When buying loudspeakers, you may have noticed that some manufacturers have a label on their product that says “magnetically shielded”. You probably have been confused by what that term means and also whether you need your speakers to be magnetically shielded. Let me go ahead and shed some light on this topic.
What exactly does this type of shielding offer? Well, have you ever noticed that when you hold your cell phone near a speaker while making a call that the speaker will make some strange noise? This noise is caused by the signal that is being radiated by the cell phone. Every wireless device emits some sort of radiation. Cell phone radiation in particular is rather strong and is sent as pulses.
This signal penetrates the enclosure of your speaker. It then interacts with the voice coil of the speaker element. If you don’t know exactly how a speaker element works or you are confused by the term “voice coil” then you should do some reading at http://www.amphony.com/products/wireless-speaker.htm to find out some more information.
Speakers which are shielded, however, do not allow a cell phone signal inside the enclosure and thus won’t generate these strange noises. It also avoids the magnetic field of the internal magnet to get outside of the speaker.