How does the 5300 differ from the 5200?
While looking through old threads I just saw that I had never answered this question. This is probably more info than anyone other than myself is interested in, but for those who might be interested, here goes...
The Shure HTS-5200 was, in terms of its Acra-Vector circuitry, almost an exact 'clone' of the original HTS-5000, but with some minor improvements to increase overall fidelity and operational ease-of-use. The headroom in the delta-modulated delay line for the surround channels was increased by several db to allow higher levels without high frequency overload (the HTS-5000 overloaded quite easily even at low levels) and Shure also increased the S/N ratio of the surround channel from 79 db to over 82 db (these numbers are from a review in High-Fidelity magazine by the awsome David Randa). The HTS-5200 also, as I mentioned in an earlier post, had the same 9-arc 'sensing' as the HTS-5300, while the HTS-5000 only had a 5-arc sensing. The 5200 also had a wireless remote, whereas the 5000 was wired only.
The differences between the 5200 and 5300 were that the circuitry was re-designed, from the ground up, to be quieter, with much lower distortion and higher overall fidelity. The vector-cancellation signals were drastically increased, from 5 'steps' to 19 steps, allowing much more accurate crosstalk cancellation over the 90 db dynamic range of the signal inputs. In most logic decoders, like Pro Logic I/II and Lexicon Logic-7, the cancellation signals are variable over the dynamic range so that for any level and direction, an exact cancellation signal is created. In the 5300, the Acra-Vector logic is basically a state-device that can only respond with set outputs at various levels - in between those levels, the cancellation signals will only approximate the exact coefficient required. Shure increased the number of 'exact' cancellation levels to 19, so that between each level there is less of a variation of the 'approximate' signal needed. Shure made sure (!) however, that even at the 'in-between' approximate levels, the residual crosstalk remained at at least 20db for all directions and input levels - basically, it guaranteed there was always +20 db of channel separation, which is enough to ensure un-ambiguous directionality. The only place they changed this was between Left-Center-Right. Center to Left or Right only has a maximum of 15 db channel separation - Shure did this to make sure a listener would never hear the L/R signals shifting between them and center - our hearing is most sensitive to the L/R directions, so this was a good compromise. 15 db of channel separation is enough to ensure that even a severely off-center listener will hear dialog coming from the center speaker and not be pulled to the side, but also low enough that audibility of the logic action is eliminated.
In addition, the time constants of the logic - the attack/decay times - were sped up in the 5300. The attack time was increased from 27 milliseconds in the 5000/5200 to 15 milliseconds in the 5300, with a decay time of 100 milliseconds in the 5000/5200 to 50 ms in the 5300. The second time constant had an attack time of 500 ms in the 5300 and a decay of 1000 ms. In addition, simultaneous sounds coming from orthogonal directions, such as Center and Surround or Left and Right were allowed to have their control signals coexist, which meant that the 5300 could enhance 2 orthogonal directions at the same time. In the absence of any directional information, the Acra-Vector circuitry 'let go' and reverted to the basic non-logic matrix, unlike Pro-Logic which "holds on" to its last direction. This is why Pro-Logic often exhibits a severe center channel "pile up" and reduction of the soundstage width.
The input signals were also delayed by 5ms, giving a kind of 'look ahead' for the logic, so that the cancellation signals were applied at the exact time a directional signal occurred. At the time, this was pretty damn advanced - only Lexicon, in their "CP" series of stand-alone Dolby Surround decoders, had a look ahead. Now, though, even Pro-Logic II uses it since it drastically decreases audible logic artifacts and makes Shure that sounds are not heard to 'steer' to their intended location - they appear there, with full separation and no artifacts.
Oh, one last thing - in the 5300 the Surround signal has only one cancellation 'state' - that of full cancellation - there's no in-between cancellation levels, unlike the front signals in the Acra-Vector circuit - so the surround signal always appears with full signal separation, making it 'stand out' much more than in a Pro-Logic design. Also, there's no gain riding applied to the surround channel - in a Pro-Logic design, the surround channel will be increased in level from 3 to 5 db, depending on when the specific implementation of the Pro-Logic decoder was designed. So, in the Shure logic, the surround channel will NEVER modulate in level due to dialog or music. This produces a much 'smoother' soundfield with less noticeable logic action.
If anyone is interested, I have some diagrams of how the Shure Acra-Vector logic works - like how/where directional information is looked for, etc...
