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TV sound: delivering audio quality when the bezel has vanished

TV sound: delivering audio quality when the bezel has vanished

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By eeNews Europe



A TV’s aesthetics are clearly vital; the success of Apple demonstrates that market dominance comes as much (if not more) from Sir Jonathan Ive’s stunning designs as it has from any technological advantages of the company’s products.

As such, the TV bezel has begun shrinking, with companies such as Samsung and LG bringing out large format TVs with very little bezel. LG’s rather beautiful LM8600 LCD TV, for example, (Figure 1) has just a 1-mm bezel.

But the story doesn’t end here as a small bezel means very little space for speakers. And this leads to a range of compromises: either tiny speakers, or speakers embedded into the rear of the TV, or an additional sound-bar, which sits in front of the TV – ruining the aesthetics that the purchaser has paid a premium for. None of these alternatives is good news for consumers.

Fig 1: LG’s stunning LM8600 – CNET described its bezel as “impossibly thin”.

The importance of audio

Audio is, aurguably, the most vital part of the viewing experience. Indeed, film production courses regularly state that audio quality is more important than image quality and, as the Production 101 film course states: “studies show that while people will tolerate the worst quality video images, they will not watch programs that have poor quality audio.” You have only to watch YouTube to know this is true.

Despite this, the importance of audio quality isn’t always recognised by the electronics industry. A good example of this comes from TV teardowns that examine the LCD / LED displays, the connectivity, the 3D system, the software… but not the speakers – see iSuppli’s 2011 teardown of the LG 50PZ950 for a good example.

Small speakers

As anyone who has been seated in a public area near (almost invariably) a group of teenagers playing songs from their phones will know, small speakers deliver an appalling audio quality.

And, while television speakers will never shrink to the level of phone speakers, the audio quality is poor enough for even the national newspaper journalists on both sides of the Atlantic to complain. For example, here in the UK the Daily Telegraph’s technology writer Matt Warman wrote:

“Televisions have never looked better – and they’ve never sounded worse…

“And as TVs are now marketed on their ultra-slim designs, with their miniature profiles as much a part of their supposed appeals as the quality of the picture, the problem has been exacerbated.”

Indeed, there have even been marketing campaigns from independent bodies, see Clarity’s It’s Time To Upgrade videos, that demonstrate the problems that are being created. [Video is at; https://youtu.be/NrmsHWJeHLE ]

Rear-firing speakers
An alternative that’s been trialled by a few companies is to use larger speakers and mount them in the rear casing of the TV, directing the sound to the rear of the cabinet and assuming that reflections from walls will convey the audio to the viewer. While this does provide more powerful audio, and audio can be configured to take reflections into account, this would need to be tailored to the room… and doesn’t solve the problem of poor audio quality.

Soundbars and audio systems

Clarity’s marketing campaign video (shown above) highlights the problem but insists that the solution is to set up a separate audio system using soundbars or stereo equipment. I disagree: this will produce better audio quality, even exceptional quality if used with a correctly configured Dolby 7.1 surround sound system. But, this is not what’s wanted by the average user.

Consumers want the TV to work out-of-the-box with no add-ons. This may accord with our instincts and sound like common sense (which can often be different to how the real world operates), but the sales figures back this up too. The number of people installing multi-speaker home cinema systems is low. And, more tellingly, sales figures for sound-bars are massively lower than for TVs.

Fig 2: Bose’s Cinemate 1SR is classed among the best sound bars available. But do customers want, instead, the equipment to work out of the box?

I’ll ignore the sales of low end TVs, where bezels are larger or people may be buying on a budget, and focus solely on smart TVs, which represent a large section of the premium TV market… Forbes has stated that 87 million smart TVs will have shipped in 2013. This is up by 30% (20 million units) on 2012. It also expects 185 million 802.11ac-equipped TVs (up 113%) to ship in 2015. Whereas the Consumer Electronics Association (the organisation behind CES, the annual Las Vegas trade show) stated just 2.8 million sound-bars shipped last year.

That’s a large difference and the gap is growing, not shrinking. We therefore have a big problem awaiting us as bezels shrink. So, what can be done?

Alternative audio technologies

Up until now, one of the main elements of engineering has gone into reinforcing the TV to enable greater structural integrity. Apple, LG and Sony, for example, have all created displays that use a single panel of glass. Additionally, materials such as polycarbonates are also being developed for TV applications.

This provides a great opportunity for audio engineers and enables a new way of looking at TV audio, allowing us to ditch the rather small, turgid speaker driver from the housing all together and use the one thing these TVs have lots of; screen space.

Systems are beginning to come to market that use piezo drivers to turn the entire screen into a distributed mode loudspeaker. Here at Redux, we use bending wave physics, a technology developed originally by NXT, to send audio waves across the surface of the screen and create 2+ audio channels.

By driving the panel at key locations with these piezo driver technologies you can deliver small amplitude, high-energy excitation and launch a dispersion of modal waveforms throughout the entire panel with a wide range of frequencies.

This means audio frequencies from below 100 Hz to over 20 kHz can be delivered from the panel, in stereo.

And glass happens to be an ideal material for delivering this. As are polycarbonates.

Challenges

There are, of course, limitations. Firstly, the OLED display relegates the audio drivers to the edge of the screen. Secondly, as we shrink the bezel we need increasingly small exciters.

The first is easy to engineer around and can be achieved through precisely calibrated algorithms. The latter is more difficult. The second is being answered through advances in exciter technology, with companies beginning to create very thin, very high power exciters that are ideal for audio systems.

Conclusion

So, when it comes to TVs, is it about the look or the sound? Customers may buy a TV for the looks, but the sound is more important in the long term.

Sound may be harder to quantify. You can’t just see it, as you can with the aesthetics of a TV. Furthermore, we don’t have a metric that’s equivalent to 1080p. It is comparatively rare for people to visit audio equipment stores with CDs in hand to test a stereo before buying it: it is, by extension of the same principle, virtually unknown for people to go to TV stores and do this. Basically, TV purchasers expect their new acquisition to work out of the box.

Great audio and great design need not be mutually exclusive aims. By moving towards more rigid screens that use glass (be it gorilla or standard glass), significant opportunities are presented to the audio engineer who’s bored with producing substandard audio solely to fit around the cabinet designer’s whims.

James Lewis is CEO at Redux Labs (www.reduxst.com). James has been involved in a number of hi-tech start ups in the electronics and semiconductor sectors.

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