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Re: Warfedale super 12 as/al woofer

Posted by Bold Eagle (A) on March 28, 2007 at 05:49:11

In Reply to: Warfedale super 12 as/al woofer posted by zman on March 27, 2007 at 19:53:21:

Finding a new surround is going to be a challange, as the Super 12 FS/AL has a larger cone than most 12" speakers, more like a 12.5". Foam is somewhat stretchy, so you may be able to make a standard 12" foam ring work.

Way back when, I had one of these. It's a full range driver with excellent sound and a great midrange. The magnet is really big and really powerful, and there is LOTS of stray flux. Keep it well away from TV's, floppy disks, credit cards, etc. I could open a pocket knife blade with the magnet!

It's Alnico 5 with Puron end plates. Puron is a very high quality iron with low hysteresis. If I recall correctly the magnet alone weighs 196 oz. The 17,000 Gauss flux density is the saturation level for Alnico 5. The idea of the high flux density was to get the best possible control of cone motion for the best transient response. G. A. Briggs wrote several articles showing scope photos of tone bursts reproduced by Wharfedale speakers and by others. The Super 12 was always the very best.

You probably don't need a mid, given the full range design, but a good 3/4" or 1" dome tweeter with a high crossover point would help. I had several Wharfedales back in the 50's and early 60's, and the tweeters were not my cup of tea. The speaker is fairly efficient, but I don't have a good idea of the sensitivity. You'll probably have to figure it out by comparison to other speakers of known sensitivity.

Because of the very high flux density, the speaker has a LOT of back-EMF. So, in spite of a low resonance, the bass is pretty anemic unless it gets some help from the enclosure. Wharfedale recommended a ported enclosure with a "bass filter" built in. The enclosure was around 6 cubic feet. Port was at the bottom front, and just above the port was a thin plywood divider with lots of parallel saw cuts in it. Wharfedale called it a filter, but it may have been a resistance element to add some loading to the cone, or to prevent booming.

Unless you can find plans for the correct enclosure, porting is going to be a trial and error process.

The Super 12/FS/AL was a very good match for a 15" Karlson Koupler. Apparently the free air resonance was too low for a 12". With a Karlson, you'd only want a tweeter. The Super 12 has a wonderfully smooth and lifelike midrange.

Jerry

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