On Sat, Jan 08, 2011 at 01:39:17AM +0100, Jörn Nettingsmeier wrote: > >Not exactly. For a well-designed decoder the pressure at LF will > >be proportional to W, even without NFC, and should not have any > >bass boost. > > need to double check, but iirc i did hear a very pronounced (read: > unbearable) boominess on my organ recordings when listening to them > on my <4m array in second order without NFC... That is very well possible. It means that you don't have the real pressure, not even at the sweet spot. Which is to be expected if your room isn't free of LF reflections, as most are. > >What you get in that case is a velocity field that > >does not match the pressure in level, > > this i understand. > > >and more important - in > >phase, and this sounds very unnatural. > > this is news to me. where does this phase delay come from? It's just a property of the higher order components in the near field. If you look at the amplitude and phase plots of the higher order NF effects, it's very evident that there is quite a large phase shift even before the amplitude starts to rise by any significant amount. Even for first order the +3dB point has 45 degrees phase shift - like a first order filter. Also if you look at Moreau's 'useful bandwidth' filters for synthesising near sources, you'll see that none of them has more than 3 or 4 dB gain before going down steeply for lower frequencies. This means that it is not the very high LF gains of the higher order components that create a near source, but the phase shifts. > i guess the myth is more correctly formulated as "you can't localize > anything except some select and very obvious mid-frequency cues in > AB stereo". of course, bose and friends would jump on this to sell > ridiculously small satellites with woofers going up to 300 hz :) With Bose you'd be lucky to localize anything at all :-) Ciao, -- FA There are three of them, and Alleline. _______________________________________________ Linux-audio-user mailing list Linux-audio-user@xxxxxxxxxxxxxxxxxxxx http://lists.linuxaudio.org/listinfo/linux-audio-user
