thank you very much for these informative and well structured comments.
I will keep them in mind in my further tests.
In fact I am not able to run any tests by using the necessary software,
as these things are not accessible.
All the best.
Arnthor Helgason
=C3=9Eann 30.7.2013 19:13, skrifa=C3=B0i :
>
> > Here is the Eight-configured recording:
> >
> http://www.hljod.blog.is/users/df/hljod/files/baejarlaekurinn_blumlein.mp=
3
> > Then the AB-setup:
> > http://www.hljod.blog.is/users/df/hljod/files/baejarlaekurinn_ab.mp3
>
> Arnthor,
>
> I gave these the Brinicombe test - listening with headphones and close
> speakers. I needn't have looked at the file names as they were like chalk
> and cheese for the stereo images. I'll try to explain why.
>
> In one recording, I heard a clean stereo image where each part of the
> water
> noise was placed within the width of the image. In other words, the
> angle of
> each stream sound was reproduced at an equivalent angle in the stereo
> image.
>
> The ratio of object width to stereo width was probably equivalent to a
> camera fisheye lens. With sound however, you get an overlapping image
> from
> the rear of the fig-8 pair, but this doesn't seem to affect this
> recording
> as it sounds fine.
>
> The other recording had a focussed centre point to the image but at
> angles
> to each side, left and right, it became more and more defocused, giving a
> stereo effect, but without any clarity. I created a left minus right "S"
> signal and this was louder than I would have expected for an accurate
> stereo
> signal. Looking at the left and right waveforms, there was a lot in
> common
> between them. With a coincident fig-8 pair, there is only a common
> sound at
> the centre of the image.
>
> Now for the theory.
>
> A coincident fig-8 pair gives volume stereo which is split between the
> channels according to the angle of each element of the sound object, ie.
> each splash contributes a proportion to the left and right signal
> according
> to its position in the sound object.
>
> A spaced omni pair gives almost identical sound in each channel except
> that
> there is a time delay between left and right or vice versa. This also
> gives
> a stereo effect, but only up to the point where the time delay is
> equivalent
> to 17cms path difference. Beyond this time difference, we stop hearing a
> stereo effect and just hear an out of phase sound.
>
> An out of phase effect is often used to create pseudo stereo, but it can
> never give a clean stereo image. An example of this is added
> reverberation
> in music to give "space", but to my mind if this space sound is equal or
> louder than the prime direct stereo sound, it reduces the overall stereo
> effect.
>
> The ideal stereo recording is a dummy head recording which has both
> volume
> and phase stereo, but if the dummy head doesn't match your own head, it
> won't work 100%.
>
> I'm less worried about low frequency differences between the recordings
> because the 3-dimensional pickup areas are different, including
> echoes, but
> I would trust the fig-8 pair to be closer to the original sound
> object. Also
> when you start mixing out of phase signals, you get all sorts of
> frequency
> effects like "comb filter" effects. On a power spectrum there is a comb
> effect starting at about 12Hz corresponding to an echo at about 7 metres
> away.
>
> Artificial out of phase reverberation is used extensively in music
> recordings and this consists of time delayed sounds as also in mono which
> has been "doctored" into stereo which keeps cloth-eared punters happy,
> but
> what the heck, stereo is an illusion after all - it's not real. :-)
>
> David Brinicombe
>
>
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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