Date: Wed, 21 Nov 2001 12:38:50 -0500 (EST)
From: Sylvain Robitaille <syl@alcor.concordia.ca>
To: Carey Dodge <dodgeroo@excite.com>
Subject: Re: speaker placement
In-Reply-To: <31718780.1006310623160.JavaMail.imail@patti.excite.com>
Message-ID: <Pine.OSF.4.31.0111211126490.28349-100000@alcor.concordia.ca>
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I wrote:

> Well, it's been about 10 years since I've seen my notes about this,
> ...

Wow!  I just now sifted through the notes.  This was from a course
entitled Sound Systems and Live Reinforcement, which I took at the
University of Manitoba in 1988!  That's just too long ago...

There actually isn't anything in my notes that I haven't already brought
up, unfortunately.  They're rather vague, but the brief summary is that
a "cluster" configuration is preferable in most situations because:

   - you can get better coverage, with less interaction between sounds
     from individual drivers.
   - acoustic coupling will most often work in your favor.

As a point of interest, my notes, (actually this is from a "handout" by
EV, entitled The PA Bible -- I'm not sure if they're still available)
never mention 30 degrees, (in fact they never mention that speakers in a
triangle configuration should be placed at any "magic" angle).
Specifically, for most of the "typical" applications they outline,
pointing the center line of the speakers at the center of the back wall
is the "basic" recommendation, with the point brought slightly forward
for speakers with narrower dispersion characteristics.

I've checked other literature I have, and there doesn't seem to be a
whole lot of discussion on speaker placement.  I'm curious to know what
the Yamaha Sound Reinforcement Handbook says on the matter, but I have
yet to pick up a copy of that one...


On Tue, 20 Nov 2001, Carey Dodge wrote:

> I think there are many ideals however, especially in the context of
> electroacoustics.

Yes, the whole idea of multi-channel diffusion certainly is a very
different point of view than I'm used to taking.  However, as far as I
know, the discussion was a 2-channel (stereo) system in someone's home.
This does bring things back to the simpler form I'm speaking of.

> Is one still able to create a strong left right panning motion with this
> speaker set up?

Yes.  Quite effectively, in fact.  Mind you, you won't get the same
degree of panning that headphones will give you, and depending on the
characteristics of the speakers involved, you might still not get as
pronounced an effect that the "triangle" layout will give you, but you
will most certainly be able to get a stereo sound field.

> How is it more ideal than 5.1 surround sound where the centre front
> speaker is a point source speaker and the others surround?

Oh, I don't know about "more ideal".  I think the surround setup
you describe is essentially the same type of configuration as the
multi-channel diffusion setup used for the EA concerts in the Concordia
Concert Hall, ie. closer to multiple point-sources than to a single
point-source.  It's no doubt more "ideal" for the applications in which
it's used than a single cluster would be, I agree.

However, from the perspective of numerous single point-sources, I think
the theory still applies.

> Or were you just creating 'the ideal' to explain this speaker set up?

No, no.  The "ideal" as I see it has existed for decades at least.
Specifically, it's sound reinforcement in a live performance.  Recall
that I did disclaim that I very likely come from a different background
than most people who were taking part in this discussion.  I realize
others probably define "ideal" much differently than I do.  However,
when dealing with a two-channel (stereo) or mono system, I can't think
of a better layout than a center cluster.

When working in a theatre at one point, I did design a sound system that
consisted of multiple (I believe there were 8, but I may be forgetting
some) point-sources, and was operated in much the same way as the
diffusion concerts we have in the concert hall.  That's essentially what
I felt was called for in that application, but I felt I was compromising
the single point of sound (essentially "the stage") in order to achieve
the sense that sounds came from specific directions, (at one point in
the production, there was a scene where it was raining, and in most,
though admittedly not all, seats in the house, the effect was as though
it was really raining right in the theatre.  The trick was to not
overlap the sound fields of the different speakers, as much as possible,
thus reducing their interactions.)

The EA diffusion concerts in the concert hall, have the exact opposite
design, as far as I can tell, but for mainly the same purpose (providing
a sense of direction).  The sound fields of each separate speaker is
purposely overlapped with others, and the best seats seem to be where
the most sound fields overlap.  I'm still trying to get used to that...

If you looked at my home setup(s) now, (including the stereo in the living
room, one in the TV room, and the "near-field monitors" (actually, cheap
computer speakers) I use when working with recordings), you would not find
a single example of "point-source", unfortunately.  The stereo systems
are compromised for the sake of aesthetics, and the computer speakers
don't (yet) have a long-enough cable for me to accomplish the cluster.

By the time my recording environment (at least) is "ideal", it *will*
consist of a center cluster for the speakers, (with much better
speakers).  In the meantime, I put up with what I have because it still
"works".

> p.s. perhaps we could move this discussion to the ea list if you don't
> mind.

I don't mind at all.  In fact, feel free to quote anything I've said to
you in private on the list.  I *had* originally responded to the list,
but yours is the only response I've seen.

> I would like to read what others have to say about speaker placement?

So would I, particularly because my views about it *do* come from a very
different school of thought...

-- 
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Sylvain Robitaille                              syl@alcor.concordia.ca

Major in Electroacoustic Studies                  Concordia University
Faculty of Fine Arts / Music Department       Montreal, Quebec, Canada
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