Mixing the low-end of your music can be difficult; this holds true for simple mixing tasks like setting the level of your bass. There must be some reason why you always mix your bass too quiet/loud, right? It's very frustrating when you finish your mix, it sounds great on your studio speakers, but then doesn't translate well to other playback systems. This guide will demonstrate why this happens, and explain what you can do to overcome the problem.
When you play sound from your speakers, sound waves interact with your room, and if your studio has been left untreated, these interactions can create significant issues in the way you perceive your music. If you ask a great audio engineer to mix and master a song in an untreated space, they’re at the mercy of the environment they’re in, and their work will likely suffer because of it.
Room modes, standing waves, nodes, and anti-nodes are just some of the critical concepts you need to be aware of when sound treating your studio. Having an understanding of these principles will allow you to identify the source of many acoustic problems and deal with them effectively.
Room Modes
Room modes, which are the build-up of resonant frequencies in your studio, are one of the biggest challenges you’re going to face when it comes to creating an adequate listening environment. Your perception of low-end is what will suffer when room modes are left untreated.
With room modes running rampant, and depending on where you’ve placed the listening position in your room, you may experience an abundance of bass or a bass deficiency. This has to do with whether you’ve positioned yourself at a standing wave’s node or antinode; two concepts that I’ll touch on momentarily. If you perceive the bass in your music as too loud, your natural inclination will be to turn it down in the mix, whereas if you perceive the bass in your music as too quiet, you’ll want to turn it up.
The goal is to achieve a near-flat response listening position so that regardless of the coloration applied by the various systems your song is played through, it will sound as close to your perception of the mix as possible. You want your mix to play back well on cell phones, laptop speakers, your car’s stereo, and on hi-fi systems.
For example, imagine your room’s acoustics cause you to perceive 44 Hz 9 dB quieter than you should. When you boost this frequency range to accommodate for your misinformed perception of it, the mix will sound balanced on your system, but when translated to another system with a flat response low-end, there will be far too much bass. Even worse, your mix may be played through a system that boosts bass, causing your exaggerated low-end to overpower the entire song.
The dimensions of your studio play a critical role in determining the fundamental resonance of the room you’re in. This room mode calculator allows you to input the length, width, and height of your room in centimeters, or feet. It predicts where room modes will occur; this will allow you to make informed acoustic treatment decisions.
Room modes can occur at more than one frequency, which makes dealing with them that much harder. If you know the frequency of a fundamental mode in your room, you can easily calculate modes further up the frequency spectrum; modes are related to each other based on the frequency that they resonate at. This will start to make more sense in the next section when we take a look at standing waves.
Standing Waves
Room modes are caused by standing waves. A standing wave is created by the superposition of two waves of the same frequency traveling in opposing directions; the wavefronts propagate through one another.
In the context of your studio, sound waves are generated by your speakers, travel towards the back of your studio, reflect off the back wall, and then return to the front of your studio. The waves headed back to the front of your studio conflict with the waves headed to the back of your studio; this is often most problematic with low-frequency waves due to their length.
In Figure 3, you may have noticed that the standing wave isn’t moving; this characteristic of standing waves is what can cause you to hear a misrepresentation of the low-end in your mix. Depending on where you’ve placed your listening position along the length of a standing wave, you might end up hearing too much bass, or too little bass.
To explore this concept further, and accurately discuss why your listening position will affect your perception of low-end, we need to take a look at nodes and anti-nodes.
Nodes and Anti-Nodes
Nodes exist where the amplitude of a standing wave remains at 0 over time. If you place your listening position here, you’ll hear a lack of bass. This can result in bass-heavy mixes, so you’ll want to avoid setting up your listening position at a node if you can.
Anti-nodes are found directly between nodes, where the amplitude of a wave reaches its maximum value. If you place your listening position here, you’ll hear an abundance of bass. This can result in mixes that lack bass.
If you to listen to a sine wave in an open field, you'll experience a full cycle of compression (peaks) and rarefaction (troughs), with an amplitude value of 0 being apart of the cycle. With a standing wave, you don't experience this full amplitude cycle when positioned at a node, which itself is the issue (silence). At an anti-node, you have the opposite problem; you experience the full amplitude cycle, but in an exaggerated form (signal amplification).
In practice, you won't end up with a perfect standing wave in your studio, even in an untreated studio, because of factors like reflection and absorption. Setting up your listening position at a node won't result in complete silence. Instead, you'll end up with a superposition of a standing wave and a traveling wave, known as a partial standing wave. In this situation, you'll simply hear an attenuation of amplitude if you've positioned yourself at a node.
Dealing with Room Modes
The big question is, “How are you meant to deal with standing waves?” If you’re unable to sound treat your studio in any way, you can move your listening position in an attempt to avoid placing yourself directly on a node or anti-node. Read “How to improve Room Acoustics Without Acoustic Treatment” for a walkthrough on how to do this effectively.
The second option is to apply acoustic treatment to the back wall of your studio. A combination of absorption and reflection should do the trick. GIK Acoustics' bass traps are acoustic energy absorbers which are designed to damp low-frequency sound energy. They offer full range absorption and range limiting, along with a built-in scatter plate to reduce the amount of low-end frequency content that reflects back toward the front of your studio; this results in standing waves that are significantly reduced in amplitude.
To accurately measure the frequency response of your listening position, you'll need to use a room analysis software like Room EQ Wizard and/or Sonarworks' Reference 4. This software works in conjunction with a dedicated microphone that allows you to capture accurate measurements of your listening position's frequency response. By taking room measurements and experimenting with different acoustic treatment types and positions, you'll be able to dial in the frequency response of your listening position; this process is beyond the scope of this guide, but it's important that I at least mention it.
Room modes, standing waves, nodes, and anti-nodes are fundamental room acoustic principles, so it’s convenient to have a basic understanding of them. Your perception of your mix is directly related to your room’s acoustics, which dictates how well your bass translates to other playback systems. Check out “How to Make Your Mixes Translate to Consumer Speakers” for more tips on making your mixes sound their best.
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