Hi David, Peter, David, I agree with your description of the problem, thanks for putting it in nice words.
I also agree with Peter Lennox about the focused sound quality at one end and the room-filling sensation at the other. It should be possible to perform a continuos transition between both sensations with a single potentiometer. The timbre of the signal is recognizable (voice, etc.) and therefore should remain unchanged throughout this process. However I still have the feeling that the point / plenum name must have originated somewhere. From what I've read, during the period in which the piece was written (1966) stereophonic reproduction was becoming popular in the BBC and this person was definitely involved in some experiments with stereophony, probably at the Radiophonic Workshop, so I was hoping to find a piece of equipment with a point/plenum knob on it, or at least a reference to the use of those terms to describe the sensation of focused vs. wide-spread sound in those early days and how they didi it. Thanks again and best regards Gregorio Garcia Karman ggkar...@musicologia.com On 18.04.2012, at 10:41, Peter Lennox wrote: > actually, to control "image size" (apparent source width), one must control > the interaural cross correlation rather finely, which in practice means > controlling (or varying) inter-channel cross correlation (though with > surround sound - ambisonic or otherwise, one actually has to control more > speakers to govern the ear signals). > > So, to go from an image as a point, to a more general, room-filling non-image > sound, there is a variety of considerations and treatments. To enlarge an > image, careful decorrelation of pairs (or more, see above) of signal feeds > (to treat individual images, we are talking about this being on the encoding, > not decoding end; in old fashioned terms, on the input side of the desk, not > speaker feeds). This can be done with slight pitchshifts, taking harmonic > slices and panning them, tiny delays, or a combination. > > Going from an enlarged image to a property of being everywhere really isnt a > case of simply routing it to all available speakers - multichannel mono > simply (because of precedence effects for off-centre listeners) pulls the > perception to the nearest speaker. So the same principles of decorrelation > as for image widening (and note - apparent source width can actually refer to > up-down as well as lateral) should be used across the array. That way, you'd > have a sense of the sound being everywhere, and nowhere in particular - which > is what I think was the original intention > cheers > ppl > Dr Peter Lennox > > School of Technology, > Faculty of Arts, Design and Technology > University of Derby, UK > e: p.len...@derby.ac.uk > t: 01332 593155 > ________________________________________ > From: sursound-boun...@music.vt.edu [sursound-boun...@music.vt.edu] On Behalf > Of David Pickett [d...@fugato.com] > Sent: 17 April 2012 23:27 > To: Surround Sound discussion group > Subject: Re: [Sursound] audio point / audio plenum > > At 15:26 17/04/2012, Gregorio Garcia Karman wrote: >> Thanks for the inquisitive responses. The text was written in 1966 and >> belongs to a composer from the circles of the BBC. It reads: >> >> "[one person] controls the volume of the total output of the platform >> speakers, as well as the stereophonic motion of the sound to and from >> between the loudpseakers, and the spread or growth of the sound from >> audio-point to audio- plenum" >> >> For me it seems as if he would be describing some kind of >> potentiometer by means of which the user can control the spread of >> sound among the stereophonic image. > > From this description, it appears to me as though the person can > control a mono signal in these ways: > > a) To pan between any two of the n loudspeakers. > > b) To increase the number of speakers carrying the signal from only > one (audio-point) to all of them (audio-plenum). > > Without knowing exactly how the platform speakers are disposed it is > impossible to say more. > > David > > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound > > _____________________________________________________________________ > The University of Derby has a published policy regarding email and reserves > the right to monitor email traffic. If you believe this email was sent to you > in error, please notify the sender and delete this email. Please direct any > concerns to info...@derby.ac.uk. > _______________________________________________ > Sursound mailing list > Sursound@music.vt.edu > https://mail.music.vt.edu/mailman/listinfo/sursound _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
