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:
http://www.diyaudio.com/forums/multi-way/121385-loudspeakers-room-system-124.html
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
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:
http://www.diyaudio.com/forums/multi-way/121385-loudspeakers-room-system-124.html
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: http://www.diyaudio.com/forums/pc-based/153446-digital-room-correction-project-5.html#post2131931
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.
Very tweakable, I enjoy it. Used in a subtle way, it's rather nice.
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.
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.
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.
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
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
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?
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?
Better wave field reconstruction does not necessarily result in better reproduction. Wittek's PhD thesis is a very interesting read:
"It is often argued that due to the high similarity between the sound fields produced by WFS and natural sources, a high quality of spatial perception is likely to be achieved. [...] However, it cannot be argued that in general a higher similarity results in a better spatial quality."
http://hauptmikrofon.de/HW/Wittek_thesis_201207.pdf
A strange way of surround sound from two channels is this:
espacenet — Bibliographic data
Speaker placement is 4x90° quadro, ideally front and rear speakers are of the same type and get the same signal.
I have this CD, that is recorded after this standard:
Amazon.com: Xenakis: Psappha/Okho/Persephassa: Iannis Xenakis: Music
For my test I had conventional speakers in the front and more diffuse radiating speakers in the rear (didn't work the other way round, and balance between front and rear is critical). I sat in the middle of the percussion group and it was absolutely clear which instrument is playing in front and which is playing in the rear.
You get demo recordings and a software that converts normal stereo and surround recordings in this 2-channel-quadro here:
AVS RESEARCH Research in psycoacoustic audio area
As with all commercial solutions it is not clear what that software does.
espacenet — Bibliographic data
Speaker placement is 4x90° quadro, ideally front and rear speakers are of the same type and get the same signal.
I have this CD, that is recorded after this standard:
Amazon.com: Xenakis: Psappha/Okho/Persephassa: Iannis Xenakis: Music
For my test I had conventional speakers in the front and more diffuse radiating speakers in the rear (didn't work the other way round, and balance between front and rear is critical). I sat in the middle of the percussion group and it was absolutely clear which instrument is playing in front and which is playing in the rear.
You get demo recordings and a software that converts normal stereo and surround recordings in this 2-channel-quadro here:
AVS RESEARCH Research in psycoacoustic audio area
As with all commercial solutions it is not clear what that software does.
Member
Joined 2003
I do...part of the time. Wide dispersion surrounds are arranged at +/-60, 90, 120 and 150 degrees. Starting from one of the processors like DPLIIx, the additional 4 channels are derived from the 7.1 surround signals using delay and frequency tapering.
IMO, the concept works extremely well in expanding the soundstage and improving envelopment. However, the implementation weakness comes from the different mixes used in the recordings...optimize for one mix and it can be all wrong for the next. (The primary objection is a change in surround level from one CD to another.) Adjusting the setup for each recording takes the enjoyment out of the music, so I settle for an "average" result and switch to stereo when the surround effect isn't positive.
IMO, the concept works extremely well in expanding the soundstage and improving envelopment. However, the implementation weakness comes from the different mixes used in the recordings...optimize for one mix and it can be all wrong for the next. (The primary objection is a change in surround level from one CD to another.) Adjusting the setup for each recording takes the enjoyment out of the music, so I settle for an "average" result and switch to stereo when the surround effect isn't positive.
Since the 1980's I have always connected rear "difference" channels up to the L+ and R+ terminals of a two channel amp. The way movies and music is recorded, this gives a nice ambient 360 Deg fill to the sound.
With two speakers in series, the load on the amp is minimal. Since 60s music is often recorded with ping pong sound, a switch can be used to turn off the rear speakers. A 68uf cap is used to keep low frequencies out of the rear channels since the speakers are small. Really, a band pass should be used since high frequency signals aren't necessary either.
With two speakers in series, the load on the amp is minimal. Since 60s music is often recorded with ping pong sound, a switch can be used to turn off the rear speakers. A 68uf cap is used to keep low frequencies out of the rear channels since the speakers are small. Really, a band pass should be used since high frequency signals aren't necessary either.
An externally hosted image should be here but it was not working when we last tested it.
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I've done this with pro amps for fun. Works great, but the amps ran hot. Maybe it needed your HP cap?
Most recent movies seem to employ surround tracks with some element of HRTF encoding. In many cases the resultant sound field (WAF unfriendly, centre seat only) is massive and enveloping over two speakers.
Underworld Evolution (borrowed). The opening credits fill my living room ahead, behind and well past the boundaries of the cheap low-end Paradigms currently in play.
2006 is not really "most recent" 🙂 Are you talking about DVD or Blu-ray? Which sound track? Your setup?
Hmm, That circuit should pose a very minimal load to the amp even without the cap, unless there is lots of out of phase content delivered. LF sounds are usually in phase for most signal to subwoofer (minimal to rear since it would cancel). I use the cap because the 60's music I listen to often have drums and bass in one channel and no need for it in the rear channel.
I use two 8 Ohm speakers in series for the rear. 4 Ohm speakers could be an issue for amps not designed to drive less than 8 Ohms although the cap should make it safe.
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