In the past I have had a problem with tube screen tvs losing picture quality when external speakers were connected-specifically the bottom of the screen was green . Are LCD tvs prone to this also? Thanks for your time.

in the past i have had a problem with tube screen tvs losing picture quality when external speakers were connected-specifically the bottom of the screen was green . are LCD tvs prone to this also? thanks for your time.
Is this speaker shielded

Someone brought in a TV for repair, Screen was blank, Removed Back, Had good picture.
Put cover back on, No Screen. Initially thought Intermittent connection. Then slowly place back on TV while watching picture slowly disappear. Noticed OverSize speaker added by the owner. Magnet was so powerful, No picture. I haven't tried magnet near LCD TV.
Old Tube TV's had a Degaussing Circuit(Demagnetizer Coil) to eleminate to effects of magnetism. Relocate speaker(s) while watching picture.