Info from Magnepan:

The following is only what I learned in the very helpful contacts with Magnepan. I am trying to relay information given, not definitive answers. This info is still to be reviewed by Magnepan, so I will update it in July if there's any change or additional information I can obtain.

Every panel is tested. The test results are written on paper labels centered above the membrane. These were covered with the black tape surrounding the panel edges on mine. Now, they apply black paint to the areas so you might not be able to read them. The data shows speaker resonance for mid, bass, and treble. Membrane clearance from the magnets is also noted. On mine they were 70 for mid, 44 & 45 for bass, and 68 & 72 for treble. They are signed and dated.

Magnepan does various things to lessen resonance effects. They don't want the speakers to reinforce each other with identical resonance in the panels. They also don't want the electrical resonance to be anywhere close to the speaker's. The "button" restraints are disks screwed through the membrane into one of the holes in the magnet array. These hold the membrane down effecting the vibrations in areas around them. For about a two inch diameter around each of these the membrane is effectively unpowered due to the wire stiffness adding to the restraint. I'm not an expert in electrical matters so you need to contact Magnepan for the XO electrical resonance issue.

If you look at your panels you can see the "button" restraints are not in identical positions on the two panels. This is addressing the Resonance issue above. Another is the application of small thin tissue paper patches over 2 or three areas of the rear magnet face. They are not always the same size and their placement varies. These cover the holes in magnet array effecting the panel's efficiency as well. They are painted black and not visible without removing the fabric. The lower panel area is the largest unrestricted section of Mylar. This produces the strongest bass response. It is also adjacent to the treble wires and effects them. The start point of the treble array is raised, I believe, to lessen the impact.

If you notice the bass intermodulation on the treble it is suggested that tilting the speaker forward will help. This effectively projects the treble from that section towards the floor slightly, lessening the first wave impact on your ears. Paco finds this helps his system. You can use the small plastic discs provided for Magnepan's stands.

Panel wires are arrayed in vertical lines of continuous circuits with top and bottom loops as you've probably noticed. These need to align with the magnets and not delaminate from the membrane.

The wires are adhered to the Mylar with two adhesives. First, they apply a contact adhesive. After the wires are aligned they apply Molexane, a water based contact adhesive. Molexane is quite rubbery, similar to rubber cement. When you order the Molexane from Magnepan to repair panel damage, they include instructions and tell you to use 3M's Super 77 contact spray adhesive before applying the Meloxane.

How, you might ask, does Magnepan get their wires to align with the magnet strips? They use a direct current with correct polarity applied to the wires. A 12 volt, 10 to 15 amp. Supply from a battery is used. They have to be careful as the wires heat and the Mylar starts to melt at 170 degrees. It doesn't take long for the first contact adhesive to dry. Then, without the current, they can apply the Molexane encasing the wires onto the surface.

Should you try varying components in your XO design, their values may vary from those of Magnepan's. One issue is the DC resistance of differing inductors. My Magnepan contact discussed this with me. Should this difference become "significant" it could effectively raise the XO point of the bass and raise the speakers midrange loudness. The question is, "what is a significant difference?".

In my discussion the figure of "approaching 50%" of relative resistance came up. In my case the 0.19 ohms was less than half of the standard 0.4. However, I was told that the inductance plus the resistance are added together to for calculating the "significant" variation. As I used a matching inductance of 3.5 mH the combined values were: 3.9 stock vs. 3.69. This was not sufficient to make a noticeable difference in the XO point and midrange performance.

As I am a novice in electrical engineering, I suggest you utilize the resources on this thread and Magnepan for any issues in this area. My inclination was similar to Paco's first XOs, get matching values if possible.

My first listen to the modified speakers revealed a knocking or rattle. It was audible with lower frequencies. As I hadn't removed the fabric, I telephoned Magnepan. It seems that this Is not the first case they've head. In rare cases the horizontal bracing steel bars on the magnet panel's rear side break away from the surface. If you have this symptom try pressing on the bars through the fabric cover. You can see the four of them with light shining through the magnets. If any of them should wiggle contact Magnepan.

In my case the previous owner had cut the inductor ties to reposition the existing components. He never tied it back, so it was resting on the bottom edge of the XO panel area, restrained by the fabric and their wire leads. 

 

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