Live Surround
E-mail
conversation with Stefan Fuhrmann, (Ilmenau, Germany)
> Fuhrmann: Did you ever do a surround mix for
the audience of a concert?
> (everything utilizing more than 2 channel stereo counts as surround)
Yes, I just put on a festival which featured several concerts of surround (both 8 channel and 5.1).
Also, I have often used a sort of pseudo 4 channel, in which the stereo signal
is sent to a left/right pair of speakers at the rear of the space as well as
to the usual left/right pair at the front. The time arrival differences, while
technically "wrong", actually accentuate the stereo material, so in
electro-acoustic music, with lots of panning, the effect is exaggerated movement
and actually a type of surround.
> Fuhrmann: If not, why? (lack of interest? too expensive? technical reasons?)
Surround is the best, but there are several technical problems. With "live"
electronics, meaning that the electronics are being performed in some way, not
simply played back, there is the problem of computer audio outputs. The standard
laptop has a stereo headphone output that is usually routed through a Direct
Injection box to balance the signal.
Multi-channel requires either an audio card (PCICMA) or an external DAC. Some
laptops (my 12 inch Powerbook for example) do not have any expansion slots,
and there are major latency problems with many (most?) firewire or USB external
DACs -- so for real time performance, where the action must be instantaneous,
the headphone output is most dependable -- but only 2 channels! The other problem
with external converters is their physical size, which is another chunk of electronics
to drag onto the the airplane when travelling around.
> Fuhrmann:
If yes, what are the biggest problems? (I can image, the Sweet Spot
> thing could be critical, because the people always sit everywhere but in
> the middle. Another thing may be difficulties in doing live surround
> panning for several sound-objects at once)
The sweet spot is a big problem for
anything except mono - so we just ignore that (it is just as big a problem with
2 channel stereo).
The production end is easy regarding surround panning, though "live"
panning would require special performance interface, like a joy stick -- but
the biggest problems are those I mentioned above:
latency on firewire & USB devices
lack of outputs on the laptops
portability
plus another:
a standardized surround sound reinforcement system (5.1 is becoming a
standard, but many avant garde works use 8 channels)
Hope that helps -- surround is cool,
but I think we are a still a little ways off from doing it easily -- however
I anticipate that latency problems will disappear with firewire 800 and faster
CPUs.
> Fuhrmann:
How could one try to circumvent these? (Using stereo only is not an
> option.)
Actually, there is "diffusion", a well established technique
since the 1970's, in which a standard two channel mix is "diffused"
in real time through a proprietary "Loudspeaker orchestra", which
has multiple channels for routing the stereo mix, from 4 to 32 (and beyond!)
pathways, and through which a performer manually "plays" the spatialization
in real time. This is actually very effective.