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Old 5th January 2006, 05:47 PM   #21
rjb is offline rjb  New Zealand
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Martin, Can I take issue with you on one minor point?

For many of us, a US distributor is no advantage, and we have learned to deal with many dealers in many countries. Being about as far away as possible from suppliers, and with only a small local market, most HiFi products are not on demo, so choosing a product is a little more difficult here, and in similar countries, than it is in if living in USA.

However this also means not being limited by geographical restrictions, and effectively a much wider range of choice is possible. Very many excellent products are not available in the USA, and many of these are made by small manufacturers that cannot afford major distribution networks. ( You can find examples in this forum).

Personally I have never had any problem with purchasing through the internet, (with care of course), whether from USA or elsewhere.
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Old 5th January 2006, 06:03 PM   #22
rjb is offline rjb  New Zealand
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To add to my previous post, compare Jordan and Bandor. Both give excellent technical information, are similar products and are similar prices. One had (has?) a USA distributor, the other doesn't.
I have heard both, (and own neither). IMO the Bandor drivers sound better.
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Old 5th January 2006, 06:29 PM   #23
MJK is offline MJK  United States
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rjb,

I can understand your position. But for me, I have decided I am not comfortable dealing with a vendor outside the US or a US dealer that is difficult to do business with conveniently. Unfortunately, I learned the hard way. It is not worth the hassle, there are a lot of good driver products available. That is just my personal preferences.
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Old 5th January 2006, 09:25 PM   #24
rjb is offline rjb  New Zealand
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Point accepted. However I am just trying to encourage others to look outside the USA, even if it means taking a slight risk.
Regards
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Old 6th January 2006, 02:13 AM   #25
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Feastrex makes me think of a Tyrannosaurus at a buffet, which wouldn't be a bad marketing idea. I'm inclined to like products featuring a dinosaur based theme.
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Old 6th January 2006, 10:21 AM   #26
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Does that mean we can throw the marketing types with a less-than-sound grip on reality to the dinosaurs? (No offence intended to anyone engaged in that worthy profession who actually speaks the truth)
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Old 9th January 2006, 11:17 AM   #27
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I just got back from CES, my first time to attend any audio/electronics show anywhere, and I got to hear some of the Feastrex drivers for the first time, including both the new Naturflux model under discussion here and also a 5-inch field coil model that had the yoke and pole piece milled from a single piece of Permendur.

Before leaving for CES, I emailed Bill's calculations to the engineer who designed the Naturflux driver and when I got there he confirmed that there is nothing wrong with Bill's calculations; rather, the drawing is an inaccurate representation of the magnetic circuit. In retrospect it would have been prudent for them have stated that it was just a conceptual diagram and not drawn to scale.

After CES had closed to the public for the day, the folks from Feastrex were quite fortunate to be able to spend well over an hour in a private session with Dr. Wolfgang Klippel and his associates, who have developed a truly outstanding, powerful, and very in-depth system (both software and hardware) for analyzing audio transducers and diagnosing the problems in them. Most of the capabilities of this system are, frankly, well beyond my comprehension, which is to be expected since I lack the requisite technical background. The engineer who designed the Naturflux driver is not all that great an English speaker but due to Dr. Klippel's use of extensive charts, graphs, and internationally standardized scientific terminology in explaining the analysis that their system had performed on the Naturflux driver, at least the engineer was able to understand the bulk of what had transpired. Anyway, among the things confirmed by that testng session there are two items that I would like to share here:

1) The behavior of the driver's suspension exhibited by far the greatest linearity that they had ever seen. It was not perfectly linear, but it was very, very close -- and typical modern-day cone transducers have suspensions that are far from linear. Now the fact that they had never encountered such linearity before is a shame, because apart from the Naturflux magnetic circuit itself, there is probably NOTHING in the driver that wasn't developed about 80 years ago, and widely used at one time. As far as the suspension is concerned, the Feastrex drivers are using materials and methods that have simply been abandoned and forgotten by the vast majority of loudspeaker manufacturers in favor of alternatives that are perhaps much cheaper and easier to implement, but to the detriment of performance. In that sense, the fact that the Feastrex drivers have outstanding suspensions stands as a sad commentary on the general state of speaker manufacturing today. "If it ain't broke, don't fix it." But I guess if the manufacturers don't keep fixing stuff that isn't broken, they won't have any "sizzle" to announce to the customers at each year's CES . . . (although the problem predates CES by many decades)

2) What Dr. Klippel found to be even more unusual than the linearity of the suspension was the fact that distortion of the flux at the voice coil gap was for all practical purposes non-existent even at the highest input level tested. [The driver is rated for 15W continuous but we stopped at 10W just to be safe, since the driver was being operated in free air.] He said it measured 0.25% but that one might just as well call it zero. And he added that this level of stability is totally unheard of. [Although it should also be remembered that alnico is generally more resistant to flux modulation than more commonly used permanent magnetic materials such as ferrite.] Now the folks at Feastrex and I can think of nothing to which this might be attributable except the new spherical yoke -- the Naturflux magnetic circuit. And, those measurement results are concomitant with the theory that gave rise to this innovation in the first place, and also with the fact that the driver just plain sounds better. Naturally the people from Feastrex were very happy at this apparent confirmation of the efficacy of their innovation.

Now, I don't want the above to be construed as painting an overly idealistic picture of the Naturflux driver. As I said, most of the analysis went right over my head, and I don't have any comparable analyses of other drivers with which I can make comparisons. One thing that did become clear to me is that there are a good dozen or more distinct types of distortion that can (and do) occur in audio transducers, and these various forms of distortion are not all of equal importance in all situations. So simply because a few types of distortion were measured to be close to zero, it does not follow that the driver is by any means to be regarded as "distortion free." On the other hand, since flux modulation is a leading cause of distortion in any dynamic loudspeaker, the Naturflux magnetic circuit would seem to be a genuine advance and not just more marketing "sizzle."

My ears were favorably impressed by what I heard. To put it in some perspective, my personal Feastrex drivers have the older more conventional type of yoke made of pure electrolytic iron, with an alnico magnet twice the size of that used in the Naturflux model, and a Permendur pole piece. As much as I like my drivers, I (slightly) preferred the sound of the Naturflux model I heard. Furthermore, I had been under the impression that the prototype units being played at the CES booth were made of pure iron, but I later found out that the yokes had in fact been cast from pig iron as a matter of expediency for protoyping. Since pig iron has a carbon content of about 4% and considerably poorer magnetic permeability than pure iron, the actual production units, which will indeed use pure iron, should sound better still. The Naturflux drivers, while still expensive, will cost only half of what my drivers cost . . . I think some of the early buyers of the older model will not be happy to learn they could have saved half the cost by waiting for the Naturflux model . . .
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Old 9th January 2006, 11:42 AM   #28
Vikash is offline Vikash  United Kingdom
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A spherical yoke? Now that does sound interesting finally.

Thanks cdwitmer for some nice feedback. What were the T/S, and FR response curves your observed? What about distortion levels and break up modes?

If you could get any more info on the spherical motor design, that would be particularly interesting to me and probably Bill.

I was under the impression (might be very wrong here) that many drivers in fact opt for progressive suspension as opposed to linear? How does this linear suspension work? and what forgotten technologies have they bought back?
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Old 9th January 2006, 11:46 AM   #29
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I expect that's why they're limited to 15W, so they don't have to use progressive suspension to control excursion, its main use.

Will Feastrex be publishing this measurement data?
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Old 9th January 2006, 02:59 PM   #30
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I expect that Feastrex will reveal data about T/S, FR response, distortion levels, etc. Obviously they will need to because they seem to be planning to sell bare units in any quantity, in addition to finished loudspeakers. It was at the end of a long, hard day and I was struggling just to process what was being said and interpret into Japanese for the folks from Feastrex, so I never was able to take time to confirm those stats, even though they interest me very much. But Feastrex does have all the data that was collected at that time.

In the meantime, FWIW, the Qts of my drivers is about 0.3, the f0 about 80Hz, and 2nd and 3rd order harmonic distortion are about -30dB at their worst, and about -50dB on average. The frequency response curve indicates that the drivers stay within 5dB of 95dB/1w/m from 80Hz to 20,000Hz, and fall off steeply outside those extremes. I would be surprised if the corresponding parameters of the Naturflux driver are much different from what I just mentioned . . .
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