Extremis shielding

Mr Teal · 28th January 2005, 04:48 AM

I got my Adire Extremises today, and was checking them out quickly. One thing I noticed, the shielding doesn't seem great. At about 10" from the center of the driver to the edge of my screen, I start to notice discoloration. Will having a box help with that at all, or do I just have to keep the woofer's a foot away from a CRT edge?

Mr Evil · 28th January 2005, 11:45 AM

A box won't help unless it's made of ferromagnetic material, i.e. steel (or mumetal if you like spending lots of money for the best).

If you want to improve the shielding, you could try wrapping some steel around the existing shielding, or attaching steel sheets to the box, or sometimes just placing a sheet of steel between the speaker and the CRT will be enough.

noodle_snacks · 28th January 2005, 12:16 PM

How thick would the sheet of still have to be to offer effective shielding if it was outside or part of the box?

Mr Evil · 28th January 2005, 03:17 PM

That would depend on the shape and strength of the field, the distance and permeability of the metal and the sensitivity of the CRT. In other words, I don't know. However, for the speakers I have tried it with, one or two sheets of steel metal abot 1mm thick each has been sufficient.

Soft steel from old PC cases and other electronic equipment is good for this, having high permeability and low (or even zero) cost.

Davey · 28th January 2005, 04:08 PM

It's interesting because the Adire website claims this shouldn't be a problem with the Extremis driver.

"The Extremis 6.8 has something the other high end drivers don't though: video shielding. The Extremis 6.8 uses a neodymium magnet system which is inherently low in stray flux. In fact, the stray field just 2" from the motor is less than 100 mG (the Earth's magnetic field is 5 times larger!). This driver can be placed within inches of a CRT or magnetically sensitive equipment without a problem. Try that with the other high end offerings, and you'll need to invest in good degaussing coils!"

Davey.

cm961 · 28th January 2005, 04:20 PM

Maybe you have faulty drivers? With specific claims like that I'd check with the manufacturer.

Or measure the fields.

Pete

morbo · 28th January 2005, 07:18 PM

This is pretty common IME. I'm playing with 3 drivers right now, all 3 meant to be shielded.

TB 871 - no distortion next to TV
CSS WR125 - no distortion next to TV
Dayton RS225 - significant distortion approaching TV

Shielding is not an 'is or isnt' thing, there are degrees of it. My experience has been that the larger drivers are rarely 'fully' shielded.

hofffam · 28th January 2005, 07:55 PM

I have successfully shielded speakers using commonly available galvanized steel roofing flashing. It is sold in rolls of varying widths and lengths and sometimes can be found in pre-cut pieces. It is easy to bend and cut with metal snips.

Timn8ter · 28th January 2005, 08:09 PM

I haven't tested mine yet. My understanding is that the stray flux from the Extremis is less than that of the AV8 which is a traditionally shielded driver.

Grahamt · 29th January 2005, 01:47 AM

My Extremi are fine until they get within about 6" of the side of the screen.

28th January 2005, 04:48 AM	#1
Mr Teal diyAudio Member Join Date: Nov 2003 Location: Saskatoon	Extremis shielding I got my Adire Extremises today, and was checking them out quickly. One thing I noticed, the shielding doesn't seem great. At about 10" from the center of the driver to the edge of my screen, I start to notice discoloration. Will having a box help with that at all, or do I just have to keep the woofer's a foot away from a CRT edge?

28th January 2005, 11:45 AM	#2
Mr Evil diyAudio Member Join Date: Aug 2004 Location: Behind you	A box won't help unless it's made of ferromagnetic material, i.e. steel (or mumetal if you like spending lots of money for the best). If you want to improve the shielding, you could try wrapping some steel around the existing shielding, or attaching steel sheets to the box, or sometimes just placing a sheet of steel between the speaker and the CRT will be enough. __________________ https://mrevil.asvachin.eu/

28th January 2005, 03:17 PM	#4
Mr Evil diyAudio Member Join Date: Aug 2004 Location: Behind you	That would depend on the shape and strength of the field, the distance and permeability of the metal and the sensitivity of the CRT. In other words, I don't know. However, for the speakers I have tried it with, one or two sheets of steel metal abot 1mm thick each has been sufficient. Soft steel from old PC cases and other electronic equipment is good for this, having high permeability and low (or even zero) cost. __________________ https://mrevil.asvachin.eu/

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28th January 2005, 12:16 PM	#3
noodle_snacks diyAudio Member Join Date: Mar 2004 Location: Hobart, Tasmania	How thick would the sheet of still have to be to offer effective shielding if it was outside or part of the box?

28th January 2005, 04:08 PM	#5
Davey diyAudio Member Join Date: Dec 2001 Location: Bremerton, WA.	It's interesting because the Adire website claims this shouldn't be a problem with the Extremis driver. "The Extremis 6.8 has something the other high end drivers don't though: video shielding. The Extremis 6.8 uses a neodymium magnet system which is inherently low in stray flux. In fact, the stray field just 2" from the motor is less than 100 mG (the Earth's magnetic field is 5 times larger!). This driver can be placed within inches of a CRT or magnetically sensitive equipment without a problem. Try that with the other high end offerings, and you'll need to invest in good degaussing coils!" Davey.

28th January 2005, 04:20 PM	#6
cm961 diyAudio Member Join Date: Jun 2001 Location: Peterborough, Ontario	Maybe you have faulty drivers? With specific claims like that I'd check with the manufacturer. Or measure the fields. Pete

28th January 2005, 07:18 PM	#7
morbo diyAudio Member Join Date: Sep 2004 Location: Guelph, Ontario	This is pretty common IME. I'm playing with 3 drivers right now, all 3 meant to be shielded. TB 871 - no distortion next to TV CSS WR125 - no distortion next to TV Dayton RS225 - significant distortion approaching TV Shielding is not an 'is or isnt' thing, there are degrees of it. My experience has been that the larger drivers are rarely 'fully' shielded.

28th January 2005, 07:55 PM	#8
hofffam diyAudio Member Join Date: Sep 2004 Location: Texas	I have successfully shielded speakers using commonly available galvanized steel roofing flashing. It is sold in rolls of varying widths and lengths and sometimes can be found in pre-cut pieces. It is easy to bend and cut with metal snips.

28th January 2005, 08:09 PM	#9
Timn8ter diyAudio Member Join Date: Jul 2003 Location: Seattle, WA	I haven't tested mine yet. My understanding is that the stray flux from the Extremis is less than that of the AV8 which is a traditionally shielded driver.

29th January 2005, 01:47 AM	#10
Grahamt diyAudio Member Join Date: Mar 2004 Location: U of Waterloo	My Extremi are fine until they get within about 6" of the side of the screen.

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