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In Reply to: RE: MGIII active crossover? posted by Skeepowder1@aol.com on August 03, 2016 at 09:22:27
You will need four (4) modules not one to get the Marchand XM-44 up and running. You need a woofer LP (low pass) and a mid HP (high pass) for each of the two stereo channels - cost is $36 plus shipping.
Understand that the "recommendation" from Magnepan is only an approximation and was done because most commercial crossovers are not very flexible and are limited in their ability. The Marchand has the ability to be customized to just about any order, slope (Q value) and frequency and thus can be designed to match almost exactly the OEM crossover.
Here is a link to my spreadsheet which will simulates the OEM crossover. Ignore the mid LP and tweeter HP as you will not be triamping. The notation for the caps and resistors may differ from that used by Marchand but Phil will have no trouble with it. The spreadsheet is written for LibreCalc (part of the LibreOffice Suite) which is available for free. I do not support Microsoft.
If you have questions, please feel free to email me.
I married the perfect woman. The downside is everything that goes wrong is my fault.
Edits: 08/03/16 08/03/16Follow Ups:
Thanks Neo, I have the Marchand XM9. I don't know if that's the same as yours regarding the XO modules. I looked at your spreadsheet and it's more involved than I want to do but thanks anyway. I'm just trying to find the crossover frequencies so I can buy the modules. I can't find a MGIII manual but I find the MGIIIa. Are they the same for the XOs? I have contacted Marchand to see if he has a recommendation but haven't heard back yet. Tomorrow I'll call Magnepan.
Mac MC7106, Maggie MG111, ADS 810 & 780, Pioneer SC-1522, Carver M.0.5T, Dahlquist 903, Velodyne, Infinity
The III uses a 1st order Mid HP filter and the IIIa uses a 2nd order filter. A simplified approach might be to use a 3rd order Woofer LP at 270 Hz and a Mid HP 1st order at 800 hz. The crossover point for the III is 380 Hz.
I beleive the XM-9 uses a variable state configuration rather than Sallen-Key. What this means is that the crossover is always symmetric and for the XM-9 this is 4th order.My experience with symmetric 4th order LR on the IIIa's was less satisfying than simulating the OEM. Also you will only need two boards for a state variableas as each board covers the LP and HP filter -- set each module at 380 Hz. Also you will have to do a little wiring change in order to account for the inverse polarity of the OEM vs the normal polarity of the LR. The easiest approach is to swap the input wires (+ and -) coming into the woofer.
I married the perfect woman. The downside is everything that goes wrong is my fault.
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