Driver suspensions

[454Casull]

Is there any practical way to center a voice coil (and former) that is NOT affected by static friction and does not resort to the use of a spider? e.g. a sliding linear bearing can definitely locate the coil former but is affected by a small amount of static friction which would basically brick-wall any signal causing less than a certain amount of force on the coil.

I'm aware of the Hartley magnetic suspension, but there must be another way to do it all mechanically.

[cotdt]

what about the dome midranges? and dome subwoofers...

[454Casull]

I don't know that they use anything other than a conventional suspension. Never heard of a dome sub, anyway.

[cotdt]

Originally posted by 454Casull
I don't know that they use anything other than a conventional suspension. Never heard of a dome sub, anyway.

there is no spider in domes. the mark audio alpair 5 also has no spider.

[454Casull]

Didn't know that. Domes tend to perform badly after going past a certain size, though. Still, I appreciate the input.

[cotdt]

Originally posted by 454Casull
Didn't know that. Domes tend to perform badly after going past a certain size, though. Still, I appreciate the input.

what is wrong with spiders? they help provide dampening

[454Casull]

Specifically, they provide returning force and a little damping. However, they are never ideal springs, and this contributes to distortion. They do have the benefit of both returning and locating the coil former, though.

[tinitus]

Fore "spider" you can use an arrangement of threads
Works fine but maybe not ideal fore big Xmax

[John Sheerin]

Originally posted by 454Casull
Specifically, they provide returning force and a little damping. However, they are never ideal springs, and this contributes to distortion. They do have the benefit of both returning and locating the coil former, though.

You can make spider-like suspensions (something with rolls) to act very, very close to an ideal spring over a given excursion range if you design it correctly. That doesn't mean there won't be other problems - resonances, etc. Anyway, typically you'd want a flat spider (no cups), and smaller radius rolls near the voice getting larger towards the OD. However small tweaks can sometimes make significant differences in the compliance curve. Another thing to consider is that unless you're trying to push the driver to its limit, the distortion produced by a spider is typically not high order so will not be as audible as other issues. Another thing to consider it that even if you have a non-linear driver suspension, if you are putting it in a relatively small enclosure where the enclosure compliance swamps the driver compliance, air is a pretty linear spring (unless, once again, you are going to the limits - having a really small enclosure and moving the cone enough to significantly change the volume of the enclosure).