Add the Polk FXi A4 surround speaker (Pair, Black) to your home theater system and enjoy dramatic rear-channel sound effects with your favorite movies. The cleverly designed speaker features two tweeters aimed 45-degree from each other for an ideal mix of direct and indirect sound. A dipole/bipole switch lets you position the FXi A4s on the rear or side walls of your home theater room, you'll get great results either way. If you place them behind your listening position, set them to bipole mode for distinct, directional sound, or set them to dipole mode for side placement and it will create a more diffuse soundfield for convincing wraparound effects. Polk carefully designed the drivers using laser testing to help identify and eliminate resonance points. The acoustically inert MDF cabinets fight internal vibrations that can compromise performance. It all adds up to enveloping surround sound that fully immerses you in the movie action.