A 416 dilemma. What to do?

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Originally Posted by airboss

You and I would not make best friends GM, but we can be civil neighbors.

Sincerely
Dan

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Now don't be so sure about that!!! I'd bet you two old geezers would get along famously over a glass of Geritol or two.. Maybe swap ideas on the best way to keep the Depends secure, you know trade secrets and all :) And how about all those studly stories you both could talk about after you've popped that little blue pill, bet you could go on for hours and hours lol :)

:)

PS, although it wasn't totally on topic, I thought my magnet zapping video was pretty cool, never saw how that was done before... You'd almost think he should of worn some type of safety glove or something?

Well anyway what was this thread about ?? :D Sheez, Hi Pano,Please bring back some nice photos of the fest or the OB you are working on.Would love to see them.

I think it has more to do with this particular pair of drivers than anything else.Were talking about 1 pair of drivers out of thousands and thousands of drivers.To me this seems very rare to come across this situation were the Alnico V fails to recharge.

Unless there are others that have had this same problem.

I think the cause has more to do with material than GPA I have dealt with them (Bill and Steve) on several occasions each and have never had a problem.Oh yeah I had one problem there was 2 lock washers missing from 1 of the Large Format Driver Studs & Gaskets (Hardware Package) I had ordered.And Bill offered to send an entire new package for 2 missing Lock washers,told him not necessary.:)

We are talking about a pair of LTV drivers aren't we.

But Pano your original question was what to do. 90 some posts later question still stands.I wish I had an answer to help you my friend.But at this point I would NOT put anymore money into these drivers,there has to be an issue with the Aluminum-Nickel-Cobalt material.It is quite intriguing because they had to be OK when they were new,so what happened to these magnets. :confused: This question probably will never be answered unless you know where and how these drivers were used their entire life.

Just a little something on magnets and magnetising:

www.oersted.com/magnetizing.PDF

I would be tempted to try re-charging one speaker(the weaker one) as the paper indicates that the magnets should take re-charge.

Cheers, Marshall.

Convert them to field coils.

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Originally Posted by mah

Seeing the magnets will not recharge they were probably from a bad batch. I wonder if there are more out there from a similar build date?

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I communicated with a few knowledgeable folks recently and they all ~scoffed at this possibility.

GM

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Originally Posted by Panomaniac

Bill told me several times that he had never seen Alnico that would not recharge. Told me it was impossible to beat Alnico so badly it would not take a charge. And yet these didn't. But that's not what I've heard from some other Altec heads. Who knows?

GPA did tell me not to worry about the measurements. "Just listen to them." I did, they suck. GPA did say "they should be pretty close to spec" but would never tell me what that was. Wouldn't look it up for me. When I finally did find specs, they were obviously way out.
A frustrating experience all around.

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This has been my experience also WRT heat sinking (extreme heat build-up), cracking, chipping. Indeed, it's not uncommon for a crack or chip to increase a slot car motor's overall performance, so short of dislodging the magnet, hitting, dropping it won't necessarily adversely affect its performance. WRT heat damage, it takes >538 deg C to start changing its metallurgical structure to where it can't take a full re-charge, so are there any Altec drivers (or any brand for that matter) with VCs capable of repeatedly getting this hot in a mega-power system for a long enough time to achieve this?

I'm thinking not, but can't find any real world numbers beyond the one Tom Danley noted many years ago that >230 deg C peaks have been measured which is lower than those I've measured. According to these folks, heat affects AlNiCo's loss due to heating at a rate of 0.02%/deg C or 0.46% @ 230 deg C, so completely insignificant WRT audibly affecting a driver's Qts.
http://www.arnoldmagnetics.com/products/alnico/index.htm

Regardless, combined with having already read/heard about enough others with what I consider less than acceptable customer service from GPA, yours was the 'straw' that had me questioning their commitment to folks needing service in general and magnet re-zapping in particular.

GM

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Originally Posted by Steve Schell

I agree with Earl that the LTV era construction may have paved the way for undersized magnets.

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Wel, the magnet would have to be considerably smaller to have a > 2x higher Qes, so weighing the driver might be enlightening, though they could have increased the pot's thickness to offset it. Maybe tapping the pot to compare its ring tone to a known good driver to judge thickness?

GM

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Originally Posted by Earl K

- I still can't let go of the fact that GPA thought your pair were close enough to spec. to ship back to you ( for your listening enjoyment :confused: ) .

- The lesson I take from this is I wouldn't bother sending old beaters to GPA for recharging & then automatic reconing until GPA can confirm that the old alnico has taken a full charge( & therefore is worth reconing ) .

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Nice to know I'm not the only one that feels this way.

GM

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Originally Posted by sba2

I have a pair of JBL d130f that, like Pano?s 416s, are sitting unused because they sound like #$%^. Mine also have the higher than spec Qes values. I wonder if a remag would create any sonic miracles !

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I seriously doubt it as this can't have the correct re-cone kit in it, assuming one is still available. A good way to tell if a re-cone is 'close enough' to spec WRT the balance between Fs, Vas, Qts is to compare its measured sensitivity to published or some known good driver and allow ~ +/-10%.

GM

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Originally Posted by Earl K

- IMO, people selling woofers on eBay with aftermarket kits in them ( & not identifying this fact within the sales text ) is tantamount to fraud .

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Agreed. Where's a good lynch mob when you need one? :mad: Fraud wouldn't be a booming career choice these days if the penalties were Draconian.

GM