Playback System Set-up

Guidance for Establishing Accurate Playback

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The content and quality of each listening experience is important to accurate listening and learning individual records. The playback system is the reader’s access to the sounds of the track. Your playback system’s sonic characteristics will be inherent within the sound of tracks you observe. A playback system might be thought of as aural sunglasses tinting all that you hear—and coloring all of the tracks you seek to study and analyze.  The issue, then, is the extent to which one’s system transforms the sound of a track.

Access to a reasonable-quality, accurate playback system that is located in an acceptable listening environment is needed to experience and learn the material discussed in Recording Analysis: How the Record Shapes the Song. It is important for the recorded examples to be heard as intended—with a minimum of change from the playback system and the room.  This is needed to fully learn the materials being discussed, to develop accurate listening skills, and ultimately to study the records you wish to understand or analyze.

High-resolution monitors in an acoustically neutral environment and a precise playback system are required for many activities performed by professionals in creating the tracks you will study. A professional quality system is not needed to establish an acceptably accurate listening condition; one that produces only minimal changes in the sounds of the track. It is possible to assemble a listening system and physical arrangement within modest financial means and typical household logistical constraints (such as the living room system described below). The goal should be to reproduce the track with as few alterations as is practical for one’s situation—and, importantly, to learn the sonic consequences of those limitations.

Some readers may be tempted to study the book’s examples and audio files from this webpage on headphones, ear buds or their computer speakers. Headphones are not a suitable substitute for accurate listening to nearly all of the examples, nor are earbuds; the wearer’s perception of spatial information is distorted and they are inaccurate in reproducing amplitude and frequency-related aspects of the recording. Even high-end computer monitors alter the sound qualities of recordings into something else, as they are intended for pleasing consumers, not providing the sonic accuracy required for audio professionals. Chapter 6 contains a lengthy discussion on these matters.  It also covers the components of the playback system, and assembling a system suitable for recording analysis.  Topics presented in Chapter 6 and in the following sections are:

• Components and specifications for a high-quality playback system to provide unaltered, detailed sound
• Loudspeaker placement and listening room interaction
• Listener distance and orientation to loudspeakers
• Monitoring levels
• Playback system testing and calibration

Take the time needed to review and understand the performance specs of the components in your playback system.  Ideally your system should produce sound with a high level of clarity and detail, have strong time/phase coherence throughout the listening range (especially around the loudspeaker crossover frequencies), be able to provide accurate tracking of dynamic changes (especially for high-pitched sounds with fast attacks), and exhibit a flat (non-deviating) frequency response (extending from the lowest octaves to above 10 kHz). The monitors should supply stable imaging and not draw the listener’s attention to the loudspeaker locations. It is important to recognize if any alterations to sound quality are a product of the components of the playback system, or if they are being created by the interaction of the loudspeakers and the listening room.

Listening Log and Loudness Levels of Playback

Keeping a log of listening conditions will ensure consistent sound qualities between listening sessions, and allow any analysis process to be most productive.  The log should verify loudspeaker positioning and listener location, or note any changes; furniture layout, presence of a writing table, etc. should also be noted, as their presence might explain inconsistent results between this session and others. The most important entries in this log are related to listening levels. On each listening session note loudness levels of playback—an accurate sound level meter is indispensable, and is not a large financial investment.  If the weather (affecting the listening room) is substantially hotter or colder, or more or less humid than normal, note this too; always seek to eliminate fan sounds in the room while listening. 

The most desirable range for monitoring is 80 to 90 dB SPL (A-weighted).  Seek to develop consistency of listening levels, with a nominal listening level at around 82 to 85 dB SPL (A-weighted).  With a nominal listening level at or slightly below 85 dB, peaks may well reach to 90 dB (or very slightly beyond). Raise the nominal level slightly if the minimum SPL dips below 78 dB for more than a few moments; this will become the new loudness setting for listening to that track on that system. Once set, the levels are not adjusted and are recalled (from your listening session notes) for the next listening session. 

85 dB as a nominal level is likely to be perceived as a loud home-listening level, but it is still a level that can be sustained throughout a work day and it is sonically accurate (in frequency response). Monitoring at this level (not higher) will also do much to minimize listening fatigue during prolonged listening periods.

Maintain a clear record of the loudness levels for each track you are examining; this is essential.  Tracks vary in their loudness levels even on the same CD, and the loudness levels between different CDs have the potential to vary markedly.  To ensure you listen at the same loudness level for each listening session, measure your playback levels with a sound level meter.  Note the starting loudness level, the nominal level, and loudness peaks and lows; even the most basic sound level meters automate these functions.  Seek to match levels precisely at each session, although exact replication is not possible.

Loudspeaker Placement, Rooms and Listener Position

This is a very general guide to placing loudspeakers within your listening space.  This is only a guide, as your sound system and your listening room will have qualities that cannot be explained here, and their interactions cannot be anticipated by even a more in-depth writing.

These general concepts and principles form a point of departure. Much science of acoustics, of playback component performance characteristics and of the processes of listening and hearing substantially influences the details of all that follows.  Your sensitive listening will help you identify matters that need attention—especially as you become more aware of what you are hearing.

Your lifestyle and the various other functions of your room also come into play here.  A shared living space will require loudspeaker placements different from those in a dedicated listening room.  Moving furniture and speakers (with their stands) for listening sessions may be an appropriate solution.  With a plan and practice, moving items around a room may be only a small task.  A dedicated home listening room and a shared living room will be discussed later.

Loudspeaker Relationships to the Listening Position

Speaker stands will improve the performance of most loudspeakers; they can be relatively inexpensive and are recommended.  They will bring the speakers to a height that places the high frequency driver or the acoustic center of the speaker (as appropriate for the speaker) at about ear-level.  This allows proper frequency balance, and ensures that the speaker’s intended sound radiation pattern arrives fully formed to the listener’s ears.

One should decouple the speakers from their stands, as stands will typically resonate (as would tables, cabinets or other surfaces where one might place speakers).  This is particularly important for the frequency response of the loudspeakers, and the timbral balance of the track.

For most accurate playback, loudspeakers should be placed 5 to 6 feet apart.  An equilateral triangle should be formed between the loudspeakers and the listening position by turning each loudspeaker inward a 30-degree angle. The most accurate and stable spatial imaging will be present with the listener at the apex of the triangle, or up to a foot inside the triangle’s apex.

Loudspeaker Relationships to Walls

Speakers should optimally be located a minimum of three feet from the wall behind them.  While this is difficult for most living spaces, it must be noted the farther into the room the speakers are placed, the more the spatial qualities of the record are revealed.  This is especially important for sound stage depth and distance cues; placing speakers nearer to a rear wall will affect the amount of low frequency information (often resulting in pronounced bass boost).

Speakers should optimally be located a minimum of four feet from side walls.  This minimizes reflections off side walls and their interference with stable lateral imaging and frequency response matters.  Clearer presence of phantom images, sound stage stability and even frequency reproduction will improve as speakers are moved further from side walls.

Remember the goal of loudspeaker positioning is to establish a neutral sound of the playback system.  When a record is played in a room that adds few extra qualities, you will be listening nearest to what the artist(s) intended.  Further, the sounds of the record seem to blossom out of the loudspeakers with breadth, depth, clear tonal balance, and great detail.

Relationship of the Equilateral Triangle Relative to Walls

There are two approaches to placing loudspeakers in the listening room: symmetrically and asymmetrically with wall surfaces.  Both approaches have advantages and challenges.  Either approach may best suit your particular situation.  Keep in mind, placing the listener position in the center of a rectangular room should be avoided, as it invites many problems of audible reflections and frequency response.

The approach to placing the array symmetrically in the room has the distance between the left speaker and the left side wall equal to the distance between the right speaker and the right wall.  This creates some balance to the reflections from the side walls, and should establish stable and accurate stereo imaging.  This control of reflections can be further established by placing the listening position at a distance 38% between the front and back walls; in this way more space is behind the listener than in front. This is the approach used in placing the loudspeakers in the listening room described below.

In certain situations, one might consider placing the loudspeaker array asymmetrically in relation to all the walls. The equilateral triangle is turned so as not to be parallel to the walls. This approach can be helpful in establishing a suitable playback environment in some rooms—as in the living room described below.

An asymmetrical placement has each speaker in a to different relationship to the walls, and will shift the way the speakers interact with your room.  The closer to the center of the room the listening position or loudspeaker positions, the more problems arise.  Moving the triangle slightly closer to one wall will change the lengths of some reflections, and those shifted proportions generate different relationships to room modes and standing waves.  The shift also changes the characteristics of the reflections and can minimize flutter echo.  Reverberation becomes more randomized as the number of wave paths increase, and the sound can dissipate more evenly.  How to angle the equilateral triangle, and where to place it in your room is a complex problem to solve. There are many variables unique to your particular situation; expect some trial and error in finding a position that best suits your needs.

Identifying and Taming Reflections and Altered Frequency Response

Parallel surfaces create problems from strong reflections, standing waves and room modes. If possible, avoid rooms with parallel walls.  Yes, this is completely impractical, as few buildings are designed in this way; to avoid parallel walls requires a remodel of nearly all spaces, and that is beyond reasonable to suggest here.  Still, we need to understand the issues of parallel surfaces and their impacts on sound produced in the room.

When two reflective surfaces face each other, sound will continue to bounce between them after the direct sound has stopped.  This is flutter echo; it can hang in the air as sound bounces back and forth between the two surfaces—two walls, and floor to ceiling.  Absorbing or diffusing materials (rug, drapes, acoustic absorbing materials, etc.) can often mitigate these reflections with considered placement.

Reflections of sound around the room also create issues of emphasized and de-emphasized frequencies or frequency areas.  The results are many and varied.  Room resonances can be excited, emphasizing frequencies at the modes of the length(s) between surfaces; these can appear dramatically while listening to some tracks, and be less noticeable while listening to others.  Comb filtering occurs from the patterns of reflections as sound bounces around a room; this causes some (usually narrow bands of) frequencies to be attenuated.

Diffusing the sound coming from speakers can help.  By introducing uneven surfaces in the room, strong reflections are dissipated into many closely spaced reflections of lesser amplitudes.  Bookcases filled with varying sized books is an example of a diffusor nearly everyone can add to a listening (or living) room.

Room acoustics is a discipline in itself, and taming listening space issues is an involved challenge.  What is described here is but a small portion and cursory sampling of the major issues that arise between loudspeakers and rooms—and no real solutions can be offered within this limited space.  Further examination of room acoustics may well prove essential to establishing accurate playback in your particular space and circumstances.

Examples of Two Home Listening Systems

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Here are two highly contrasting home listening systems.  Both are in this author’s own home.  Each system serves a different function: one is for careful and detailed listening and is useable for my most demanding work, and the other is for more casual listening and also for observations that contrast with the much more accurate listening room (on a system offering less precision and detail, and more representative of what avid amateur listeners might hear).  The difference is between an entry-level audiophile system and a professional quality monitoring system.

Listening Room

My listening room (family room) is used for critical and analytical listening. This may lead to analyses of records, working on production projects, on-going research projects, continual study of new recordings, grading student projects and assignments, etc.  These activities are central to my work and profession; thus, dedicating a room in my house to this activity is not at all superfluous—though it is certainly a luxury and an expense many cannot enjoy.  It may be helpful to recognize I did not have such a space in my home for the majority of my career.  The room is sometimes used for other purposes, but rarely.

The listening room occupies a 20 foot by 21 foot family room with a vaulted ceiling that is 15 feet at the ridge peak.  The space has an open balcony that is part of the considerable space behind the listening position. Loudspeakers are 6 feet apart and form an equilateral triangle with a sofa listening position; about 60% of the room volume is behind the listening position. The front wall is 21-feet wide, and each speaker is located 3 feet from the front wall and 7(+) feet from the side walls. The volume of the space, the distance of the speakers from walls, the brick wall behind the listening position (dispersing reflections), and the paths of direct and reflected sound minimize the imprint of the room at the listening position. Few strong reflections arrive at the listening position, and the percentage of reflected sound relative to the direct sound from loudspeakers is negligible there; the room at the listening position is largely neutral.

The listening room loudspeakers themselves are from the same manufacturer and have a similar design concept as the speakers in the critical listening room system on my campus.  The speakers are full-range two-way (active crossover at 1.5 kHz) world-class powered studio monitors with discrete digital amplifiers (dedicated 270 watt and 50 watt amplifiers power individual speakers in each cabinet); each front-ported cabinet contains an 8-inch driver and a wide dispersion planar ribbon high frequency transducer. The loudspeakers deliver accurate transient response and significant timbral detail; their cabinet design eliminates signal diffractions from the sides of the cabinet; operating range is 36 Hz to 40 kHz.  Each speaker stand is fixed in place by spikes into the carpet; the stands are filled with sand to minimize resonance and the speakers are decoupled from the stands.  A professional grade Blu-ray/DVD/CD player with high-resolution DACs provides the signal that is routed through a passive volume controller on its way to the powered monitors.

The mid-field relationship between speakers, room and listening position allows the room to contribute to the sound, but subtly.  The imprint of the room is barely audible, though the space adds a sense of openness that seems to assist the ear to not tire over extended listening sessions.  The room/system presents stereo imaging that is clear and stable, substantial and intricate timbral detail, a frequency response that is almost ruler flat, and an accurate and substantial depth of sound stage.  When sound stops, the room provides little reverberation tail at the listening position.  The system itself vanishes from the listener’s sense of loudspeaker sound emanation, and reproduced tracks are vivid in their sonic qualities and their dramatic presence.

Living Room

My home living room is arranged for everyday living—reading and relaxation, entertaining guests, and so forth. When I want to use the system for active, attentive listening I move a chair out of the room and move each loudspeaker from its next-to-the-wall and out-of-the-way location to a specific position on the area rug; this takes little more than a minute, as I know how to precisely position each speaker stand on the rug pattern.

The room is 11.5 feet by 17.5 feet.  The speakers are not symmetrical in the room, one is 2.5 feet from a side wall and the other 4 feet from its side wall. The room’s front wall is 4 feet or 6 feet behind the speakers respectively; part of the front wall has a slight angle accommodating the fireplace. Speakers are separated by 5 feet and form an equilateral triangle with the sofa listening position. This positioning works acoustically in this room. If the room had no other uses, alternative positioning could be pursued, though a substantial improvement in the sound is not likely.

Near field monitoring is used to minimize room sound, though the room does play a role in what is heard. While the impact of the room on the track cannot be neutralized, the playback still exhibits stable imaging, considerable depth of sound stage, a frequency response that is largely consistent throughout its range, and wave tracking that is respectably accurate. The loudspeakers are rear-ported two-way dynamic bookshelf design with a stand designed for the speakers; each contains a 1-inch tweeter and a 7-inch driver (with a phase-coherent crossover at 1.5 kHz); their operating range is 59 Hz to 20 kHz. The speakers are driven by a multi-channel receiver/amplifier that can produce 100 watts/channel (the receiver also drives a separate pair of bookshelf speakers in another room and is capable of simultaneously powering a modest home theatre system). CDs are played on a universal disc player (capable of CD, DVD, DVD-A and SACD playback).

This system as it has been arranged in this room is useable for analyzing tracks.  The system does distort the essential content and character of tracks, but does so minimally and consistently. It is sufficiently detailed and precise for one to observe the traits of tracks accurately.  The qualities the playback system and room impart are, all in all, workable for analyzing records because I am aware of their inherent qualities and how they transform the sounds of tracks.  The price point of the system (speakers, stands, amplifier and disc player) should be within reach of many readers, though certainly not all.

Playback System Testing and Calibration

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 Audio files 8, 9 and 10 are included on this webpage.  These have been prepared to assist the reader in evaluating the quality of their playback system and to help them prepare for accurate listening sessions.  Download these files from the webpage, and ensure that they have not been compressed from their original format (.wav). Get them ready for playback through your system.

Verify your playback system does not have a loudness button or other tone controls engaged.  Loudspeakers should be located carefully (see above), and the listener seated appropriately.

Audio File 8:  Setting an Appropriate Listening Level

Pink noise is played in two 8-second segments. The first segment should be at a nominal listening level. The second segment is 5 dB higher, and represents loudness levels that might typically be reached during a typical music recording.

Set your loudness level so that the first segment is at a comfortable, though somewhat loud level. Your sound-pressure level meter should read approximately 85 dB SPL (A-weighted).  This will be your nominal listening level, and should become the average level of the program material you will hear.  [Note: during your actual listening sessions you will need to adjust the output of your amplifier to obtain a playback level of 85 dB SPL, because individual tracks will be at different sound levels.]

Do not adjust the level. The second segment will be substantially louder, but it should be tolerable and should not cause distortion within your playback system.  If it is not tolerable, lower the level slightly and listen to (and measure with your SPL meter) the first segment again.  If you are noticing a distortion in the sound, your playback system is in need of attention. You must address this situation before using the playback system for analyzing recordings.

Audio File 9:  Checking Loudness Balance between Left and Right Loudspeakers

Pink noise is now directed to individual channels.  In 5-second segments, pink noise will appear at the left speaker, the right, then center (each speaker equally). This sequence is repeated three times.  All sounds are at the same loudness level and should be played back at your nominal listening level that was set above (while working with audio file 8).

Use this sequence to explore the following three matters.  Each matter should be engaged sufficiently before moving on to the next.

• Use these pink-noise segments to ensure that the loudness relationship between the two speakers is correct.  Your SPL meter will be very useful for identifying the loudness levels of the two speakers. Measure the sound at the listening position to verify SPL is consistent between left, right and both speakers simultaneously.
• Use the pink noise sequence to examine reversed loudspeaker polarity; listening carefully, one should seek to identify any differences in spectrum (frequency response) and amplitude (loudness) between the speakers and when they are combined. Any detectable differences between the left and right channels are cause for concern and need to be traced.
• Finally, use the pink noise to listen to the room.  While the noise is playing, stand in different positions in the room, and seek to identify any changes that appear at various specific positions.  Pronounced emphasized or attenuated frequencies or frequency bands may be noticed, as well as reflections and reverberation after the sound has stopped.

Audio File 10: Evaluating Frequency Response

 Six 5-second sine tones are presented in the following order:

• 1 kHz
• 100 Hz
• 5 kHz
• 500 Hz
• 15 kHz
• 40 Hz

All sounds are at the same sound pressure level, and you should be playing them back at the same nominal listening level that was set in audio file 8. The first four tones should be readily apparent, and very near the same loudness level. If this is not the case, a serious problem is present in the monitoring system that must be corrected before using the system to evaluate tracks.

The last two tones are at the extremes of the hearing range and are likely near (or just beyond) the limits of your playback system.  These two tones will appear significantly softer, though they are recorded at the same SPL as the other four.  While this should not cause alarm, readers need to be aware of the limits of their playback systems as well as their own hearing. These tones provide a first step that will lead to that knowledge.