Timbre Matching Loudspeaker Timbre Matching

What timbre matching is

Timbre is the tonal color that lets you tell a violin from a viola playing the same note. Timbre matching is choosing speakers that share that color, usually by buying every speaker from one maker's family, so a voice or effect keeps its character as it moves between channels. No single number describes it: KEF says it is not possible to develop a subjective scale for timbre, and Aperion says no spec or graph will describe it. What you can match is construction. Aperion defines a family as speakers that use the same tweeter, the same woofer cone material and matched crossover voicing. Tweeters come in silk, aluminum, titanium, beryllium and paper, and the crossover is configured to bring out each material's good qualities.

Why panning is the test

Panning moves a sound across several speakers, and any tonal gap shows up at the handoff. ITU-R BS.775-4 places the left and right front speakers at the ends of an arc subtending 60 degrees, with a center between them and the side or rear speakers within 100 to 120 degrees of center front. Dolby's Atmos guidelines add that Atmos mixes use discrete full-range audio objects that can move anywhere in three-dimensional space, so overhead speakers should complement the frequency response, output and power handling of the listener-level speakers. As arithmetic: on that 60 degree arc at a 3.0 m listening distance, the left and right speakers sit 2 x 3.0 m x sin 30 degrees = 3.0 m apart, and the two handoffs, left to center and center to right, each span 1.5 m. With mismatched speakers, Aperion says one stands out, and you hear the sound jump from speaker to speaker instead of moving continuously around you.

The center channel carries the most

SVS says the center channel carries roughly 70 percent of the entire soundtrack, including most dialog and musical vocals, so a tonal gap between the center and the left and right speakers is the easiest to hear. The best match is three identical speakers, which SVS says is possible behind an acoustically transparent projection screen but hardly an option for most people. The next best is a dedicated horizontal center from the same maker. SVS says the best centers use a 3-way design, with a vertically aligned midrange and tweeter flanked by a woofer on each side. That layout radiates a wider horizontal field and, with a lower crossover to the woofers, reduces lobing and comb filtering. Aperion's Verus II Grand Center uses a vertical array and a 3-way crossover and is built to blend with its Grand Tower and Grand Bookshelf. See acoustically transparent screens.

Overheads and surrounds: Dolby's numbers

For a 7.1.4 reference layout, Dolby puts the overhead speakers at 45 degrees of elevation from the listening position, adjustable between 30 and 55 degrees, with the left and right fronts at plus or minus 30 degrees. At 45 degrees, an overhead's height above ear level equals its horizontal distance from the listener, so a pair 2.0 m ahead sits 2.0 m above ear height. Overhead side-to-side separation should be 0.5 to 0.7 of the overall layout width. Overheads with a wide dispersion pattern, approximately 45 degrees from the reference axis over 100 Hz to 10 kHz or wider, can face straight down, while narrower ones should be angled toward the listening position. Dispersion belongs in a timbre discussion because tone off axis is part of what you hear when a sound pans overhead.

What drives timbre, and what barely does

Aperion calls the tweeter the easiest place to hear a timbre difference because of our sensitivity to higher frequencies, and the crossover shapes how each driver material is used. Subwoofers matter least: Aperion says that at the bottom of our hearing range timbre plays less and less of a role, so any good subwoofer pairs with any speaker system. Harman's research points the same way for the rest of the system. Audio-Head's account of a visit to Sean Olive's lab describes blind tests behind an acoustically transparent curtain, run one speaker at a time because listeners are more discriminating of off-axis problems than in stereo or surround. In the same visit, Olive's research found people generally agree on what a good speaker sounds like in terms of frequency response. For how that is measured, see spinorama and CTA-2034 and controlled directivity waveguides.

Room correction does not replace matching

Dolby says home AVR auto-calibration handles level setting, delays and frequency response correction adequately, but that such systems are not perfect, and it recommends a manual calibration sweep plus skilled listening to ensure channel-to-channel timbre consistency. Its target is 79 to 82 dB SPL(C) at the central listening position per full-range speaker, driven with pink noise at an RMS level of -20 dBFS. Equalizing at the seat can reshape one speaker's response at one position, but it cannot change that speaker's dispersion, which is why two differently built speakers can still sound different after the same EQ. Compare Audyssey MultEQ XT32 and Yamaha YPAO R.S.C. for how each system treats speakers.

Families and which positions matter

KEF says its speakers are timbre matched from series to series and advises matching the front three (left, center, right) as closely as you can, with the surrounds equally important if you listen to a lot of music mixed to 5.1 or higher. SVS says all of its Prime and Ultra Series speakers are timbre matched and can be used interchangeably, so a Prime tower pair can sit with either a Prime Center or an Ultra Center. Identical models in every position are not required. Aperion points out that an ideal system would use identical speakers everywhere, but in today's home theater that is not necessary because each position has a specialized role. A practical order: match the front three first, then any overheads that receive panned objects, then the surrounds, and treat the subwoofer as the least critical. For layout angles see our speaker placement guide and best center channels.