Check it now Dave. I had to do it with my phone so not sure I did it right.
Eric
Christian,
I'm not certain that I understand what you are saying/asking, but the measured impedance did show peaks around 2kHz. The first was really small, and the second a bit larger. The two peaks did appear at a bit lower frequency, and smaller peaks, in the measurement, than in Dave's revised hi res sim.
Eric
Christian...I think it's a whole nightmare of complexity
The link in Post #1 is still not the correct one. I used the link in Christian's Post #6 to download the latest version.
Eric, I think it would be good if Dave also has editing rights for Post #1 to update future links. It is as simple as asking a moderator to arrange that.
twocents,
Such little faith you have in me! Haha.
I think the link is correct now, at least it's the one Dave asked for. I was traveling for work all last week and couldn't do any editing except via my phone, which I'm not so good at. Meanwhile I did request for Dave to be given editing rights. No response just yet.
Eric
I just noticed that Dave put up a new video last month when he put up version 1.4.2. The thing I just learned is that you can toggle on/off the surface velocity plot while the simulation is running. Until now I had just assumed it had to be set on or off before starting a run.
Eric
Eric
I checked and the answer was no. The reply (in part) was this:
Allowing a user access to another users thread/post for editing is something that's never going to happen. Just the way it is.
Eric
Here are the results of my recent work to model a range of exciters... the math and everything behind all of this is something that I'm going to save for a publication, so that'll hopefully be out later this year.
first, graphs of the measured and simulated impedance when the exciters are simply stuck to a desk.
Also - graphs of measured and simulated impedance when attached to my aluminum panel. The exciters that have missing graphs are the ones that didn't survive being removed from the desk 🙁
It's interesting to note that the majority of exciters are modeled pretty well here. The DAEX32Q-8 is not well modeled, unfortunately, because it has a pretty complicated construction. That one probably needs a much more complicated model. Also, the "EX" exciters rather than the "DAEX" exciters are the ones with the plastic disc coupling surface rather than the voice coil ring, and these seem to have a much faster drop-off in impedance peak amplitudes with frequency than the ring ones. This corresponds to a drop in panel velocity and volume, so these exciters appear to work only at pretty low frequencies. I'll have to do more work on this and see if these results carry over to over plates/materials as well; not totally sure yet what to make of that.
PS I had a bunch of DAEX19CT-4's, so the simulated and measured impedances use different individual units. This can give us a rough idea of the manufacturing tolerance in these exciters.
first, graphs of the measured and simulated impedance when the exciters are simply stuck to a desk.
Also - graphs of measured and simulated impedance when attached to my aluminum panel. The exciters that have missing graphs are the ones that didn't survive being removed from the desk 🙁
It's interesting to note that the majority of exciters are modeled pretty well here. The DAEX32Q-8 is not well modeled, unfortunately, because it has a pretty complicated construction. That one probably needs a much more complicated model. Also, the "EX" exciters rather than the "DAEX" exciters are the ones with the plastic disc coupling surface rather than the voice coil ring, and these seem to have a much faster drop-off in impedance peak amplitudes with frequency than the ring ones. This corresponds to a drop in panel velocity and volume, so these exciters appear to work only at pretty low frequencies. I'll have to do more work on this and see if these results carry over to over plates/materials as well; not totally sure yet what to make of that.
PS I had a bunch of DAEX19CT-4's, so the simulated and measured impedances use different individual units. This can give us a rough idea of the manufacturing tolerance in these exciters.
Hello Dave,
Impressive collection and basis of an excellent database.
An exciter has 2 moving masses, the voice coil and the magnet. Between them the spider and force based on the current and the magnet. There are 2 resonant system depending the voice coil or the magnet is fixed. In the Xcite specification both frequencies and parameters are specified.
The plots before show the fixed voice coil situation.
Generally I am more considering the fixed magnet situation, probably as an heritage of the impedance simulation of a cone loudspeaker but also because my final use of an exciter is with a fixed magnet.
This might explain I haven't understand the parameters you gave in post 205...
Have you also considered the fixed magnet situation?
Opening one Xcite specification, I see they give a unique value of the compliance which make sense; it is the same spring if the voice coil or the magnet moves but there are 2 values of Rms.
Some weeks ago, doing impedance measurements by adding weight, I came to the observation that Rms depends on the mass or maybe something else. To explain more clearly, if I have the value Mms, Cms, Rms for one Mms situation (ie free voice coil), the simulated impedance with the according RLC circuit is pretty correct. If I increase the Mms (ie + 1 to 5g), the change of the according electrical component is not enough to get a correct impedance curve. The Rms changed.
Do you know the explanation to that?
Christian
Dave,
Any idea what's up with the 25FHE-4? The one's I have seem to be similar to your measurement. Both of mine have a peak at around 27Hz/20ohms when the voice coil is attached to a rigid mass. Any idea why the sims show the peak almost 10 Hz higher (as best as I can guess from your plot).
Oh, and any luck getting any Xcite units?
Eric
Any idea what's up with the 25FHE-4? The one's I have seem to be similar to your measurement. Both of mine have a peak at around 27Hz/20ohms when the voice coil is attached to a rigid mass. Any idea why the sims show the peak almost 10 Hz higher (as best as I can guess from your plot).
Oh, and any luck getting any Xcite units?
Eric
I have 28.5Hz/23Ohms
To give an illustration to my question of the Rms, I did this graph some weeks ago. It is a small cone speaker. I could do the same for an exciter. The height of the peak decreases when the adding mass increases and in consequence when the resonance frequency decreases.
With a constant Rms, the peaks should have all the same height.
Does it mean Rms is a function of the frequency? Leading to a nice constant Q?
Yes, I suppose, but I haven't experimentally tested that on the plates. It's a pretty simple case, though, you just set the magnet mass to infinite, so I assume the model will be pretty accurate.
Yes, possibly - these are the types of experiments that we were doing to develop the electromechanical model. There are quite a few additional components in addition to what could be considered Mms, Cms, and Rms, and several of them are frequency dependent. My model is probably not 100% accurate, but seems to work pretty well and the parameters are easy to measure. I need to write a paper about this by the end of the month, so I should be able to provide more information soon!
Probably just a typo when my student noted down the derived values. I'll have to revisit that one at some point. Could have been two different samples, not sure.
No, haven't tried yet. I have way too many other research things going on - unfortunately, this work is on the backburner right now. It's still on the list of things to do!
Yep!
Rms is frequency dependent, and there are a few other components that are as well (Cms is for some exciters). Not sure if the Q would be considered constant - it probably depends on the exciter.
Here's a screenshot from the PETTaLS "advanced" version, showing that you can simulate multiple exciters, weights (the weights are a little hard to see - they're little black dots. I'm still working on the best UI for that), radiation bubbles, etc. This simulation shows a FFFF aluminum panel with 4 different exciters near the middle (each with 1W of power being delivered to it), 4 attached masses closer to the corners, and corner stands. My main topic of interest back in the day was exciter arrays, shading functions, and varied exciter polarities, so there's a lot of playing around with those parameters that can be done with this version!
We're working to make this available through my University soon, and I'm hoping that I can let some people here have access for free so that I can get feedback. I'm still hoping to integrate support for piezoelectric exciters and sandwich boards, but as I keep saying, this is kinda on the backburner right now, unfortunately!
I'm still trying to think of a better name for the software, too. Nothing has stuck.
We're working to make this available through my University soon, and I'm hoping that I can let some people here have access for free so that I can get feedback. I'm still hoping to integrate support for piezoelectric exciters and sandwich boards, but as I keep saying, this is kinda on the backburner right now, unfortunately!
I'm still trying to think of a better name for the software, too. Nothing has stuck.
Dave,
What are the options for "stands"? How about the centers of each side? If not, I suppose one could put a very heavy mass wherever you wanta "stand", yes?
Eric