ABOUT STEREO QUESTIONS NOT ASKED YET?
Is the stereo system enough to produce reliable stereo image and is it, in theory even, capable to produce identical /real sound?
The answer author should like to amend with his own definition what he considers „the trusty sound” and what „the real sound”
REALITY is subjective feeling of trust in actual acoustic environment where one stays. He may stay in the same compartment where sound is produced or next to it. It incorporates full information about sound produced and about the acoustic characteristic of room where sound is produced. Listener is aware about sound existence in room and room by amending it’s reflections to sound becomes part of a listening reality.
IDENTITY of sound is coherence of what the audio system delivers with speakers with what is heard in environment where it has been recorded. Acting toward IDENTITY in reproduction of sound forces stripping the room of it’s own acoustic (damping similar to non-echoic chamber) and thus strips of the outer reality. Sound of instruments stripped of the reflections is dry and without filling of subjective presence.
Lets go to the point: when targeting the trust of sound it is forbidden to amend in visible way amplitude/frequency curve. The frequencies differing much in phase should differ minimum two times in frequency (so that it may be perceived as two different tones and not chord). It’s frequency band is supposed not to exceed human’s perception ability. The reason of this is that heard frequencies are in connection to physical dimensions of objects producing them in nature and which are passing information about size. The frequencies out of that range even if they are received by listener are not fully readable. It is worth notice that listening in closed compartment amends range toward natural decrease (in nature high tones are consumed or dispersed by almost all things), understandable and improves psychical comfort.
Our desired outcome :
difference φ = 0 when distance L = distance R
At drg. 1 as we can observe it is impossible to get it for two ears instantly. If for simplifying we calculate this difference according to drawing as distance between ears x sin 45% it shall be about 14 cm. If we search for the frequency which is most affected by (-180)deg phase it shall be 28 cm – near 1 kHz.
Conclusion is that for length of wave 28 cm we are getting worst condition – else one ear gets full volume and other „O” and stereo image is unexpectedly waving, or in symmetrical situation it shall affect 1 kHz simply in both channels – decreases the identity of reproduction For all other frequencies it is straight proportional to frequency and difference of distance and produces interference.
In contra to stereo, mono reproduction with one speaker produces phase differences which are a vital part of information about direction identical as in natural listening and is 100% understandable.
Conclusion is that only mono system with one speaker localization may achieve completely trusty and real performance. For mono listening, when facing the speaker, dif φ = 0 . It is because one speaker cannot produce the same harmonics with two phases.
In case of multichannel reproduction effect of interference shall be condensed but it does not mean more reality. Polyphony shall be worsened .
WHAT IS LISTENER’S ADAPTATION TO COMPARTMENT?
It is unconscious learning of given listening room by listeners hearing sense. All induced by us amendments to acoustic environment are perceived only in limited, not long time. Then brain „learns” compatibility of room layout to room reflections and does not perceive the way his new visitors perceive it at beginning. That is the point to think about for audio salons. Customer shall never perceive the same in his not treated room as in treated salon..Anyway author would like to state that at home it shall be more real for him.
Perception of reality depends also on reverberation included in recorded material – strong and short, comparable to room reverberations, alter reality perception by superposition to listening room reverberations. Longer reverberations – (listening to live big concerts) nicely compose to them.