.DYNAMIC PROCESSING


Both compression and limiting change the peak to average ratio of music, and both tools reduce dynamic range.


Compression

Compression changes sound much more than limiting. Think of compression as a tool to change the inner dynamics of music. While reducing dynamic range, it can "beef up" or "punch" low level and mid-level passages to make a stronger musical message.


Limiting

Limiting is an interesting tool. With fast enough attack time (1 or 2 samples), and fairly fast release (1 to 3 milliseconds), even several dB of limiting can be transparent to the ear.

- Consider limiting when you want to raise the apparent loudness of material without severely affecting its sound;
- Consider compression when the material seems to lack punch or strength.

Remember, the position of your monitor volume control has a tremendous effect on these matters of judgment. If it sounds properly "punchy" when you turn up the monitor, then maybe all you need is to turn up the volume rather than add another DSP process! If the music sounds adequately punchy, yet high levels are not approaching ZERO (reference -14 dBFS) on a VU meter, then consider limiting to raise the average level without significantly changing the sound.


Equal-Loudness Comparisons

Since loudness has such an effect on judgment, it is very important to make comparisons at equal apparent loudness. The processed version may seem to sound better only because it is louder. That's what makes the Finalizer's unique "matched compare" system so important. Adjust the gain so that there is no apparent change in loudness when the processing is bypassed. This puts everything on a "level" playing field. You may be surprised to discover that the processing is making the sound worse, and it was all an illusion of loudness. If the sound quality is about the same, then you have to decide if you really need the loudness gain. Don't join the loudness "race" (which has no winners); make an informed, not arbitrary, decision. To judge the absolute loudness of the Finalizer, you need average metering, and a calibrated monitor. See the appendix for references on calibrated monitor and metering systems.


Manipulating Dynamics: Creating the Impact of Music

Consider this rhythmic passage, representing a piece of modern pop music:
shooby dooby doo WOP...shooby dooby doo WOP...shooby dooby doo WOP
The accent point in this rhythm comes on the backbeat (WOP), often a snare drum hit. If you strongly compress this music piece, it might change to:
SHOOBY DOOBY DOO WOP...SHOOBY DOOBY DOO WOP...SHOOBY DOOBY DOO WOP
This completely removes the accent feel from the music, which is probably counter productive. A light amount of compression might accomplish this...
shooby dooby doo WOP...shooby dooby doo WOP...shooby dooby doo WOP
...which could be just what the doctor ordered for this music.

Strengthening the subaccents may give the music even more interest. But just like the TV weatherperson who puts an accent on the wrong syllable because they've been taught to "punch" every sentence ("The weather FOR tomorrow will be cloudy"), it's wrong to go against the natural dynamics of music. Unless you're trying for a special effect, and purposely creating an abstract composition. Much of hip hop music, for example, is intentionally abstract....anything goes, including any resemblance to the natural attacks and decays of musical instruments.

- Back to "Shooby doo". This kind of manipulation can only be accomplished with careful adjustment of thresholds, compressor attack and release times.

If the attack time is too short, the snare drum's initial transient could be softened, losing the main accent and defeating the whole purpose of the compression.

If the release time is too long, then the compressor won't recover fast enough from the gain reduction of the main accent to bring up the subaccent. If the release time is too fast, the sound will begin to distort.

If the combination of attack and release time is not ideal for the rhythm of the music, the sound will be "squashed", louder than the source, but "wimpy loud" instead of "punchy loud". It's a delicate process, requiring time, experience, skill, and an excellent monitor system.

Here's a trick for compressor adjustment:

Find the approximate threshold first, with a fairly high ratio and fast release time. Make sure the gain reduction meter bounces as the " syllables" you want to affect pass by. Then reduce the ratio to very low and put the release time to about 250 ms to start.
From then on, it's matter of fine tuning attack, release and ratio, with possibly a readjustment of the threshold. The object is to put the the threshold in between the lower and higher dynamics, so there is a constant alternation between high and low (or no) compression with the music. Too low a threshold will defeat the purpose, wich is to differentiate the "syllables" of the music.

Note! With too low a threshold and too high a ratio EVERYTHING WILL BE BROUGHT UP TO A CONSTANT LEVEL.


Multiband processing can help in this process

Transients (percussive sounds) contain more high frequency enegy than continuous sounds. By using gentler compression or no compression at high frequencies (e.g., higher threshold, lower ratio), you can let the transients through while still "punching" the sustain of the sub accents or the continuous sounds. Practice by listening to the impact of the percussion as you change compressor attack times. With care, you can have punch and impact, too. But with overcompression, or improperly-adjusted compression, you may get the punch, but lose the transient impact. Most music needs a little of both. Multiband compression also permits you to bring out certain elements that appear to be weak in the mix, such as the bass or bass drum, the vocal or guitars, or the snare, literally changing the mix. Learn to identify the frequency ranges of music so you can choose the best crossover frequencies.


Compression, Stereo Image and Depth

Compression brings up the inner voices in musical material. Instruments that were in the back of the ensemble are brought forward, and the ambience, depth, width, and space are degraded. But not every instrument should be "up front". Pay attention to these effects when you compare processed vs. unprocessed. Variety is the spice of life. Make sure your "cure" isn't worse than the "disease".


At the ballet, do you notice the music first, before the dancers?


Quelle: Bob Katz