The center speaker is the unsung hero of any good home cinema system. Between the impressive rumble of the subwoofer, the realistic soundstage created by the two front speakers and immersive effects from the back speakers, the center gets little attention. Yet this speaker is responsible for making movie dialogue distinct and realistic. From a primal scream to a gentle whisper, a good center presents all vocalizations naturally and harmoniously.
The following explains what qualities make an exceptional center speaker for the highest level of home cinema enjoyment.
What does the center speaker do?
Most people are aware that the center speaker is responsible for playing back film dialogue. While this is true, it’s not the only thing the middle channel in a classic 5.1 setup is used for. A part of a film’s musical score and certain special effects are also mixed for this channel. Given the spectrum of sounds it produces, the center needs to meet the same requirements as the two front speakers. That is, it must be able to play back dynamic, clear and distortion-free sound along a wide frequency spectrum.
The center speaker’s main job of playing back dialogue takes place mostly along the midrange of the frequency spectrum. For men, the fundamental frequency is between 100 and 125 Hz and between 200 and 250 Hz for women. However, while speaking, singing and screaming, the human voice can achieve much higher frequencies. Higher frequencies will also be required of the center speaker by most film music. In order to cover the entire frequency spectrum, a good center speaker will be equipped with a 2-way system comprising a tweeter and midrange driver. Some even feature 3-way systems with separate drivers for the treble, midrange and bass.
Particular challenges for the center speaker
Our ears are trained to perceive speech as coming from a distinct and very specific location. After all, people only open their mouths a few centimeters when they talk. For this reason, the most authentic home cinema experience results when all dialogue comes from a single sound source. In loudspeaker parlance, this means a “point sound source” which is more of an acoustic ideal than something any speaker system can realistically implement.
The specific localization required of the center is the opposite of the effect created by the surround speakers which disperse sound very diffusely throughout the room. For this reason, there is always only one center speaker in a home cinema system. While it’s possible to create a so-called “phantom center” over the two front speakers, this won’t normally produce the same naturalness as a single dedicated center channel. Another way to approximate a point sound source is to use a coaxial driver. Coaxial drivers position a tweeter in front of a midrange or midbass driver so that the sound from both emanates from the same location.
In addition to functioning as a discreet and localizable sound source, the center speaker needs to be able to disperse its sound over the broadest possible area. This will ensure a generous sweet spot in which all viewers experience the same sound. For this reason, the center is the one speaker in a surround sound system that’s positioned horizontally, not vertically. A horizontal positioning of a center also happens to be the most practical option for placing this speaker below a television or mounted to the wall above it. Many centers also employ a D’Appolito driver arrangement. This involves placing a tweeter between two midrange drivers, a configuration which is very conducive to a broad sound dispersion.
The optimal placement of a center speaker
The name basically says it all: Center speakers should be placed centrally either below or above the display. The two front speakers are best positioned equidistant to the center. Due to its longer horizontal construction, the center is fairly easy to accommodate. Note, however, that it should never be placed directly on the ground, but rather at least 40 cm above it. If it is absolutely necessary to place a center on the ground, the speaker should be angled slightly upwards so that the sound reaches the viewers’ ears.
Teufel’s star vocalists
• ✔ Center L 430 C used in the LT 4 5.1-Set: The 3-way speaker not only produces a highly precise, high-resolution sound, it also endows voices with a very naturally character. From pure fury to the depths of despair, emotions can be easily discerned at even normal to low volumes. The center speaker features a premium aluminium enclosure and handy base for easy placement.
• ✔ Center H 600 CF used in the Theater 6 Hybrid 5.2-Set: A sophisticated look underscores the high-end technology within for high resolution and incredibly natural playback. A flat design is ideal for either wall mounting or placing beneath a television.
Coda: The pivotal role played by the center speaker
• Sound mixed for 7.1 and 5.1 sound contains a discrete channel for the center speaker
• Center speakers are primarily responsible for playing back dialogue but also some film music and sound effects
• Like the two front speakers, the center speaker needs to be able to produce precise playback over a wide frequency spectrum
• In order for voices to sound realistic, it’s important for the center speaker to produce sound from the smallest possible area
• Centers generally lie horizontally either above or below the display in order to disperse their sound over the widest possible area
• Center speakers should be ideally placed exactly mid-way between the two front speakers and centered to the display.