Magnet recharging centers

[jw5115]

Since Alnico magnets loose 50% of their charge in 100yrs, It would be very helpful to compile a list of speaker repair centers that are capable of bringing these tired relics back to their optimal performance levels.
Anyone who has dealt with these units over the years knows to excite a voice coil with a 9v battery to see how "crisp and sparkly" it sounds.If one has not this experience, ther is no "Reference" to compare.
shipping drivers around the country is much more expensive than the recharge price itself and "packing to survive the trip" is an art itself.
I would like to start this list with 3 places I have used Orange Co. Spkr in California, Great plains Audio in Oklahoma, and Weber Spkrs in Indiana.
If your running 40+ yr old speaker componants and have not had them recharged, your missing a lot.
jw5115

[Lee in Montreal]

That's a pretty interesting and usefull thread. I suspect that the pair of 2441 I aquired with the 2395 lenses are quite weak. I didn't have to fight against my screwdriver like I used to with the other set of 2441s.

Any place in Montreal?

[Mr. Widget]

Since Alnico magnets loose 50% of their charge in 100yrs...

While I think your goal of assembling a list of remag centers is a good one, you may be over stating the case just a bit. Alnico has been covered here.


Widget

[tesla]

I have been following this discussion with interest.

I have a question, however, on the need to have a magnet "recharged".

I would bet that JBL no-longer does this, and they are the only ones I would trust 100%.

Since JBL published the gauss of the magnets, could the centers that offer this service measure the magnets, tell me if it was off, (and by how much), and show me the magnets had been restored to the original gauss ratings?

Also, how much is off? 1%? 10%?

Sorry for being a sceptic, but if I get my magnets "recharged", I want to know it has actually happened.

Since Alnico magnets loose 50% of their charge in 100yrs, It would be very helpful to compile a list of speaker repair centers that are capable of bringing these tired relics back to their optimal performance levels.
Anyone who has dealt with these units over the years knows to excite a voice coil with a 9v battery to see how "crisp and sparkly" it sounds.If one has not this experience, ther is no "Reference" to compare.
shipping drivers around the country is much more expensive than the recharge price itself and "packing to survive the trip" is an art itself.
I would like to start this list with 3 places I have used Orange Co. Spkr in California, Great plains Audio in Oklahoma, and Weber Spkrs in Indiana.
If your running 40+ yr old speaker componants and have not had them recharged, your missing a lot.
jw5115

[Gregegg]

I am interested in measuring magnetic flux, since being remote from the facilities mentioned, the cost of shipping a basket is the major cost in using a recharge facility. It may be that the magnetic field is in tolerance and that a recharge is superfluous. Has anyone tried any of the chinese instruments?

http://cgi.ebay.com/Tesla-Gaussmeter...-/190489841896

If so, is there a process or method of measurement with cone in place with consistent results. This would allow comparsion of woofer pairs. I realise that cone in place would be a precarious and somewhat risky procedure since the dust cap would have to be penetrated with the measurement probe to access the VC gap. Perhaps the measurement with the VC in place could be taken into account with the data obtained.

Any experience with measurement procedure, data and uncertainty of measurement would be of interest for sure. Please post here. Tar!

[herki the cat]

...., could the centers that offer this service measure the magnets, tell me if it was off, (and by how much), and show me the magnets had been restored to the original gauss ratings?.... I want to know it has actually happened.

Relax!!
The charging cost is peanuts compared to the shipping costs. You do not be concerned about "how much the magnet flux is off, or complete recharge" with "Orange Co. Spkr in California, & Great plains Audio in Oklahoma." They know their business, and their charging machinery is capable of delivering all the magnetic energy your speaker magnets can retain without fussing around.

I am sure they will include the resulting flux mesurement data upon request.

Your worst problem concerns proper packaging to prevent shipping damage to the service center and return to you.herki[quote/]

[tesla]

Ah, but I am concerned! I agree with the other poster, I would want to see the proof! As for the Chinese gaussmeter, let the buyer beware, they might be good, but who knows?

As for OCS....yes, relax, they are less than an hour and a half away, so no shipping charges. I will call them to get more info, and report back.

Relax!!
The charging cost is peanuts compared to the shipping costs. You do not be concerned about "how much the magnet flux is off, or complete recharge" with "Orange Co. Spkr in California, & Great plains Audio in Oklahoma." They know their business, and their charging machinery is capable of delivering all the magnetic energy your speaker magnets can retain without fussing around.

I am sure they will include the resulting flux mesurement data upon request.

Your worst problem concerns proper packaging to prevent shipping damage to the service center and return to you.herki[quote/]

[Robh3606]

You do not be concerned about "how much the magnet flux is off, or complete recharge" with "Orange Co. Spkr in California, & Great plains Audio in Oklahoma." They know their business, and their charging machinery is capable of delivering all the magnetic energy your speaker magnets can retain without fussing around.

I wouldn't be too sure. We have had at least one member get cores recharged that were not done properly. All that It took was a measure of the BL using a WT2 to find out what the problem was with the drivers. They had to go back after a couple of months of trying to figure out what was wrong with them.

As far as recharging everything, there is no need to, especially the compression drivers and other short coil drivers. Read Greg's note that Widget linked too.

Steve Schell has measured vintage drivers with a gauss meter and found many to be just fine. As far as using the meter the probe has to be in the gap so it must be thin enough to get in there. In addition you can't do it with the voice coil in the gap. So rip out your cone kits. That means that the people doing the recharge can't do it either unless you send them baskets.

Rob

[Earl K]

Any place in Montreal?

Yes, Belisle Acoustics advertises this service ( though I don't know if their machine is capable of generating the larger gauss levels needed to restore large compression drivers ) .

[Lee in Montreal]

About demagging.

http://www.audioheritage.org/vbulletin/showthread.php?10280-Recharging-Alnico-Ferrite-magnets&p=110522&viewfull=1#post110522

Yes, Belisle Acoustics advertises this service ( though I don't know if their machine is capable of generating the larger gauss levels needed to restore large compression drivers ) .

Thanks for info. They are located 1 hour away from me. Not far. Also, the reason for wanting to remag them is that those 2441 are 30 years old and were used in a commercial rig, not home. Therefore, I have no idea about their condition. For $50, I'll have peace of mind, knowing they are to spec. Anyway, what is $50 extra on a 2395/2441 combo?

[Rolf]

After what I have read, and personal experience too, the loss mostly happens with woofers. At the time I discovered this forum (the old one before what we now have) this was one of my first questions. At that time I had the 4333A, and when I wanted to play a little laud, "strange cracking" came out of the woofers. I also noticed the the magnets got really hot.

After advice from one of our most experienced members, I got this checked out. It was clear that the magnets was not as they should be. I got them re-charged at one of the few speaker producers we still have here in Norway. Problem solved.

I have never heard of any mid or high freq drivers that had these problems. But, what the h... do I know. Just my experience.

[herki the cat]

I wouldn't be too sure. We have had at least one member get cores recharged that were not done properly. All that It took was a measure of the BL using a WT2 to find out what the problem was with the drivers. They had to go back after a couple of months of trying to figure out what was wrong with them.

Rob

Rob, a fair question, who was the service regarding Quote: "...We have had at least one member get cores recharged that were not done properly..." I have four 2427 Ebay bargains severly demanetized that have me standing on a razor blade, edge up.

There is a history of by a prestigous Service Center improperly packaging the massive 2440's resulting in severe damage to the point of shearing off the driver cap bolts and crushing the diaphram. I doubt very much it was GPA.herki[Quote/]

[Earl K]

One should always excercise due diligence when dealing with GPA or any other reconer/remagnetizer ( ie; test your woofers before & after servicing ) .

Here's one example of why , to not be blindly trusting ( the story is a mammoth read ) .

<>

[Rudy Kleimann]

Who and where was the "faulty" recharging done?

Based on their history, reputation, and personnel, I have a hard time believing Great Plains Audio would be the culprit. OCS, maybe, simply because they are a big outfit and mistakes can happen, but they've been around too long to not have heard about this before. And, as has already been pointed out, the actual flux cannot be checked with a cone and coil in place.

I have 2 pair of 12" AlNiCo that I suspect are suffering from overpowering demag and have often wondered myself about this service and if it could be done without removing the cones.

Someone with personal experience with remagged drivers, esp. with cones installed, please chime in here and lay this gossip to rest. The shop name, tech. name, and approximate date of the remag. would be appreciated. PM me if you prefer not to post on the thread.


I recall a thread post somewhere quoting G.Timbers performing a "Q modification" by briefly and intentionally overpowering a test woofer that seemed to be overdamped, saying "that's about right" after retesting, rather tongue-in-cheek. Couldn't find the post, but it was a rare moment of humor, to be sure...



Thanks,

Rudy

I wouldn't be too sure. We have had at least one member get cores recharged that were not done properly. All that It took was a measure of the BL using a WT2 to find out what the problem was with the drivers. They had to go back after a couple of months of trying to figure out what was wrong with them.

As far as recharging everything, there is no need to, especially the compression drivers and other short coil drivers. Read Greg's note that Widget linked too.

Steve Schell has measured vintage drivers with a gauss meter and found many to be just fine. As far as using the meter the probe has to be in the gap so it must be thin enough to get in there. In addition you can't do it with the voice coil in the gap. So rip out your cone kits. That means that the people doing the recharge can't do it either unless you send them baskets.

Rob

[Rudy Kleimann]

I posted my reply before seeing you had posted after. I peeked at the link enough to see it needs following through. Maybe this weekend I'll have time to read it all.

One should always excercise due diligence when dealing with GPA or any other reconer/remagnetizer ( ie; test your woofers before & after servicing ) .

Here's one example of why , to not be blindly trusting ( the story is a mammoth read ) .

<>