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    What is Good Quality Audio: Part 3

    October 5, 2017 by Dolby Developer

    Critical Listening: Imaging and Sound Stage

    In the second part of this series we evaluated frequency balance, dynamic handling, and timbre. These aren't the only set of characteristics to listen for, though. Assuming you're listening on a system with more than one speaker, you'll also need to listen for where sounds are placed in the listening environment around you.

    The Soundstage

    The concepts of imaging and sound stage refer to the sound system's ability to make it sound like elements of the mix are physically located in space across the listening area. This idea of a physical space where sounds are placed is called the sound stage. A good system will be able to place, or image, sounds in distinct locations, or take up the entire sound stage depending on the creative decisions made when the content was created.

    To test this, first make sure your speakers are set up properly. In a stereo system, the two speakers and your head should form the three points of an equilateral triangle, with each leg of the triangle at least several feet long. The speakers should be equally 'toed in', pointed inwards toward the listener's head. The point of the equilateral triangle where you are sitting is called the 'sweet spot'. It is the ideal listening position and the place you should sit to avoid audio coloration and artifacts beyond those characteristic of your system.

    Play some cinematic content with a lot of dialogue or music with vocals in the center of the mix. On a set of stereo speakers set up properly this should create what's called a phantom center image directly in front of you. It should sound like the voice is coming from the space between the speakers, even though there isn't actually a speaker in that location. If you are hearing good imaging for the first time, you will likely be blown away by the precision with which sounds can be located in the sound stage. The sounds can be almost tangible and should exhibit a pronounced sense of depth. The audio image should not sound flat. Not only should the sounds inhabit their own space across the sound stage, but it will sound like some are nearer or farther away, depending on how the content was mixed. Listening to a spacious mix on a system with excellent imaging, the sound stage can be particularly large and deep, with sounds painted across the entire space in front of you (and possibly beyond), generally with no elements sounding like they're obviously coming from a specific speaker (unless placed that way with intent during content creation).

    Improving Your Listening Skills

    • Build up a small selection of content that you will become familiar with.
      • The content should have enough variety to exercise the various qualities you're listening for.
      • Try some movie content with a lot of dialogue, some loud and bass heavy action scenes, modern pop/rock/EDM music, and high dynamic range classical or jazz pieces.
      • Pick content you'll enjoy as you will listen to these pieces many times on many different systems.
      • The content you listen to should be of sufficient resolution (CD or better) and in an uncompressed format. Don't listen to low bitrate MP3s as these have been lossily compressed to an extreme degree.
      • Listen to professionally produced content, especially content that is considered to be particularly well recorded, mixed, and mastered. That iPhone recording you took at the last Taylor Swift concert isn't going to help you judge audio quality.
      • Look online for specific critical listening content suggestions.
    • Listen on different systems in different environments. The more variety, the better.
      • I highly recommend listening in a high-end showroom. If you can manage it, listening in a high quality professional recording studio or mastering facility's control room will also be illuminating.
      • If those options aren't available to you, many Best Buy locations have a decent home theater demo room that will be worth a visit. There may also be local meet ups or conventions for audio enthusiasts in your area, giving you access to a variety of high quality systems (though sometimes in non-ideal listening conditions).
      • It's not possible to understand how good something can sound until you've experienced the best there is (or close to it). You can describe the color blue all you want to somebody who is completely color blind but they won't truly understand it until they are able to see in color.
      • Similarly, you won't know how compromised some systems are until you've heard some of the worst out there (old clock radios, built-in TV speakers, cheap car systems).
      • Listen to similar types of devices (mobile phones, for example) at comparable price points to get a sense for audio quality differences amongst directly competing products. While it's important to have an absolute sense of quality, often it's relative differences that you are comparing when deciding between one product and another.
    • Your playback system consists of more than just an amp/AVR and some speakers.
      • As mentioned before, the content you play matters and will affect your listening experience. You can't judge a system's bass response without playing content that exercises those frequencies.
      • The environment you're listening in is part of your audio system. You won't be able to judge nuances if there is a lot of intrusive background noise.
      • The room you're listening in is a significant and often overlooked component in your system. Whole books can be (and have been) written about room acoustics. Suffice it to say, this is out of scope for this article. Nonetheless, this is crucial. Bad acoustics, poor choices in seating position, and incorrect speaker placement can make even a great system sound terrible. Most likely, if you haven't done anything to improve the acoustics of your room, your listening environment is not optimal and is coloring everything you hear in that space. That being said, by listening in different environments you will get a sense for how good your content can/should sound and you'll be able to make judgments despite the acoustic conditions in your regular listening space. At a minimum, remember to toe in your speakers properly and sit in the sweet spot. Moving speakers (with the exception of subwoofers) and seating away from walls and corners will also help.
      • Your ears are part of the system as well! Get your hearing checked and be aware of any anomalies in your hearing. We tend to lose the ability to hear higher frequencies as we age and can acquire other hearing problems with prolonged exposure to high SPL sounds (like at concerts).
    • Practice
      • Critical listening is not a skill gained overnight. Audio professionals hone these skills over years.
      • While you don't have to go to that extreme, the more you practice listening critically, the more able you'll be to trust what you hear.
      • There are many online resources for training your critical listening abilities and forums for discussing home theater and professional audio.
    • Don't let your brain trick you!
      • When making subjective assessments, we can often be tricked into hearing differences that don't actually exist.
      • Listen at a healthy level, not too loud or too quiet. Give yourself breaks from listening to refresh your hearing. Yes, ear fatigue is a real thing.
      • Think for yourself; don't just buy into the hype and get swayed into believing a system sounds better because your friends say it's good, it's more expensive, it comes in your favorite shade of pink, etc.
      • If directly comparing two systems side by side, listen to both of them at the same level. Our brains generally tend to think that louder sounds better. If you want to be particularly precise, bring a sound level meter and play a calibration tone through the systems so you can be sure that you're listening at the same level.
      • Also, when directly comparing two systems, be aware that our auditory memory lasts only around 5 seconds. Don't blindly trust comparisons when there is more than 5 seconds of switching time between systems. Ideally, you'd have a way of instantaneously switching between systems without pausing or restarting the content.

    TL;DR

    In this series of articles, we discussed a few fundamental characteristics of audio playback systems, ways to subjectively assess a system's capabilities, words to use when describing timbral qualities, and practical tips for building your critical listening skills. That's all well and good but what is "good quality" audio? In a nutshell, it's audio devoid of detrimental artifacts in frequency, amplitude, time, color, and space.

    No system is perfect and at the end of the day, a "good" system is one that doesn't impede your ability to enjoy your entertainment. You don't have to be an expert to have an opinion about a sound system, nor do you have to own speakers that are worth as much as a small country's GDP. With practice and an awareness of what to listen for, you will become a more discerning judge of audio quality. You'll be able to articulate what you hear, understand the cork-sniffing jargon your audiophile friends bandy about, and develop the ability to judge whether a system alters the sonic signature of your content.

    Most importantly, you'll be able to determine whether that "sounds good" to you.

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