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Old 16th October 2007, 07:14 PM   #121
Bill F. is offline Bill F.  United States
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Anybody notice anything strange . . . ?
I had a similar reaction when I first saw it--see my take starting in post 8.

None of this is to say they don't sound good. It's just a little mystifying...
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Old 16th October 2007, 10:39 PM   #122
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Always useful to get an independant view. Cheers for that Clark.
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Old 17th October 2007, 06:55 AM   #123
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I had a similar reaction when I first saw it--see my take starting in post 8.

None of this is to say they don't sound good. It's just a little mystifying...
I saw your the model you made, thanks for the FEMM tip! Excellent piece of software. I have a question about the model: What mesh size did you use for the air? While playing around with FEMM I noticed that a coarse mesh results in very few 'air points' in the gap, this seriously affects the results. As a solution I created an air block in the gap with a very fine mesh.
A fine mesh also allows you to plot the flux density along the gap.
If the FEMM results are any indication of what's going on in the gap, it seems very difficult to get a homogenous flux in the gap. The results of my FEMM play can be found here .

Back on topic: Mystifying is exactly the term I was looking for. From what I read about these drivers they're excellent, sound as well as craftsmanship. They don't need fancy advertising.
Which leaves the question of who came up with that drawing and why the engineer didn't kill it.

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It's understandably just an illustration.
I know, but this is no reason to completely ignore the laws of physics.
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Old 17th October 2007, 11:53 AM   #124
Bill F. is offline Bill F.  United States
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I posted that sim a while ago, and I'm not sure I saved it, so I can't answer your question about mesh size. I remember that I wasn't using extremely fine meshes for the sake of time. Your findings about how mesh size broadly influences the calculated flux densities are very interesting. Next time I model, I'll be sure to compare results with multiple sizes.

Your little walk-through is exactly how I use FEMM as a layman--intuitively and iteratively. It's fun to tweak this and that until you end up with a ruler-flat B(x) plot. It's eye-opening to see just how much difference tiny changes can make.

At the same time, while I value FEA sims and wouldn't design without them, I don't want to hit people over the head with them, especially artists like Mr. Teramoto. I admire his drivers as works of functional art whose value has little to do with science or established metrics of transducer linearity.

I'm also open to the possibility that they sound subjectively better than some or many drivers rigorously designed by the book. Science has been able to identify plenty of transducer distortion mechanisms, but our understanding of their relative importance and how they correlate to human perception has a ways to go.

Where I draw the line is when manufacturers market via misleading pseudo-science, or just plain lies. I do not feel Feastrex does this. Their approach is an honest one, coming from the standpoint of whole-hearted intuitive artistry from a non-scientific background.

So I still say, "Bully for you, Feastrex!"
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Old 17th October 2007, 12:08 PM   #125
Vikash is offline Vikash  United Kingdom
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I agree Bill, also, what I DO like about the Feastrex motor design is the simple and intuitive concept. Anyone who has played with FEMM will know that it's often a case of coercing flux smoothly around the circuit. Using angles and corners to channel flux is the way to saturate the air gap.

The conceptual image used for the marketing appears flawed, but the idea is interesting and just look at us jumping on the designer for that!

Shall we have a go at the DIY Parthenon again Bill
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Old 17th October 2007, 12:25 PM   #126
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Your little walk-through is exactly how I use FEMM as a layman--intuitively and iteratively. It's fun to tweak this and that until you end up with a ruler-flat B(x) plot. It's eye-opening to see just how much difference tiny changes can make.
Let there be no doubt about it, I'm a layman on this subject.
I too found it quite an eye opener to see how tiny changes in gap geometry influence the linearity of the flux and what it takes to get the flux linear.
BTW, the field coil model I made bears close resemblence to a Fertin 20EX driver.

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At the same time, while I value FEA sims and wouldn't design without them, I don't want to hit people over the head with them, especially artists like Mr. Teramoto. I admire his drivers as works of functional art whose value has little to do with science or established metrics of transducer linearity
I fully agree with that. Let's not forget that the magnet is only part of what makes a great driver.
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Old 17th October 2007, 01:38 PM   #127
Bill F. is offline Bill F.  United States
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Shall we have a go at the DIY Parthenon again Bill
That was a fun dream exercise. Actually, it's another example of something whose value was more in the realm of art than science and practicality. Just contemplating such a transcendent, beastly bass device of such arcane configuration with enough X-max and power to reach out and slap you across your listening room was reward enough without ever having to build it or listen to it.
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Old 17th October 2007, 07:37 PM   #128
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Originally posted by cdwitmer


The black leather surround is visible, but the felt ring around that has been cropped . . . a very tasteful editing job for such a "real time" report.
I would be interested in a 5" Peta-certified field coil version.
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Old 17th October 2007, 11:53 PM   #129
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Click the image to open in full size.

I finished the Moosey Beavers today. Glad they finally have a name... (???) hahaha

Anyway, yeah they sound awesome. Bass is extended, fast and tight. There is no suckout. It is physical, I can feel it in my chest. Mids have some resonance which needs to be tweeked out, but overall tone is excellent. By far, the best single driver speaker I have yet heard. There is very little lacking in this.

The drivers are just screwed to baffle now, but I will decouple them next. Also dampen interior reflections, etc. The speakers make music that is alive and in the room with you. I'm glad I made them out of wood and not MDF.

Be sure to really tighten the phase plugs before playing. I heard a distortion before tightening, but they were not actually loose.

More http://puremusicgroup.com/yabb/YaBB.pl?num=1190822408/69#69

Thanks Scott, congratulations on a successful design!! Can I lift them off the floor to raise imaging height without killing the bass? I will try it tonight, but curious about your analysis of the idea.

I will do a FR on them in the next few days before tweaking. More to come.
Rich
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Old 18th October 2007, 12:41 AM   #130
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Default Moosey Beavers

Nice Job....
I really like the total pine box...
I can't wait to get the drivers in hand ...(next week)
I have a few questions:

Did you mount the drivers at 6.5 inches below the top or 5.75" ???

and what are the slot dimensions???


Thanks
Phil
Santa Fe
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