Shure HTS-5300 Acra-Vector Decoder

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Disclord

900 Club - QQ All-Star
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May 19, 2005
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I recently bought a Shure HTS-5300 Acra-Vector Logic decoder on eBay for a dollar. For those that don't know, Shure was the first company to create a logic-based surround decoder that emulated the Tate DES based Dolby CAT-150 decoder in theater processors... (Fosgate was using their own Logic design and not trying to match Dolby processors) this was before Dolby developed their Pro-Logic system. Listening to the Shure decoder today, I like it better than Pro-Logic because it has a more 'open' sound and can enhance 2 orthogonal directions simultaneously, which the Dolby can't do. The most amazing thing about the Shure though is its directional display - instead of displaying the output levels, the display is fed from the directional logic signals. It's kinda hard to describe, but you see what the decoder is actually doing - like if L/R are active and CF comes up, the L/R lights dim down - in other words, you see the signals being cancelled.

Shure also used digital delay with a comb filter on the surrounds to simulate a large number of speakers - something THX later copied.

Pro-Logic spelled the death of the Shure Acra-Vector logic system - they just couldn't compete with a Dolby Approved logic design. The Shure was licensed directly from Peter Scheiber but Shure developed their Acra-Vector Logic system independently and it was patented http://www.freepatentsonline.com/4696036.pdf

I just wish modern decoder designers would incorporate a display like the Shure - using the Logic signals as the display.
 
I was a consultant in Hollywood for Shure StereoSurround, the professional end of Shure’s consumer HTS. (Hence, my avatar.)

Shure’s idea was to leave the film market to Dolby and Ultra Stereo to fight over. Shure would go after the broadcast, video and music market. The program got off to a great start, signing up several TV series, specials and sports broadcasts.

Then Dolby noticed, and Dolby is a fierce competitor.

Shure, as a manufacturer, was selling the equipment and giving away the license. Dolby’s profits primarily come from their licensing. So, we would go in, install the equipment and let the production company try it out. If they liked it, they would buy it. If not, we would remove it. At first people liked it and bought it.

But then Dolby started coming after us, and when Dolby heard we were working with a post facility or production company, the Dolby reps would come in and give them encoders. Dolby wanted the Dolby logo at the end credits, not the StereoSurround logo. Dolby didn’t want any threats to their licensing fees.

When you are a manufacturer selling equipment, how do you compete with free? Especially when you are the new kid on the block, and everyone already knew of Dolby. Shure saw the writing on the wall, and closed the division. It wasn’t even around long enough to make the QuadraphonicQuad logo bar.

Being wideband, I do think the Shure StereoSurround is a superior encoder for video and music where you do not have to deal with the limits of the optical soundtrack.

I still have a couple.
 
Wow, thanks for all the info and documents!

It's funny, because when Shure was originally designing the Acra-Vector Logic, Dolby was right there to help them - in fact, Dolby would publicly state that the Shure decoder came closer than any other to the professional theater processor. But once Shure started actively competing, well, Dolby couldn't allow that! Also, the Shure decoders were being used more and more for monitoring movie mix-downs since it could decode things the Dolby processor couldn't, mixers could be more adventurous - the movie "Spacecamp" has several instances where there are two simultaneous dominant sources at once - even today, only the Shure can decode it correctly.

I remember CBS used the Stereosurround process quite a bit - I vividly remember the logo appearing at the opening of many programs. Do you know if it was ever used on any CD music releases?

As I said in my first post, I think the Acra-Vector logic still beats out Pro-Logic - of course, Dolby has changed the Pro-Logic spec a few times, so not all decoders sound similar - some pump quite badly due to Dolby adding rear-channel gain-riding, which allows the surrounds to pump up and down as the Logic enhances the various signals. It's too bad Shure couldn't get the Acra-Vector design onto an IC that could have been licensed widely. But then, I don't think Shure has always been too financially healthy to be able to afford an undertaking like that. It's sad that their full HTS speaker system wasn't taken seriously until THX came into the business. And Museteax/Meitner (SP?) did nothing with the technology when Shure gave it to them... from the trademark filings, it looks like all the trademarks were abandoned in 1993.

Do you happen to have the brochures for the original HTS-5000 and the HTS-5200 decoders? Or the instruction manuals for either? I got the manual for my 5300 off of Shure's website - I was surprised they still had it available! Now I just need to find the wireless remote for my unit - the seller didn't have it - but for the dollar I paid, I can't complain. Especially considering the decoder is in first-rate shape and works perfectly.
 
The Shure HTS 5000 was my very first decoder way back when. Complete with a wired remote. When I upgraded to Pro Logic II it became my unit for extracting LFE from my rear channels on quad tapes. Still use it for this purpose. I remember it did work pretty good for movies but I rarely have time for movies anymore. Maybe if I get another system up and running in the future I will give it another shot. And yes I did love the directional display.
Phil Spinner
 
I will look for the brochures.

I have schematics and service manuals for some of the stuff. Handy if you want to check the alignment.

The schematics are full size blue-prints with hand written changes, and I don't have a good way to scan large format documents.

Yes, we did supply encoders to music studios. I have a dozen or so StereoSurround CD's in a box somewhere. Mostly classical, but some pop and country. A couple of what we now call World Music.
 
I can see if I can make JP1 files from the remote if that would help you.

Do you have a learning remote that handles JP1?
 
I will look for the brochures.

I have schematics and service manuals for some of the stuff. Handy if you want to check the alignment.

The schematics are full size blue-prints with hand written changes, and I don't have a good way to scan large format documents.

Yes, we did supply encoders to music studios. I have a dozen or so StereoSurround CD's in a box somewhere. Mostly classical, but some pop and country. A couple of what we now call World Music.

I'd love to have copies of the service manuals. I know the trouble with scanning blue prints - I have the schematics for the Sensurround Mod-I (optical, mag and 70mm) control box for the movie "Earthquake" and it's so big I have never figured out a way to scan it.

If you can make a list of the names of the CD's, I can see if my library has them.

It's really too bad that Shure's system 'died' while the massively inferior "Circle Surround" system caught on pretty well - especially considering how crude Circle Surround is, with its simple gain-riding, instead of real vector cancellation like the Shure Acra-Vector. The Shure Acra-Vector logic decoding would also work really well for "Surround EX" type decoding since it kept the front soundstage from piling up to center.

I can see if I can make JP1 files from the remote if that would help you.

Do you have a learning remote that handles JP1?

No, sadly I don't - my learning remotes all require the remote to be learned.
 
The Shure HTS 5000 was my very first decoder way back when. Complete with a wired remote. When I upgraded to Pro Logic II it became my unit for extracting LFE from my rear channels on quad tapes. Still use it for this purpose. I remember it did work pretty good for movies but I rarely have time for movies anymore. Maybe if I get another system up and running in the future I will give it another shot. And yes I did love the directional display.
Phil Spinner

The HTS-5000 was a little different than the later two decoders (HTS-5200/5300) and the professional decoder - the later decoders 'looked' for directional information in 9 evenly spaced arcs/locations across the front soundstage, whereas the 5000 looked for information in only 5 arcs. The additional locations improved the accuracy of pans, so they moved smoothly and didn't 'hop' from point to point. In all other aspects, such as applying the cancellation signals only in 5 discrete steps/levels across the front and one across the back, the decoders were the same.

No other surround decoders have matched the Shure's for the directional display. It's just wonderful.

I've never been able to love PL-II - it's too 'flabby' - that's the only word I can think to use. Like on the movie "The Hindenburg", when they are up in the body of the ship, the surrounds are fully active with creaks and rumble of the motors, while left, center and right have sound effects and dialog. PL-II simply can't decode this without audible shifting, pumping and leakage of dialog into the surrounds. The Shure Acra-Vector decodes it perfectly, keeping effects in the back and dialog up front with no audible problems. It sounds fully discrete. (oh, how I wish Universal would make "The Hindenburg" available with its original 4-track sound - it was an amazing experience.)
 
Interesting thread. I wonder how much dolby strong-arming happens today? I would think alot, given the otherwise illogical prevalence of surround releases using dolby digital. I say illogical because in my opinion, dolby digital has to rank as one of the worst surround formats available today. I'd like to know how dolby manages to dupe the majority of Hollywood as well as more recently, many of the few remaining who are currently releasing surround music. It seems like the dolby digital bully is still king of the playground. Someone needs to call the principal.
 
The HTS-5000 was a little different than the later two decoders (HTS-5200/5300) and the professional decoder - the later decoders 'looked' for directional information in 9 evenly spaced arcs/locations across the front soundstage, whereas the 5000 looked for information in only 5 arcs. The additional locations improved the accuracy of pans, so they moved smoothly and didn't 'hop' from point to point. In all other aspects, such as applying the cancellation signals only in 5 discrete steps/levels across the front and one across the back, the decoders were the same.

No other surround decoders have matched the Shure's for the directional display. It's just wonderful.

I've never been able to love PL-II - it's too 'flabby' - that's the only word I can think to use. Like on the movie "The Hindenburg", when they are up in the body of the ship, the surrounds are fully active with creaks and rumble of the motors, while left, center and right have sound effects and dialog. PL-II simply can't decode this without audible shifting, pumping and leakage of dialog into the surrounds. The Shure Acra-Vector decodes it perfectly, keeping effects in the back and dialog up front with no audible problems. It sounds fully discrete. (oh, how I wish Universal would make "The Hindenburg" available with its original 4-track sound - it was an amazing experience.)

The Shure HTS 5000 sounded a little sluggish to me which would confirm what you said. I wish I held off for the later 5200 or 5300 models. I'm Shure they did sound better.
Phil
 
Interesting thread. I wonder how much dolby strong-arming happens today? I would think alot, given the otherwise illogical prevalence of surround releases using dolby digital. I say illogical because in my opinion, dolby digital has to rank as one of the worst surround formats available today. I'd like to know how dolby manages to dupe the majority of Hollywood as well as more recently, many of the few remaining who are currently releasing surround music. It seems like the dolby digital bully is still king of the playground. Someone needs to call the principal.

This isn't a defense Dolby's practices, but at the time Dolby Digital was selected for HDTV and DVD, there wasn't anything really better - MPEG-2 had major problems with its compatibility matrix and coder unmasking, plus its variable bitrate didn't allow it to easily 'fit' into the required bitrates. Tests a few years ago by the EBU showed that AC-3 was, and still is, the best choice of coders. While DTS at 1.2/1.5 Mbps is 'good', its performance at 758k is audibly inferior to AC-3 and it has noticeable errors in coding. It scored lower in every single test. While newer codecs are available, there is no easy way to 'fit' them into existing equipment without breaking compatibility. Thus, AC-3 is it - which Dolby has improved with DD+.
 
Wow, thanks for all the info and documents!

It's funny, because when Shure was originally designing the Acra-Vector Logic, Dolby was right there to help them - in fact, Dolby would publicly state that the Shure decoder came closer than any other to the professional theater processor. But once Shure started actively competing, well, Dolby couldn't allow that! Also, the Shure decoders were being used more and more for monitoring movie mix-downs since it could decode things the Dolby processor couldn't, mixers could be more adventurous - the movie "Spacecamp" has several instances where there are two simultaneous dominant sources at once - even today, only the Shure can decode it correctly.

I remember CBS used the Stereosurround process quite a bit - I vividly remember the logo appearing at the opening of many programs. Do you know if it was ever used on any CD music releases?

As I said in my first post, I think the Acra-Vector logic still beats out Pro-Logic - of course, Dolby has changed the Pro-Logic spec a few times, so not all decoders sound similar - some pump quite badly due to Dolby adding rear-channel gain-riding, which allows the surrounds to pump up and down as the Logic enhances the various signals. It's too bad Shure couldn't get the Acra-Vector design onto an IC that could have been licensed widely. But then, I don't think Shure has always been too financially healthy to be able to afford an undertaking like that. It's sad that their full HTS speaker system wasn't taken seriously until THX came into the business. And Museteax/Meitner (SP?) did nothing with the technology when Shure gave it to them... from the trademark filings, it looks like all the trademarks were abandoned in 1993.

Do you happen to have the brochures for the original HTS-5000 and the HTS-5200 decoders? Or the instruction manuals for either? I got the manual for my 5300 off of Shure's website - I was surprised they still had it available! Now I just need to find the wireless remote for my unit - the seller didn't have it - but for the dollar I paid, I can't complain. Especially considering the decoder is in first-rate shape and works perfectly.
I purchased an HTS 5200 a few years ago for $75.00. At that time, they were retailing used for $300.00 so I thought I got a great deal. I telephoned Shure and got the original full color operating manual for free. I was also able to purchase the remote control $60.00 if you were a repair center and $80.00 to the general public.
 
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...
 
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... :)
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...

Thanks much for your reply - I'll be reading it a few more times in order to properly analyze. Another question: are the surrounds presented in stereo in the 5200 & 5300, or is it a single mono signal x 2?
 
Thanks much for your reply - I'll be reading it a few more times in order to properly analyze. Another question: are the surrounds presented in stereo in the 5200 & 5300, or is it a single mono signal x 2?

When the Shure HTS decoders were designed they stuck to the Dolby MP Matrix standard, which was a single mono surround channel presented over 2 or more speakers and rolled off above 7kHz and below 100 Hz. But Shure did something different - they sent the single rear channel through a non-complimentary digital comb filter to give the 'effect' of a "U-shaped" array of speakers, like a theater would have - Shure called it the "Acoustic Space Generator" - it makes the surrounds sound HUGE and spacious without any localization to the individual speakers themselves. THX tried to copy it with their decorrelation circuit, but IMO, the Shure works much better. The Acoustic Space Generator is also used in the "Mono Surround" mode - in that mode the mono sound is sent through Center Front with lesser amounts to Left and Right and then through the Acoustic Space Generator at a lower level to create the feeling of a slightly enlarged soundfield, but without sounds coming from all over like other systems "mono" modes do. Plus, Shure included a trimpot on the bottom of the unit so you could adjust the amount of stereo synthesis in the mono mode, which was a nice touch.

If you don't have a Shure decoder, pick one up on eBay - some people think they are worth $$$ and price them accordingly, but others put them up for like 20 bucks - as I said in the OP, I got mine for a dollar. I think it sounds better, in both basic fidelity and in steering behavior, than Pro Logic or Pro Logic II, and makes movies sound much more 'discrete' - since there are a lot of 2 channel Dolby Stereo encoded films on DVD, I'm using my Shure 5300 every day now and loving it. And I recently got the remote on eBay for a few dollars - the remotes used an analog infrared signal that can 'drift' so at first, it wouldn't control my 5300, but there's a single pot inside the remote that adjusts the IR signal and now it works like new for me. So my total investment has been around 20 dollars, total, for a Shure HTS-5300 and the remote. I love that I have a pristine unit that cost over a grand when new.
 
Is it correct in saying that the stereo surround synthesis mode for music outputs the surround channels in mono as well?

Yes, in the stereo synthesized surround mode the surrounds are in mono - although sent through the Acoustic Space Generator. In addition, the Acra-Vector Logic steering is completely disabled. Only the Dolby Surround mode uses the Acra-Vector Logic Steering. The overall fidelity of the 5300 is so high, and the steering so "open" without collapsing the front Left and Right soundfield to the Center Front, that I use the Dolby Surround mode for all sources, even non-encoded stereo. BTW, back when the 5300 was on the market, only Fosgate made Dolby licensed decoders that had Stereo Surround modes - and because they pulled L/R around to the back, didn't work too well with motion pictures, I feel (someone on the left of the screen, whose voice is panned to the left, shouldn't be heard with their voice coming from the surrounds, which is what the Fosgate's of the time did in their "Wide" mode - in all other modes, the surrounds were mono - Dolby didn't allow a "licensed" consumer decoder to have stereo surrounds or full-frequency surrounds until Pro-Logic II came out - before that, in the official "Dolby Surround" mode, the surrounds had to be mono with Modified Dolby B noise reduction and 7kHz HF/100 Hz LF roll-off. Extra processing, like the Acoustic Space Generator or THX decorrelation, to make the surrounds more non-localizable, could be applied, but true-stereo surrounds were not allowed because they were not licensed by Peter Scheiber to sub-license any other method of MP matrix decoding)

I've been playing a number of my DVD-A's and quad DTS CD's/DVD's via the 2 channel outputs of my Panasonic Blu-ray player where they are mixed down into the Dolby MP Matrix and then decoding them through the Shure 5300, and except for the fact that the rear L/R are summed to mono, I'm amazed at how well the Shure keeps the soundfield "open" and discrete sounding, without any noticeable logic action. The digital Pro-Logic decoder in my Yamaha DSP-A1 and the Pro-Logic II decoder in my Kenwood Sovereign THX receiver (and its Pro-Logic emulation mode) don't sound nearly as good in terms of the steering and phantom imaging - I can hear the logic working, where I can't with the Shure. Both Pro-Logic and Pro-Logic II don't sense/enhance positions in-between speakers as well as they do directions representing a 'real' speaker output, while the 5300 has individual sense/control/cancellation parameters for in-between phantom positions, giving them a much greater precision of image. That's one of the reasons the Shure decoders started to get so much use in Hollywood encoding films and such - mixers simply got better results with the Shure.

The Kenwood's dts Neo-6 mode keeps the soundfield very discrete sounding, since it uses multi-band decoding (I wish all matrix decoders would use multi-band steering!), but its basic fidelity is simply awful.

I have a Circle Surround II decoder and am really shocked at how poorly it performs as compared to the Shure and Dolby decoders - it's a gain-rider, so it's non-constant power and you can hear the soundfield shift, etc...

One system I've never heard is Lexicon's Logic 7, although it's been changed substantially over the years by inventor David Gresienger. Nor have I heard Fosgate's (misleadingly named) Six-Axis Logic decoder. I really want an Aphex ESP-7000 decoder - they always seem too high priced on eBay when they come up though - to me, NO stand-alone matrix surround decoder, other than a Tate, is worth more than about 20 bucks.
 
Have fun with your new toy! Cool that you posted to this thread instead of a new one. It's always fun to see Disclord's avatar pop up under what's new. I believe he did most of his auditory evaluation using movie & easy pop (he always did love Olivia Newton John) so with your priority of classical music I look forward to your experience.

This unit was pretty low on my radar as I pretty much considered it good for movie but not what I was looking for in music reproduction. But I have just read the patent & the encoder manual & I probably under-estimated the Shure StereoSurround.
Random thoughts: It is good to be wideband, not so good that automatic input balance is done LED/photocell control. I prefer to simply manual balance. Not so good that the rear ch surrounds are mono but very interesting that they have this Acoustic Space Generator. Ty says it makes the rear space sounds huge which might be very complimentary to classical & opera. I think it's interesting that Sansui's first surround product the QS-1 used attempted something similar with a photocell R/C phase shift circuit driven be 8 Hz lamps.

Also I noticed that in fig 3 of the decoder patent it shows the typical Dolby matrix parameters to create L,C,R,S but also produced a left surround & a right surround. This was derived from the good 'ol Scheiber coefficients of:
Ls= .924 Lt - .383 Rt
Rs= .924 Rt -.383 Lt
These were not meant to be speaker feeds but aided in directional control signal generation. I don't know of any other decoder that did this.
Gene, I'd suggest dropping a PM to Bonzodog aka John Owens for schematics & manuals. This way he'll get pinged by e mail as well as in the forum. I don't know if Ty ever procured this material so maybe you can give it a try.
 
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