[LAU] question about FOSS WFS implentations

[Fons Adriaensen]

On Tue, Dec 17, 2013 at 10:14:45AM -0500, Ivica Bukvic wrote:
 
> I had an opportunity to listen to their system and even though it was quite
> sparse it still delivered a very compelling image even close to the
> speakers. If the system was using anything in the way of ambisonics it
> would have done so only using the actual horizontal array. Given that
> highest repreducible frequency is directly related to the distance between
> the speakers I am wondering if this may be because they are also trying to
> render waves from virtual speakers as they propagate through the real
> speakers as well as using a selection of speakers to render certain sounds
> as per recent publications in this area.

'Filling the gaps' with virtual speakers doesn't change things - for the
same reason that you can't pull yourself up by your bootstraps.

Consider the simple case of a plane wave from a direction orthogonal
to the line of speakers. All speakers will get the same signal. To
create a virtual speaker between every two adjacent real ones, those
two would just have to get more of the same signal. So nothing changes,
except at the ends of the line (and you may rediscover tapering).

Ambisonic reproduction will create images 'projected on the line of
speakers' a virtual source in between the speakers will appear at
the same distance as the real speakers. It's possible to change this
using near-field compensation, but only for low frequencies.

Distance illusions can be created by exploiting psycho-acoustic
effects rather than physics. I suspect systems such as S.E. are
particularly good at this.

Ciao,

-- 
FA

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It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)