I've been contemplating building my own bookshelf speakers for awhile and only recently seriously started considering their use in a home theater setup as rear surrounds which begs the question... what is the best design for such speakers?

Obvious to me, the standard "bookshelf" design is very directional, perhaps too much so, for this purpose. Do any of the alternative designs offer significant improvements? Bi-pole, radial, etc?

Lately I've been playing with a pair of Optimus Pro LX5s that feature dual ribbon tweeters on top that I believe, at least in theory, mean that they radiate the high frequencies in 360 degrees with a specific interference pattern in the design because of the close proximity of each of the ribbons. They DO sound nice but in actual use I'm not sure if this design offers real-world improvements when used in this fashion. Below is a photo (click to see the larger version) of this model with the ribbon tweeters exposed:



Polk and Klipsch, to name two, make a triangular shaped speaker with dual drivers firing in opposite directions with each other. This wouldn't be too terribly difficult to design but I've never experienced this sort of speaker myself.

The actual goal I am after is build a pair of speakers that can act as rear surround speakers in a home theater setup with a broad sound stage that favors a small "sweet spot" to a lesser degree than conventional bookshelf type while still conveying a sense of channel separation and detail.

Opinions?

i dont know what the best design would be for use in a surround system, but i suspect that it would come down to ones preference in sound. if i was going to try a diy project for this, i would give serious consideration to the kits from parts express. inexpensive and solid quality. as an alternative i would look for something like Athena S1 or S2, again solid performance at a budget price.

I guess what I'm shooting for is strength as a surround speaker above how it might sound musically by itself. As the rear surrounds are filtered and processed with delays and such the actual sound quality isn't as important in this particular case as is the broad sound stage (letting everyone sitting in my living room enjoy the surround fx as opposed to just one sweet spot) and that in turn must not overwhelm a speaker's ability to place a sound FX in the virtual surround environment that it belongs in.

I've had lots of theater speaker setups lately and while they all had their moments none of them (so far) has fulfilled those basic requirements of mine, hence impelling me to maybe try my hand at fashioning a pair from scratch.

Has anyone heard those triangle shaped bipoles that could comment on their abilities as surround speakers? Something like these Polks are what I'm thinking about:
http://www.polkaudio.com/homeaudio/product...dividual/lsifx/