RULE 3 - LOUDSPEAKER PLACEMENT
Strategically position loudspeakers and
establish the sweet spot
You will recognize an audiophile by the way they positioned their loudspeakers and the listening seat.
Unlock the potential of your audio system
To recap the progression towards a high-resolution system, the first rule establishes that you have no hearing impairment to hear the audible spectrum. Additionally, you are also schooled in the art of critical listening. So, when you can and know how to listen, the second rule, suggests we select audiophile-quality recordings to optimize the listening experience. For critical listening, selection should be based on familiarity to include relevant music for evaluation purposes. The first 2 rules are imperative and help facilitate the positioning of your loudspeakers and the sweet spot. Before we get into this important discussion, I will like to plant a flag here, you don’t own the listening room from here on, it belongs to your loudspeakers. You must surrender the room to your loudspeakers otherwise, you will never realize your system's potential no matter how expensive your system is. Any other loudspeaker and listening positions other than best practices are just compromises, that’s just the way it is. Your journey toward a high-resolution system may prematurely end here depending on your priorities.
A pair of loudspeakers are required to achieve a stereo reproduction from stereo recordings. Stereo provides a semblance of a live musical event where there is an inherent ‘soundstage’ – music that is spread out instead of coming from one direction (as in a mono recording or playing with only one loudspeaker). To realize a stereo soundstage and in the audiophile world, a dimensional soundstage as intended by good mixing engineers, we need to integrate the loudspeakers and the listening seat (sweet spot) in conjunction with room boundaries (floor, ceiling, sidewalls, rear, and front wall). All loudspeakers sound different no matter how similar they measure or similar measurements listed in their specifications sheet. They will further sound different when paired with different companion components or when set at different positions in the listening room. You will be glad to know, that there is no such thing as an accurate loudspeaker, accuracy against what reference, therefore accuracy is a subjective term period. A similar make and model of a pair of loudspeakers will sound different in different room settings. Therefore, loudspeakers' in-room performance is highly variable depending on the acoustic space, relative placement, and loudspeaker design type.
Hence, the loudspeakers, listening position, and the room must be integrated to work together in harmony to achieve the ‘right’ balance and produce the quintessential loudspeakers' voice. Finding the right locations for loudspeakers and the best listening position will dial in that voice. The preferred positions will provide the best tonal balance, bass definition, and a coherent soundstage of width and depth. The goal eventually is to provide a virtual listening experience resembling that of a live event and in this instance, ghostly images conjuring within a dark space give you goosebumps.
Practical room dimensions are an important factor for good sound reproduction
A room with odd-dimensional ratios and or a rectangular-shaped one is ideal for achieving the best loudspeaker placement. Unless you build a dedicated room from scratch, most of us, have to deal with the cards we are dealt. Two notorious acoustical phenomena influence how sound is perceived in the listening room. They are standing waves and early boundary reflections which are discussed in the next article; Rule 4: Room Acoustics. Therefore, strategic positioning of the loudspeakers relative to the room boundaries, listening position, and their physical distance from each other is necessary to mitigate those effects. Strategic locations for loudspeakers may be found at the 1/7, 1/5, 2/7, 1/3, 2/5, and 3/7 positions along with the room which produces the least amount of standing wave. These locations are easily identified by dissecting the listening room into a grid for both loudspeakers and the listening position. Measure the width, length, and height of the room to the nearest inch and use only hard surfaces as reference i.e., no false ceiling or cornices. The goal is to try to keep all boundary distances relative to the loudspeakers at different ratios and, in the process, try to achieve as wide and as deep a soundstage during playback as possible. The best configuration is applying the rule of thirds by dividing the room into a grid of 6 blocks to mitigate those two interferences.
The acoustic center of a loudspeaker is at the front baffle (see illustration) and as such, is used as the reference point for all measurements. Similarly, the back and center sides of the listening chairs would be the reference point for all measurements.
Firing down the long side on the 1/3 grid (preferred method for rectangular-shaped rooms)
Firing down the length (long-side) would be best for planar designs, subwoofer(s) reinforcement, tower loudspeakers, or full-range loudspeakers (<40hz). These positions afford greater depth of field, with minimum problems of standing waves hence providing a better bass definition. The long side of the room should be divided into thirds where the loudspeakers are placed at the point where they intersect on one end of the one-third intersection away from the front wall and one-fifth away from the sidewall along the long side. The sweet spot should be sited on the one-fifth area at the other end of the room (behind the listener) for the best bass response.
Firing down the long side on the 1/5 grid (second choice position for rectangular-shaped rooms)
For the second-choice position, the loudspeakers are sited at the one-fifth intersection position away from the front wall and the one-fifth intersection position away from the sidewall. The sweet spot should be sited on the one-third area on the opposite end for good bass response. The second choice is also desirable if you don't want your loudspeakers to be too intrusive (out into the room). Each configuration offers a great soundstage but experiment for your circumstance.
Firing down the short side
Firing towards the width (short-side). The loudspeakers are sited at an intersection that is one-third position away from the sidewall and one-fifth position away from the rear wall. The sweet spot should be sited on the one-fifth area on the opposite end for good bass response. The orientation would be good for a wider soundstage and afford a near-field listening position. It is also a desirable position for a bookshelf or mini monitor loudspeakers and loudspeakers with a questionable bass response as the proximity to the back wall will augment the bass.
Square room placement (worst case scenario – no choice)
Divide the room on a diagonal. If the 1/3 position from the diagonal brings the loudspeakers too close together for a practical wide soundstage, then adopt the 1/5 position instead. Do not ever locate the sweet spot in the middle of the room, otherwise the system will sound ‘boomy’.
L shape room placement
Fire the loudspeakers down the long side with the sweet spot at the L-shaped end. The rule of thumb is to always maintain symmetry for the loudspeakers to room boundaries for uniform reflections. This would include room cavities.
Asymmetrical rooms
For rooms that are asymmetrical in shape and dimensions which are many, you should first decide the distance you want between each loudspeaker which should not be less than 6 feet apart. Using this as a basis, determine the centreline at any part of the desired listening space and site the loudspeakers away equidistant from the centreline keeping a perfect equilateral triangle where the sweet spot is at the apex of that triangle. This is your starting point, then experiment by moving the sweet spot backward along the centreline but no more than 1.5 times the distance between the loudspeakers.
Choosing the distance between loudspeakers is a compromise between a wide soundstage and a well-defined center image. The farther apart the loudspeakers, the wider the soundstage, however, the center image may become diffused and you may even have a ‘hole-in-the-middle’ effect in extreme situations. If loudspeakers are placed too close together the soundstage will be 'seen' as constricted or scaled-down. You must remember not to have equal room boundary distances from the woofer to sidewalls, woofer to ceiling, woofer to the floor, or woofer to the front wall which should be kept at odd ratios respectively.
Sweet Spot
The listening position is called the sweet spot because it is the only location where the loudspeakers will sound their best after being placed strategically having optimized their voice and character with minimal room interferences. This will create a dimensional soundstage that is only possible if the sound from both loudspeakers arrives at the sweet spot at precisely the same time. The sweet spot should not be situated at the standing wave null or peak points being mindful that the distance from the rear wall (behind the listener) should be at least 3 feet away to avoid time-smearing reflections. Good locations to alleviate standing wave null or peak areas may be found at the 1/3, 1/5, 2/5, or 2/7 distance away from the rear wall.
Near-field listening
This is a position where the loudspeakers and the sweet spot are relatively close to each other. It is recommended that the sweet spot is located equidistant with precise symmetry away from each loudspeaker in a perfect isosceles triangle where the loudspeakers reside at the base angle points and the listener's head at the vertex angle point. The base distance could vary between 1.2 to 1.5 times the distance between each loudspeaker’s acoustic center.
That means the mid-point between each loudspeaker is tracked to form a centreline right down to the base point. For example, if your loudspeakers are 6 feet apart, then your sweet spot distance (vertex) should be a minimum of 7.2 feet away from the mid-point and no more than 9 feet (see illustration). The ratio also offers flexibility in finding the best spot away from any standing wave peak or null points. You should find a position providing the most linear bass response within the room.
Advantages of near-field listening
If the efficiency of your loudspeaker is low (<89dB) and your amplifier has inadequate power to drive them, you may not have to crank up the volume to reach the favored listening level when seated at the near field. Therefore, you can avoid amplifier clipping when at peaks causing distortion or a system that is weak in delivering macro-dynamics.
Recommended for rooms with little or no absorption or reflective treatments. You will get superior image resolution and a better-perceived soundstage.
Your proximity to the loudspeakers mitigates early wall reflections hence maintaining relative tonal balance and a feeling of better dynamics which makes music more appealing.
Disadvantages of near-field listening
Relatively scaled-down soundstage
It may not be practical when using tower-type (over 6 feet tall) loudspeakers
Note: The equilateral triangle method commonly used in recording studios to position the studio monitor loudspeakers for translation purposes allows the mixing engineer to ‘move’ the images around to their desired location when creating the soundstage. This is not recommended for listening to music as the up-your-face perspective is not an ideal listening position to appreciate the soundstage and imaging in all its glory. However, this position easily aids the mixing engineer to develop the mix down with as little room interferences as possible. The more the mixing engineer distance himself from the loudspeakers, the more of the room he will hear which affects his ability to render the mixdown appropriately.
You can also explore another method that will help you to find the sweet spot which is called "The Bass Hunter Technique 2.0" from AcousticsInsider.com. However, this method is designed for home studios where an equilateral triangle is formed for locating the loudspeakers and the listening seat, but you can vary the loudspeaker position by forming an isosceles triangle instead.
Loudspeaker off-axis response
An ideal loudspeaker would have a good off-axis response for reflections to arrive at the same time toward the sweet spot. Therefore, the sweet spot should be positioned no more than 60 degrees off-axis for loudspeakers with a poor off-axis response, otherwise loudspeakers should be toed in towards the sweet spot. This will afford more direct sound with less reflected ones.
Listening height
You should also ensure that the loudspeaker drivers' acoustic center (see illustration) is approximately positioned at ear level when seated at the sweet spot. You can achieve this by either getting a customized loudspeaker stand or by getting the right listening chair that will get you closer to your listening height. The listening chair should be a single-seater that enables you to always be at the center point when listening to your loudspeakers. The chair should not be a high back design otherwise you will have time-smear reflections directly to your ears. You can use aftermarket seating cushions to get to the required height or ideally customized you own.
Fine-tuning
Your hearing disability, room reflections, poor loudspeaker placement, poor equipment design, electronic parts, or manufacture may cause your 'known' center image to be slightly off-center. Therefore, as a final tweak, you need to move your sweet spot laterally in fine increments to capture the center image. You would want to mark the legs of the listening chair on the floor as a reference to always get to the correct position every time. You should use a test LP or CD to check the acoustic center first before making any adjustments.
Toe-in
Toeing refers to canting (angling) your loudspeakers inwards towards the sweet spot instead of `firing’ it straight ahead. Toe-in is recommended to minimize side wall reflections. The ratio of direct to reflected sound increases with toe-in. A toed-in loudspeaker will present energy that is directed mostly toward the listener. Toeing affects many aspects of sound reproduction, including mid and in particular high-frequency balance. It may limit soundstage width but will provide precise image localization and enhance the illusion of a deeper soundstage. To acquire toe-in symmetry for both loudspeakers, align the inner sides of the loudspeakers as seen from the sweet spot. That means at the sweet spot you can see the same amount of loudspeaker inner cabinet panels of both the front and rear edges as being flushed (single line – see illustration). Toe out if treble energy is excessive i.e., bright sounding. You could use a mobile app (KRK Audio Tools – Monitor Align) to easily get an asymmetrical toe angle for both loudspeakers.
Planar loudspeakers
Electrostatic or ribbon designs have a unique radiation pattern (see illustration) where placement away from the front wall is crucial to avoid time-smearing colorations. Ideally, they should be placed as far away from the wall as possible so that the radiating back wave is sufficiently delayed before reaching the sweet spot. Try having them start at 2/7 away from the front wall working in golden ratio sections such as 3/7 and 5/7. Planar loudspeakers are velocity devices instead of pressure, the sound pressure level (SPL) never quite reaches its maximum at these positions. They should not be placed parallel (90 degrees) against the wall as the back wave will interfere with the relative motion of the diaphragm corrupting their waveform. Therefore, Planar designs are best toed in.
Mini monitors or bookshelves loudspeakers
Some loudspeakers are designed for placement close to the front wall, as they need wall reinforcement for a more natural tonal balance. Mini-monitor loudspeakers may benefit from wall placement at the expense of good imaging. The wall placement may boost their warmth and upper bass register while trading off the sense of depth and focus due to increased time smearing from wall reflections. The midrange is also affected by induced coloration. Just be careful not to closed-off the rear-ported designs. The ports are designed to extend the bass frequencies and should not be restricted when blocked by a wall or objects otherwise you discount the designer's intention. The better solution is to position them off the wall to achieve a soundstage and use subwoofers to extend the lower frequencies instead. There is one caveat, your monitor loudspeaker should be able to play below 100Hz otherwise the 80 to 200Hz region would not have enough energy to produce for example the bite of a snare on the drums. You will not experience the mid-bass kick that is essential to certain genres of music.
Subwoofer Placement
Position the main loudspeakers first for the best soundstage, tonal balance, and dynamics. Thereafter place the subwoofer where it would least excite standing waves. You can explore subwoofer placement by using a calculation table provided by Harman which identifies the best locations to avoid standing wave peaks. You can download their Excel spreadsheet by googling “Harman room mode calculator” and inputting your room dimensions for the best subwoofer placement. You could also use the 'Room EQ Wizard" if you are familiar with the system to ensure that the crossover points achieve the best integration with minimum nulls and peaks on the graph as you move the subwoofer around for the best location.
Subwoofer crawl method
There is a school of thought which suggests placing your subwoofer at the listening position, then crawling around the room to hear the best bass definition, and using that exact location to position your subwoofers. They also use this method to site the main loudspeakers. There are problems with this method although it may seem like a reasonable method. The first is that the 'best’ location may not be a practical location to site the subwoofers. Second, the position of the subwoofer at the sweet spot is normally somewhere near the middle of the room, therefore the bass response because it's omnidirectional at those low frequencies, tends to spread out evenly until they reach the walls before they bounce off and will not couple with any wall. However, the final position that may have been chosen may be too close to a wall boundary and when the subwoofer is operated, it will be coupled with the wall and provide a bass boost. The amplitude of the boost is dependent on the number of boundary surfaces that are coupled with the subwoofer(s) as previously mentioned. Moreover, when placing the subwoofer at the listening position, do you need to calibrate the subwoofer first? - adjust the settings such as Phase, Frequency range, and volume?
Subwoofer integration
Generally, you would want to set the crossover frequency range at a starting point of 60Hz if the main loudspeaker woofers are 8", 80Hz if they are 5 to 6", and 120Hz if they are 4". If you are using loudspeakers that have an extended range (Full range floor standers); best to start the crossover frequency at 50Hz.
Next, set the phase switch in the positive phase (0 degrees). Phase refers to the movement of the actual woofers where the woofer cone moves in and out during operation. The goal is to have all the woofers in the system moving in the same direction and at the same time. If the woofer of the main loudspeakers is pushing out and the subwoofer is pulling in, they will cancel each other providing a weak bass response. The phase switch is to help the subwoofer and the main loudspeakers be synchronized. You should also confirm if you have connected on both ends of the loudspeaker's positive and negative sides correctly to the terminals on the amplifier's end as this will affect the integrity of the drivers moving in phase.
Placement is the challenge, and you should start either on the inside or outside of the main loudspeakers slightly behind or next to them respectively. If using only one subwoofer then it can be on either side or in between. However, if the subwoofers are small (10" woofer or lower), it is best positioned in proximity to the wall (side or back) which will add a 3 dB output of gain to the volume. If placed in the corner wall then proximity to both sides would add a 6 dB gain. This strategic position may be considered if the subwoofers are lacking in amplification power (150 watts RMS and below). This strategy of using the walls to augment the bass response is desirable so that you can dial down on the volume to achieve better headroom. Moreover, the wall coupling would start the pressure wave at a single point which would minimize room modes. The corner placement for a front-firing subwoofer facing out at a 45-degree angle would achieve the longest bass throw for the lowest possible frequency response whose frequencies are dependent on the diagonal length of the room. For example, to produce a bass sound of 60 Hz, it needs a wavelength of about 18.75 feet, while a bass sound of 250 Hz has a wavelength of about 4.5 feet.
Next, connect the RCA interconnects at the low-level input (RCA L and R), or the LFE (RCA) if the preamplifier has this facility thereby using only one RCA cable for which it is sum to a mono signal from the preamplifier. You can also choose to connect the high-level inputs using the amplifier's output terminals to the subwoofer high-level inputs via loudspeaker cables. You may also choose to connect another set of RCA interconnects to your Preamplifier outputs instead (Daisy Chain method) and direct into the inputs of the subwoofer and the RCA outputs of the subwoofer to the amplifiers. This would send only the crossover signals that have already been filtered in the subwoofer leaving the main loudspeakers to contend with manageable frequencies that would not tax the main loudspeaker woofers and amplifiers similar to the advantages of adopting a bi-amping system.
Position an SPL meter (set at slow and at 'C' weighting) at listening height at the sweet spot with pink noise fed into the system. You want to achieve similar loudness with the main loudspeakers and all other subwoofer(s). Connect the main loudspeaker one at a time with the first one either the left or right and set it to 80dB on the SPL meter. Do the same thing for the other loudspeaker, you can use the volume control on the amplifier if available to gain match the loudspeaker pair. For the subwoofer(s) you should set it to 74dB instead and use the volume control on the cabinet to gain match them. If you are not using the SPL meter, then set the volume to the mid-level on the subwoofer as a starting point and thereafter fine-tune by listening.
After the physical setup is achieved, you can use technology to choose the subwoofer location that will best integrate seamlessly into the main loudspeakers and room. This is where the "Room EQ Wizard" would be helpful if you have invested in one already. Choose the best location where there are minimal peaks and dips on the graph.
It is said that subwoofers are best seen and not heard which is indicative of successful integration. Use familiar music with consistent and sustainable bass including soft bass like the plucking of an upright double bass that you are familiar with. Adjust the volume first to make sure that you feel it's natural, the bass notes should not stand out or the subwoofer should not call attention to itself which is the test with each type of music played. If the bass has too much boom, reduce the volume level in small increments until it is gone, and if it's lean likewise increase it. Next, try fine-tuning the crossover point by listening to certain signatures that would suggest a colored bass (bloated) with each type of music played. At this point, you should not hear the subwoofer at the listening seat which suggests that they have integrated well into the main loudspeakers. Be mindful, that not all recordings are the same and you should not adjust the settings again because you cannot compensate for sound that is not there. You should fixate the knobs with tape to protect against accidental adjustments such as cleaning activities or children tampering. If at any point during the listening phase, you find that the bass lacks the punch or weight, try shifting the phase switch to the negative phase (180 degrees) if it's a binary switch, better if the phase control has an incremental setting. The idea here is to correctly time align the subwoofer driver to the main loudspeaker woofer where the soundwave reaches the listener at approximately the same time. Sometimes the subwoofer design and placement choices caused certain bass frequencies to cancel out.
Once satisfied, you should let your subwoofers burn in for at least a week if they are new. The final test after listening to the subwoofers in the system for a while and being familiar with the new sound is to cut off the subwoofer completely. Determine if you appreciate your system now without the subwoofer after listening for a while and see if you feel that you miss your subwoofer(s) or not. If you do, then switch the subwoofer power on and you should be able to experience better depth of field, bass information would have more kick and slam, and vocals would be more natural, warm, and not thin.
Ideally, 2 subwoofers should be used for better control due to placement issues (room modes) and you will benefit from a stereo pair achieving better coverage to average out (smoothen) standing-wave peaks and nulls when situated at strategic locations. This will also offer better positioning of the listening seat. Bass volume (in this context not loudness, but control) will be tighter, faster, and more linear. Placement should be one at a time, ideally with the aid of the Room EQ Wizard. The subwoofer will benefit if it's raised off the ground by at least 6" by a customized stand or ideally a wooden sandbox that is a little larger than the subwoofer base. The second subwoofer if used should be at 12" off the ground.
For best integration, your subwoofer size (diameter) should be similar or at the most one size larger than your main loudspeakers for woofer speed consistency. For example, suppose your main loudspeaker woofers are 10". In that case, you should use a 10" subwoofer or a maximum of 12". However, if your main loudspeakers are driving a pair of 10" (both active i.e., one is not a passive driver) on one loudspeaker, then you should use a 12" subwoofer. Likewise, 2 x 12" equates to a 15" subwoofer. However, you may achieve the speed at the expense of a lower frequency response. Therefore, a compromise for a larger diameter subwoofer (one size up) from your main loudspeaker woofer or a twin subwoofer of the same diameter as your main loudspeaker woofer is strongly recommended. A larger woofer if all things are equal has the potential to provide lower frequency information provided you have a higher power amplification to drive those woofers to their full potential. Larger woofers, higher-powered, and large sturdy cabinets are imperative for achieving absolute dynamics for most music genres.
Troubleshoot poor loudspeaker placement (assumption – good quality recordings are used)
Hole-in-the-middle soundstage - Loudspeakers too far apart
Poor width - Loudspeakers too close together
Constricted Soundstage - Sweet Spot is close to the loudspeakers, toeing angle of loudspeakers is ‘cross-eyed’
Diffuse imaging - Sweet Spot too near or too far away
Poor delineation of images - Placement not symmetrical, poor acoustic treatment
Shorten Soundstage - Loudspeaker’s height too low or the listening chair too high
Little depth - Loudspeaker too close to the front wall, no toe-in
Weak bass - Loudspeaker frequency design deficiency and or placed in an area of cancellation, or loudspeaker wiring out-of-phase
Boomy Bass - Sweet Spot placed in a standing wave peak, or loudspeakers too close to room boundaries, poor acoustic treatment, small room with large loudspeakers
Too Bright - Poor tweeter design, poor amplification, too much toe-in, no acoustic treatment
Too Dark - No toe-in, tweeter height off-axis (too high or too low) away from the ear height, loudspeaker grills on, too much acoustic treatment (dead room)
Note: Nothing should be placed in front of the loudspeakers i.e., no line-of-sight obstructions between the loudspeakers and listener e.g., coffee table. Anything in the sound path between your loudspeakers and ears will distort the sound waves before they reach you including the loudspeaker grills. Grills should be off when listening critically, otherwise, you lose high frequencies and the sound may appear ‘dark’.
Loudspeaker placement tools that may be used for easy setup
Familiar audiophile recordings - to evaluate soundstage, tonal balance, and dynamics
Test CDs or vinyl - relevant test signals to evaluate loudspeaker placement
Relevant computer software programs for setting up loudspeakers such as the "Room EQ Wizard" with a corresponding calibrated microphone and laptop to measure the frequency sweep and find the best location where you would receive the flattest desired response or with minimal nulls and peaks.
Spectrum Analyzer with calibrated microphone - to measure peaks and dips in the audible frequency spectrum
Sound Pressure Level (SPL) meter - to set ideal listening levels at the sweet spot
Pink noise generator – to measure SPL and frequency levels
Ball of twine (non-stretch string)
Measurement tape
Masking tape
Laser leveling measuring tool
Distance measuring device
Harman room mode calculator – excel spreadsheet
KRK Audio Tools – smartphone app
Chalk
Conclusion
The typical listening room is ironically a hostile environment for loudspeakers, especially if the room dimensions are at even ratios. Every room impacts loudspeaker response and will be different at different frequencies, locations, and different listening positions. Your bass performance correlates directly to the placement of your loudspeakers within the room. The loudspeaker and the sweet spot should always be integrated (coupled) acoustically with the room to sound its best. The room modes (standing waves and wall reflections) are inevitable when music is reproduced. If the loudspeakers and the sweet spot are not carefully sited to mitigate those modes, your audio system will not sound as good even if you use state-of-the-art components.
Therefore, correct loudspeaker placement will extend a loudspeaker's frequency response by complementing its natural roll-off and avoiding peaks and dips in its frequency response. An ideal loudspeaker placement and listening position will provide a well-delineated soundstage, pristine imaging, natural tonal balance, and great dynamics. A well-delineated soundstage should be favored instead of stronger bass which muddies the midrange. Remember the most important part of the music is in the midrange. Before you start upgrading components or using acoustical treatments, realize first your system's potential. An audio system benefits most when attention is paid to the loudspeaker and sweet spot.