linuxaudio.org

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

quoted text
> >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

quoted text
> >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

quoted text
> 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@lists.linuxaudio.org

http://lists.linuxaudio.org/listinfo/linux-audio-user