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    What is Good Quality Audio: Part 2

    September 6, 2017 by Andy Vaughan

    Critical Listening: Frequency Balance, Dynamics, and Timbre

    In the first part of this series we discussed the concepts of frequency response and dynamic range in relation to a speaker system's capabilities. While these are important properties, they don't tell you everything about how a system sounds. To do so, we'll have to learn how to listen critically and describe what we hear.

    Frequency Balance

    Play some music on your system and listen carefully. Does the system reproduce the lows and highs adequately? Notice whether you can hear the lowest bass notes and the highest cymbal chimes. Listen for unusual resonances, i.e., parts of the frequency spectrum that tend to ring or linger longer than they should. Does the bass dominate the audio presentation to the detriment of details elsewhere in the mix?

    Do voices stick out too much or not enough? Try to get a sense for where elements of the mix lie on the frequency spectrum. How low is that keyboard part? Does it contain frequency components that are noticeably lower or higher than the bass drum? Lower or higher than the singer?

    Of course, what you hear will depend on the particular piece of content you're playing and the way it was intended to sound. By listening to a wide variety of familiar content in a variety of playback environments you should start to get a sense for whether a system has a suitably neutral frequency response.

    Dynamic Handling

    Listen for the system's dynamic handling capabilities. Bring the volume up slowly while playing content that has a fairly consistent level throughout (most modern pop music). Hopefully the system gets as loud as you'd ever need it to without obvious signs of degradation.

    For example, does the system sound like it's straining or not playing as clearly as it was at a lower volume? Are there crackling artifacts or any other signs of the audio being affected in a negative way? Are there signs of physical stress on the system, such as speaker cabinet rattling or a chuffing noise from a subwoofer? Be careful not to overload your system; decrease the volume to a safe level if you hear any of these warning signs.

    Also, test how your system handles content with a wide dynamic range. Symphonic classical music and action movies tend to work well here. With your system set to a comfortable level, listen to how well it reproduces the loud parts of the content and whether the quieter moments are still audible above the background noise in your typical listening environment. If bass heavy music or cinematic content is important for your use case, you may want to specifically test high amplitude low frequency content. Large explosions in movies are a good test for this, such as the hospital explosion scene in Christopher Nolan's 2008 film, The Dark Knight. Again, be careful to not overload your system; this scene in particular is challenging even for the most capable systems.

    Lastly, listen for how the system deals with sounds that rise and fall in level very quickly. Such 'transient' or 'impulsive' sounds, such as a sudden drum hit or clap, can reveal deficiencies in an otherwise capable system. Is the sound's attack, or onset, as short and sharp as it should be? Or is the attack smeared and rendered less impactful?

    Timbre

    Next, let's listen for differences in 'timbre', which Wikipedia describes as "tone color" or "tone quality". This is a bit nebulous and difficult to describe but think of timbre as the characteristics that make two singers sound different, irrespective of pitch and volume.

    Play a piece of music you're familiar with on two different systems at roughly equal loudness. Focus on a particular element in the mix, such as a bass line, synth stab, etc. Does this element sound the same on both playback systems? Does it sound more natural on one system? Does it have the same impact on both systems? Is it as present on both systems? Do you hear more detail in the element on one system or the other? Is it more muffled or less distinct on one system or the other?

    Comparing the listening experience on speakers and headphones can be particularly revealing but don't fret if you struggle to hear differences at first; the more you listen to the same content on different systems, the more obvious these differences will be.

    Your personal listening preferences will influence which system sounds better to you, but there are a number of obviously negative qualities that a good system should not exhibit. Unfortunately, describing these timbral qualities often involves descriptive terms that sound like jargon to a novice listener. I've listed a few common words below that people commonly use to describe timbre and attempted to provide definitions. While this is no means a definitive or exhaustive list, it should provide a reasonable starting point for describing what you hear.

    • Bloated - A negative characteristic indicating excess bass that tends to linger longer than it should and obscure other low end details.
    • Boomy - A negative characteristic and similar to "bloated." Sometimes indicates a slightly different part of the low end spectrum than "bloated," but I'm not splitting hairs here.
    • Bright - Indicates an emphasis on the treble end of the frequency spectrum.
    • Dark - Opposite of bright.
    • Detailed - Usually positive, indicating clarity in the higher frequencies and good transient response (response to sounds with a quick attack, like a drum hit or clap). Somewhat self-explanatory, allows you to hear details in the audio that might not be as obvious on other systems. It is often easier to pick out details on headphones than it is on a pair of speakers.
    • Harsh - A negative characteristic indicating overly loud and possibly distorted higher frequencies. Unpleasant and possibly even painful to listen to.
    • Muddy - A negative characteristic indicating excess lower midrange frequencies and sloppy transient response, possibly with boomy characteristics. In some ways, the opposite of detailed.
    • Punchy - A positive characteristic indicating good transient response. For example, drums that sound sharp and clear on the attack. If loud enough and with enough supporting bass frequencies, you may actually feel physical chest pressure when the drums hit.
    • Thin - A negative characteristic indicating a sound that lacks weight (or the opposite of warm (see below)).
    • Transparent - Usually positive, indicating a flat frequency response and accurate transient response. Most audio professionals strive for systems to be as transparent as possible.
    • Warm - Usually positive, indicating a pleasant increase in the lower midrange frequencies, decent bass, and present but not harsh highs. Vacuum tube (or valve, depending on which side of the pond you live) amplifiers are often described as having a 'warm' sound.
    • Weight - A positive characteristic indicating good bass response. The bass isn't bloated, sounds solid and supports the rest of the mix, i.e., giving the sound 'weight'.

    An acquired skill

    Evaluating frequency balance, dynamic handling, and timbre are crucial aspects of critical listening. However, these skills take time to develop; don't be discouraged if you struggle to detect and describe differences between systems at first. With practice, you'll find that these nuances are easier to identify. On that note, the final part of the series will introduce one more aspect of critical listening and provide some practical tips for improving your listening skills.

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