Who listens surround from stereo source?

[el`Ol]

Hello all!

First a quote from Floyd Toole's book "Sound Reproduction - the Acoustics and Psychoacoustics of Loudspeakers and Rooms":

…a pair of loudspeakers deployed at +/-30° or less is not an optimum arrangement for generating strong perceptions of envelopment… Perhaps this is why audiophiles have for decades experimented with different loudspeaker directivities (to excite more listening room reflections), with electronic add-ons and more loudspeakers (to generate delayed sounds arriving from the sides and rear), and with other trinkets that seem capable only of exciting the imagination. All have been intended to contribute more of “something that was missing” from stereo reproduction experience. The solution to this is more channels.”

This thread mainly deals with loudspeaker directivity:
Loudspeakers and room as a system

I have gone the way of non-standard loudpeaker directivity, but I am also interested in multi-speaker solutions. So feel free to post anything about your systems, listening experience with other systems, links about the topic,...


Oliver

[boconnor]

Originally Posted by el`Ol

I have gone the way of non-standard loudpeaker directivity, but I am also interested in multi-speaker solutions. So feel free to post anything about your systems, listening experience with other systems, links about the topic,...Oliver

I'm doing some experiments with a multi-speaker setup - rear (3.1) speakers playing concert hall impulse responses to provide rear channel reverb. See this thread: Digital Room Correction Project

[markus76]

Dolby - What is Dolby Pro Logic II?

[el`Ol]

I don't find any useful information. Typical for proprietary commercial technologies.

[Pano]

I use the old Yamaha DSP-1. It generates 4 channels of surround from a 2 channel input.
Very tweakable, I enjoy it. Used in a subtle way, it's rather nice.

[markus76]

DTS | DTS Audio Formats | DTS NEO:6
DTS | DTS Audio Formats | DTS Neural Surround? UpMix

[soongsc]

The interaural nature of using speakers is always a problem. The most perfect solution is recording with mics right outside the ear and playback using headphones.

[brucemck2]

I prefer to listen to two channel via Meridian's Trifield surround processing. It's a marked improvement over straight two channel, and to my ears, much more "natural" than ProLogic.

On the Linkwitz site he profiles a setup where straight two channel goes to the Left and Right speakers, with a "parallel" surround processor feeding only surrounds. I've used that too, and it works remarkably well, retaining the "purity" of a great two channel chain while adding subtle ambience.

[Elias]

Hello,

First, I think diyaudio needs a dedicated SURROUND FORUM. Now the information is scattered all over the place and hard to find. And I think it's better to name the forum as surround instead of multi channel since surround is not tied to any number of channels. Generally 'multi channel' means 5.1 or 7.1 which are incarnations of commercialism. One can do better.

The most intriquing methods for two channel surround are ambiophonics and ambisonics.

www.ambiophonics.org
www.ambisonic.net


I tried Ambiophonics and was satisfied.


Next I would like to try Ambisonics. Ambisonics is interesting because it is mathematically 'correct' method. Ambisonics is a wavefield synthesis with additional psychoacoustics enhancements.

How to use Ambisonics with stereo source:
1) first convert stereo to B-format. For example using equations like these:
http://r3aktor.com/int/Members/lossius/lostblog/588
http://www.ambisonia.com/wiki/index.php/Super_Stereo

2) then use standard B-format decoder to generate the speaker feeds. Use 6 speaker hexacon layout, propably better results than 4 speakers.


One of the original Ambisonics papers
http://www.epanorama.rackhost.net/schematicsforfree/Audio/Circuits/Equalizers/Multisystem%20Ambisonic%20Decoder.pdf


How is Ambisonics with 6 speakers using stereo source better than conventional 2 speaker stereo? In Ambisonics all the speakers contribute to the forming a phantom source. It is a "push-pull" system. It generates a wavefield that is more closer to the true wavefield a real source would generate. Conventional 2 speaker stereo has fundamental problems with the wavefield. The same problems are inherited to 5.1 and 7.1 when 2 speakers are used to form a phantom image which is allways the case in practise.


- Elias

[cuibono]

I've recently become more interested in surround too, but it seems there isn't too much going on here at diyaudio, wrt it.

I'm still looking for a more in-depth description of what is done to the stereo signal to create the surround channels. Anyone have any links?

I was looking into stand alone units ('prepros'), because the prices seem attractive for mass market stuff - a few hundred dollars for your preamp/processor/power amps is a pretty good deal. But reading up on other forums, people don't take them serious - the 'serious' units start at around $1000, and rapidly go up. For that much money, I'd be inclined to use a computer running Reaper and a surround upmixing plugin, and build a few gain clones. Way more versatile, cheaper, but just not as slick. Any thoughts?