Re: RE: concerts


Subject: Re: RE: concerts
From: KEVIN AUSTIN (KAUSTIN@vax2.concordia.ca)
Date: Fri Jun 04 1999 - 07:41:18 EDT


>> > Out of interest, what is the speaker configuration? Is the tape ADAT?

>> Each of the composers has used a different configuration. Both have
>> used the 8 to create a circle rather than a cube around the audience.

Sorry not to have been clear. I guess the first consideration is that all
eight speakers are on a plane (at the same level). The next part would be
to say whether they are spaced equaly around the audience, (in some form
of circle), or or in a front-arrayed set-up.

(use mono font)

                   A B

         C D

E F

              xxxxxxxxxxxxxxxxxxxxxxx
              xxxxxxxxxxxxxxxxxxxxxxx
              xxxxxxxxxxxxxxxxxxxxxxx
              xxxxxxxxxxxxxxxxxxxxxxx

       G H

(The speaker positions, E/F, could be more to the side.) This situation
tends to approximate the visual field, and is also somewhat closer to the
listeners' normal ability to perceive direction ... as small as 5 degrees
to the front/center, decreasing as the sound source is more than 80
degrees from the front [IME].

>> Paul has Left: 1,3,5,7 and Right 2,4,6,8 (a kind of 'main' eight setup)
>> While Ross has used a 1 - 8 clockwise setup, using each channel as
>> a mono, rather than stereo.

Given a circle configuration, two possibilities are a "stereo" pairing:

            A B

            C D

            E F

            G H

or the (so-called) "double-diamond"

                  A

       B C
             xxxxxxxxxx
             xxxxxxxxxx
D xxxxooxxxx E
             xxxxxxxxxx
             xxxxxxxxxx

       F G

                  H

Where the two 'squares' (A, D, H, E), and (B, C, F, G) exist. Speakers
A/B/C, F/G/H are sometimes in a straight line. There are certain
complexities introduced regarding time delay (precedence effects), when
the speakers are not "kind of" equi-distant.

(This year we added a delay to the side speakers to try to overcome this
localization problem.)

And there are other less standard options (space permiting) ...
For about 5-6 years in the early 70s, the live electronic music
improvisation ensemble, MetaMusic, used (among others) speakers set up in
two concentric circles. The group sat in the center of the hall: four
speakers around the group faced outwards, four speakers in the corners of
the space faced in. Each player had one or two channels available.

The audience sat in a circle around the group.

A B

             (audience)
     a a
     u C D u
     d MM d
     i i
     e E F e
     n n
     c c
     e audience e

G H
       
This set-up means that there is no "prefered" listening position, and
each place has a very different mix of the sounds. This may be
appropriate for certain kinds of installation / mobile forms where there
is not a "single artistic object" to be heard.

>Why are both of these difussion set-ups termed 'octophonic' when they
>are completely different?
>Would it not be more accurate to describe these works as being for
>8-track tape.

The question can be broken into two parts: are the eight speakers? are
there eight sources? The speaker configuration can be termed octophic (or
whatever the greek version of 'octo' -- eight -- is).

The eight channel tape could also be a distribution (upward mix?) of an
original stereo tape (source).

Some work, started in the 50s, conceived of multiple speakers as point
sources for sound (the Philips Pavillion in 1958), and sounds were freely
panned over the 'surface' of the 425 speakers ... though it seems that
there were only 20 channels of amplification [? Chadabe p 61].

Chadabe, Electric Sound (Prentice Hall), and Roads, Computer Music
Tutorial (MIT), along with Bregman, Auditory Scene Analysis (MIT) are
good starting places, in english for some technical info. The two
recently re-published "L'espace du Son" I / II (Musique et Recherches -
Belgium) contain much aesthetic and historical thought (mostly in french,
but even the pictures and diagrams are worth the $).

Best

Kevin
kaustin@vax2.concordia.ca



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