Installation Profile: THX at Home
Aug 1, 2008 12:00 PM, By Dan Daley
Quality-assurance specifications dictate a budget built for acoustics.
The remarkable When We Left Earth: The NASA Missions series on The Discovery Channel earlier this year reminded viewers of one of the sore points of those crewed NASA missions to the moon: We labored so hard to reach the moon, and yet, after a scant few visits, we left — never to return.
It might be like that for the first and, thus far, only reasonably scaled home theater to have been constructed to THX-certified standards — from the technical components to the construction methodology. (It's a given that there are some moguls along the lines of a Spielberg or a Lucas who probably have something akin to a high-end public theater in their five-figure-square-foot abodes, but that's obviously not the kind of scale we're talking about here.) The theater — in the suburb of Hillsborough, Calif., south of San Francisco — was designed and built by nearby integrator Ambleside Logic, and it cost $325,000.
But Aaron Rosenbaum, president of Ambleside, points out that instead of allocating most of that budget to trophy-level technology, half of that amount went to the physical properties of the room — especially its acoustical aspects. In fact, in keeping with the THX protocol's strict adherence to the use of only THX-certified products and systems in any installations that bear its imprimatur, the pool of technology available to any project is finite — and the short list of accessible systems that are appropriate and affordable is shorter still for installations with non-palace budgets. That reinforces the vision of audio pioneer Tomlinson Holman (who co-developed the THX standard — hence the initials “TH” in “THX”) that the nature of the space, not the gear, defines the sound of the room. And sound is certainly what makes a home theater the immersive experience that it's meant to be.
Translating the THX protocol, with which major-motion-picture audio is mixed, to a residential environment is first and foremost a matter of scale, according to Rosenbaum. It is, inevitably, an ongoing series of compromises to allow a 300-square-foot space to reproduce audio in the same manner that a 750-seat-theater can. The 13.5ft.-wide shoebox allocated to the theater put the squeeze on the owner's request for two rows of four seats. Rosenbaum responded by using seats with shared armrests.
The thickness of the finished walls also put pressure on the design. In order to meet the THX standard for sound isolation, the walls have a total of 9in. of treatment on them beyond the drywall. Of the 50 percent of the budget allocated to the physical space, Rosenbaum estimates that between a quarter and a third of that was spent on acoustics.
The design, created in conjunction with subcontractor Performance Media Industries (PMI, whose president, Anthony Grimani, was once an executive at THX), called for 6.5in. of acoustical treatments — including sheets of QuietSolution QuietRock 545 paneling and steel-fiber-reinforced generic-mineral wall finished off with mass-loaded vinyl covering. It also called for 2.5in. of isolation, including the use of Acoustical Surfaces RSIC-1 Resilient Sound Isolation Clips to minimize wall-borne vibrations. Even the backs of the wall light sconces have special putty from QuietRock to dampen vibration from the walls.
Helmholtz resonators were installed at strategic points within this depth of wall to absorptively counter low-frequency buildup from the 16 Triad Bronze/6 subwoofers stacked in four arrays of four each (the LCR uses Triad's InRoom Gold series loudspeakers with Triad OnWall Gold surrounds). Of the three primary means of controlling bass frequencies, the tube trap and the resonant membrane cover a broad operational bandwidth and are good for generalized treatment. The Helmholtz resonator, however, is very much frequency-specific, and its narrow bandwidth of operation makes it ideal for treating single-frequency anomalies.
Acceptable Use Policy blog comments powered by Disqus