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Question re: K55-V driver


Kenneth Brookshire

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If you have a modern flat-screen TV you don't need shielding.   That is to say an LED, OLED, or Plasma.  It was only the old CRT type which was bothered by magnetic fields.  The cathode rays were actually a stream of electrons and they would be deflected by coils causing magnetic fields but also the stray fields of the driver magnet.

 

Actually I don't know how the K--55 and brothers do as far as sheilding.  I recall that just about all similar ferrite speakers did need it. 

 

Maybe an alnico driver needs it less.  Back in the early days of TV (like when The Honeymooners were in first run) the CRT units used alnico based speakers without shielding.  It was only later with ferrite based speakers that mu-metal shilds were added to prevent distortion of the picture.

 

I don't quite know why but it may be that the field of the alnico mmagnet was weaker before being concentrated by the pole piece and magnetic circuit and there were not magnetic fringes coming from the structure.

WMcD

 

 

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Makes sense that modern TV's are not affected by magnetic fields, & yes I have a newer TV.  I'd heard that the K55V was shielded to a degree.  Previously I tried to shield with iron plates, but I guess that was unnecessary.  Remember those old VPI blocks to corral transformer hysteresis fields?  They were a nice wooden block that simply had several steel plates inside.  Ha, ha.

Thank you, I'm going to use them in my center channel.

Regards / Ken

Edited by Kenneth Brookshire
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I had a 35" CRT TV sitting on top of my Belle centre speaker for a couple of years with no issues, other than its crushing 180-pound weight.  Maybe the distance from the K-55V was enough to keep it out of trouble, since the tube was above the TV's speakers and base, so it was nearly a foot above the driver.

 

Now it's supporting a 120-pound plasma TV, so it's probably much happier.  The new LED TVs are much lighter again, and unlike CRT TVs, don't leak magnetic fields at all.

 

BTW, your picture shows a K-55V, not an M-55V.  Most Klipsch driver and horn part numbers start with K, for obvious reasons.

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I should have added:  The issue in general also came up when computers had CRT monitors and manufacturers hung speakers off the sides of them.  I took apart some Compaq speakers and the magnet did have the shielding cup.  Also a mini passive radiator.  

 

Some or all CRTs have a degausing coil around the face of the tube.  At turn-on it makes a pulse of some sort of signal to degause (demagnitize)  the system though maybe it is mostly the mask of color sets. 

 

One Saturday afternoon I took a magnet to the face of an office computer and it distorted the image pretty well.  I was afraid it might be permanent but turning the CRT off and on cured the situation.  No one was the wiser.

 

FWIW the shilding cup is make of out something called mu-metal which is a type of iron which is very conductive of magnetic fields and thus shorts out the field or confines it.  

 

FWIW I was reading that trans-Atlantic cable and other long telegraph wires had phase issues which caused the pulse of the dots (and simimlar dashes) to smear out over time and thus run together making them unitelegable.  (This reminds me of Chris A's work on DSP phase delay.) 

 

In the case of the telegraph systems, the patron saint of mad scientists,  Oliver Heaviside, found a solution of adding effective inductance and this was done by wrapping the center conductor in mu metal.

 

We now return you to the normally scheduled program. 

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