I have an L shaped room for which I selected the Polk SurroundBar50, aimed down one leg of the L. It provides five audio channels, and does so without depending on reflections from the side walls. In my particular room one 'side' has no side wall.

Does the SDA Surround technology work as well as having discreet side surround speakers? No, but it actually is fairly good.

My own Polk SurroundBar50 (apparently no longer in production) is configured to provide center, left, right, and surround left plus surround right. To complete the 7.1 audio in my case I also have two discreet rear speakers located on the back wall. Plus a subwoofer, of course. All driven by a seven channel AVR amplifier.

With the discreet rear speaker pair disabled the Polk SurroundBar by itself still provides a reasonable sense of space and five channel surround sound. For five channel surround it works fairly well, with no other speakers needed for a decent surround effect.

The SurroundBar uses speaker driver phasing to create the surround channel effect despite the audio being directly transmitted from speaker to your ears. Each of the 'surround' speaker channels uses a pair of drivers, two in each end of the bar, all facing forward.

When I did my research a couple of years ago there were very few options. After excluding those that depend upon side wall reflections for the surround effect, that narrowed it down to the Polk and another very similar product from the same parent company that owns Polk.

I do not recall why I dismissed the Yamaha brand sound bar product at that time, perhaps it is a sound reflection design, or there was some other issue that I had with it.

Judging from the current product descriptions, Polk now supplements the original SDA technology with DSP processing and in some models in-speaker amplifiers.

Hope this is of some help.