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cdwitmer wrote:

I'm probably revealing my ignorance by even asking this, but I'm curious to know if a field coil ribbon tweeter could be practical. It occurs to me that if one could be made, it would be a lot safer since it wouldn't be a black hole for magnetic objects -- at least when the power is turned off

I proposed the electromagnetic as an option purely for Alex’s benefits, but I personally with my objectives did not have a strong desire to go there. If you read my examination about the electromagnet-converted Vitavox S2 driver

http://www.goodsoundclub.com/LatestPosts.aspx?ThreadID=1929

then you would know that I am a not such a huge and undutiful supporter of the field-coil idea. I am not saying that electromagnet is bad but it is as good as anything else: has own merits and own problems. The field-coil, if to drive it very hot and dissipating a lot of stray flux, might give extra 2dB to the “Water Drop” but it is absolutely unnecessary as my Macondo’s horns channels are calibrated for 109dB, and the 109dB is exactly what the “Water Drop” does. Also, do not forget that the “Water Drop” is line source and working with point source (horns) it has already a few decibels advantage at listening position. It should be also considered that to make the critical core size for the field-coil the “Water Drop” back should be much larger and I meant to keep the water drop shape as small as possible in order to minimize diffractions, the  bouncing back etc, and make the tweeter as much as possible optimum for the HF-type-only tweeter. Furthermore, with more (unnecessary) magnetic force we would not be able to make the cheeks of the gap as they are as we would need to change the entire magnetic shape of the tweeter. The tips of the cheeks are currently completely saturated and we would need to make them bigger… that would not be optimum for the given narrow gap of the small ribbon.  So, we went with perm neodymium magnet, conceding also the fact the Alex had practical knowledge what would be best magnetic force in the gap vs. the worthless stay filed and considering that the force of neodymium perfectly fulfill our objectives.

I am very much not saying that electromagnet tweeter would be a bad idea, we juts decided to do what we know already know and go to the direction where Alex has proven and predictable relationship between actions and the actual sonic result of the actions. You see, above 12.5K there is no sound in a normal science but rather a stream of noises that are should be viewed differently then sound. With the introduction of the new type of ribbons in “Water Drop”:

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=4259

we got that “crispy softness” that makes me see no needs to think about other magnets. Still, the only direction that I would like to explore is to try making ribbons to go all the way up in dynamic range like the compression drivers do but it has nothing to do with magnet. Currently Alex is working on a new type of transformer that I presume might be able to deliver what I expect. I will report it is it. So, the need for electromagnet tweeter is not on my radars. I feel that is a lot of other prominent things that should be taken care in a HF-only tweeter that I feel might make the type of the magnet to have very secondary meaning. Anyhow, if I had a second change to do the “Water Drop” again with an objection for a different magnet then, considering what I know about HF and magnets, I would go for Alnico magnets but not for the electromagnets.

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