How strong magnets do I need for the front grille?

[Rullknufs]

I was thinking of making a front grille for my floorstanding speakers.
The frame would be of either MDF, birchply or some kind of hardwood. I was planning to glue magnets to both the grille and the inside of baffle.

The baffle is 18mm thick and I don't think there's anyways I can remove any material on the back side of the baffle now that the cabinet is glued and done already. The speaker holes are only for 6.5 inch woofers as well.

I have been looking at some round neodymnium magnets, for an example these Super Strong Rare-Earth RE Magnets (20mm x 2mm / 10-Pack) - Free Shipping - DealExtreme

Would they be strong enough? Or is there any way I can calculate how strong they are at the specific distance/gap? I am not afraid of doing some pretty high level maths.

Are there any specific magnets you would recommend? Or any other tips in general regarding making front grilles?

 

[balerit]

That's a bloody good idea, those magnets are pretty strong, I would go for the 10mm by 5mm of which I have about 10.
Mac

 

[Rullknufs]

5mm is a litte thicker than I'd like. I want the grille to be as close to the cabinet as possible, so 2mm would be better I think. And since I have space for 20mm diameter magnets, wouldn't they be a better choice?

 

[oz7aff]

If you want the grill close to the speaker, then you can use Velcro stripes

Velcro | The Networking Nerd

 

[Rullknufs]

If you want the grill close to the speaker, then you can use Velcro stripes

Velcro | The Networking Nerd

Yes, but that means I have to put Velcro stripes on the baffle which isn't very aesthetically appealing. I want a clean look with the grilles off, therefore I want to use magnets since that's the most invisible solution.

The grilles will be off most of the time but some times I might have visitors. And in about two months my speakers will be at a school exhibition so some kind of grilles must be ready by then to protect the drivers from meddlesome schoolkids.

 

[balerit]

I'm sure they'd be fine. I was thinking that you would drill holes in the speaker deep enough for the magnets to be glued in. If you look at my avatar my speakers don't have grills but if they did that's how I'd do it.

 

[sofaspud]

+1
Put a little glue in the hole and tap the magnets in with a rubber mallet, or a small wood block between them and the hammer. That should work great, look nice, and be a permanent install.

 

[Rullknufs]

That's how the baffle and braces look like. I don't think I'll be able to drill any holes on the inside of the speaker unless you come up with some crazy idea of doing it.

And yes, the cabinets are permanently glued up and done already so the only way to access the inside is via the speaker cutouts.

 

[sofaspud]

Inside? I was thinking just the four corners of the baffle and four corners of the grill frame. Done right, the magnets could be flush with each surface.
If the grill will be full-length, you may want more than four per, but the idea is the same.

 

[phase_accurate]

I don't think I'll be able to drill any holes on the inside of the speaker unless you come up with some crazy idea of doing it.

You'd best hire some dwarf to drill from the backside of the baffle !!!

This one here also has neo magnets on the backside of the baffle. They are about 3mm thick and 8mm in diameter. If you put them directly together they are quite difficult to take apart again by hand. I drilled holes on the backside of the baffle in order to place the magnets grill and 4 pieces inside) is just right to hold a light grill.

http://www.d-amp.org/include.php?path=forum/showthread.php&threadid=1192&entries=17

Regards

Charles