Any update?
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Any update?
No, they are a GPA. Guess I'll give Bill a call tomorrow. I'll be out of town all next week for work.
Just got the driver back from GPA. Looks like the "reverse remag maneuver" worked.
Big thanks to Todd and Bill.
The better woofer didn't change much, but the "bad" one did. Went from a Qts of 0.6 to Qts of 0.4 and that results in a gain of a few dB. Vas is closer, too. Polarity is now correct.
The calculated BL (force in the gap) went way up on the bad driver. From 8.6 to 12.3. That's a big improvement and really makes the drivers usable. And the 2 drivers are now much closer to each other. They match better than the 416s I'm using now. Even the impedance curves are close.
They aren't as efficient or as low Qts as the 416-8As I bought from O.G. in the A7s, but that may be for a reason. Perhaps GPA is building voice coils and cones with solid state amps in mind. What I have now should work well with low output impedance solid state amps. Better than the old spec drivers that where meant for tube amps.
Thanks to everyone who helped on this. :thankU:
This was a neat experience for us Altec users. A pair of 416's were saved and should be in play for another 30+ years.
A great story with a happy ending.
Matt
Thanks guys! Yes, these went from an expensive pair of ashtrays to real, live speakers thanks to the keen eye of Todd White and the good work of GPA. And as you say, we all learned something.
Next week I'll pop these in my 828 cabinets to hear how they sound. Really looking forward to it!
Yes Todd hunted down the info on that reverse switch on the re-magnetizer. Top - Notch Todd, great work.Those drivers were almost trashed and what a waste that would have been.....
Gee - thanks guys. Just tryin' to help...
Don't mention it Todd. Good Job !!! Mike was heading to a dead-end with those drivers.Saved him some nice coin! :2thumbsup: :coffeedrinker:
One question I've not seen answered. What was your total cost out of pocket?
Total cost? Wow, I don't know. More than I want to think about. Most of it in shipping. UPS was the winner in this deal. ;)
More than a good used pair would have cost me, I'm sure. But these have now have strong magnets and new cones, so should last me the rest of my life. That's saying something.
It's always nice to see a ending like this for sure! :2thumbsup: I'm curious as to what Bill said when you mentioned to him that the re-magnetizer may have been reversed.
Never heard from Bill. He fixed them, that's about it. All in a day's work, I suppose.
I've sure fixed my fair share of production mistakes. Part of doing business.
In my business I would have paid the customers cost of shipping for my mistake, but that's just me.
I told Bill what Jerry Hubbard said, and, of course, he understood the issue, he was just surprised that it could have happened. Being a small company, it's easier to pay more attention to detail and make sure things like this don't happen. But, no one's perfect, so they do sometimes...
Well I was wrong - I did hear from Bill but the email slipped by me.
He went to quite a lot of trouble and work to fix my drivers - including replacing a magnet! I've asked him for permission to post his findings here.
I knew Bill would come through.That's what happens when you deal with good PEOPLE. :2thumbsup:Quote:
Originally Posted by Panomaniac
I hate to even ask but, how would one tell if his 808-A's were done correctly?
I suppose too I ought to call and find out if they got my 416 frames ok. It's been weeks.
Yes, definitely call. The phone is how GPA does business.
OK, here is Bill's reply to me about what he found with my drivers. Bill said OK to post this.
"When I received your speakers I found that one of them had to be reconed because the speaker was packed in a plastic bag and the edge had stuck to it damaging the cone."
(note from Pano - don't put your drivers in a plastic bag!)
"So I decided I would just tear them both down, when I did I measured the magnetic flux and it was 8.0 Tesla and the polarity was backwards, the Altec spec sheet rated it at 12.0 Tesla. So I then re magnetized it twice to reverse the polarity and bring the flux back up, however it did not, the polarity reversed but the flux stayed at 8.0. I then torn down both magnets and totally de-magnetized the parts, after re-assembling them and re magnetizing them there was still no change.
I then called my magnet vendor and spoke to their engineer, he told me that I should have no trouble magnetizing the Alnico whether I torn it down or not and that Alnico should not even loose it magnetism unless it was dropped or the plates slide."
"Next I measured and weighed your magnets and the ones I currently use and they were the same and agreed with the Altec spec 2.4 pounds. So the only thing I could think of was trying a brand new piece of Alnico in your structure from my stock and when I did the gap flux went up to 10.5 to 11.0 Tesla which is lower then what Altec states but I believe to be what it needs to be."
(note from Pano: I measure a BL of 12 on each, so right at spec).
"I am now going to send in your slug of Alnico to the magnet manufacturer to let them analyze it to see why it will not magnetize. This is for my interest."
"I did not get a chance to do the T/S parameters the guys shipped it out before I had a chance. But I think it will be ok with the higher gap flux that is matched and the coil DCR is also matched."
So it does seem that there was something wrong with the Alnico slug after all.And all the re-magging will not help.Very Interesting I hope you follow up on that I'm curious as a new puppy with a new toy. :D Like to hear what they come up with on this one.
Well at least you have an operational pair of 416's now. :)
2 pair, actually. I am spoiled.
Yeah, if Bill tells me what he hears back form the lab, I'll share it here. Maybe it was a dud magnet from day one. Or maybe the aliens zapped it. Only the lab tests will tell.
One thing that Bill may have forgotten to mention - Jerry Hubbard said the voice coil flux density measurement could vary depending on the method used. Bill mentioned this to me, too - that the amount you measure depends on the method you use. That could account for the difference between the Altec spec sheet and the current measurements.
Bill Hayes might be able to shed some light on this - I need to call him and see how he's doing anyway - I'll let you guys know what he says as to the way they measured it back then.
Looking forward to that !!!