View Full Version : Unshielded speakers in edit suites
20-06-2007, 12:04 PM
Question: do unshielded speakers create the same issue with flat screen monitors (LCD or Plasma) as they do with CRTs?
I'm assuming not, but want to check.
20-06-2007, 12:37 PM
I have never seen it happen with LCDs.
My understanding is that the effect on CRTs is caused by the magnets messing with the CRT guns and warping their path, so no CRT guns - no problem.
Enzo is right, but it's not the CRT gun per se that causes the problem. The display technology in CRTs uses a stream of electrons that is made to scan by means of deflection with magnetic fields. You add an additional magnetic field and you stuff things up. An unshielded speaker can add that additional field. On precision monitors even the earth's magnetic field has a significant effect.
LCDs use the phase change of liquid crystal elements which are directly switched by transistors built into the display. No electron beam, no magnetic field problems. Well very little anyway.
Plasma displays use spots of hot ionised gas created at the intersections of conducting arrays to drive the display. Again, since they don't require an electron beam they are thus insensitive to stray magnetic fields.
Very strong magnetic fields can affect either technology, but we're talking way stronger than a leaky unshielded speaker.
I often read your stuff John and it makes me think: "How useful it must be to have a brain!"
Yes, it would be nice....
22-06-2007, 09:16 AM
Not only does John have a brain, but he is always ready to share its contents.
Many of you may not have met John, so I have attached a picture of him to help put things in perspective.
Cheers to all . . .
he looks younger than i thought!
Neil, I know where you live!
23-06-2007, 09:32 AM
See, Gandalf knows all!
Seriously, though JWRL - you're a massive asset to these forums... thanks for sharing the wealth.
Awwwwww, I'm blushing now!
a final cut pro
14-08-2008, 05:17 PM
No magnetic filed don't kill flat sceen monitors but Quad splits with permanent 100% white keys do! In our media exchange area we have a number of nice HD Panasonics with multiple sources permanently plugged in via Quad splits, after a while we managed to switch on the TV function of these (ahem) monitors and lo' there was copious burn-in. Now I know that Plasmas have had this problem but even our Techs said this was impossible in LCD technology. Well no it isn't and I can sell you the dodgy screens as proof.
14-08-2008, 05:27 PM
Anyone that thinks LCD is impervious to burnin is severely misguided. With our Sony 'broadcast' LCDs, we need only leave the aspect markers on overnight to see a burn in the morning. It fades after a while, but not good.
But then CRT's were no different, so...???!!
a final cut pro
14-08-2008, 07:20 PM
i guess the reason for higher expectations lay in the method of function. The CRTs project that beam at a spot at high energy (relative to black), whereas the LCDs only occlude the light source from behind to show black, I suppose those areas exposed just forget how to occlude as well as the other areas.
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