UHJ, Ambisonics, other odd CD and DVD formats

[Dave2002]

I just put one of Vlado Perlemuter's 6 CD Chopin set NI1764 into my drive, and I noticed that it says Stereo Ambisonic UHJ encoded on the CD. Are there any viable ways of playing this as a multi-channel/surround sound source these days? There used to be decoders, but I suspect they've long gone.

Mostly CDs have survived as a fairly strong, and generally satisfactory standard, but there have been a few variations along the way. SACD ought to have been good, but has largely been bypassed. Although CDs are pretty standard, some use pre-emphasis, which isn't always supported well, I believe. HDCDs are yet another variant, which at least should notionally give better quality 20 bit/sample sound.

The default situation for most of these formats seems to be that at least they should play as regular CDs. A mistake which some of the early SACD releases made was that they could not be played in CD players.

However, enough digression. What about Ambisonic/UHJ?

[Tony Halstead]

I have owned a 'Minim' ambisonic decoder since the 1980s and it was still working OK a couple of years ago.
The inconvenience factor, physically, is that you need not only four loudspeakers but two amplifiers.
To save living-room space I dismantled it and now listen with a normal stereo system.
Most of the rather mushy, hazy 'Nimbus' ambisonic recordings are rendered clearer and more listenable-to when played via an ambisonic set-up.
These links are interesting:

http://ambisonic.info/info/ricardo/decoder.html

http://www.ambisonic.net/ambi_AM91.html

http://184-106-235-187.static.cloud-ips.com/q/ambisonic-decoder-details-anyone.html

I note that 'Minim' still has a Business Directory listing at
23 Gore Road Burnham, Slough, Berkshire SL1 8AB
p: 01628 663724
but they seem not to have a web site.

[Ferretfancy]

Dave 2002,
You've raised a very interesting point. I had a couple of early quadraphonic decoders for the various matrix systems, including Ambisonic UHJ back in the days when I spent hours tinkering with my loudspeakers, adjusting cartridges etc.etc. The problem with all these analogue systems was that they inevitably suffered from poor channel separation, as they all relied on trading front stereo separation for a degree of front to back. The available decoders were all passive devices, although some American designs had gain riding circuitry which allegedly improved matters.

The SQ system was promoted by EMI, while Decca issued a few LPs in QS.They both used conventional techniques, with microphone placing in the studio used to create the rear channels. The Ambisonic system was supposed to use a single specially designed sound field microphone to create a coherent field around the listener, and the BBC made a few broadcasts using the system. It was heavily promoted by Nimbus,and like the Quad recordings their issues were supposed to be stereo compatible, but they seemed to suffer from over distant balances and too much reverberation

In spite of the shortcomings, I became very used to listening to my LPs with rear channel ambience, using a modified Hafler system which allowed me to adjust the rear channel gain. The problem was that my KEF speakers never sounded as they should have done in my room, so I resorted to all sorts of experiments with graphic equalisers and what not.

Finally, ten years ago I bought a complete Meridian surround system which handles everything digitally up to the loudspeakers, which have their own DACs and amps.
The Meridian decodes film systems like Dolby, but also provides facilities for what you might call synthesised surround. Unlike the earlier analogue systems it does this without compromising the separation, and to my ears gives a convincing feeling of the natural space around the performers. There is a choice of options for differing types of material, but in practice I prefer the Super mode which seems to give the best results generally.

If I watch something like The Lord of the Rings in Dolby surround ( with the neighbours away !) the rear channel speakers really come into their own, but on the music presets the result is much more subtle.

Of course, Boothroyd Stuart were involved in the development of Ambisonics, and so their equipment carries it, but interestingly they do not support SACD. If I play an SACD compatible disc, I am still listening in normal stereo, but using the extracted rear channel information from the sound processor.
I would be curious to know if the performance of SACD would be a whole step better than I'm getting now. It would mean making a wholesale change to incorporate it, but I'm quite happy with it as it is.

Incidentally, if I play an ambisonic encoded CD, using the ambisonic preset, the results are good, but not spectacular. SACD discs are fine in stereo mode, but I sometimes detect a slightly steely quality at the top end. Meridian say that the SACD system is over-engineered, which strikes me as a slightly odd statement, as ambisonics is fairly complicated !
One final point, I've learned over the years that the choice and placing of loudspeakers in the room is one of the most important factors for good sound, and this requirement is too often overlooked. This is just as important where the rear loudspeakers are concerned, and correct level settings are crucial for good results. Once established, hands off! I've wasted too much time in tweaking in the past.

[Martin.Leese]

I just put one of Vlado Perlemuter's 6 CD Chopin set NI1764 into my drive, and I noticed that it says Stereo Ambisonic UHJ encoded on the CD. Are there any viable ways of playing this as a multi-channel/surround sound source these days? There used to be decoders, but I suspect they've long gone.
...
However, enough digression. What about Ambisonic/UHJ?

Details of decoders are available in the Ambisonic Surround Sound FAQ (which I created and maintain). See sections 17 and 18. The only decoders currently available are from Meridian (mentioned by another poster). Used decoders occasionally come up on eBay. The trend these days is to move to software decoders (players) but, while these exist for Ambisonic B-Format, I don't know of one for UHJ.

A possibility is to use another matrix decoder such as Pro Logic II or even the old Hafler circuit (as mentioned by yet another poster). These decoders will not decode correctly, but will give you an idea of what is possible. An Hafler circuit is offered on my website.

Also, Nimbus were not the only company to release UHJ encoded recordings. (They were the only company to record in a highly reverberant room, giving the well known "bathtub" sound.) A UHJ discography is available.

Finally, Ambisonics is still around, and is gaining a niche market in video games. This is described on the Wikipedia page.

Regards,
Martin

[Martin.Leese]

Dave 2002,
You've raised a very interesting point. I had a couple of early quadraphonic decoders for the various matrix systems, including Ambisonic UHJ back in the days when I spent hours tinkering with my loudspeakers, adjusting cartridges etc.etc. The problem with all these analogue systems was that they inevitably suffered from poor channel separation, as they all relied on trading front stereo separation for a degree of front to back.

While it is true that the matrix systems showed poor channel separation, you only need about 3 dB separation for the speakers to sound separate, so this was really a wild goose chase.

...
Finally, ten years ago I bought a complete Meridian surround system which handles everything digitally up to the loudspeakers, which have their own DACs and amps.
...
There is a choice of options for differing types of material, but in practice I prefer the Super mode which seems to give the best results generally.

You may be interested to hear that Super Stereo uses Ambisonic technology to "decode" stereo recordings. Even the old 1980s Ambisonic decoders had a Super Stereo mode.

Regards,
Martin

[Martin.Leese]

I have owned a 'Minim' ambisonic decoder since the 1980s and it was still working OK a couple of years ago.
...
I note that 'Minim' still has a Business Directory listing at
...

I own several Minim decoders. Minim do not currently manufacture a decoder; I would avoid them until they have product ready to ship.

Regards,
Martin

[Ferretfancy]

Martin,

Yes,as you say, the Meridian system does use Ambisonic technology to extract ambience from stereo recordings. I should have said 'extract" rather than synthesise, since it relies on difference information that is already there. It also has presets for Dolby Prologic and Trifield. The latter is designed for use on instrumental and chamber recordings and gives improved imaging.
On material that has been recorded using simple microphone techniques, results are very impressive. I would love to compare the Meridian "surround" with SACD material, but the signal processor would have to be replaced and that would be very difficult to do.
My first decoder ( analogue ) was made by Integrex, a company who worked closely with Michael Gerzon and others in the development of Ambisonics. It was a bit "cobbled together on the workbench "