Keith Kidder's 4eleven

[Zaph]

Zaph, you refered to the issue of the cupped spider rather than a flat spider in terms of inducing distortion.....could explain that a little further? How can you have a flat spider, when it needs to movwe up and down a certain amount? Thanks. Greg

Well, lets start out by saying a spider needs to be spaced away from the top plate of the magnet to avoid damage during maximum inward Xmax. There are several ways it can get that spacing. The first is with a plastic spacer ring, popular on subwoofers. The second is with a specially designed frame that supports it the right distance. The better designs like this (Scan Speak, Seas Excel, etc) allow venting under the spider. And the final method is with a cupped spider, which is just like a normal spider, but it's got sides to it, formed right from the same material as the rest of the spider. Including the sides, the spider has a cup shape.

See the attachment below. Flat spiders have no dimension C because they are designed to mount to the frame or to a spacer piece. Cupped spiders do have a dimension C, and the bigger the dimension, the worse the distortion.

Cupped spiders cause distortion because they become non-linear as excursion increases. The sides flex in and out while the spider flexes up and down. The problem is that the outward flex rate is not the same as the inward flex rate. This "Tension variance" directly affects voice coil movement, and then you have distortion. So, I say there is no such thing as a good cupped spider. They are a workaround for a poorly designed voice coil length and frame combination.

Flat spiders generally have a symetrical up and down movement, resulting in lower distortion.

And while we're on the subject, progressive spiders lower distortion even more with a linear increase in tension as the voice coil gets close to the design Xmax.

 

[27ph]

Check ut the Audax midranges. I was recommended the HM130C0.

vH pH

 

[ScottG]

though the HCM130C0 is a bit pricey I've heard this and its good..

http://www.partsexpress.com/pdf/296-063.pdf

cheaper alternatives to consider that have similarly slightly def. output and less than flat on-axis curves:

Focal Access 5A:

http://www.zalytron.com

and the GR Research M-130:

http://www.gr-research.com/drivers.htm#grt1

with budget constraints I'd prob. pick the Access 5A, especially considering the current sale price.