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Multi-Way Conventional loudspeakers with crossovers

Corrosion SEAS Magnesium Drivers
Corrosion SEAS Magnesium Drivers
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Old 28th December 2017, 11:33 PM   #81
ICG is offline ICG  Germany
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Location: I had a Déjà Moo - I've seen that BS before!
Okay, airbrush is an option I haven't thought of, that could work. Nonetheless, you still need a lot of practise on it.
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Old 28th December 2017, 11:35 PM   #82
globalplayer is offline globalplayer  Germany
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You can practice using paint. Of course not on the driver.
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Old 29th December 2017, 04:26 AM   #83
navin is offline navin  India
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Quote:
Originally Posted by Zvu View Post
If old drivers are destroyed after let's say 15 years,

Protect everything with tape and spray it on.

The thing is that spots didn't happen on the whole cone but on some places.
If I can get 15 years life out of a pair of speakers I will be happy. I will be 55 in Feb and another 15 years would mean I'd be 70 before my speakers die.

Yes I will have to protect the rubber surround and every thing that it NOT the cone itself (including the gold center dust cap).

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Originally Posted by ICG View Post
Even if my estimation of the added weight would be off by x, it clearly shows what happens, the simulations are very accurate regarding
such things. Everyone should judge for themselves if that's acceptable or not.

And you can't observe the back side, if the voice coil heats up, it may get removed on some areas without notice, especally on the back side.

Don't forget your mids and rear speakers, they will sooner or later have the same problem.

Oh, another thing, if you use the rears in the 'wrong' way, you should take out the ribbon and re-mount it 90° rotated, that will give you a much better dispersion.
Yes I agree that the simulations are very, very, good. In the years before 1995 I had LMS and LEAP (LienarX) and used these to measure and design several speakers (about 30 pairs). Today (20 years on) I am sure computing power offers very accurate results.

I will discuss heat resistance with 3M. I have already contacted the technical people at 3M-India and they are willing to send me samples of all the products they sell locally. Their reply was "try everything and buy what works for you".

My rear speakers (W16NX) for this system are aluminum cone. My bedroom rear speakers are Mg cone but oddly enough they are not affected. These speakers were not veneered and polished but wall papered (with the same wall paper we applied on the wall. (see pic). Thing is we let the polish dry for 2-3 weeks before installing the drivers. So I don't think it is the polish.

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Originally Posted by ICG View Post
Well, you have to do a lot of taping and you have to be extremely precise with it.

The issue is, you have to cover the back of the membrane too! The opening of the basket and the resulting angle to spray it on is very bad for spray painting

Like I said, a hell of a work you have to do perfectly for an unsure outcome, high risk and effort for a medicore outcome, which you probably only see in a few years.

Your arguments are good but not far sighted enough IMO. You don't 'only need to protect it a bit better', you need to protect it lasting.
Yes I realize the effort involved. I don't shy away from effort. I don't think any of us DIYers do (or we'd be buying speakers instead of building them).

I can't spray on the rear as the basket will get in the way. I would have to use some sort of foam applicator. So I will be testing the thickness of wax applied by a foam applicator as well.

Given my age, if I get 15 years life I am content. I will get the itch to build a new pair before that anyway (my wife calls it a disease ).

Quote:
Originally Posted by cumbb View Post
More than THD, TMD, frequency-response... Wooden and metal are complement. Do not forget to clamp;-)
You mean to clamp the rear magnet to the backside? Oh I did not do that for this pair. I did do it for the bedroom pair (which uses ScanSpeak 18WU woofers).

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Originally Posted by ICG View Post
..and (besides the actual truth about these 'facts') how does that help preventing the corrosion?
I am about that too!

Quote:
Originally Posted by Zvu View Post
Old drivers are good enough for testing if it will hold or not. ...There are a number of clear coat varnish for Al and Mg. If it holds on to a car rims in heavy conditions, it'll hold on to a cone.

But if my theory is solid it would solve a problem for Navin and at least a few others. Airbrush can get the job done.
Airbrush is a brilliant idea for the front of the cone. The rear might require a more "precise" method given that the basket is in the way.

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Originally Posted by ICG View Post
Okay, airbrush is an option I haven't thought of, that could work. Nonetheless, you still need a lot of practise on it.
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Originally Posted by globalplayer View Post
You can practice using paint. Of course not on the driver.
Another brilliant idea. You guys are in "the zone" today!

Thank you ALL of you! I don't know how far I would have gotten without your support.

I sincerely hope others on diyaudio also benefit from this experience. There are several Mg Excel SEAS builds. Take this one for instance.
DIY my dream come true and ...go!

In my email to SEAS I did link this discussion so maybe they can take care to protect their drivers better as well. I intend to resend the mail I sent yesterday to SEAS on Jan 2nd so that this does not get lost in the volume of mail they have received over the holidays.
Attached Images
File Type: jpg rear bedroom.jpg (23.7 KB, 143 views)
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Last edited by navin; 29th December 2017 at 04:32 AM.
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Old 29th December 2017, 05:45 AM   #84
diyaudnut is offline diyaudnut  United States
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I would really wait to hear from SEAS.
Its an active product they sell and has major corrosion issues in some parts of the world.
They have either figured out the right protective coating or should advice you on how to protect your drivers.
I would be surprised if they refuse to take this seriously.

Last edited by diyaudnut; 29th December 2017 at 05:47 AM.
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Old 29th December 2017, 08:32 AM   #85
navin is offline navin  India
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Quote:
Originally Posted by diyaudnut View Post
I would really wait to hear from SEAS...I would be surprised if they refuse to take this seriously.
I pray and hope that you are right. They might surprise us all in which case I would be the happiest to report the same.
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Old 29th December 2017, 10:02 AM   #86
navin is offline navin  India
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One thing that came to mind is that SEAS has been making these Excel Magnesium drivers since 2004 or maybe even earlier. I remember this superb build
Seas Excel TMM (finished) from a few years ago
and this one that is current...you got to see the whole thread - the internal bracing and woodworking is simply fantastic.
DIY my dream come true and ...go!

I would think that by 2012 (when I ordered my drivers) they would have sorted out this corrosion issue. Maybe it occurs far too rarely?
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Last edited by navin; 29th December 2017 at 10:05 AM.
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Old 3rd January 2018, 09:57 AM   #87
navin is offline navin  India
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Update Jan 3rd 2018:

I have re-emailed SEAS. I suspect my earlier email might have got lost in the volume of emails they received over the holidays.

I found the email IDs of Håvard Sollien their Product Manager, Claus Futtrup (who is the CTO), and Jorge Lopez (who is in R&D). Since this is a technical problem, I assume these are the right guys.

Meanwhile I still wait for the ceramic coat from someone who treats Mag-Alloy wheels for Super Cars.
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Old 3rd January 2018, 10:00 AM   #88
globalplayer is offline globalplayer  Germany
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Sometimes a phone call will be better than just an email.

Ceramic coat.
Not bad.
I wonder how it will affect the sound.
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Last edited by globalplayer; 3rd January 2018 at 10:05 AM.
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Old 4th January 2018, 07:54 AM   #89
navin is offline navin  India
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Quote:
Originally Posted by globalplayer View Post
Sometimes a phone call will be better than just an email.

Ceramic coat.
Not bad.
I wonder how it will affect the sound.
I got a reply from SEAS. I am quoting the relevant sections below. The rest is about contacting my sales channel.

"The white powder is Magnesium corrosion, which stems from the speakers being stored (or used) in a hot and humid climate. I think you know this already. The corrosion doesn’t affect performance (until there’s an actual hole in the cone), but we admit it doesn’t look good. The only way to prevent this from happening is to make sure the speakers are kept in a fairly dry condition at all time.

Please go through the sales channel to process your complaint. Maybe they’ll give you a good offer on the replacement drivers, as you suggest. SEAS doesn’t manage end-users directly, since we’re strictly an OEM business. Our limited manufacturer warranty is 3 years from production date...."


I guess the warranty is only for 3 years so I will have to rely on whatever discount the original sales channel I used to buy these drivers provides. I have been offered a discount of 25% from the sales channel but I was hoping that SEAS would have taken some responsibility. Oh well.

To reiterate I have 2 choices:

a. Ensure the coating I have found protects the drivers without significant effect on T/S or sound and avail of the 25% discount.
b. Do a complete redesign using other drivers. This would mean no discounts.
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Old 4th January 2018, 08:36 AM   #90
globalplayer is offline globalplayer  Germany
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Imho Seas could be more "cooperative". One reason more for another brand/speaker.
A identical replacement will probably "go down the same route" after some time without coating. You can't prevent the coating from affecting the tsp. Therefore I would look for other more durable candidates.
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