ho trovato su audioasylum questo post di Jean-Michel Le Cléac'h.
Chiedo se qualcuno ha approfondito queste considerazioni.
PS se l'inglese dovesse essere un problema posso postare un sunto in italiano.
tratto da: http://www.audioasylum.com/scripts/t.pl?f=hug&m=100530
There is not a lot of low phase distortion crossovers. By example the Linkwitz-Riley crossover has a large phase distortion. This is illustrated on Linkwitz webpage by the shape of a square wave as calculated by Linkwitz himself. Look at the square waves given inside the JBL document the URL of which was given in another reply: those square waves are really bad (due to the use of the Linkwitz-Riley crossover)!
I introduced my own method of setting up crossovers and aligning loudspeakers. (it is known under the name "Jmmlc crossover" or "Jmmlc alignment") which allows using conventionnal crossovers (Butterworth 3rd order filters) a minimal phase distortion. Also the in-coincidence. Sometimes ago on this forum I described the Excel spreadshhet that I designed specifically to calculate the group delay curve , the in-coincidence curve of a multiway system.
You can download that spreadsheet at:
http://ndaviden.club.fr/outils/filtre_simul.zip
In 2004 I gave at the European Triode Festival a conference in english about phase distortion in multiways systems. You can download it at:
http://www.triodefestival.net/members/c ... _etf04.zip
Recently I improved a bit the content of the conference and gave another conference in French at the assoication Melaudia:
You can download the PPT document of that conference at:
http://ndaviden.club.fr/outils/distorsion_de_phase.pdf
You'll find in the PPT document both simulations and measurements of pulse and square response and an enlightning comparison of the square vaves response of the Linkwitz-Riley and the Jmmlc crossover.
Also about the audibility of phase distortion I think the better document available on the subject (with a synthesis of older works) is Daisuke Koya's thesis that you can download at:
http://www.music.miami.edu/programs/mue ... e_page.htm
Best regards from Paris,
Jean-Michel Le Cléac'h
tratto dal pdf http://www.triodefestival.net/members/c ... _etf04.zip
settings of a 2 ways system according the proposed method
1..........Only Butterworth 3rd order filters are used.
2..........The relay frequency Fr between the low-pass and the high-pass is defined at -5dB.
3..........The cut-off frequency Fl (at -3dB) of the low-pass filter is calculated by: Fl = 0.87 x Fr
4..........The cut-off frequency Fh (at -3dB) of the high-pass filter is calculated by: Fh = 1.14 x Fr
5..........If the 2 drivers are aligned at the same distance of the listener, then the low-freqeuncy loudspeaker has to be moved toward the listener of a distance equal to 0.22 x wavelength at Fr.
6..........The polarity of the high frequency loudspeaker has to be reversed.
Grazie per la comprensione
Bruno
dixit et salvavi animam meam
.
