- Stereo Loudspeaker Placement
Stereo Loudspeaker Placement
Loudspeaker placement. The other 1/3 of your system's performance
Most of us can have an instant 33% improvment in our audio system's performance without spending a dime. How can that be you say? By taking the time to properly set up your loudspeakers you can tap into the hidden potential of your music system. While some of you have already taken the time to optimize speaker placement, the truth is that most of us either do not know how or do not take the time to properly position our loudspeakers. The following information is meant to simplify this process, and hopefully inspire you to take action.
Before the flames begin , let me say that the perfect article on "correct" speaker placement does not exist. Simply because every situation requires a different approach to optimization. Further, one's personal preference may vary slightly from the optimum.
What tools you will need
- A friend to move speakers while you listen for changes
- A roll of string. You will be using a single piece for measuring distance from each speaker to your listening position.
- A laser pointer, or level for accurately dialing in speaker toe-in.
Some acoustic facts about your room
Your room affects the sound of a speaker by the reflections it causes. Some frequencies will be reinforced, others suppressed, thus altering the character of the sound. If we were to listen to our speakers outdoors (or inside an anechoic chamber), much of the coloration we’ve been used to hearing would disappear. This is a major reason loudspeaker designers test their creations in such an environment, not wanting their design decisions to be influenced by the colorations of any given room. The real world, however, requires that our speakers occupy our living quarters, which are quite unlike the anechoic chamber they were designed in. Therefore we must absolutely deal with the room as a significant contributing factor.
In any listening environment, what we hear is a result of a mixture of both the direct and reflected sounds. Direct sound travels straight to our ears from the speaker diaphragms. Reflected sounds are many, bouncing off most any hard surface and reaching our ears after the direct sound. In general, the direct sound from the speakers are primarily responsible for the image, while the reflected sounds contribute most to the tonality of the speaker (richness, leanness etc). Any boundary surface (back wall, side wall, floor) can cause a reflection, and all need to be considered during placement. The trick is to place the speaker (and/or treat the room) in a location that will take of advantage of the desirable reflections while diminishing the unwanted reflections.
Distance to the listener
For proper imaging to take place, sound from each speaker must arrive at the listening position at precisely the same moment. This requires that the speakers be exactly the same distance away from the main seating position. Precision is key here. Differences of less than ¼" can be audible in better systems to careful listeners.
Using a tape measure for this procedure can be cumbersome, so I like to use a string. It's easy and very accurate. Simply tape a string to the midpoint of the listening chair, trying for a spot as close to ear level as possible. Now, unroll enough string to reach one of the speakers, then pull the string taught to a reference point on the speaker, I like to use the tweeter. Grasp that point on the string with your thumb and forefinger, then walk to the other speaker to see how it compares. Simply adjust the distance until each speaker is exactly the same distance.
Distance to side wall and back wall. There are two acoustic characteristics to be dealt with here: bass and soundstage. It's well known that the closer a speaker is to a boundary (wall, floor, ceiling) the more bass reinforcement . Changing the location in relation to these surfaces will dramatically affect both the quality and quantity of the bass. Note: moving your listening position can have as much affect on bass as moving the speaker. The speakers excite room nodes which create low frequency standing waves. Because of bass frequencies long wavelengths, these waves are present regardless of where the speakers are located. Moving the listening position however, determines whether that point is with relation to areas of additive or subtractive bass pressure. If you have the option, try moving the listening chair a foot or two in each direction to find the optimal position.
With regards to soundstaging, you'll find that depth is dramatically influenced by rear wall proximity. Increasing the distance from the speaker to the wall behind will increase soundstage depth. However, pulling the speaker too far out may degrade focus. In most cases, room layout dictates the maximum distance the speakers will be allowed to intrude into the space, so experimentation is key.
Most speakers need to be a minimum of a foot or two away from the side and back walls to reduce early reflections (early reflections reach the listener out of step with the direct sounds, causing image degradation). Distance to reflective surfaces, speaker radiation pattern and toe-in all contribute to the amount and intensity of early reflections. Minimizing these reflections is key to maximizing soundstage and focus.
Differences among speakers can also influence positioning. A planar, for instance (which radiates sound both front and back with null points to the sides - a figure-of-eight pattern), may be less critical of a nearby side wall, but very critical of the distance to the back-wall. Just the reverse is true for many dynamic designs whose propagation pattern is mainly to the front, with some to the sides and little to the rear (cardiod pattern).
You'll find that the side wall distance will affect both soundstaging and tonal balance. In general, proximity to the sidewall will more influence midrange balance while the distance to the back wall will have more impact on bass.
It is most important to insure that the distance to the back and side walls are unequal. Do not place the speaker, say, 20" from both back and side walls. That said, be sure both speakers are set the same; symmetry is very important. By that we mean if the left speaker is 20" from the back-wall and 30" from the side-wall, try to place the right speaker in the same way. This may not be possible in all situations, but do your best to give each speaker a similar acoustic environment.
Precision alignment of the distance between the speakers will be determined by the distance to your listening position, the particular speaker you own and, to a great measure, your own personal preference. I generally prefer to start with an equilateral triangle, the apex of which is located at the listening position and the two speakers forming the base line (here, speakers placed 6' apart would suggest a listening position 6' away), and experiment to produce the best soundstage. Note: Some manufacturers recommend a specific measure for speaker separation. Use this measurement, if available and your room permits, but remember that any recommendation is only a starting point. You'll find that increasing the distance between the speakers will widen the soundstage (until, at some point the center image falls apart), decreasing the width will narrow the stage and increase center focus. As mentioned previously, this is partly subjective. I listen to a lot of female voice and a strong center focus is really important to me. You may concentrate on orchestral works and prefer a wider stage and be willing to sacrifice some specificity of image for the extra bloom. Select recordings with which you are very familiar.
As discussed previously, the distance to the side walls affects mainly the midrange tonal balance. As we move the speakers closer or further apart, the relationship to the side walls change. Further, the proximity of one speaker to the other will influence tonality as well.
The amount of toe-in required depends on three factors: the particular speaker you have chosen, the room and your personal preference. Some speakers sound best with little or no toe-in, others may require a great deal to perform properly. Follow the manufacturer's recommendations or, start with no toe-in and begin turning the speaker inward (pointing more toward the listener) until the right amount of center-fill, without sacrificing soundstage width, is obtained.
The best method for setting toe-in employs a laser pointer. You'll need a "target" for the laser, ideally something positioned at ear level. A pillow propped up in the listening chair, or a point on the wall behind the listener can be used as reference points. Place the pointer on top of the speaker, making sure it's square to the front of the enclosure, and adjust toe-in until the laser focuses at exactly the same point on your target.
Adjust the position of the target itself to correlate with the speaker manufacturer's recommendation for where the speaker output should intersect. Speakers requiring a large amount of toe-in will intersect at or just behind the listener, that point moves further back when less toe-in is indicated. Some manufacturers are adamant regarding the amount of toe-in, others are less specific in their recommendations. In general, more toe-in increases center focus, but reduces stage width. Less toe-in widens the stage, but center focus will be sacrificed if you go too far. Sometimes it's a balancing act based on the room, the speaker and the preference of the listener.
Note: Toe-in and distance between the speakers are often interrelated. You may find that it will be necessary to revisit the distance between your speakers after you have experimented with toe-in.
Tilt, (fore and aft) also can be very important in influencing the sound of a speaker. Although most speakers today should be level, some designs recommend specific tilt (generally rearward) for proper imaging. I recommend starting level, and experimenting rearward from there, if necessary. It's very rare that tilting the speaker forward will be of use. Use a carpenters level for accuracy, and remember to check both front to back and side to side.
Listening Height. Every speaker has been designed with a specific listening height in mind. Generally speaking, your ears should be on axis with a point midway between the tweeter and woofer (two-way) or tweeter and midrange (3 way). Again, consult your owner's manual for specific recommendations.
Summary and additional tips
- Experimentation is the key to optimum results. Trial and error will tell you a great deal about how the speaker reacts in your environment and help you to better balance strengths and weaknesses of each position you try.
- Once you have found a rough position, place two pieces of masking tape on the floor, one marking distance to back wall, another noting positing from the side wall. Mark the tape in one-inch increments. This will allow you to move each speaker exactly the same amount, without having to re-measure each time.
- Exact distances are critical! Always use a tape measure, 1/4 of an inch can make all the difference in the world.
- Bear in mind that the best location for creating a spacious soundstage, may not be the ideal location for bass. We are searching for a balance, a compromise of parameters that comes closest to our personal definition of ideal.
- When setting up new speakers, don’t rush through the process. Take your time and slowly find the ideal location over a few weeks of listening. Pressing to find the right position can be very frustrating. Also note that the sound of the speakers will change during break-in. Play the speakers for at least 100 hours before fine tuning placement.