How to preserve dynamics in your final product
Is your music very loud? So it may not be loud at all!!
Let me put it this way: If a piece of music is the same loud volume all the way through, is it really loud at-all? If there are no quiet parts, then how can we define the loud parts? Often a chorus naturally wants to be louder than a verse to give it impact. Going from a whisper to a scream requires a large dynamic range. When we create and produce music we can use the dynamic range to aid musical expression.
Much of the music being produced today isn’t music at all. It’s best described as anti-music. It’s anti-music because the life is being squashed out of it through over compression during the tracking, mixing, and mastering stages. It’s simply, non musical. It’s no wonder that consumers don’t want to pay for the CDs being produced today.
The amount of compression/limiting used in mastering drastically increased between 1990 and 2000. We can see some examples in the pictures below showing how headroom for peaks has been gradually decreased throughout the years.
Music dynamic range can be measured using the “Crest Factor” which is the ratio between Peak and Average level of the audio material. The Dynamic Range (DR) Scale shown in the picture below shows the classification of Dynamic Range conditions according to this Crest Factor. Follow this link to view a large database of Dynamic Ranges in the record industry in this respect.
For the purpose of demonstrating the detrimental effect of over compression to music I have created two versions of the same mixed material. One with a Crest Factor = 14 dB (Falling within the “Good” Dynamic Range Category in the scale) and the second one, an over-compressed version of it, which has a 4 dB Crest Factor (Falling within the “Bad” Dynamic Range Category in the scale). I have also normalized both versions to equal loudness (i.e. Average RMS for both are the same) just to focus on perceiving the effects of compression in the second version. Please use the following video link to listen to both versions (Use headphones and pay attention to the dynamics and transients of sounds).
Link to Video: https://youtu.be/KMd0z7Hlyk4
Now that we have listened to both versions, let’s try to explain what happened and why the Crest Factor=4 dB version sounds much worse. First of all, in order to create a louder material I need to compress it. In the final mastering stages, a Brick-Wall limiter – which is a specific type of Compressor which reduces level of all signal above the threshold down to the threshold level – has been applied to prevent clipping and in order to increase overall average loudness (i.e. prevent exceeding 0.0dB FS). This effect will squash any sounds peaks above the threshold and consequently will create a flat section of the waveform in place where the peak should have occurred instead. Even though the algorithms used for these limiters are relative transparent, our ears (at least the trained ones) can still perceive its effect as a distorted sound since the limiter attack time needs to be set to “fast” to prevent clipping.
Secondly, mostly all the dynamic range of the music is gone, so now the music will lack punchiness and its intended perceived impact which comes from leaving the peaks untouched.
Essentially, everything will sound exactly at the same level, but louder in average than the original version. Or In other words, the life of music is all gone and we get flatness and distorted sound instead. And even if we have done all this to get a louder master, we will eventually have to turn it down during playback since our ears will get tired (See “Listener Fatigue” ) much faster than from wider dynamic range material.
So how do we prevent this from happening in our music production process?
First off, as mentioned above, we should be careful of how we handle compression in the individual tracks during the mixing stage. Remember that once a track is compressed, it cannot be reverted back to its original dynamic range, and the combined effect of compression in the different tracks will be reflected in the quality of the raw material in the mastering stage.
You need to use a monitoring/analyzer system, along with your trained ears, to follow loudness criteria and you may need to calibrate your speakers to standards such as the one suggested by Bob Katz K-System.
But even if you have not calibrated your speakers, you still can use audio signal analyzers plugins such as Voxengo Span (free plugin) to monitoring the audio levels and get you in the right spot by understanding what’s going on in the track: The most important parameters are Peak and average RMS. These will provide you with a ball park idea on how loud your material is and what is the available dynamic range you have at hand. As mentioned before, you must use your ears when listening through the monitors, as perceived loudness might be different from signal loudness, depending on several factors such as material frequency spectrum and its transient’s nature. The overall idea behind this is to maximize signal level in the mastering stage while keeping the material dynamic range at acceptable levels for the specific type of music we are mastering. For most contemporary music, and as ball-park guidelines, you should be able to maintain a 5dB (Minimum for peak RMS) and also you will set your compressors and limiters such that the material average RMS is between -15dB to -13 dB when your limiter has been set to -0.1 dB FS. Classical music may require lower average RMS probably in the -20 dB range if still peaking at -0.1 dB to preserve a greater dynamic range. Once this setup has been achieved use your ears to confirm through the monitor system that the perceived loudness is acceptable for the standards you should be working by.
Remember that a material which is rich in dynamics, and sounds alive and crispy, can always be turned up to listen at higher volumes as needed. This is what music is all about. On the other hand you can’t ever restore quality of an over-compressed material, and eventually, you will end up up turning it down any ways due to ear fatigue and lack of comfort listening to it.
Finally: Don’t be discouraged if your music doesn’t sound as “loud” as in the record industry pro masters. Whoever likes the music you have produced, will be more than glad to adjust volume to enjoy the beauty of non-over-compressed material. Have fun!!
Dynamic Range Evolution
Dynamic Range Standard Scale as Function of the Crest Factor