Hi Stefan,
The "stereo triangle" page you pointed to says, "By making the
distance between the speakers and each speaker to you (the center
listening point) the same, you have made an equilateral triangle.
This stereo set up ensures that the sound from each speaker has the
exact same distance to travel to reach you." The first sentence is
true. However an equilateral triangle is not necessary to ensure that
each speaker is at the same distance to a laterally central listener.
For an equilateral triangle the sound would travel the same distance
from one speaker to another as it does to travel to the listener. I
don't see that this is of any importance. OK some sound from each
speaker would be reflected by the other, but this would be off axis
from the source speaker and reflected backwards due to the speakers
being angled inwards towards the listener. I would suggest that this
would be barely audible in comparison with other acoustic room effects.
The -3dB central panning level is a result of the sine/cosine panning
law. One speaker is at zero degrees, the other at 90 degrees. When
fed a mono signal an angle of 0 results in a gain of one to one
speaker and zero to the other. 90 degrees reverses the result. 45
degrees gives a gain to each speaker of 0.707, or -3dB. This appears
to result in a good phantom central image. With a linear panning law
the gain to each speaker would be 0.5 or -6dB, which appears to
result in a "hole in the middle".
Why plus and minus 30 degree separation for "normal stereo" is still
a mystery to me.
Ciao,
Dave Hunt
From: Stefan Schreiber <st...@mail.telepac.pt>
Date: 28 March 2016 19:07:14 BDT
To: eero....@dlc.fi, Surround Sound discussion group
<sursound@music.vt.edu>
Subject: Re: [Sursound] OT Stereo stage width - Was: Static stereo
source in rotating soundfield, possible?
Eero Aro wrote:
Hi Dave
I have a feeling that this subject has been discussed in Sursound
many times
before.
The point in my reply was that when you use two channel stereo in the
surround sound field, a wide angle between the virtual
loudspeakers doesn't
work too well.
I don't know where the 60 degrees angle between the stereo
speakers originally
came from. Blumlein used a 30...35 degrees angle between the
speakers.
When I started to work in broadcasting in 1977, all control rooms
were equipped
with a stereo listening setup. The speakers were arranged so that
they were in a
60 degrees angle from the mixer's seat.
I have noticed with students, that there is a wide spectrum of
people, most do
can integrate a stereo sound image between the loudpeakers with 60
degrees.
I have met people, who tell that they cannot hear any kind of a
stereo image
between the loudspeakers, whatever the angle. They hear sound from
two speakers.
At the other end are people, who can hear an integrated stereo
image with 90
degrees.
I don't know. Anyway, in music industry and boradcasting, you need
to have some
standard. The broadcasting house I worked in, had then 250 radio
studios. The
listening conditions needed to be at least somewhat similar
between control rooms,
so that you could continue the work in another studio another day.
Why 60 degrees
was chosen, I don't know.
Eero
Because of the < stereo triangle > concept?
http://www.centerpointaudio.com/SpeakerPlacementAndPositioning.aspx
"Equilateral", bla bla bla... the angle is 60ยบ in the equilateral
bla bla bla ....
Best,
Stefan
From: David Pickett <d...@fugato.com>
Date: 28 March 2016 19:33:08 BDT
To: Surround Sound discussion group <sursound@music.vt.edu>
Subject: Re: [Sursound] OT Stereo stage width - Was: Static stereo
source in rotating soundfield, possible?
The problem with speakers at +/- 45 degrees is that one needs a
wide room if one is to sit at a decent distance from them.
However, it can be impressive. I have found the effect even better
if a centre speaker of the same typeis added. Gerzon gave the
ratios necessary for matrixing 2 channel stereo into this 3 channel
format. It is not simply a question of feeding the centre speaker
with a -3dB sum, but quite easy to implement.
David
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