In the EU the patent has expired http://www.google.com/patents/EP0643899B1?cl=en#legal-events
don't know about the US and Canada. On Tue, Apr 8, 2014 at 8:40 PM, Marc Lavallée <m...@hacklava.net> wrote: > > I made a Trifield decoder a few months ago (with the help of Aaron > Heller, to understand how to use Faust), and it works surprisingly > well! The distances can be adjusted, so it would work with 3 speakers > on a plane. The only problem is the patent... So I'm not sure I can > distribute it. > > -- > Marc > > Tue, 8 Apr 2014 20:00:57 +0200, > JQ Adams <jqad...@google.com> wrote : > >> Trifield is new to me. Thanks for this. >> >> I'm not entirely certain what is said in this article...: >> >> *Each filtered signal then passes to a sine/cosine potential divider, >> which >> > is set differently for each frequency band. Only with this >> > arrangement, Gerzon found, could a wide stereo image and sharpened >> > central focus be traded off effectively against one another across >> > the entire audible spectrum.[image: Inline image 1]* >> >> >> This seems to be saying that different weightings of energy gets sent >> to the middle versus side speakers. I would presume the center >> channel would receive the greater proportion of low frequency >> content, but it's not said here, directly. >> >> Funny enough, I did have in mind to ask in followup whether the the >> L/R speakers could effectively be just small tweeters, as my >> understanding is for a person to decode direction, it's most >> important that high frequency energy is reproduced well. Practically >> (for me) it simplifies/reduces cost/is more discreet to have small >> drivers added to the sides of monitors. I had not thought about a >> need to reduce the high frequency energy to the center channel...but >> in a way that sorta sounds reasonable... >> >> One further question I would pose is that of necessity of delays. In >> my instantiation, the loudspeakers would all be on a plane (the front >> wall), and thus for a centered listening position, the center >> loudspeaker would be closer. Given that we may have a dual video >> screen system, the perceived angle may be upwards of 90° for a >> near-seated participant. Imagining this as a 45-45-90 right triangle >> with the listener at the right angle, the loudspeakers would be on >> the hypotenuse at distances of *s*, sqrt(2)/2**s*, *s* for left, >> center, right. This would seem to indicate a delay on the center >> channel that scales in magnitude with the size of the room. When *s* >> is 3m, the distance variance would be about .88m, or about 2.5ms, >> which I don't know whether is significant... >> >> >> On Tue, Apr 8, 2014 at 7:06 PM, Paul Hodges >> <pwh-surro...@cassland.org>wrote: >> >> > --On 08 April 2014 18:45 +0200 JQ Adams <jqad...@google.com> wrote: >> > >> > > My question pertains to play back to a three speaker setup (left, >> > > center, right)...would it be most correct to send the 'mid' signal >> > > directly to a center speaker and the 'side' signal to speakers >> > > left and right, phase inverted from each other? >> > >> > Have you thought of Trifield as a possibility? >> > >> > < >> > http://www.stereophile.com/content/upward-mobility-2-channels-surround-page-2 >> > > >> > >> > Paul >> > >> > -- >> > Paul Hodges >> > >> > >> > _______________________________________________ >> > Sursound mailing list >> > Sursound@music.vt.edu >> > https://mail.music.vt.edu/mailman/listinfo/sursound >> > >> -------------- next part -------------- >> An HTML attachment was scrubbed... >> URL: >> <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140408/a0d76726/attachment.html> >> -------------- next part -------------- A non-text attachment was >> scrubbed... Name: image.png >> Type: image/png >> Size: 38014 bytes >> Desc: not available >> URL: >> <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140408/a0d76726/attachment.png> >> _______________________________________________ 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 _______________________________________________ Sursound mailing list Sursound@music.vt.edu https://mail.music.vt.edu/mailman/listinfo/sursound
