LaScala center-shielding for tv?

[Ed Cook]

Thanks for previous help.

Considering upgrading center ch to LaScala (between '70 K-Horns) and 2 rears to Cornwalls.

Will there be problems with magnetic shielding for a current conventional TV or future HDTV atop the LaScala?

If this causes problems, does anyone have recommended solutions?

[colterphoto1]

The magnetic field will only affect the picture on a conventional CRT type television. Plasma, LCD, and projection are immune.

The standard solution is to separate the components or shield the speaker. Shielding is accomplished with 'bucking magnets' which are magnets of same strength as that of the driver, placed back to back, so as to actually cancel, rather than shield the magnetic field.

If you place a tv on top of a LS, I'd guess that the woofer is far enough away so as to not interfere, but the mid driver might. I've had a 36" Mitsu nearly right next to a Cornwall with little interference.

Michael

[mark1101]

I just set up my HT and have a coventional tube TV sitting directly on top of my center channel Lacala. I did this about two weeks ago and have not noticed any problems YET.

Most of the CRT type TVs made over the last few years run a deguass cycle every time they turn on. Some, have it in a menu and allow it to be done manually.....which "fixes" the screen temporarily.

[jheis]

I had a '84 vintage MGA 20" CRT sitting directly on top of one of my Cornwalls for well over ten years - no problem.

LaScala uses the same mid driver, but it's located a little closer to the top of the cabinet. Try it and see. If there is a problem, I think you are going to see it right away.

James

[WMcD]

One of the issues or non-issue may be as follows:

The old Alnico drivers reportedly were self shielding, the did not have the magnetic fringes that ferrite drivers do. The K-55v and plain old T-35 were Alnico. Therefore, it should be that older speakers cause fewer problems.

A little off topic. I've speculated that in the early days of TV, the speakers within the set were Alnico and were not shielded. Later the speakers had ferrite magnets and these did have to be shielded. I saved the small speaker from a 1986 vintage Trinitron. They are shielded.

Gil

[mark1101]

Gil,

Funny you bring this up. As luck would have it my center LaScala is a 1977 with Alnico drivers. My L/R are 1990 LaScalas with mud magnet drivers. As I mentioned above still no issues yet. I didn't know anything about these differences relevant to shielding. Thanks

[WMcD]

Mark,

Thanks for your comments. Sometimes I don't know whether I'm setting out "common knowledge" and every rolls their eyes and yawns.

If I may set out some other observations.

Some years ago I had some fun taking a cabinet latch type magnet to the front on a CRT computer monitor. It created some pretty neat distortion. I thought the de gausing circuit would clear it once the magnet was removed. It did not at first. It took three turn ons.

I think the speaker magnet nearby a CRT continuously is another issue. It is warping the electron stream, the "cathode rays". Degausing may not cure it. This is why sheilding or bucking magnets are necessary.

- - -

In another thread on this forum there is discussion of the Shorthorn (model T?) which served as a platform under the typical TV receiver of those days. NTSC TV has FM audio (that, big in its day) and some smart cookies demonstrated just how good it could be with a full range speaker like the Shorthorn. Then, as now, the speaker in a TV can be put to shame by a dorm room stereo.

It must have been frustrating to TV audio engineers that they were sending good sound down the transmission line, but TV receivers had speakers like those used in an
AM table top radio, usually positioned at the side!

The interesting thing is that the Shorthorn T seems to have used the same Alnico drivers as the rest of the Klipsch line. I don't see any reference to sheilding, etc. So those guys blessed with '50s speakers had a very CRT friendly set of drivers without thinking about it.

Gil