I guess I should note though, that the magnet structure could be charged either before or after the installation of the basket and cone, without the strength being affected.
For what it's worth, it is my understanding that alnico magnet structures have to be magnitized after assembly, not before. GPA informs me that if you dissassemble the structure it will lose fully half of it's strength.
I guess I should note though, that the magnet structure could be charged either before or after the installation of the basket and cone, without the strength being affected.
I'm unsure of the etiquette of adding to a 5-year-old post so hear goes:
For any fellow Canucks in need of speaker remagnetizing there's a place in Vancouver that did a swell job on a pair of Tannoy HPD-385's with a 6db difference between drivers due to that problem. They can do it on assembled drivers according to their blurb. Here's the link:
Vancouver Audio Speaker Clinic - Magnet recharging
Best regards all,
Jon Archibald
Vancouver Audio Speaker Clinic - Magnet rechargingOriginally Posted by aeyb701
I will always use GPA for any repair work of my Altec drivers but thanks very much for posting this link--some really interesting info there. I recommend everyone here check it out (and let us know if any of the info isn't accurate). Here are a few things that caught my eye right off the bat:
"Disassembly If an Alnico magnet structure is opened, such as to re-centre a shifted pole-piece, repair a broken throat, or remove a bug-screen, the magnetic field collapses instantly. While this type of damage is not common, ill-advised repairs create very unwelcome problems."
Wow, am I glad I never removed the bug screens from my 802-8G's!!!
"Pulse loss Most Alnico compression drivers (JBL LE85, LE175, 375, 2410, 2420, 2440, 2441, Altec 288, 290, 802, 804, 806, 808, Emilar EA-175, TAD 2001, 4001, Goto Unit, etc) have tall magnets, short voice coils, and modest power inputs, so do not suffer degaussing. Those compression drivers with low aspect ratio magnets, especially if used <500Hz (Vitavox S2, University ID series, Klipsch K-55-V, Electrovoice 1823M etc) can suffer flux loss, and will benefit from remagnetization. "
I think my 802's and 902's are safe.....
"Pulse loss For example: Low frequency drivers with 4-inch voice coils (JBL D120, D130, D140, LE15, 2205, 2215, 2231, Gauss, or TAD drivers) can lose 2~3dB, becoming 'dull' or 'slow' sounding, unless they have been grossly abused, in which case they more and sound dreadful. Drivers with short Alnico slugs and 3-inch voice coils, (JBL 2213, 123A, etc) are effected more severely, so typically show 3dB sensitivity loss, while small alnico woofers (JBL 116A, 125A, 127A etc) are commonly 4dB down after quite modest use. Conversely, speakers with higher coercivity ( taller Alnico slugs) and short voice coils, such as Tannoy dual concentrics, Altec and EV woofers, rarely suffer unless they have been badly abused."
Gotta love Altec (alnico) woofers!
Last edited by voice of the theater; September 13th, 2011 at 07:22 PM.
Being of "Sound" Mind
What's badly abused? Can't I just add 30 or so computer magnetic drive super magnates and increase the "back to the future" flux capacitorism? I assume they will self align?
Last edited by VolvoHeretic; September 13th, 2011 at 08:09 PM.
Just wire a small flux capacitor across the terminals of your Alnico unit. Should it be abused it will automatically travel back in time and restore itself to new.
Your neighbors called. They like your music.
Aluminium(or other electrical conductor) in a changing magnetic field:
Eddy current - Wikipedia, the free encyclopedia
Opinion is only as valid as its verifiable supporting evidence.
Certainly a magnetic field can induce a current in any conductor.
It just plain period end of story ain't gonna blow the frame out of the charger though. And frankly, the induced current can be ignored in this case.
You've suggested a great name for a band ....is the world ready For Eddy Current and The Generators?
Your neighbors called. They like your music.
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