Adding super magnet to tweeter; any experience?

[elac310]

Hello all,

Powerful neodymium magnets are for sale on Internet (Bay etc) under the name "killer magnet", "neodym magnet", "super magnet" etc. Shapes available include for instance disks of 80x20 mm (that can reportedly lift 600+ pounds).

Question: has anyone tried to stick one of those on the back of a tweeter or high frequency driver and if so, what were the observations? I'm tempted to get a couple and stick them on the back of my Beymas cp21 to experiment ...

I've read that some earlier experiments on various types of speaker drivers have not been very conclusive (+1dB max, slightly lower Qts in case of use on a woofer etc.) but if I remember, the extra magnets used by experimenters where very basic, weak ferrite ones, not these very strong ones.

Chris.

[Robh3606]

Once the magnetic assembly gets saturated that's it right?? I would assume it's real close as it is no??

Rob

[elac310]

Good point.
I could imagine, however, that there is still some margin on every design (not to mention cost considerations when it comes to mobilising material, powerful and heavy magnets).

If one takes the Beyma, this is suposed to be a copy of the famous JBL slit tweeter (075 aka 2405) ; however, I understand the magnetic flux is about 10% higher on the JBL - the magnet is also bigger in fact. So if there is some margin on the JBL...

[tinitus]

its usually used to "eat" magnetic field

remember to mount it so that it repells the back pole plate
(well, thats what I have been told)
once touching the pole iron it should stay, but only just
still need additional fixing
after mounting, apply some glue around inner hole edges
and maybe some taping around it too, if possible

I only experimented with woofers, never tweeters
though, my Vifa XT19 tweeters are factory mounted with such additional magnet

[tinitus]

Originally Posted by elac310

however, I understand the magnetic flux is about 10% higher on the JBL - the magnet is also bigger in fact. So if there is some margin on the JBL...

maybe poleplates are less thick too, and thus still matches the smaller magnet

[Robh3606]

All good points above. Do you know what the gap is in the Beyma? In that tweeter series 2402, 2403 and 2405 they all had a .025 gap. If the gap in the Beyma is wider that could also account for the difference. There really are a bit of variables that could effect the gap flux.

Rob

[woody]

I tried this with the Radioshack 40-1197 and it gained about 1 db.
When I tried this with a big magnet on the super 8 sub that Apex jr.
sells the QTS was about 20% lower.
But when I tried this with a JBL pro midrange and an Audax Pr170mo
driver nothing much happened.

And I seem to rember that adding a stronger magnet than is on the driver
may realy harm the performance instead of helping it.