Where have you seen this image before?
In another patent? Not Herger's, by the way?
What about fig. 4 and fig. 5, and fig 6? Have you seen them before in another patent?
Here's another Danili Herger patent, https://patents.google.com/patent/US11758330B2/en
for comparison... Does it remind you of something?
for comparison... Does it remind you of something?
More riddles. If there is some point you want to make, just say it. Then we can have a meaningful conversation.
Eric
I was reminded (by Christian) that the proper units for stiffness would be Nm, rather than Pa. I was thinking of the elastic modulus, which has units of Pa, rather than stiffness. Of course, for a flat plate of uniform thickness, stiffness is in proportion to elastic modulus, so in the end it is the same, in terms of their ratio. That is, if the elastic modulus in one direction is twice the elastic modulus in the other direction, it is also true that the stiffness in the first direction is twice the stiffness of the other.
Crap, now I realize I should also be a little clearer myself about which direction is which. So let's say the panel stiffness in the long direction is 20 Nm, and in the short direct is 10 Nm, what is k for that case? And what is the proper adjusted ratio for the length to width, according to the rule of this patent?
Eric
Of course, we can. Your post? So, you must have seen the other patents as well, haven't you?
An exciter doesn't necessarily have to look the way we typically envision them; they can take the form that the jolly Brit demonstrated. It's as simple as that. Take a look at the last image displaying the interior components.
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The last image you are talking about just shows partially covered exciter available for a long time:
https://www.alibaba.com/product-detail/50-100W-Powerful-8ohm-Flat-Panel_1600078111958.html
https://www.alibaba.com/product-detail/50-100W-Powerful-8ohm-Flat-Panel_1600078111958.html
gorovik,
You could be right. Looks very similar. Right down to the sewn in electrical leads. But it seems they are using the 4 ohm version.
Eric
You could be right. Looks very similar. Right down to the sewn in electrical leads. But it seems they are using the 4 ohm version.
Eric
I was happy to see the impedance plot in the review of the Tefra speaker, we don't see those often shown for commercial DML's or within this thread (except from me or very few others).
It is interesting to compare it to some of my own impedance measurements, on my own prototypes. Below are impedance results for three builds with the same panel with a balsa core and carbon fiber skins. In the three versions, I useddifferent materials where the panel attaches to the frame around the perimeter. In the first, the perimeter has a foam mounting tape that is very soft, and low damping. The second has a butyl rubber mounting, and the third uses a very high damping Poron foam around the perimeter. They are plotted on the same scale as the plot above, with the curves offset for clarity. In the plots below, for comparison to the Tefra plot, you should ignore the low frequency peak at 20-30 Hz. None of my prototypes used a support for the exciter, so there is an extra impedance spike at the magnet/spider resonance frequency. That peak would disappear with a proper support on the exciter, as it apparently does for the Tefra speaker.
Now what's interesting is first, that at low frequency, the Tefra seems to have relatively weak damping, as indicated by the sharp/tall impedance peaks at aroud 70 Hz and 160 Hz, similar to the peaks of my "low damping" build. But at higher frequency, the sharp peaks virtually disappear, and it behaves more like my "high damping" build. I wonder what is the reason for that? One possibility I can imagine is that the Tefra could have more damping built in to the panel itself, perhaps via the coating used, compared to my cf/balsa panel, and that the internal damping becomes more effective at high frequency? I'm just guessing here. What other possible explanations are there?
The second interesting thing is the big hump in the impedance curve between 500 Hz and 5 kHz. I've never seen that. Could that simply be because that is the crossover region? And the impedance of the two combined is greater there? Other reason?
Eric
lekha,I suppose that's why they just covered it up. Really?!
I never know what you mean! That we are idiots for thinking that is the one they use? Or that they are idiots for thinking they "hid" it with the tape?
I do like the double spider shown in the image, and which described in some of those patents ("centering washers" I think they called them). Seems more effective than a single spider at keeping the voice coil aligned.
Eric
This is how I would interpret it Eric. It would be great to try real life measurements, but I have not searched for it yet. You might have posted some measurements yourself.
If you consider plywood, the stiffness in the (normally used) long direction should be higher than the short direction because of the odd number of plies. Now if we use your figures - the stiffness is 20MPa in the long direction and 10MPa in the short direction, then
k = 20/10 (Long/Short) = 2
That gives a new panel ratio of
9*2/5 = 18/5
Much in line with your aspect ratio preference for plywood panels (3:1 or higher)
If you would use this new ratio for plywood then that would give a panel of 1080 x 300, compared to 1200 x 300 of the Tall Blondes.
So, yes, I think this ratio can work.
If you consider plywood, the stiffness in the (normally used) long direction should be higher than the short direction because of the odd number of plies. Now if we use your figures - the stiffness is 20MPa in the long direction and 10MPa in the short direction, then
k = 20/10 (Long/Short) = 2
That gives a new panel ratio of
9*2/5 = 18/5
Much in line with your aspect ratio preference for plywood panels (3:1 or higher)
If you would use this new ratio for plywood then that would give a panel of 1080 x 300, compared to 1200 x 300 of the Tall Blondes.
So, yes, I think this ratio can work.
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Hello Eric
Here are the 2 graphs of your post combine in 1 and adjusted in both scales.
In my understanding, the 2 areas pointed by the arrows "LF unit", "HF unit" show the increase in impedance due to the inductance of the exciters. The HF unit has an inductance similar to yours, while the LF unit has one much more important (or a serial one)?.
The hump shows for me also the X over area. Below is a LTspice simulation with a very simple model that matches not too badly (without spending time in adjustment of the component values + sorry the white trace of the simulation is difficult to see). To get the impedance value in the 5kHz area, my best assumption is a 8Ohm HF unit.
The patent of this exciter was shared here maybe on year ago. An other noticeable point is the motor structure with the coil above the magnet (not in a gap) plus if I remember 2 magnets. It would be great if somebody could share information about the efficiency and about the distortion of this motor...
That's what it was meant to convey, an older variant.
Not for you, as you aren't even meant to have a look at it, but from the local crowd, who are rather sceptical. Tefra is not intended for the ordinary user, but for commercial users—conference rooms, bars, and so on. The ones that were offered to the ordinary client at agreed individual prices are never made available for review.
By the way, the other speakers do not use balsa or similar wood panels; instead, they utilise a composite made from paper. The surface is treated with a specific natural stone powder. The next version will be made from a composite of rice paper. Innovation is an ongoing process.
Regarding the patents, you would notice that D. Herger is mentioned as the inventor... Sotis AG is a patent and business agency.
The coil can be positioned vertically against the magnets, as in a standard speaker driver, or it can be flattened, as is vehemently disputed here...
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What lekha might be trying to say is that the drive unit in this picture is not standard.
It has two sets of lead out wires in the spider.
I doubt it is a duel coil.
Probably is some sort of tweeter midrange in the centre of the coil.
But I think he is in a long winded way trying to hint that it could be a flattened coil of some sort, maybe.
Hopefully we can all get some sleep now 😴 🙏
Steve.
That interesting article was this,
And if you are referring to the image below, yes, the misdirection was intended.
You can, of course, go to sleep at 6 p.m.😉
And there were no "two sets of lead-out wires in the spider" in that article. What was interesting there was the turbine effect, and the transverse sound wave.
And if you are referring to the image below, yes, the misdirection was intended.
You can, of course, go to sleep at 6 p.m.😉
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twocents
I'm sure now that you are correct. The US patent application here:
https://patentimages.storage.googleapis.com/36/6e/0e/4acfab59c6b64a/US20220345821A1.pdf
has clearer wording, which confirms your interpretation:
I am working on a little analysis with FEM to see just how using this ratio actually works with respect to the distribution of natural frequencies. But I wanted to be sure that I was using the "rule" properly before I tried assessing it.
Eric
Here again, I don't think anyone actually disputes that. There are those that are skeptical that it offers any significant advantage over a typical exciter, but none that dispute that a flattened coil (with an electrical current in a magnetic field) could be used to drive a panel.
Eric