Exciter-based speakers as a solution for Direct View / LED screens

[Marcel Birgelen]

More and more people believe that "Direct View" screens like giant LED screens may be the future of exhibitions. While current LED screens are still more expensive than most projection-based solutions, those screens see continuous development and as such, the price of this technology may come down significantly over the coming years.

A direct view screen has a few interesting advantages, mainly the enormous potential contrast, but it also comes with a challenge. Where cinema has traditionally placed most if not all stage speakers behind a more or less "audio transparent" projection screen, most Direct View screens are all but transparent when it comes to audio. As such, speaker placement becomes a challenge.

I recently stumbled upon this video. It's just one video in a whole series, where they build a bunch of cheap speakers out of some polystyrene panels and a bunch of audio exciters epoxied onto those panels. What they're doing seems to be legitimate and the results seem to be pretty convincing. There's no way for me to verify if what they did is any good, but my Sony OLED TV also uses a bunch of transducers mounted to the back of the OLED panel for sound reproduction and that sounds pretty good.

So, I was thinking if an exciter-based solution could work in conjunction with a LED wall, where the LED wall itself essentially becomes a big array of "Distributed Mode" speakers.

I obviously can think about a bunch of challenges, but it would solve the problem of speaker placement for such setups. it would be interesting to hear some opinions from the people on this forum if such a thing could ever work, etc.

Edit: Someone link-fixing

[Mark Gulbrandsen]

Like planar speakers, these are going to be very directional, plus not sure how they'd be full range without dividing up the system as a 2 or 3 way. Planar speakers are full range, made out of one mylar panel that could be flat black, and can be made in any size needed. Years ago I owned a large Magnaplanar based system that sounded fantastic. It was also pretty efficient.

[Marcel Birgelen]

They won't be full range, as they'll not be able to hit the low end of the spectrum, you'll still need some traditional subwoofers for the low end. But placing those subwoofers should not be a problem, as you should be able to leave sufficient room below the screen to stow away one or more.

You potentially have the entire screen surface to work with, so dividing them up into frequency ranges, if needed, should also be possible.

My concerns would be more with the LED wall construction:

- How will the vibrations affect the construction, internal connections, etc. especially over longer terms?
- Will the LED components itself affect the sound via e.g. unwanted resonance?
- Can a compatible surface still be sufficiently cooled?

Another issue I think may arise is how to properly isolate the vibrating surface from the rest of the environment and how to avoid the different speaker "zones" to interfere with each other.

If I look at my OLED TV, it implements the three front channels, L/C/R. There are three transducers/exciters mounted onto the surface from the back. There does not seem to be any isolation between the channels, yet I can clearly hear the distinction between L/C/R. It's also nice to be able to hear that the sound emanates from the screen itself, this is primarily obvious for the center channel.

The OLED layer is one thin epoxy-bonded stiff glued-together affair though. The OLED surface itself is extremely stiff, almost as if it would've been backed by something like carbon fiber.