A one-dimensional two-channels stereophonic standard - diyAudio
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A one-dimensional two-channels stereophonic standard

Posted 7th February 2017 at 01:47 PM by Grasso789
Updated 25th March 2017 at 03:11 AM by Grasso789

Recently it has been archieved to capture, store, propagate and play back audio with the full human hearing frequency range (16 to 16000 Hz) and contrast (7 Bel). Still, if a big sound source or several sound sources at once are the matter of content, such playback sounds artificial, because all is emitted from one small single acoustic source. In order to hear, what is going on, we use both ears simultaniously, turn our head in different directions and will detect the electro-acoustic device.

While an indetectable electro-acoustic reproduction incorporated six microphones, storage and transmission channels and a house-sized sphere covered by loudspeakers on the inside and containing the listener, we can help imagination at least a little bit by introducing sonic differences between left and rite. We also want this stereo, after Greek stereos shape, to integrate thoroly and easily with already existing mono electro-acoustics. We may double transmission and storage channels, for example by using vertical stylus movement or a frequency-shifted band for L-R information, while L+R is on the old mono channel.

This is one-dimensional stereophonics, which has two electric channels encoding any sources placed at the horizon in front of the listener.

Since mono devices must not play a stereo record back worse than a mono one, stereo recordings must have both channels in sync. This can be done by picking up both channels in the same acoustic spot. Co-incidence also known as synchronous and intensity microphonics does this. Two cardioids at rite angle record well front hemisphere (196 2pi-is-360-degrees degrees) in stereo.

Since stereo devices must not play a mono record back worse than a stereo one, stereo playback must have both channels in sync. This premise is hard to fullfill with loudspeakers, because run-time between loudspeaker and ear is rarely the same for a left and a rite loudspeaker, and never for both ears and both loudspeakers at the same time. Just two loudspeakers cannot do stereophonics.

A possible kind of playback, which is rather easily done, is a pair of headphones. As our brain uses phase difference between left and rite ear for localisation, our syncro-stereo as pressed on vinyl and broadcast with FM results in only a weak stereophonic impression. In order to improve it, we tap each channel, lopass-filter (just like our head shades sonic waves from left for rite ear) and delay (just like sonic waves from left reach rite ear later) the tap and add it to the other channel. This processor is mono-compatible, because it treats center signals with head transfer function. It must become adjusted to head size.

For loudspeakers stereophonics one needs a concave array of many loudspeakers, each getting a special grade of +-xL+-yR. There are ruffer and finer estimations, but only two loudspeakers do not cut it.

Three loudspeakers, for you know left, center and rite one, driven by Elias' principles with sides further attentuated in order to further improve center playback, is not perfect but a start. This can be done passively; connect an Y circuit with Z=8R eta=0dB sides and Z=2R eta=+6dB center to a two-channel amplifier with common ground.

A special case of the three-loudspeakers stereo is the beam stereo, which radiates all mono sound from one spot but beams left and rite channel to different directions. The stereo impression is archieved in conjunction with listeners' memory and reflective side walls of the room, in whom the listeners are in. I designed GA13, which flavours clean mono with a grain of stereo.

A x large curve consisting of y many loudspeakers can put out stereophonics, if x and y are sufficiently large. In order to keep cancellations above hearing range, the farer the listener is allowed to move to the side, the larger the product of x and y must be. For example a pantomimical single or six ears on a sofa need(s) a 6 meters wide semi-circle consisting of 64 loudspeakers, altho there might be tricks allowing to cut this effort in half.

Monophonics and mono-compatible stereophonics in a nutshell:
* Co-incidence-stereophonic recording with two microphones, or monophonic recording
* Transmission of at most two channels, obligate L+R and optional L-R
* Most efficient playback over a headphones processor and a pair of headphones, or mono headphone(s)
* More social and grounded playback over loudspeaker(s), either for proper stereo a large array at a dedicated place, for beginner's stereo a three-loudspeakers or beam one, or a mono loudspeaker
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  1. Old Comment

    What does "one-dimensional" really mean here? What is "one-dimensional"? You have written that the standard shall be "one-dimensional".

    Posted 20th February 2017 at 07:45 AM by TNT TNT is offline
  2. Old Comment
    Hi, it means, that there shall occur sonic differences in one dimension, the lateral one, say from left to rite hand side.
    Posted 22nd February 2017 at 02:44 PM by Grasso789 Grasso789 is offline
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