Over the past two weeks we have been discussing items pertaining to the audio spectrum at large. In this article we’ll begin breaking down the audio spectrum into its component parts. Though we disagree a bit on our subdivisions, Jay’s primer has excellent listening examples to hear each section individually.
Generally speaking, sounds can be lumped into three basic segments of the audio spectrum: Bass, Mid, and Treble.
The associated ranges would be approximately:
Bass 25 to 300 Hz.
Mids 300 to 2.4k Hz
Treble 2.4 to 20 kHz
Additionally, they can further be broken down in numerous ways depending on how people want to define sections:
Sub 25 to 45 Hz
Bass 45 to 300 Hz
Low-Mid 300 to 600 Hz
Mid 600 to 1.2k Hz
High-Mid 1.2 to 2.4 kHz
Treble 2.4 to 15 kHz
Super Treble 15 kHz to ~ 100 kHz
This Interactive Frequency Chart, much like the Carnegie Chart in the earlier article will help you understand how the frequency ranges match up with practical instrumentation.
For practical purposes, Sub-Bass should be anything that sounds below the lowest fundamental note of your song. This can include percussion and any sub-harmonics, resonations, formants, and room tones. These are frequencies that would really only be reproduced by sub-woofers and large format PA/sound reinforcement systems. Some of this is undesirable—if you’ve ever watched an NFL game on windy day with a system that has a sub, pretty much everything is a big bass wash because of low-frequency wind noise. We’ll go more in depth on that next week.
Bass should be reserved for the fundamental notes of the changes. That is, the lowest sounding note of each chord progression. This typically would include all the notes that would normally be played by a bass (Victor Wooten excluded). This would also include bass playing synths and the left hand of the piano in many instances.
The Low-Mids and Mids include fundamental notes for melodic instruments as well as the first few orders of harmonics. Harmonics help us distinguish sounds from each other and play a very important role in presence and clarity. More on this when I examine the mid frequencies in two weeks.
The High-Mids deserve their own category because these frequencies contain sudden transient content. For percussion, this would be the sound of sticks or mallets hitting the drum heads and cymbals. For guitarists, this would be the sound of picks striking strings. For vocalists, this would be the sound of hard consonance and sibilance. All of these can be problematic, but also contribute greatly to impression of presence.
The treble portion of the audio spectrum contains almost nothing but upper harmonics of treble instruments and room tone. This helps lead instruments and vocals sound present and full, but also adds brightness and clarity to a mix.
Over the next few weeks I’ll go into greater detail on problems with each part of the frequency spectrum.
More from Phil’s Audible Spectrum series: