 2.9m width / 2.6m height, your room modes will be:
343/(3.8x2) = 45.1hz
343/(2.9x2) = 59.1hz
343/(2.6x2) = 65.9hz
This means that your frequency response will show peaks and nulls around these frequencies and their first harmonic (90.2hz, 118.2hz, 131.8hz), depending on where your mic is placed when measuring, and the RT60* graph will show a longer reverberation time at those same frequencies.
*RT60 = The time it takes for a certain frequency to decay by 60db.
Don’t worry about the mids and highs just yet; we’re focusing on 150hz and lower for now.
Enough with maths and physics for now! Let go on to the best and most satisfying part of this process: Defeating the room modes!
3. Set your bass traps
The easiest DIY way to trap bass is using absorption – broadband bass traps. The downside of this approach in small rooms is real estate, as absorption consumes more space than other traps (membrane or resonators), but don’t get me wrong – absorbing bass is THE BOMB! There are also many “useless” areas in the room where the bass is emphasized and can be absorbed. Built-in cupboards could work great as a bass trap if placed on the narrow wall of the room (your soon-to-be back wall).
Let go back to our room example: 45.1hz is the length mode. This frequency will be enhanced against the front and back wall and canceled out in the midpoint of the room. Its first harmonic, 90.2hz, will be enhanced at the front, back wall and midpoint, and canceled out in the quarter and ¾ points of the room. You can demonstrate this easily by generating a sine wave of the mode frequency via Room EQ Wizard, strolling the room front to back, then changing the frequency to the first harmonic and doing the same. Pretty cool, isn’t it?
Since 90.2hz (the first harmonic of 45.1hz) is a fairly high bass frequency, it’s not very difficult to absorb. Placing enough absorption on the front and back wall will, most likely, eliminate the resonance from both mode frequencies. (In a larger room, you might need to add bass traps at the midpoint of the room on the side walls to absorb a lower first harmonic or add to the width of the front and back traps).
Bass trap construction
To absorb bass and reduce its RT60, we will need traps at least 25cm deep. I would recommend 1m width/2m height. The absorbent material could be layers of 40-80kg/m3 mineral wool or 30-40kg/m3 open-celled polyurethane foam (from any mattress manufacturer). The biggest advantage of foam is that it doesn’t need a casing, so it can easily be moved around during the process and requires no drilling of holes in the walls for installation.
Place the first bass trap on the floor between the speakers up against the wall. Then, make your second measurement. Yes, I repeat: Up against the wall. Directional frequencies have the least amount of energy when encountering the walls, so an air gap is efficient where the room mode bass frequencies are most enhanced up against the wall.
On this second measurement, you will see a significant improvement in both your frequency response and RT60.
Place 2 or 3 bass traps alongside each other on the floor up against your back wall (depending on your room width) and make a third measurement. This should result in a minimal or no peak at your lowest room mode frequency and 0.2-0.4s RT60 in the low frequencies.
If you still see a peak in the room mode freq., or the RT60 is over 0.4s, add another layer to the back wall (1 bass trap for the second layer may be enough). Generally speaking, adding depth to a bass trap is more efficient than spreading them across the same boundary.
Place one more trap against each side wall, front corner. Measure. These traps will take care of the second room mode and its harmonics in the low-mid area.
Add 5-10cm of absorbent material, with an air gap, at the early reflection points that are still untreated (ceiling and side walls), and measure. Now, start pulling the speakers away from the front wall towards the listening position and move the mic accordingly—repeat measurements every 5cm movement. Distancing the speakers from the front wall will add clarity and depth but can also cause phase issues in the bass.
Find the best sweet spot position where the phasing doesn’t occur. Your RT60 should now be around the 0.2s across the whole freq. range. If it goes lower than that in the mid and high frequencies, your room is too dry, and you must continue reading.
Screw the acoustic treatment to the walls (polyurethane can be glued to the wall with a hot glue gun), and you’re ready to go!
Too perforated may not help the dryness of the room, and not perforated enough may result in slap delay. Trial and error is the only way to go.
Wide stereo imaging makes everything sound big and impressive but sound smaller in a different listening environment. I recommend you work harder with a smaller stereo spread to make your mixes sound huge on that, and they’ll sound huge everywhere.
In summary, I can’t promise you a flat frequency response because the truth of the matter is that every room is different in size, shape and materials. But by performing these steps, you will improve your listening experience and your mixes significantly. I hope you enjoyed the process.
For any further questions, you’re welcome to DM me via Instagram @ Omer.K.Acoustics
Omer Karni is a well-renowned acoustician and has built hundreds of studios for artists and mix engineers, including the Infected Mushrooms and the Waves Audio HQ.
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