we used a much cruder version of this back in 2002 - decoding a hemispherical
32 speaker array to second order, but crossed over the B-format at 90Hz (I
think) to a horizontal-only 8-sub array, decoded in 1st order. This was on the
basis that we couldn't fly the subs, and anyway, elevation discernment, being
largely due to pinnae affects, was not appealed to by the subs anyway. Had to
work on the time alignment (the sub decoder was analogue, the mid'n'tops 32
speaker array done in software) and spatial alignment (rotating the subfield to
match t'other, in the b-format feed). It worked well, though could have been
further refined; it was a one-off installation.
But the principle of using decreasing order with decreasing frequency made
sense from the point of view of efficient use of transducers.
It made me wonder whether the same principle extends the other way - increasing
order with increasing frequency, to make up for the deficiencies in spatial
resolution of lower orders at HF.
Given that it should now be reasonably 'easy' to align the fields of multiple
cells - even having differnt numbers of speakers for each frequency band, there
might be less reason to assume that point source speakers are strictly
necessary.
We're still using speakers designed as stereo projection systems, and it could
even be that starting again, thinking about real-world usages of ambisonics,
that one could revisit the speaker design theories.
Going off on a tangent, it might be that (as others have experimented with,
before) that the trasnducer design for the programme material which is
'ambient' (reflected sound, from no particular source, and therefor not
requiring precision in phantom imagery) might differ than that for the'virtual
sources' ('images')
So I experimented with 12 very modest nxt-type flat panels which were rotated
thru' 90 deg. to what you'd expect, as it were - that is, they didn't 'face'
the centre but were at right angles to it. The results (given the modest set
up) were better than they had any right to be - most especially for ambient and
distant sounds.
I know they used to use multiple dipoles on the walls in cinemas for conveying
the surround channels of 5.1 material (they might still do, I never go to the
cinema because of the loud, poor sound) - so this seems to be a similar
principle.
Just a few ramblings
cheers
Dr. Peter Lennox
Senior Fellow of the Higher Education Academy
Senior Lecturer in Perception
College of Arts
University of Derby
Tel: 01332 593155
________________________________________
From: Sursound [sursound-boun...@music.vt.edu] On Behalf Of Jörn Nettingsmeier
[netti...@stackingdwarves.net]
Sent: 16 October 2015 12:15
To: sursound@music.vt.edu
Subject: Re: [Sursound] Advice on new loudspeaker array... Genelec 8010
speakers?
On 10/15/2015 10:51 PM, Dave Malham wrote:
> One of the things that should be investigated in conjunction with higher
> order Ambisonics material would be to "fade down" the higher order
> components as the frequency drops, thus spreading the bass over more
> speakers, reducing the strain on the individual speakers whilst maintaining
> the spectral balance - hey, wasn't that Richard Lee's Powered Integrated
> Sub concept from several years ago?? Doesn't help with first order materiel
> but....
>
<ears pricked up>
Intriguing idea, that. So we would apply zero-phase high-pass filters to
the second and higher components?
Should be nice for a test run, but how to keep latency down for live
electronics and A/V sync? How would we phase-align an IIR filter?
Allpasses on the lower components?
The spectral balance would be maintained despite the filters, since
we're in LF, where each new order "takes away" as much as it "adds", so
to say. Unlike at HF, where we have to add energies and any such
filtering throws the spectral balance of kilter, as Eigenmike users will
know...
--
Jörn Nettingsmeier
Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487
Meister für Veranstaltungstechnik (Bühne/Studio)
Tonmeister VDT
http://stackingdwarves.net
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