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Referring to the link posted to Permanent Magnet Selection and Design, page 11 section IX " Modern high coercive force magnetic materials do not significantly degrade over time...... Most magnetic material will encounter degradation from corrosion,heat,or mechanical impact long before their magnetic properties would degrade because of time....." As most of our loudspeakers used in a home environment are safe from these hazards we will probably suffer degradation to our listening experience from the effects of time on our hearing before the magnets used in our speakers give out. Scotty
"Go out out of alignment" is very different from "demagnetize." Going out of alignment is caused by some sort of external shock, such as being dropped hard. (Or, I suppose, the weight of the magnet acting on the frame, if the frame is a thin cast variety; I've never personally seen that problem, though. Demagnetization, in the case of Alnico magnets, happens with ordinary use, as the thread to which you linked also states. That flaw, IMO, makes Alnico unsuitable for high-fidelity loudspeakers when we have two much more stable magnet technologies in ferrite and neo. Fortunately, the SAM1 didn't use drive units with Alnico magnets, so it's not an issue for those fine speakers. I presume the SAM2 doesn't use drive-units with Alnico magnets, either.Alnico is unique among the major magnet technologies used in loudspeakers in the ease with which it demagnetizes. The Mark Dodd* designed Dual Concentrics (mid-1990s D-series and Saturns for "home;" NFM, Studio and System series for "pro") are vastly superior to the old Alnico-magneted ones. A cutaway of a Dodd-designed Dual Concentric is my avatar.So if you see, say, a System 10 DMT II, run to go hear it. An old Arden or Berkeley or whatever...sure, it's better than most current speakers because at least the midrange polars are not so bad (but not something well-designed using modern parts, like the SAM1) but it's more a curiosity than anything else.Mr. Dodd, who designed the "Tulip" phase plug for Tannoy that was such a massive improvement over their old "Pepperpot" design, was later poached from Tannoy by KEF/Celestion, where he designed "Tangerine" phase plug used to such great effect in the concentric mid/tweeter used on, inter alia, the SAM1. IMO, Tannoy has not yet recovered from the loss of Mr. Dodd to KEF.
I presume the SAM2 doesn't use drive-units with Alnico magnets, either.
So, the M2 woofers use these, I take it?
No. Nor the M1. Hence my concerns about tour. More weight = more shipping drama chances. The M1 tour pair took a pounding. These aren't typical 2 way 5-6" monitors either, by a long stretch.
Referring to the link posted to Permanent Magnet Selection and Design, page 11 section IX " Modern high coercive force magnetic materials do not significantly degrade over time...... Most magnetic material will encounter degradation from corrosion,heat,or mechanical impact long before their magnetic properties would degrade because of time....."
That kind of stability is out of scope of the discussion. The problem is not that Alnico sits there and degrades. Alnico's flaw that makes the stuff unsuitable for high-fidelity loudspeakers is that flowing current through a voicecoil it demagnetizes an Alnico structure around it.And yes, Tannoy uses Alnico (along with that Pepperpot phase plug, which does not perform as well as their more modern Tulip phase plug) in their most expensive speakers, because their most expensive speakers are overwhelmingly targeted to (mostly Far Eastern) retro fetishists.
I guess you know what the half life of an Alnico magnet is?
No, I don't. I and many others know something higher-level, though. We know that the "half life of an Alnico magnet" is irrelevant to its suitability as a permanent magnet in a loudspeaker. So whatever its half-life is, an intelligent person has no reason to care unless s/he is heavily invested in Alnico futures or something like that.What does actually matter here is the fact that Alnico degrades in the presence of an electromagnetic field. Such as that caused when one puts power to a voice-coil. For loudspeakers, it's obviously better to use a magnet that doesn't degrade like that.
Thread officially derailed.... Back on track....hey AJ, where's those demos....lol.
Neekomax:Since you are interested, I post the following link:http://www.audiocircle.com/index.php?topic=52321.0Jim
What you need is a Mid Atlantic rep willing to offer auditions to those interested. It would be a tough job, but I'd be willing to volunteer. You have my address to send a complimentary demo pair....
Getting back on track, Roscoeiii was over last night for a spell, and we had a good time putting the SAM-2 through its paces. I think it was unanimous, the SAM-2 kicks serious but, and really takes things to a whole other level. Incredible. Very cool to have someone over who was so knowledgeable, homeboy has a deep repertoire of cool test tracks. The SAM-2 imaging is quite good, with the ability for those images to hang in the air holographically. Things like wind chimes are scary real. The SAM-1 is not like that, but has other great attributes of course. Who is going to get the second pair
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