Lecleach paper on crossovers

swak

Member
2003-07-23 7:06 pm
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I have read his very good presentation and I have been asking myself if there are not other variables afecting phase response (I am almost sure I am missing something...). When I model an enclosure I can see phase shift, drivers alone as BP devices induce shifts, op-amps, output transformers, etc. Now I think the spreadsheet asumes all these as linear phase devices, but to my surprise the measured responses he shows very good phase tesponse troughout the freq range.

I would appreciate if someone could help me with my difficulty.
 

Jmmlc

R.I.P.
2005-10-05 12:30 pm
Hello Swak,

on the document downloadable at:
http://freerider.dyndns.org/anlage/LeCleach.htm

On page 52: this is a pulse response I measured on a two ways system using a Le Cléac'h crossover (the bass enclosure is a bass reflex quasi 2nd order using a low tuning frequency, its response is nearly the one of a closed enclosure, low group delay below 70Hz).

Page 68 of the same document: this is the pulse response measured on the system I brought at ETF2004. THe measurement was done the day before the conference I gave on "phase distortion".

You can see others pulse measurements and curves derived from pulse measurements on the document:

http://www.melaudia.net/zdoc/distorsion_de_phase.pdf

page 78: this is the result of the sommation performed with a simple resistor sommator at the outputs of a DCX2496 digital crossovers. Different classical crossovers are compared to the Le Cléac'h crossover, only the first order Butterworth (LP and HP in phase) is a bit better than the Le Cléac'h crossover .

page 82 and 83 using the spectrogram to align a 2 ways system using a Le Cleac'h crossover

Notice: page 46 group delay curve (delay T is expressed in equivalent length d calculated by d = T . c with c = celerity of sound) for Marco Henry's Jerzual horn (reference J321). If you use the horn above 750Hz the delay variation is less than 6 centimeters (expressed in equivalent length). If you use a high pass frequency lower than 750hZ then there will be some difference with the simulated response obtained using my excel spreadsheet. Same thing happens if you use a too low frequency for the low pass of a bass driver (when the group delay rises).

Best regards from Paris, France

Jean-Michel Le Cléac'h

swak said:
I have read his very good presentation and I have been asking myself if there are not other variables afecting phase response (I am almost sure I am missing something...). When I model an enclosure I can see phase shift, drivers alone as BP devices induce shifts, op-amps, output transformers, etc. Now I think the spreadsheet asumes all these as linear phase devices, but to my surprise the measured responses he shows very good phase tesponse troughout the freq range.

I would appreciate if someone could help me with my difficulty.