A Tannoy pro monitor was purchased for use as my center channel. It is too heavy to sit on top of my RPTV, so it sits out front. I expected to have the same problem that you describe. A search on the internet and several forums gave the following suggestions:
1 Use a product called MagnaShield. Paradigm uses this to shield their speakers. I could find no source for this product.
2 Cut panel(s) from 12 gauge mild steel, and place between TV and speaker.
I was lucky that my center speaker did not distort the video. I have not tried either method.
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analogmusic
Outlaw 950, M200's, LFE-1; Tannoy Westminster (2), GRF Memory (2), System 12 DMT II; Hitachi Ultravision RPTV; Xbox 360 w/ HD-DVD; Pioneer DV-6600A; Bix TT w/ Blue Note Tonearm; Dual 1246 TT; Seduction Tube Phono mm Stage