Installation Profile: THX at Home

Quality-assurance specifications dictate a budget built for acoustics. 8/01/2008 8:00 AM Eastern

Installation Profile: THX at Home

Aug 1, 2008 12:00 PM, By Dan Daley

Quality-assurance specifications dictate a budget built for acoustics.

With a budget of $325,000, Ambleside Logic recently designed and built the first reasonably scaled home theater to be constructed to THX-certified standards.

With a budget of $325,000, Ambleside Logic recently designed and built the first reasonably scaled home theater to be constructed to THX-certified standards.

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.

Sixteen Triad Bronze/6 subwoofers are stacked in four arrays of four each, and the LCR uses Triad’s InRoom Gold series loudspeakers with Triad OnWall Gold surrounds.

Sixteen Triad Bronze/6 subwoofers are stacked in four arrays of four each, and the LCR uses Triad’s InRoom Gold series loudspeakers with Triad OnWall Gold surrounds.

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.

Installation Profile: THX at Home

Aug 1, 2008 12:00 PM, By Dan Daley

Quality-assurance specifications dictate a budget built for acoustics.

“To meet the low-frequency specifications of THX and get the bass coherently in between the seats, we found that more and smaller subs did the job better than the fewer 18in. subs we modeled,” Rosenbaum says. “This was a great example of how a less expensive solution was able to achieve the THX specification, allowing us to allocate more of the budget to the acoustics of the room. I've been in theaters where larger and much more costly subs didn't perform as well in their space as these do.”

Isolation was challenging. The theater could not be mechanically decoupled from the home's concrete slab, and the owners wanted the entrance to the theater at the same level as the anteroom. To serve both purposes, the design included a one-step riser for the first row and a two-step for the second with variably tuned Helmholz resonators beneath each of them.

The THX specification called for a Noise Criterion (NC) level of 30 — the theater, as measured in THX's certification process, came in at NC 17. It could have gone even lower if the situation had allowed for a spring ceiling like those found in many commercial THX theaters. “We're heavily protected across the spectrum from noise from below and from the sides and from the HVAC system,” Rosenbaum says. “But if someone is walking in high heels in the kitchen [above the theater], you might hear it. It's one of the compromises of residential THX.”


Equipment choices for THX on a residential scale are circumscribed — although Rosenbaum says that helped the process in a way, removing the temptation to pursue “trophy” gear.

“There's a whole suite of performance constraints and performance benchmarks along the audio chain that have to be met, and THX requires using equipment certified by them to achieve it,” Rosenbaum says. This includes a difference in volume of less than +/-3dB between seats and the ability of the space to handle 105dB without distortion. “That's why the isolation was so important. It had to achieve the same level of volume as a commercial theater.”

Among the systems that met THX certification standards and were appropriate for this residential install were the Triad loudspeakers, the Lexicon MC-8B DSP digital controller, Ashly Audio ne24.24M matrix processor, and QSC Audio DCA Cinema amplifiers.

This equipment was installed in a rack next to the home's whole-house audio and home-automation systems in a separate control room, allowing for easier integration with other functions of the house. Existing motion sensors from the security system and feedback from the lighting system, through the home's Crestron CNX-PVID8X3 video-distribution system, enable an integrated alert and monitoring system. When motion is detected, the alert system shows output of the proper camera on either the touchpanel or the screen. The lighting system is used to make sure the camera has adequate light. If the screen is chosen for alert monitoring, the movie or TV show is automatically paused. (When just the owners are using the theater, interruptions triggered by the security and monitoring systems will automatically pause the show. There is also a guest mode that lets the movie continue to play and the alert simply lighting up the Crestron TPS-15 touchpanel controller with the appropriate indications.)

Installation Profile: THX at Home

Aug 1, 2008 12:00 PM, By Dan Daley

Quality-assurance specifications dictate a budget built for acoustics.

Even without all that, there is still plenty to control from the theater — including a TiVo Series3 DVR, a Kaleidescape Player 1, a DirecTV HR20, an Xbox 360, a Denon DVD-3910, and an Antex Electronics SRX-3 TriplePlay Sirius satellite radio tuner. The owners did not want to compromise the immersive aspect of the theater with a large control panel in front of the seats. Instead, the main Crestron TPS-15 touchpanel controller — the interface for the Crestron PRO2 processor — is located in the rear row of seats. The command chair has only a Crestron ML-600 handheld remote.

“A touchpanel entices you to do just that — touch it,” Rosenbaum says. “Putting the main controller in the rear row removes that distraction, while also opening up more space between the front row and the screen.”

The coda to this installation was the final inspection and measurement by THX, and a passing grade is virtually ensured if the THX protocols were implemented throughout the design-and-build process.

“The whole process is night and day compared to conventional [home] theater construction, which can be a tussle between the owners, the GC, and the integrator,” Rosenbaum says. “The end result of that is inevitably subjective to some extent, and the integrator faces some financial risk if it doesn't turn out right in the end. The THX process removes the subjective elements — if it passes THX's inspection, then you know the room is performing as it should. This makes the theater engineering-centric, as opposed to a sales person trying to make the owner feel good about individual equipment purchases.

“One of the biggest challenges of working on high-end theaters is managing [the clients'] expectations. And this does it very well because the outcomes are highly predictable. If it were up to me, this is the way I'd like to build every home theater.”

Costs of THX

THX declined to disclose the actual cost of the license and design fee it requires to certify a home theater as THX-compliant, but Graham McKenna, senior PR manager for THX, confirms that is a set fee and not based on room size or budget. He says that the typical budget for a THX-certified room is in the $200,000-to-$300,000 range. Some industry sources estimate the fee in the low five figures.

The process goes as follows: THX will do a feasibility review of the room design to see if THX certification can be achieved. If the room meets initial criteria, the one-time fee is then charged to the developer or homeowner, which covers the design process during which THX works with the systems integrator to implement THX standards for audio and video reproduction — including acoustic parameters, sound isolation, viewing angles, and the effect of room aesthetics on picture quality. Once the room is built, THX engineers perform testing similar to what they do for cinema and professional studio projects, all covered within the design and licensing fee. Additional services and costs include THX's recently launched post-completion video calibration services or more in-depth room design services prior to the build.

The fee isn't as onerous as it might appear, says Aaron Rosenbaum, president of Ambleside.

“I was able to use $25,000 worth of speakers that I knew would meet the spec, and within that context, they outperform speakers that might have cost $200,000,” he says. “It removed a lot of anxiety from technology choices, like not needing a three-chip 1080p projector, because the THX design optimizes the performance of the single-chip projector — that saved $20,000 right there. When you have a blueprint like THX that essentially guarantees an outcome, the budget is now accountable to meeting the criteria, not looking for the best in show in terms of technology.

“For a theater with a budget over $250,00, I'd say it's very worthwhile,” he adds. “This room kicks ass over many $1 million rooms.”

Equipment List


Tivo Series III
Kaleidescape Player 1
DirecTV HR20
XBOX 360
Denon 3920 DVD
Antex SRX-3


Sim2 HT3000E T2 Projector
Screen Research CMASK 96” WIDE


Triad Gold LCR (3)
Triad Bonze/6 Subwoofer (16)
Triad Gold Surround (4)


Lexicon MC-8B
Ashley 24.24M Matrix Processor


QSC DCA Cinema 3022 2×900W Amplifier (4)
QSC DCA Cinema 1622 2×500W Amplifier (2)
QSC DCA Cinema 1824 4×170W Amplifier (1)

Systems Control:

Crestron PRO2 Processor
Crestron CENET-1 Ethernet Card
Crestron C2N-SDC Shade Drape Controller
Crestron TPS-15 Touch Panel
Crestron ML-600 Handheld Remote


Cinematech Valentino Incliners (4)
Cinematech Valentino Recliners (4)
WAC Lighting 12V fixtures
Crestron CLX-1DIM8 Dimmer
QTran Transformers (custom)
MSR Acoustic Treatments (reflectors/absorbers)

Sound Isolation:

QuietRock 545
RSIC-1 Isolation Clips
Acoustic Sound Door - custom by Ambleside
Zero International 7770 Jamb seal
Zero International 367 Automatic Door Bottom
Zero International 564 Jamb Saddle
Zero International 950 Cam Hinge

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