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The 3Pi is shaping up to be the L/C?/R choice. The surrounds will have to be corner mounted midway up a 9' wall and the 1Pi or 2Pi look more easily adapted than the 3Pi. Are these a good tonal and sensitivity match for the 3Pi using the AE woofer and B&C tweeter? Should the cabinets be triangular for 45 degree wavelaunch into the room or conventional and mounted on the rear wall alone in or near the corner? Also, could you send the 1Pi and 2Pi plans?
For surrounds, I usually see the one π and two π speakers as pretty much interchangeable. Both work very well, and as surrounds they are an excellent match for three π or four π mains. The only difference is the two π speakers have a little bit fuller midbass. In your case, being near corners, it might sound better to use one π speakers for surrounds. But I'll bet the two π speakers would sound great too. Usually the surrounds are just ambience and effects but sometimes they have some pretty serious content and that little bit extra midbass from the two π's might be an advantage on those soundtracks. As for orientation, just like the front left and right speakers should be toed-in 45° so their forward axes cross just in front of the listening area, the surrounds should be toed-in so their forward axes cross just behind the listening area. This makes the surround speaker toe-in very severe, like 80°. The surrounds should be positioned just behind the listeners and to the sides. It is good to have them on the side walls, just a few feet behind the listeners. In this position, they are oriented nearly 90°, usually something between 70° and 80° compared to a forward facing position.