The Importance of Dynamics

The word dynamic can mean different things to different people. For musicians it basically equates to the change in volume, but in Hi Fi and recording studios it is much more nuanced. For example recording studios can decrease dynamics to increase the apparent volume of a recording! Confused? For those interested you can read about it in the link Loudness wars.

Dynamic Sound is: Powerful, Explosive, Effortless, Exciting, Fast, Projecting notes into space, has attack on leading edges of notes.

Bass Dynamics will usually manifest in a fast, tight bass with spring and “snap”. This is a far cry from an overblown, slow “soggy” bass, which some mistake for a dynamic bass.  Dynamic bass carries Authority, punch, impact, speed, confidence, and breathes easily.

Other words describing a bass lacking in dynamics can be:  “Laid back, soggy, slow, lethargic, congested, woolly, strangled, stifled, bland, boring, lean, light, with softened transients”.

Frequency extension – Deeper bass and higher frequency extension beyond the hearing range can improve dynamics through the combining of different frequencies.

The whole subject of frequency extension is interesting. Many systems don’t reproduce the actual fundamental bass frequency recorded at all but the harmonics are reproduced and this is perceived as the real bass. As frequency drops off on most speakers somewhere above 50Hz many bass frequencies are weaker than they should be and that affects the overall experience. In many rooms, modes cut and exaggerate bass frequencies creating a completely different canvas on which the painting is crafted.

Dynamics give more texture and shading in the music.

Dynamics in photography mean you have greater contrast and more shades in the colours. Sound quality has similar effects, you can hear more detail and depth to the music, sound feels more alive and present.

The ear perceives dynamic sound as more prominent.

In other words if you play the same music, at the same volume through a system with good dynamics and then one with poor dynamics, your ear perceives the dynamic system as slightly louder. 

The reason this observation is important is that sometimes you can observe 2 products with a level frequency response but one will sound bright and not the other. Why? Often the treble on the “bright” product has better treble dynamics than bass dynamics. Unfortunately this sort of behaviour is not shown on the “averaged” output of whatever test equipment is used. This is particularly true of cartridges and speakers but applies to all other components as well. 

Dynamic sound travels further:

When played at the same volume dynamic sound travels further than one which lacks dynamics. For example:

• Reviewers say that going round a Hi-Fi show, you can usually hear the sound is good in a room from outside the door before even going in.
• Church bells travel for miles – if you played a speaker at the same volume it would not travel the same distances.
• Professional violinists say that a high quality violin will reach the back of the concert hall where a poor quality one will not.

What creates Dynamics?

Dynamic sound travels further because it includes transients (short lived bursts of energy) which possess much greater instantaneous amplitude and energy in brief moments of time than a non dynamic sound.

Most of the time other notes will be well below these transient peaks and these produce the average loudness whereas dynamic transients have little effect on volume but a lot on perception. Interestingly the ear notices dynamic peaks and they improve the perceived quality of the sound – the eye works in a similar way when it comes to dynamic range in photographic images.

A Dynamic transient is formed by the peaks of the various frequencies in the music all piling on top of each other to create a transient of enormous amplitude but for a very short period of time. These transients are so large they can travel an awful long way before they become  inaudible. Unlike clarity or tonality, this is the hardest thing for an audio system to do. It must have the headroom to follow such large transients, have an accurate phase response so that the various frequencies all pile on top of each other at exactly the same time, and not suffer from things like thermal compression which will reduce the height of these transients. All reproduced sound systems suffer from these effects.

How to judge dynamics

The only way to hear proper dynamics is from live instruments and voices where the resonant structures have no trouble creating these transients.

Bass dynamics sounds like a contradiction, why do you need fast transients for the lower “ slower “ frequencies? but they are more important here than anywhere. Good bass needs to be quick and powerful, not slow and ponderous. It needs to stop as quickly as it starts with no booming. Good bass is felt in the chest cavity as much as it is heard by the ears. Good bass is often considered lightweight by people too used to reproduced music and I would encourage everyone to get the texture in the bass from a good grand piano in their head and then listen to their system.