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(Note: this is not available as a separate part.)
Magnetic shielding of the parts in a speaker becomes important when the magnet structures will be placed near a cathode ray tube type monitor (old TVs, oscilloscopes, etc.).
The stray magnetic fields will cause the streams of electrons inside the tube to curve in their paths, hitting the wrong phosphors on the front of the tube. This can result in some pretty bizarre effects (none of which are permanent, since modern CRTs are self-degaussing). These effects are only interesting for about 90 seconds, after which they simply would be described as "ruining the picture."
To prevent this, we alter the magnet structures of drive units so they do not radiate strong fields outside the speaker cabinet. In the case of most of the HUMAN drivers, this is accomplished by adding a second magnet on the rear of the assembly, with a reversed polarity.
I always used to prepare the parts for the C2 center channel this way; upon request and for a slight additional cost it can be done to any model, if you will be using them near a monitor.
While this option is basically obsolete, I can still do it, if for some reason you expect to place your speakers near some device that is sensitive to strong, static magnetic fields.
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