Bruce;
TRIPOLAR:(& Integrated Three-Way Constant Directivity Speaker Array:)
[Link: home-entertainment.co.uk]
Henley Designs' £800 HCC 205-6 is a new fit-and-forget package comprising identical left, centre and right front speakers, a pair of 'tripolar' surround speakers.
Also some intersting info at: (but I think it is dated (re Ultra2): (there are others as well) [Link: dolby.com]

16. "Should I use bipolar, dipolar, or tripolar surround speakers?
Surround speaker placement, room acoustics, and personal preference are as important as the speakers’ radiating characteristic. These factors vary greatly, so Dolby Laboratories cannot recommend a particular speaker for home theater use." (oh really! check out the Ultra2 THX approved sets!)

TRIPOLAR: (found in general use in many places)
Bipolar, dipolar, and tripolar surround speakers use speaker drivers aimed towards the front and back of the room to achieve a diffuse soundfield like that created by the multiple surround speakers used in movie theaters. Your room’s acoustics will effect these designs more than conventional direct-radiating speakers, which, when placed properly, can also make effective surround speakers.

Re:(within Dolby 2 separate paths)I also found this little interesting ditty on a tech post site " there could be a difference in the DSP algorithm between the Dolby Digital™ version and the THX® version. I could always re-install the old software and remove the expansion board for a definitive answer."
Bruce: If you read the following articles & can understand them enough to apply the tech to your situation I think you get a certificate or something. (but the articles do make a lot of sense): [Link: sound-technology.com]
I think the paper at the follwing more leads to what Ultra2 is heading for first with the speakers then I think the processed signal has to be dealt with in a different way - is this then not DPL2?!! or at least where it is heading?: [Link: sound-technology.com]
I will get back to you when I get the DTS info.
RE: DTS vs. THX
I read on Dolby's site (got to find it again)Dolby's response paper to DTS- boy do they rip it apart!! "Sound Wars" - It was more focuses on the way DTS "tweeked" the sound in its format as compared to Dolby. The main arguments put foward by Dolby were supported by graphs & test results & they slighted DTS for not providing any. I will try again to find it 7 also if DTS ever responded to its claims & supported it with scientific data, graphs etc.
Dougofthenorth

This message was edited by Dougofthenorth on 12/21/01 09:44.18.