Al Sekela's RF-Choke Tweak
The chokes are 10 microhenry RF chokes made by J.W. Miller and available in small quantities from Mouser Electronics. The part numbers are 5502 and 5522. I used the 5522 because I found some in a local surplus electronics store and liked what they did. Other inmates have tried the 5502 and found they prefer it to the 5522. The 5522 is made from heavier wire and has a higher DC current rating, so it may affect the treble.
Still other inmates have used two chokes in parallel (this gives 5 microhenrys net inductance), or a choke in parallel with a resistor of 1 to 2 ohms. It is possible to experiment cheaply and without damaging the speaker to dial in the treble to your taste. The chokes block RF noise without reducing the audio level. The cement resistors supplied by Magnepan have some inductance, so they do a little of both.
The MG-3.6 and MG-20.X speakers have treble attenuator ports, and the chokes fit in place of the supplied jumpers. They can be added to the cables for use with the midrange and bass panels if desired, but the crossovers already have inductors between the amp(s) and midrange and bass elements. I would recommend trying them if you use an active biamp setup with no passive crossovers.
I would not use a choke with a value larger than 10 microhenrys with the tweeter. This would attenuate the audio band treble.
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