Crossover network mounted upon the speaker magnet

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I did some experiments on this. A 1mH coil on a thick metal plane changed to 0.827mH and even outputted audibly to a nearby tweeter coil. Coils interact tremendously with each other and nearby thick metal ground planes, hence we try to arrange them at right angles and use point to point wiring without circuit-board ground planes at all.

AFAIK, resistors and capacitors just don't interact at all. So you can stick them on the back of a speaker magnet. Arpeggio Loudspeaker - diyAudio
 

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frugal-phile™
Joined 2001
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At a bare minimum, inductors are magnetic.

An RC XO has no inductors… so it won’t be affected that way. Capacitors have some inductance so they may be skewed.

I have hung a capacitor of tweeter terminals, and many a vintage speaker had the tweeter blocking capacitor attached to the midWoofer terminals, but not on the magnet.

dave
 
Not uncommon to see a rudimentary XO (i.e. C & maybe R only) hot glued to the space between basket & magnet assembly on cheap car audio or ceiling mount coaxials; larger film caps could cause some issues with reflections, so on the back of the magnet as per Steve's photo makes a bit of sense.
 
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I have done this when I needed a bigger coil than I had. Measuring right now, 0.908 becomes 1.113 mh when I put the small ferrite core coil on the back plate of a 6" woofer. Another goes from 1.117 to1.225. Air-core, 0.558 becomes 0.593. Maybe you can't always get the coil you want, but if you try sometimes, you get what you need.


apologies to the RS

edit: a big lam-core, 11.64mh becomes 9.47mh winding axis coax to the voicecoil, checked the others, aircore is simple, iron cores can increase, decrease, or stay close, depending on orientation.
So, use a meter, check your positioning, and it's adjustable. Interesting.
 
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edit: a big lam-core, 11.64mh becomes 9.47mh winding axis coax to the voicecoil, checked the others, aircore is simple, iron cores can increase, decrease, or stay close, depending on orientation.
A coil on a speaker magnet may increase in inductance because it's near the iron plate. That can move the crossover frequency and response, but it may not be the worst problem.

An iron core in a constant magnetic field will be "DC biased" and thus will go into saturation at a lower coil current. This would cause really big distortion above a certain volume level.
 
The OP mentioned that the inductors are mounted elsewhere but I still think it's not a great idea to mount the R and C components on the magnet assembly. Since the inductors are elsewhere you may as well mount the rest of the crossover there also. It would be interesting to measure the capacitors whilst bringing them into contact with the magnet assembly. (I might experiment with that). Also some claim that capacitors can suffer from mechanical microphony when placed too close to a driver. I have my crossovers in a separate enclosure. It makes tweaking a lot easier.
 
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