Simple XO-question

Klimon · 28th November 2006, 03:19 PM

What does a LC network (in series), mounted parallel with a woofer do? My guess would be a series notch filter where the resistance of the coil acts as resistor but allas it's definitely something else...

Here's my short story:
I'm trying to understand the low-pass filter of my ipl transmissionlines (6,5" alu cone woofers), the original design is a normal third order but with an extra coil in series with the parallel cap (= the weird combination I described above). The designer talks about a zobel filter in the crossover so I guess that must be it, no classical RC circuit to detect.

I later had the crossovers redesigned and that guy used a low-pass as follows: 1mH coil in +leg /// parallel with woofer: 0,56mH coil and 1,2µF cap in series.... I've drawn a schematic below|

Please disregard the ¨¨¨¨ signs.

"+" ____coil________
¨¨¨¨¨¨¨¨¨¨¨¨¨|¨¨¨¨|
¨¨¨¨¨¨¨¨¨¨¨¨coil¨¨¨|
¨¨¨¨¨¨¨¨¨¨¨¨¨|¨¨¨woofer
¨¨¨¨¨¨¨¨¨¨¨¨cap¨¨ |
¨¨¨¨¨¨¨¨¨¨¨¨¨|¨¨¨¨|
"-" __________|____|

Any hints are most welcome!!

Simon

Kent Smith · 28th November 2006, 07:33 PM

My math shows that the LC circuit resonates at 6.14 KHz, I assume to notch out a nasty peak in the woofer response.

Klimon · 28th November 2006, 10:16 PM

Hi Kent,

That makes sense! The woofer has nasty alu break-up peaks starting at around 6khz so that would be about right.

I hope that with a very low Fx frequency (1650hz) and 3rd order electrical filter the woofer will be rolled of plenty to make that and the following peaks inaudible. (about -35db?)..... Notch filters rob off too much of the soundstage magic imo.

Thanks alot!!!

Simon

Kent Smith · 29th November 2006, 02:50 AM

That sounds good.... I'm crossing a metal cone (Dayton RS 8") at 2 KHz and not hearing much cone breakup.

Good Luck,
Kent

Klimon · 29th November 2006, 04:01 PM

Thanks - same for you!!

Simon

28th November 2006, 03:19 PM	#1
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	Simple XO-question What does a LC network (in series), mounted parallel with a woofer do? My guess would be a series notch filter where the resistance of the coil acts as resistor but allas it's definitely something else... Here's my short story: I'm trying to understand the low-pass filter of my ipl transmissionlines (6,5" alu cone woofers), the original design is a normal third order but with an extra coil in series with the parallel cap (= the weird combination I described above). The designer talks about a zobel filter in the crossover so I guess that must be it, no classical RC circuit to detect. I later had the crossovers redesigned and that guy used a low-pass as follows: 1mH coil in +leg /// parallel with woofer: 0,56mH coil and 1,2µF cap in series.... I've drawn a schematic below\| Please disregard the ¨¨¨¨ signs. "+" ____coil________ ¨¨¨¨¨¨¨¨¨¨¨¨¨\|¨¨¨¨\| ¨¨¨¨¨¨¨¨¨¨¨¨coil¨¨¨\| ¨¨¨¨¨¨¨¨¨¨¨¨¨\|¨¨¨woofer ¨¨¨¨¨¨¨¨¨¨¨¨cap¨¨ \| ¨¨¨¨¨¨¨¨¨¨¨¨¨\|¨¨¨¨\| "-" __________\|____\| Any hints are most welcome!! Simon

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28th November 2006, 07:33 PM	#2
Kent Smith diyAudio Member Join Date: Jun 2004 Location: Wylie, Texas	My math shows that the LC circuit resonates at 6.14 KHz, I assume to notch out a nasty peak in the woofer response.

28th November 2006, 10:16 PM	#3
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	Hi Kent, That makes sense! The woofer has nasty alu break-up peaks starting at around 6khz so that would be about right. I hope that with a very low Fx frequency (1650hz) and 3rd order electrical filter the woofer will be rolled of plenty to make that and the following peaks inaudible. (about -35db?)..... Notch filters rob off too much of the soundstage magic imo. Thanks alot!!! Simon

29th November 2006, 02:50 AM	#4
Kent Smith diyAudio Member Join Date: Jun 2004 Location: Wylie, Texas	That sounds good.... I'm crossing a metal cone (Dayton RS 8") at 2 KHz and not hearing much cone breakup. Good Luck, Kent

29th November 2006, 04:01 PM	#5
Klimon diyAudio Member Join Date: Apr 2005 Location: Leuven	Thanks - same for you!! Simon

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