Crude looking woofer - magnet misalignment

[Jeff_C]

Hi

When I first took my AR-16 woofers out of their cabinets 20 years ago, I was slightly surprised at how crudely made they looked, although they sounded great. Since reading some of the threads on CSP I have seen mention that worn stamping machines and such can give rise to slightly poor looking speaker baskets and that it is no big deal, but I am curious about the magnet assembly on one of the woofers in particular. Unfortunately I did not take a photo of it before restoring the speakers a couple of months ago, so I have found a picture of a similar woofer albeit 10 inch instead of my eight.

The magnet at the back of the my 8 inch woofer has a square magnet, one woofer looked normal (in its own crude way) the other had the end square piece of metal twisted at about 20 degrees to the piece it was attached to below. Curiously if I look closely at the speaker image reproduced from the 'net it looks like it is twisted 1 or 2 degrees.

So, is there a reason for this?

Jeff

[RobHolt]

Hi Jeff,

I don't think the rotation of the magnet assembly is a problem. The magnetic forces are acting on a circular voice coil aligned in a very small gap around the pole piece. So long as this is all correctly aligned there would be no issue. If the assembly were dislodged to one side then you would certainly get misalignment.

On the baskets, yes they look horrible and it's interesting to learn that's likely due to old and well used stampers. Again, if the vital parts are all properly aligned, no problem.

Something you might try is to glue pieces of acoustic foam on the inside of the basket struts. I used 8mm acoustic tile foam which fits well leaving plenty of space for cone excursion. It will help reduce reflections from the inner surface of the basket and gives a slightly smoother response at the top of the driver output. You can also bitumen damp the outer basket.

I used these. UK but the package is small and light so postage would be low.

http://www.efoam.co.uk/foamshapes.php?cp_n=adwords&cp_a=CutToSize2&cp_k=Efoam&gclid=CMO0ooDOybwCFSvHtAodG1oAVg

Whoops - sorry you are in the UK

Never mind, still a good link for our international friends.

Jeff, I've got some spare foam and bitumen which I'd be happy to post FOC.

[Jeff_C]

Thanks for that reassurance Rob and the offer to send me some foam to try. I've sent you a PM.

[RobHolt]

PM received Jeff.

Will get those posted tomorrow.