From: chrisc@gold.gvg.tek.com (Chris Christensen)
Newsgroups: rec.audio
Subject: Re: need recommendations for center channel speaker
Date: 14 Oct 92 23:05:46 GMT
Article-I.D.: gold.5424
Organization: Grass Valley Group, Grass Valley, CA

In article <1992Oct10.221008.11325@mnemosyne.cs.du.edu> tlode@nyx.cs.du.edu
(trygve lode) writes:
>In article <5410@gold.gvg.tek.com> chrisc@gold.gvg.tek.com (Chris Christensen) writes:

>>I recently read a suggestion by another poster to locate the surround
>>speakers on the side wall, pointed forward.  This positioning
>>_excluded_ the listener from the surround sound field.

>Quite the contrary--actually it's an extremely effective technique when 
>used with bipolar speakers.  At the moment, I'm actually using four bipolar
>speakers,

I wasn't speaking about bipolar speakers in this quoted portion of my
posting.

>one pair on each side wall facing forward, one pair a short
>distance in front of the listening position, the other a short distance
>behind.  With the front speakers turned off, you can hear the sound
>generated by the surround speakers, but the sound is, quite literally,
>surround, with an absense of any directionality or perception that the
>sound is coming from the speakers.  

Your approach is that of brute force,  and that sometimes works. 
The fact that, with the front speakers off the sound envelopes you
actually points out the faults of the system.  

The sound emination from the surround speakers, with the front
speakers off,  should actually eminate, rather distinctly, from the rear as
the "wall-O-Sound (tm).  The WOS being non directional.  Purposely
generating a surounding suround soundfield defeats the way it was
designed to work!.

The surround soundfield is "generated" by the amplitude cancellation
between the surround array and the front speakers.  Having speakers at
the side of the viewing/listening position shunt bypasses the ability
of the surround soundfield to do it's thing.

If you are happy with the effect than don't let me change your mind!
:-)

>There's also the advantage with this
>approach that it is fairly immune to listening position--even being fairly
>far from the center seat doesn't impart a directionality to the sound.
>With the front speakers activated, this arrangement does a particularly
>good job of "steering"--sounds from off-camera really do sound like they
>are coming from the appropriate location.  

This statement concerns me but maybe it's just terminology.
Off-camera sound, to me,  is sound that comes from far screem left or
far screen right.  There are other off-camera effects that come from
the surround channel.  

Here is a situation: If the OCS is intended to be screen left and
1/2 the distance between the front and the rear, your side mounted
speakers cannot achieve that effect.....

Look at the surround soundfield as a box with the front speakers at
one end of the box and the surround speakers at the rear of the box.
The surround soundfield is generated in the space _between_ the front
and rear speakers.  It is possible via the use of the surround mix
joystick to place a sound source in the space between the front and
rear speakers.

With that model in mind place your side speakers in the box and you
can easily see the shunt bypass of the surround effect.

My suggestions are based on the methods that are used to record the
surround field as well as the professional methods used to reproduce
it.

-- 
Chris Christensen                  The opinions I express are my own,
chrisc@gold.gvg.tek.com            and sometimes they are wrong!
916-478-3419 FAX 916-478-3887      After all, I *AM* only human.
Newsgroups: rec.audio