Multiple Small Subs - Geddes Approach - Page 58 - diyAudio
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diyAudio Member

Join Date: Jul 2004
Location: Finland
After EQ.
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 3rd February 2009, 12:31 PM #572 Banned   Join Date: May 2008 Location: Switzerland Looks like this box is pretty effective if you want to automatically EQ a single listening position. 225 Euros is ok. Best, Markus
diyAudio Member

Join Date: Dec 2004
Location: Novi, Michigan
Quote:
 Originally posted by markus76 Looks like this box is pretty effective if you want to automatically EQ a single listening position. 225 Euros is ok. Best, Markus

I think that was Todds point earlier. If all you want to do is a single point then its a far easiler problem.

diyAudio Member

Join Date: Dec 2004
Location: Novi, Michigan
Quote:
 Originally posted by john k... I think the problem is the way Morse write the relationship G(R,Ro) = g(R,Ro) + X(R) This says X(R) = G(R,Ro) -g(R,Ro) . Obviously X is a function of Ro. However, X(R) is a solution to (here we go again) the homogeneous wave equation with inhomogeneous boundary conditions (finally got that right). This is were the dependents of X(R) on Ro comes in because the boundary conditions are dependent upon the value of g(R,Ro) evaluated on the bounding surfaces. So while the dependence of X on Ro is not explicit, there is implicit dependence of X on Ro from the BC's. Perhaps it would have been better if Morse had written X(R) is a solution to the homogeneous wave equation with inhomogeneous boundary conditions, BC = F(g(Rb,Ro)) where Rb is the position vector defining the bounding surface. Change the source position and the X changes as well. I guess I saying that I'm not particularly worried about what Morse says he does or doesn't do. If I have G(R,Ro) and I know g(R,Ro) I can drop in the values of R and Ro and find the value of X (R) for any values of R and Ro in the bounded region. But it's all academic because there is no need to worry about X if we know G(R,Ro).
John

Agreed. I had always viewed this subtraction of the direct field as approximate at the boundaries, never exact. I think that's the part that may be getting lost. You are correct that G(r,r0) is exact and what is needed, it just converges very slow near the source. I suppose that one could use the near field term for points close to the source, but drop it further out. This would work if the source is not too close to a boundary. If the source is close to a boundary then using an image source or sources would work as the combination is always zero at the boundary.

Banned

Join Date: May 2008
Location: Switzerland
Quote:
 Originally posted by gedlee I think that was Todds point earlier. If all you want to do is a single point then its a far easiler problem.
I didn't argue against using an EQ. I just expressed my doubts that ringing can be completely eliminated in a real room by applying an EQ.

Talking about that box, how does it determine the target magnitude?

Best, Markus

 3rd February 2009, 03:21 PM #576 diyAudio Member     Join Date: Mar 2005 Location: Taiwan If the RT60 decay is slower than the real environment, the probably playback fidelity is also effected. __________________ Hear the real thing!
 3rd February 2009, 05:18 PM #577 Banned   Join Date: May 2008 Location: Switzerland Talking about magic little black boxes: http://www.krksys.com/ergo/intro.php Best, Markus
diyAudio Member

Join Date: Jan 2009
Quote:
 Originally posted by markus76 Talking about magic little black boxes: http://www.krksys.com/ergo/intro.php Best, Markus

I was about to laugh, then I saw that it is "Room Perfect", which was developed by Jan Pedersen, for Lyngdorf. At least there's some science involved.

 3rd February 2009, 08:56 PM #579 Banned   Join Date: May 2008 Location: Switzerland Why laugh? Because it uses FIR?
 3rd February 2009, 09:07 PM #580 diyAudio Member     Join Date: Dec 2004 Location: Novi, Michigan Markus Because its too simple to do what it says. And its all talk with pretty pictures and no apparent science. __________________ Earl Geddes Gedlee Website Read about the highly acclaimed Geddes loudspeakers

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