Rule #5: Listening height affects tonal balance.
Most loudspeakers exhibit changes in frequency response with changes in listening height. These changes affect the midrange and treble, not the bass balance. Typically, the loudspeaker will be brightest (i.e., have the most treble) when your ears are at the same height as the tweeters, or on the tweeter axis. Most tweeters are positioned between 32" and 40" from the floor to coincide with typical listening heights.
The degree to which the sound changes with height varies greatly with the loudspeaker. Some models have a broad range over which little change is audible; others can exhibit large tonal changes when you merely straighten your back while listening. Choosing a listening chair that sets your ears at the optimum axis will help achieve a good treble balance. For stand-mounted speakers, selecting the right height for your speakers and listening position is vital.
Rule #6: Toe-in (angling the loudspeakers toward the listener) affects tonal balance, soundstage width, and image focus.
Toe-in is pointing the loudspeakers inward toward the listener rather than facing them straight ahead (see Fig. 3). There are no rules for toe-in; the optimum amount varies greatly with the loudspeaker and the listening room. Some loudspeakers need toe-in; others work best firing straight ahead. Toe-in affects many aspects of the musical presentation, including mid- and high-frequency balance, soundstage focus, sense of spaciousness, and immediacy.
Most loudspeakers sound the brightest directly on-axis (directly in front of the loudspeaker). Toe-in therefore increases the amount of treble heard at the listening seat. An overly bright loudspeaker can often be tamed by pointing the loudspeaker straight ahead. Some models, designed for listening without toe-in, are far too bright on-axis.
A toed-in loudspeaker will present more direct energy to the listener and project less energy into the room, where it might reach the listener only after reflecting from room surfaces. As we'll see later in this chapter, sound reflected from the sidewalls to the listening positions can degrade sound quality. Toe-in often increases soundstage focus and image specificity. When toed-in, many loudspeakers provide a more focused and sharply delineated soundstage. Images are more clearly defined, compact, and tight, rather than diffuse and lacking a specific spatial position. The optimum toe-in is often a trade-off between too much treble and a strong central image. With lots of toe-in, the soundstage snaps into focus, but the presentation is often too bright. With no toe-in, the treble balance is smoother, but the imaging is more vague.
Toe-in also affects the presentation's overall spaciousness. No toe-in produces a larger, more billowy, less precise soundstage. Instruments are less clearly delineated, but the presentation is bigger and more expansive. Toeing-in the loudspeakers shrinks the apparent size of the soundstage, but allows more precise image localization. Again, the proper amount of toe-in depends on the loudspeaker, room, and personal preference. There's no substitute for listening, adjusting toe-in, and listening again.
Identical toe-in for each loudspeaker is vital. This is most easily accomplished by measuring the distances from the rear wall to each of the loudspeaker's rear edges; these distances will differ according to the degree of toe-in. Repeat this procedure on the other loudspeaker, adjusting its toe-in so that the distances match those of the first loudspeaker. Another way to ensure identical toe-in is to sit in the listening seat and look at the loudspeakers' inside edges. You should see the same amount of each loudspeaker cabinet's inner side panel. Identical toe-in is essential to soundstaging because the speaker's frequency response at the listening position changes with toe-in, and hearing the identical frequency response from each speaker is an important contributor to precise image placement within the soundstage.
Keep in mind that all loudspeaker placement variations are interactive with one another, particularly toe-in and the distance between loudspeakers. For example, a wide soundstage can be achieved with narrow placement but no toe-in, or wide placement with extreme toe-in.
The Final Touch
After you've found the best loudspeaker placement, install the carpet-piercing spikes (if any) supplied by the manufacturer. Level the spikes so that the loudspeaker (or the stands on which the speaker is mounted) doesn't rock: the loudspeaker's weight should be carried by all four (or three) spikes. If you have wood floors that you don't want to mar with spikes, place the round metal discs that are often supplied with the loudspeakers beneath the spikes.
Loudspeaker positioning is a powerful tool for achieving the best sound in your listening room, and it doesn't cost a cent. Take advantage of it.