[Postman]

Cheesehead is right. Take a look at pg 10 of the user manual for this 7.1/5.1 to stereo downmixer. One of the choices for output is called "Lt-Rt". Probably not the same as Dolby's term "LtRt" but I might guess very similar in overall concept. The manual implies phase/time manipulation, probably differently done than Dolby's, The description certainly sounds like a matrixing scheme to me but that is only my guess. I haven't auditioned it and have no plans to.

Cheesehead, is the "Lt-Rt" output listenable as stereo? The manual would seem to suggest it is, and it makes sense in the context of the suite of plugins.

PTE shows how well they could encode individual surround channels of sinetone into "Lt-Rt" and then restore them into the proper surround channels. I'd be more interested in how this Lt-Rt encode/decode process deals with complex surround sound. Dolby Pro Logic II has no trouble encoding/decoding 5.1 individual channels in the same way as PTE demonstrates here. Problems arise when a lot of channels are playing at once. With Dolby's systems you'll rarely get all the same material from all the same speakers and there are the infamous "steering" problems.