Re: TV - Speaker proximityOn Wed, 26 Dec 2007 09:03:43 -0800, speedo wrote
(in article <l6SdnSec4YDyFO_anZ2dnUVZ_jOdnZ2d@pghconnect . com >):
> Having always heeded those warnings not to place my LFT-3 dynamic
> planar speakers anywhere near a TV set, I now wonder:
> Does this apply to my new [Samsung] HD flat panel LCD TV?
Since flat screens don't use flying electron beams (which can be deflected
with magnetic and electrostatic fields) to paint the pictures on the screen
the way that cathode ray tube based TVs do (conventional "picture tube" type
TVs and some types of front and rear projection TVs), this is not a problem.
It's also not a problem for LCD projectors or solid-state "light-valve"
projectors such as "DLP" based TVs.
The reason its a problem with CRT-based (Cathode Ray Tube) TVs is that the
three electron beams that come from the cathode of the picture tube are
"aimed" very precisely at the screen so as to hit the correct color phosphor.
You want the beam representing the red picture signal to hit the red
phosphors only and the beam representing the blue picture signal to hit the
blue phosphors only and the beam representing the green picture signal to hit
the green phosphors only. When this is perfect, the picture is said to be in
proper convergence. Even a slight lack of convergence causes one or more of
the colors to not line up with each other perfectly on the screen. This is
characterized by a slight fringe of color around objects on the screen. This
particular characteristic is most noticeable on black-and-white images. While
projection TVs tend to use three separate picture tubes (one for red, one for
green and one for blue) and convergence is mostly done optically (the three
projected pictures are converged on the screen), stray magnetic fields can
still physically move the picture around on the individual CRTs, thus ruining
conversion.
Plasma screens and LCDs work by turning permanently fixed (as in they cannot
move) red, green and blue picture elements on or off as required by the
signal. Since these types of displays cannot, by definition, get out of
convergence, stray magnetic fields will have no effect. So it is not
necessary to keep speakers at a distance from these types of TVs.