Producing Sound Without Speakers

MSE Solid Drive (L) - LG/Sony Crystal Sound Exciter (R) Examples
MSE Solid Drive (L) - LG/Sony Crystal Sound Exciter (R) Examples. Left Image - MSE, Right Image - Robert Silva

In order to hear sound from our smartphones, stereos, home theater systems, and TVs, you need to use speakers (even headphones, earphones, and earbuds are just tiny speakers). Speakers generate sound by moving air via a cone, horn, ribbon, or metal screens. However, there are actually ways to produce sound without the use of traditional speakers.

Using a Wall, Window, or Other Solid Surfaces To Produce Sound

Solid Drive - Designed by MSE, Solid Drive is a technology that allows the production of sound without any visible speakers.

The core of the Solid Drive concept is a voice coil/magnet assembly that is encased in a short, sealed, aluminum cylinder (reference photo at the top of this article).

When one end of the cylinder is attached to the speaker terminals of an amplifier or receiver, and the other end is placed flush with a drywall, glass, word, ceramic, laminate, or other compatible surface, listenable sound can be produced.

The sound quality is on par with a modest speaker system, able to handle up to about 50 watts of power input, with a low end response of about 80Hz, but with a low high-end drop-off point at about 10kHz.

For more technical details, including installation/use options for the MSE Solid Drive, refer to their Official Information Sheet.

Options Similar To Solid Drive - Other examples of devices similar in concept to MSE's Solid Drive, but more suited to portable use (such as with smartphones and laptop PCs), include the vSound Box and the Mighty Dwarf.

Also, if you are adventurous, you can even make your own. For details, check out How To Make A "Vibration Speaker".

Using A TV Screen To Produce Sound

Today's TVs are getting so thin, trying to squeeze in an internal speaker system is getting more difficult.

To provide a possible solution, in 2017, LG Display (an LG sister company), and Sony, announced that they had developed technology similar to the Solid Drive concept, that enables an OLED TV screen to produce sound. For marketing purposes, LG Display uses the term "Crystal Sound", while Sony uses the term "Acoustic Surface".

As developed, this technology employs a thin "exciter" (see photo attached to this article) that is placed within an OLED TV panel structure, and is connected to the TV's audio amplifier. The exciter then vibrates the TV screen to create sound.

Experiencing this tech hands-on, one interesting observation is that if you touch the screen you can feel it vibrating. What's even more interesting is you cannot actually see the screen vibrating. Surprisingly, the vibrating screen does not affect image quality. Also, since the exciters are located horizontally behind the screen and vertically at the center level of the screen, sounds are more accurately placed in a stereo sound stage.

In other words, even though both exciters are vibrating the same OLED panel, the panel/exciter construction is such that the left and right channels are isolated enough to produce a true stereo sound experience, if the sound mix includes separate left and right channel cues. Obviously, the perception of the stereo sound field would depend on the screen size—with larger screens providing more distance between the left and right channel exciters.

However, this system isn't perfect. Although the exciters are able to produce mid-range and high frequencies, they don't do well with lower frequencies needed for full-bodied sound. To compensate for this, an extra-but-compact traditional slim-profile speaker is mounted on bottom of the TV (so as not to add thickness to the screen). Also, another thing that comes to mind is that lower frequencies would vibrate the screen more aggressively, which, in turn, might make both the screen vibrations visible and also affect the image quality.

On the other hand, the overall Crystal Sound/Acoustic Surface approach is certainly an audio solution for ever-thinner OLED TVs - exclusive of connecting the TV to a more capable sound bar or home theater receiver and speakers.

Unfortunately, the LG Display/Sony Crystal Sound/Acoustic Surface TV audio solution, as of this point, can only work with with OLED TVs. Since LCD TVs require an added layer of LED edge or backlighting, which adds more structural complexity, implementation of Crystal Sound/Acoustic Surface technology would be more difficult.

The first TVs to reach the consumer market with the Acoustic Surface audio solution is the Sony A1E Series, which also happens to be Sony's first OLED TVs produced for the consumer market. LG is expected to produce Crystal Sound-branded OLED TVs in the near future, perhaps beginning with the 2018 model year.

Speaker-Less Headphones

With the popularity of listening to music on mobile devices, headphones and earphones are a needed accessory in order to hear that music without disturbing others. However, as mentioned previously, headphones, earphones, and earbuds are just very small speakers that either cover your ear or inserted into them. Not only that, but they all, to varying degrees, separate your ears from the rest of the world - great for privacy, but can be a safety issue.

However, the speaker technology used in headphones and earphones isn't the only way to deliver sound to your ears. You can also transmit sound to your ears using bone or surface conduction.

One company that has come up with this type of solution is Hybra Advance Technology, Inc.

Instead of speakers, Hybra Advance Technology employs system that it labels as Sound Band. This system employs small curved frames that are placed just behind your ear. The frame incorporates a vibrating bar that transmits sound directly to your ear without having to move air.

Check out more details, including images, on the development of the Sound Band.

More Info

The technologies and products profiled in this article are just some examples that are able to produce sound in a home or mobile entertainment environment without using traditional speakers. This article will be updated periodically with any speaker-less sound technology alternatives that may be significant.

Also, for everything you need to know about traditional speaker technologies, refer to our companion article: Woofers, Tweeters, and Crossovers - The Language of Loudspeakers.

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