To hear sound from smartphones, stereos, home theater systems, and TVs, you need speakers. Even earphones, headphones and headphones are just little speakers. Speakers generate sound by moving air through a cone, horn, ribbon, or metal screen. However, alternative technologies also work and may even be better suited to specific use cases.

Use a wall, window, or other hard surface

Designed by MSE, solid drive is a technology that produces sound without any visible speakers. The core of the Solid Drive is a voice coil/magnet unit encased in a short sealed aluminum cylinder.

When one end of the cylinder is attached to the speaker terminals of an amplifier or receiver, and the other end is flush with drywall, glass, wood, ceramic, laminate, or other compatible surfaces, an audible sound is produced.

Sound quality is on par with a modest speaker capable of handling up to 50W of power consumption, with a low frequency response of around 80Hz but low rolloff at around 10kHz.

MSE Audio Solid Drive Example

Other examples of devices similar in concept to MSE’s Solid Drive but more suitable for portable use (such as smartphones and laptops) include vSound Box .

Plus, if you’re adventurous, you can even make your own. For details, see how to do video «Vibration Speaker» on YouTube.

Use your TV screen

Modern TVs are getting so thin that trying to fit a speaker system into them is becoming increasingly difficult.

As a possible solution, in 2017 LG Display and Sony announced that they had developed a technology similar to the Solid Drive concept that allows OLED TV screen play sound. For marketing purposes, LG Display uses the term Crystal Sound, in while Sony uses the term Acoustic Surface .

This technology uses a thin exciter placed in the OLED TV’s panel structure and connected to the TV’s audio amplifier. The exciter vibrates on the TV screen to create sound.

Photo LG Display Crystal Sound - Sony Acoustic surface exciter

If you touch the screen, you will feel vibrations. However, you cannot see the screen vibration. Screen vibrations do not affect image quality. Also, because the drivers are positioned horizontally behind the screen and vertically at the center level of the screen, sounds are more accurately placed in the stereo soundstage.

Even though both exciters vibrate on the same OLED panel, the panel/exciter design is such that the left and right channels are isolated enough to produce true stereo sound if the audio mix includes separate left and right channel signals. The perception of the stereo sound field also depends on the screen size, with larger screens providing more distance between the left and right channel drivers.

The exciters produce mid and high frequencies, but they don’t work well with the lower frequencies needed for a rich sound. To compensate for this gap, ultra-low but compact traditional thin-profile speakers are mounted at the bottom of the TV (so as not to increase the thickness of the screen) for low frequencies. Also, lower frequencies vibrate the screen more aggressively, which in turn can make the screen vibrate and affect picture quality.

On the other hand, the overall approach of Crystal Sound / Acoustic Surface is undoubtedly an audio solution for thinner OLED TVs, short of connecting the TV to a more functional soundbar or receiver and home theater speakers .

The LG Display / Sony Crystal Sound / Acoustic Surface TV audio system is currently only available on OLED TVs. Because LCD TVs require an extra layer edges of LEDs or backlight which increases the complexity of the design, the implementation of Crystal Sound / Acoustic Surface technology will be more difficult.

The Acoustic Surface audio solution is available on Sony OLED TVs. LG is expected to release OLED TVs under the Crystal Sound brand at some point.

LG Display Crystal Sound - Sony Acoustic Surface Demo

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