Diy speaker mag swap ...

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[454Casull]

I assume those discs help stiffen the cone?

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Originally posted by 454Casull


those discs

somthing like the fostex hyperbolic paraboloid -


http://72.14.253.104/search?q=cache:...&client=safari

Physical Characteristics
The Fostex NF-1A active monitor’s enclosure is a two-way, bass-reflex design with dual flared elliptical ports. The enclosure is made up of 7/8-inch-thick vinyl-covered MDF on the sides, while the black-painted baffle includes an additional 1/2-inch of thickness at the woofer. Transducers are recessed in the baffle and secured with wood screws. The interior sides and top of the cabinet are lined with 1/2-inch Fiberglas, while the back and bottom each include “hyperbolic paraboloid” deflectors to damp standing waves and any internal back waves reflecting inside the enclosure. The amplifier compartment is isolated from the rest of the enclosure by the 7/8-inch-thick MDF.


On-axis impulse response: Impulse response shows decent alignment of woofer and tweeter but not great. Good decay, but not the smoothest.
The visually impressive woofer design of this near-field monitor blends new and old technology: The hyperbolic paraboloid cone design, which Fostex labels HP, is based on well-established structural engineering principles. Harry Olson used these principles to design a similar complex-topology loudspeaker cone for the RCA LCA-1A studio monitor, and JVC also introduced a speaker system using a similar woofer cone in the 1970s. Today, to minimize weight but retain tensile strength, soft drink companies manufacture plastic bottles with hyperbolic paraboloid bases. The HP cone offers extended bandwidth (no puckering on the extreme low frequencies and reduced breakup on the high end) and the cone and surround allow this transducer to operate well past 5 kHz.

The foam surround is also well-thought-out. Fostex calls it a UDR (Up Down Roll) tangential edge, which comprises alternating up half-roll, down half-roll sectors, divided by a tangential wall. (Tangential crease or pleat surrounds have long been used on tweeter and compression driver diaphragms to minimize diaphragm rocking modes.) Other key features on this cast-aluminum frame woofer are double-stacked flat 33/4-inch-diameter spiders, a 11/2-inch-diameter aluminum bobbin voice coil assembly and a vented pole piece. The conventional ceramic-magnet motor structure is magnetically shielded by a bucking magnet and shielding can. Terminations are 0.205-inch and 0.110-inch male tabs.


http://mathworld.wolfram.com/HyperbolicParaboloid.html


http://en.wikipedia.org/wiki/Paraboloid

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