Through-glass opportunities

Through-glass opportunities
Through-glass audio and video technologies can make for impressive installations – if you know what to look for. Tim Kridel explores the options for integrators.

A room at the Hotel QT in New York City’s Times Square starts at €212. One way to justify that on an expense report is to put it down as a fact-finding mission to the sauna rooms, which feature a through-glass loudspeaker system.

Hotel QT has two sauna rooms that flank a shower, with floor-to-ceiling glass walls dividing the three areas. One option would have been to install conventional loudspeakers in each area, but the heat and humidity would have shortened their life span.

“No matter how weatherized it is, eventually the heat is going to destroy that speaker,” says Glenn Polly, owner of VideoSonic, the integrator on the project.

Instead, VideoSonic chose SoundTube’s SolidDrive system, which consists of hockey-puck-sized loudspeakers with mid and high drivers. Those were mounted on the glass walls, making the glass radiate sound in both directions. VideoSonic hid the SolidDrives behind custom-made, brushed-aluminum end caps, with their cables dressed up to look like the type of sleek, modern art found in boutique hotels.

“It made it cool-looking,” Polly says. “Nobody even knew what they were until we turned on the sound. They’ve been running very well for three years.”

Although Hotel QT’s system was designed to blend in, through-glass video technologies often are made to stand out, drawing attention to the client. That ability is one way that, for example, a retailer can draw attention to its storefront in a mall where other shops have run-of-the-mill LCD and plasma displays.

“The growth of digital signage in retail is driving the need for unique, eye-catching displays,” says Mark Schuleman, marketing manager at 3M’s optical systems division, whose through-glass products include Vikuiti Rear Projection Film.

Vendors and integrators say that the market for through-glass systems is growing, partly because like LCD and plasma displays, the technology can be used in so many places.

“Our target audiences are car showrooms, estate agents, exhibitions, museums, public information, retail, travel agents and wayfinding,” says Aubrey Wright, managing director of Handy AV, which makes a variety of through-glass products.

Know your glass

It goes without saying that the glass itself can significantly affect the audio or video experience. For example, storefronts frequently have tinted windows, and green or gray tints can affect the color of the projected images – one of many things to look for when deciding whether a through-glass system is viable. Another factor is the thickness of the glass.

“Depending on what angle you’re viewing it from, the thickness can cause some distortion because the light bends through the glass to get to your eye,” Polly says.

Some through-glass video systems include a touch screen, where a curtain of infrared light is draped across one side of the glass. In those applications, the clearer the glass, the better the system performs, due to the way that tinting affects infrared.

“The glass does have to be surveyed before clients are given wrong info,” says Greg Jeffreys, director of Paradigm Audio Visual, a maker of through-glass technologies. “For example you can make it work through double glazing but it needs testing and also [client] acceptance that you can’t achieve normal high-touch accuracy.”
The glass generally is less of a factor for audio systems – not surprising, considering that many through-glass products also work with materials such as wood and metal.

“We’ve tested it on quite a few, and the only thing it doesn’t work on is bulletproof glass,” says Devin Howells, SoundTube’s creative director. “If you get too many laminates on a window, they’ll stop the vibration.”

Byproducts of their environment

The environment also can affect performance, particularly for through-glass video systems.

“The largest and by far the most significant consideration that should be given is position relative to direct sunlight,” says Mark Cambridge, managing director of Zytronic, which makes a variety of screen film products. “The ability to offer through-store window interactivity is enormously beneficial to vendors and customers alike. But if it can only be used at night, or during cloudy weather conditions, then opportunities for use are greatly reduced.”

The amount of direct sunlight varies by the time of day, and the practicality of a through-glass video system depends partly on what the client expects at different times of the day. For example, retailers in downtowns and other dense urban areas often have the most passers-by during the early morning and early evening because that’s when many people are walking to and from work.

“There tends to be indirect light at those hours, so the projection screens work best at that time,” Polly says. “In the middle of the day, when the sun is low and blazing through the window, there’s not a lot you can do to make that image visible. You’re competing with ambient light whenever you’re doing video projection.”

That also highlights the importance of how a thorough understanding of environmental factors is key in setting the client’s expectations – and avoiding multiple trips out to tweak a system that shouldn’t have been installed in the first place.

“You definitely have to check out the area where you’re using it very thoroughly,” Polly says. “You must take into account the different times of day when the sunlight shines through the window. You have to work it out with the retailer: Is it really worth the investment to put it in this window, or is it going to be a total wash-out?”

Although each generation of through-glass video technology has better ability to hold up in bright sun, it still can be overwhelming.

“Regardless of display technology type, ambient lighting control is critical,” says 3M’s Schuleman. “Currently, nothing beats direct sunlight. Many end users can become unhappy with installations when integrators do not take into account where the sun is [or] how the surrounding buildings reflect light.”

Another consideration is that through-glass speakers radiate sound is both directions. In some installations, such as Hotel QT’s saunas, that can be an asset. But in a retail setting, it may be challenge to balance the level so that people on the street can hear over the traffic, but without blasting the inside of the store.

Ear of the beholder

Through-glass audio systems turn the glass surface into a speaker, so they’re a potential fit for applications where conventional loudspeakers might look out of place. They also can be used in medical facilities, where the transducer resides on the non-sterile side of the glass in an adjacent viewing area. And by disguising themselves, they also allow people to focus on the experience rather than what’s producing the sound.

“When you’re listening to a conventional speaker, you can pick out where the source is,” says SoundTube’s Howells. “This is using the whole piece of glass, so it’s radiating at you, and there’s no real sense of where the source is coming from.”

Another benefit is that by spreading the sound over a large surface, people – such as those walking past a storefront – aren’t suddenly hit with a blast of sound. Vendors also say that the sound can be localized, which can be a plus in malls, downtown shopping districts and other areas where the retailer doesn’t want to interfere with neighboring merchants.

One trade-off is the frequency response.

“Through-glass speakers are best for voice applications,” Polly says. “With music, it’s not going to give you the low-frequency response that you’re accustomed to.”

However, vendors such as SoundTube say they’ve expanded the range of their products to accommodate a wide range of content.

“This is our second version, and we’ve improved the frequency response quite a bit: 600 Hz through 15 kHz,” Howells says. “For voice and most instruments, we cover the range.”

Sizing up the options

Through-glass loudspeaker systems frequently are paired with through-glass video systems for applications such as storefronts. That pairing can involve products from two vendors or a single vendor’s all-in-solution.

“We sell rigid screens with sound, where the sound actually emanates from the screen itself,” says 3M’s Schuleman. “No speakers are attached.”

Size is one important consideration. For example, some screen materials are available in widths of up to 48 inches, which can be too small for some applications. But flexibility is increasing.

“Handy AV will be releasing the large-format HandyTOUCH Through Glass Film,” Wright says. “We will offer integrators either a standard range of sizes or customized sizing.”

On the audio side, size can be even more important because the more glass there is, the bigger the speaker is.

“We recommend 20 square feet of glass,” Howells says. “You can go smaller, but you’re not going to get the full output. If you want constant coverage, we recommend that you put these [units] every 12 feet.”

Making the business case

A variety of factors determine the cost of through-glass audio and video installations, including the screen film material, the number of transducers required and the projector’s brightness. Depending on the vendor, a 4,000-lumen projector runs about €3,000, with another €2,000 or so for the screen. “You probably could do a [video] installation with audio and a DVD player for under $10,000 [€7,400],” Polly says.

Although a 4,000-lumen projector might not sound sufficient, especially when there’s a lot of ambient light to overcome, anything more can be overkill.

“With rear projection, if you’re thinking about going more than 4,000 or 5,000 lumens, you’re wasting your money because you’ll wind up cranking the projector down,” says Polly, who’s done about 20 such projects. “Anything over that is going to ‘hot spot.’”

Hot spots are when the projector’s light is visibly radiating through the screen material. Besides using the right amount of power, another way to avoid hot spots is by choosing products that are more resistant to that effect.

“The Dilad and Vikuiti [products] tend to diffuse the light much better so you don’t get a hot spot,” Polly says. “You get an evenness of color and contrast throughout the entire image.”

But in some cases – such as holographic systems – a powerful projector may be necessary.

“If installing a rear projection system, a high-lumen projector needs to used, especially on larger sizes and when using holo screens,” says Liam Slattery, founding director of U-Touch, whose products include through-glass holographic systems.

Costs also can be an issue, with some clients looking to save money by using consumer equipment.

“If you’re using a LCD display as your source of image, you need to make sure it is a commercial display, not domestic,” Slattery says. “Otherwise, you run the risk of the display overheating and the LCDs going black.”

Vendors and integrators recommend making the client aware of on-going expenses. One example is the projector bulb, which may have to be replaced frequently in applications such as storefronts, where the system may run continuously, even when the store is closed.

“If it is anticipated that the application will be in use 24 hours a day, 7 days a week, then the ROI [must factor in] projection bulb life,” says Zytronic’s Cambridge.

By Tim Kridel

Tim Kridel is a freelance writer and analyst, who covers technology and telecommunications. He’s based in Kansas City in the United States and can be reached at

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