A 416 dilemma. What to do?

OK - Jerry said that if the cone moves away from the listener (in this case, toward the magnet), then they've been recharged with the polarity reversed and will need to be demagnetized, then recharged with the correct polarity.

With regard to remagnetization, Jerry said that any Alnico magnet that has partially lost it's charge can be successfully remagnetized without being discharged to zero first. In fact, he was adamant that discharging one while there was still some magnetism left in it was totally unnecessary.

Further, he said that if, after remagnetization, the flux density in the gap should be measured to see if it is within specification tolerances, then it should be reconed and the T/S's should be carefully measured to see if they are within spec as well.

My suggestion is to:

1. Send the woofers back to GPA.
2. Tell Bill what you've found and ask him to recharge them with the correct polarity and measure the flux density once he's done.
3. Recone them and measure the T/S's to make sure they are within specifications.
4. Include a record of the above measurements when they are returned to you.

I might add that this could have easily been a simple mistake that wasn't really anyone's fault - it just happened - and that the sooner it's cleared up, the better.

I hope this helps!

Hey Todd. Looks like we are making progress, thanks.

I'm not sure that I want to pay for another recone of these drivers plus all the shipping. =(
Having already done that. Will have to think about it. It's a chunk of change.

Let me see what I can do about that - just send them on in...

How would the proper polarity in a pair, not just one, of woofers get reversed?

If the polarity is reversed, why would another re-cone be necessary? Is this because a polarity reversal requires dis-assembly of the motor?

Is there a way to test the motor polarity before re-coning?

Thx...

Quote:

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Originally Posted by Panomaniac

Hey Todd. Looks like we are making progress, thanks.

I'm not sure that I want to pay for another recone of these drivers plus all the shipping. =(
Having already done that. Will have to think about it. It's a chunk of change.

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Well having said that I think the responsibility lies on Bill's shoulders.After all you sent them in for a re-cone and remag wouldn't that be Bill's responsibility to make sure they were re-charged correctly.Bill's good people I think you will be OK Pano ;)

Yes, I'm sure we will get this all sorted out just fine. Todd has found us some very useful information. A learning experience for all!

Now I just gotta see if I still have the boxes....

They have to be un-coned, then magnetized correctly, then re-coned.

What happened at Altec, Jerry Hubbard says, is that the capacitor-based remagnification unit has the ability to be switched from polarizing the magnet one way to the other. With Ceramic, you charge it with the polarity set one way, and the reverse for Alnico.

The woofers are on their way to GPA. Should be there next week.

Gonna be very interesting to see what happens when reversing the polarity. I'm keeping my fingers crossed.

I'm wondering about the compression horn drivers. They work the other way but I think that's because the coil is turned around, not the polarity of the magnet. But they still might be re-magnetized wrong. How to tell?

Great news Michael,

I guess someone just forgot to switch the machine back around after doing some ceramics? Hope no one else has this problem.

Todd, what a slueth! I knew someone had to figure it out. It just wasn't making any sense.

Michael, you'll have your woofers again. Woohoo!