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Certifiably Excellent Sound

KEF’s new home theater joins its Music Lounge and puts a spotlight on the impact that THX Certification can provide.

KEF THX Theater - Rear 1
A rear-view look at the theater shows the side speakers, the in-wall subs, the rear speakers, and the fabric-covered ceiling. Photo by Acoustic Innovations.

There are people of a certain age who, when they hear the name “THX,” their minds immediately recall sitting in a theater right before the main feature was to begin and hearing (and feeling) a stirring, impossible-to-ignore tone leading to those letters appearing on screen with the tagline, “The audience is listening.”

Though the title card may be gone, THX remains a force in both commercial and home cinema, with its certification process offering dealers and their clients peace of mind that a certain level of quality will be met. For its architectural speakers, KEF has taken the steps to ensure their products carry THX Certification, with some even achieving the higher THX Certification Ultra.

“One of the reasons for THX certification of our products is that, unfortunately, many dealers do not have a showroom that will allow the consumer to hear exactly what they are going to be purchasing,” says David Kroll, vice president, KEF America. “They’re doing it based on a recommendation and a reputation — but they’re being asked to spend quite a bit of money on a project that they’re taking on faith. We felt that by going through the THX Certification process that it would give the consumers an extra level of comfort. It’s not just KEF saying it’s good, and it’s not just the dealer telling them it’s good, but you also have THX saying that it has tested them, and they meet all the performance requirements to deliver this level of theater experience.”

Still, even with the endorsement of KEF, the dealer, and THX, nothing beats a live demonstration, so the company recently added a 9500-square-foot THX-Certified home theater to its KEF Music Lounge, located in Marlboro, NJ.

KEF THX Theater - Front Eye View
Lights up on the elegant space designed by KBK Interior Design. Photo by Peter Rymwid Photography.

“We felt it was very important to have a space where we could demonstrate our home theater speakers in a B2B level for our dealers, and to give them a tool to use in a B2C capacity for their clients,” says Kroll.

For assistance in building the room, KEF reached out to sponsors Parasound, Epson, Straight Wire, Acurus, and Seymour Screen Excellence. Interior design was by KBK Interior Design, and the acoustic design and installation was handled by Acoustic Innovations.

“When you’re setting out to do a THX-Certified room, it’s really about following the guidelines,” says Jay Miller, founder and CEO of Acoustic Innovations. “As theater designer, fabricator, and installer of all the soft elements in the room, we already tend to follow a lot of the principles that THX requires. If you’re familiar with what needs to be done, then it’s easier to get to that point than if you’re just starting from scratch.”

The sizable room is part of the KEF Music Lounge, which has many examples of KEF sound in action. Because of that, Miller knew that the theater would need a fair amount of isolation, and not just from sound escaping, but also from sound coming into the room.

“You want the room’s noise criteria level to be as low as you could possibly get,” he says. “We knew we would need a room within a room, so the contractor built a shell, and then within that shell, they put in a wood structure that is basically studs. We then filled those cavities between the studs with a mineral wool insulation that essentially gave us control of the mid to low frequencies.

“We used a fair amount of diffusion in this room because we had reflections, as there are a lot of parallel wood surfaces, which is somewhat unusual, but if it’s handled correctly, it’s not overly difficult to overcome some of the challenges that you have with that.”

The wood surfaces were an aesthetic choice by KBK Interior Design, which also designed the other areas of the KEF Music Lounge. KBK’s seating design, materials, wood, stone, and finish choices were all supplied to Acoustic Innovations, who worked with them to make sure the room sounds as good as it looks.

KEF THX Theater – Side View
The side view in full light shows one of the main subwoofers at the front of the room. Photo by Peter Rymwid Photography.

Sweet Spots for All

A key metric in designing a THX-Certified room is controlling the first reflections — the sound that bounces off the sidewalls closest to the screen. “The time it takes the sound to leave your front speakers and reach your ears directly is so close to the time that first reflection arrives,” says Kroll. “It tends to cause a blurring of the sound image, and so controlling that first reflection becomes very important.

“Some people control it by using a very directional loudspeaker, but the off-axis response of our Ci Series loudspeakers, which uses KEF’s Uni-Q technology that places the tweeter in the middle of the mid-range, is such that you can get to between 140 and 160 degrees of off-axis response before you hear any change in tonal balance. What you hear from both the left and the right loudspeaker is virtually the same, no matter where you sit, as long as you’re in between the left and right loudspeaker. So there’s not one perfect seat at the center of the couch. Every seat in the theater is a perfect seat. That is why we control that first reflection and don’t do it by making things very directional.”

The 9.10.6-channel cinema features LCR speakers behind the acoustically transparent screen from Seymour Screen Excellence, left and right side speakers, two each, on either side of both rows of seating, and two rear surround channels. The left and right speakers are placed slightly higher than ear level, where the wide off-axis response allows the full sound to be heard even if people are sitting on either side of you. Subs are located in the front on the slightly angled corners near the screen, and also beneath both sets of left and right speakers.

“We have two primary subwoofer locations at the front, and they’re producing about 80 percent of the bass impact,” says Kroll. “And then we have in-wall subs in the sides, and because we are driving bass from so many points in the room, it is seamless. There were no audible low-frequency holes or standing waves.”

KEF THX Theater – Right Angle
The theater features two rows of theater seating with bar seating at the rear. Photo by Acoustic Innovations.

Looking Up

For the height channels, Miller had to get creative with the acoustic design. “There are a number of the atmospheres up in the ceiling, and they had critical placements,” he says. “We built eight inches of space between the acoustic fabric and the ceiling for diffusion. We had to build speaker mounts that held the Atmos-capable speakers. They were properly set so that the fabric wasn’t causing any type of audio refraction when the sound would pass through it.

“The ceiling was built in such a way that, if KEF has to get to any speaker, the fabric is easily removable. It was installed on a fabric pretension track, so if they decided that they wanted to change something or, for that matter, even adjust the acoustics of the room, we could easily pull this fabric out, do whatever needs to be done, and then, using a special tool, you tuck the fabric back into the track. It also allows for changing tastes if you want to swap it out.”

The result of all this meticulous acoustical treatment is a room that sounds great even when the system isn’t turned on. “When you walk into some acoustically treated theater rooms, the timbre and the tone of your voice sounds different from when you’re in the room versus outside of the room — or even in different places within the room,” says Kroll. “And that is not a good job of acoustically treating a space because what you are doing is you are grabbing just a narrow band of frequencies and you’re not adequately controlling the room as you should.

“At the KEF theater, there is absolutely no difference to the timbre or tone of your voice anywhere you are within the room because we’ve controlled the reverb time. It’s almost perfect. We’ve created the ability to absorb the first reflection beautifully, there is diffusion on the side and rear walls, and the ceiling is balanced with some absorption so that all of the wonderful energy from the side and rear speakers, after you hear the direct sound, becomes scattered, spacious, and full.

“If you treat the room properly, you will have the control over the Atmos and over the motion as you should. But once that energy has done its primary job, it should be scattered to add to the general effect so that you feel like you’re within the environment and swept up by the emotion. And that’s what we’ve achieved within the space.”

KEF THX Theater – Entrance
The entryway into the KEF Music Lounge. Photo by Peter Rymwid Photography.

Fine Tuning

Once the room was built, KEF spent considerable time tuning it to make sure it was up to both its and THX’s standards. “When we were doing the final calibration, I learned something that was such a simple concept, but in 30 years in this industry, no one had ever vocalized it to me before,” says Kroll. “When we calibrate theaters, we tend to use either the pink noise that is built into the surround processor or we use an outboard computer with a set of calibration microphones, which also generates pink noise. That noise is generally not bass-managed, so what we end up doing is calibrating the left-center-right, sides, and rears to be at the same level down to the crossover frequency, but because that signal is not bass-managed, it’s just highpass, we’re not doing anything about the low frequency. We then play the LFE track and match that level to the left-center-right, sides, and rears, but nowhere have we touched the bass-managed energy from all of the side channels.

“If you use an external calibration disc that produces noise per location, like the Dolby Atmos disc, then the noise is coming in ahead of the processor and is steered to a channel and is bass-managed. You can calibrate all of your speakers to be at the same level, but you can also calibrate the bass management subwoofer energy to match and integrate perfectly with the side speaker. So when you do that as the first part of the process, now you’ve got a perfectly seamless integration between your satellites and subs for the bass-managed energy. Then you’re calibrating the effects to match those two together. The integration is just breathtaking.

“It takes a long time because you’re having to calibrate each channel to the subwoofers and balance it and then listen to them as a whole before you even calibrate the LFE. But the tightness, the control, the accuracy, the smoothness, and the steering is tenfold better if you take the time to do it.”

KEF THX Theater - Front Left
The Greatest Showman is one of the preferred demos in the space, along with Ford v. Ferrari. Photo by Acoustic Innovations.

The Audience is Listening

For demos, Kroll likes to use the opera scene from The Greatest Showman. “The control over the height is so good that you actually hear the orchestra depressed a couple of feet below her on the stage,” says Kroll. “So where the stage comes to the bottom of the screen, that’s about 36 inches off of the floor. The orchestra sounds like it’s actually at the floor coming out of the pit, and we’ve had industry veterans who have heard many theaters listen to that demo and suddenly say, ‘Well, is your center channel down at the floor?’ No — our center channel is actually dead center on the screen image, but the Atmos height control in here is so much that it pulls you that far down.”

He also likes to demo the room using the scene from Ford v. Ferrari where Henry Ford is given his first ride in a racecar. “When that scene is done,” he says, “when you bring the lights up, you find everyone pushed back in their seats, gripping the front of the couch, just like they went through what Henry Ford does.”

For clients who come and experience the room, the reaction is pretty much the same as the industry vets. “After the consumer experiences a better loudspeaker in a residential setting, every single one of them has left here and the discussion is nailed down to, ‘Do I buy the next-to-the-top speaker or the top-level 8-inch model?’” says Kroll. “Once the consumers understand what it does in a real environment, and they know they’re going to live with it for a long period of time, they become more willing to make that investment.”