Видео

I wrote this. It's not available yet, but it should be soon through the University of Minnesota.

@@earthtoneselectronics The University of Minnesota is the owner then?

Yes, for sure, I already have that capability in the model, but it's going to take time to verify that I have the correct way of measuring boundary damping rates for weather stripping foam and other things people use!

University of Minnesota Duluth

@@earthtoneselectronics You create DMLs at the university as part of a project? if so, what type of DMLs? What type of exciters? Or, just hypothetical panels and hypothetical exciters?

@@ostrol325 I worked on this stuff during my PhD and for a few years afterwards, from roughly 2013-2020. I primarily worked with smartphone companies who were looking to integrate speakers into the case and screen of phones, mostly using piezoelectric exciters. Along the way, these models were developed for understanding the effects of exciters (or exciter arrays) on the vibroacoustics of plates. After having not thought much about for a few years I decided to develop a model for others to use when designing speakers. I don't make these speakers myself much anymore these days, outside of trying to make some really bizarre sounding large plates for art installations!

@@earthtoneselectronics Can you show those bizarre sounding large plates? And, why they sound bizarre?

It's hard to see in the pictures, but here's an example: mozartandcircuits.com/sonic-landscapes/sonic-topographies/ DMLs often suffer from sharp frequency response peaks, ringing in the impulse response, and rapid acoustic directivity shifts. Most designers (including myself) have come up with methods to mitigate these effects. If you design a panel speaker to really accentuate these effects, you can achieve some pretty interesting sounds and spatial illusions, especially with speech.

Thanks for the comment - these are all really great points. I'll try to respond in order... 1. Yes, damping is (inaccurately) set to the same value for all materials right now. You're right that acrylic has super high internal damping and aluminum/glass/etc will have very low damping (and high Q modes). A lot of these material-dependent parameters will have to be calculated empirically, which I'm hoping to do in my lab for common materials. I can also just create a user input box for quality factor as a temporary solution! The edge damping is something I can model for sure, but I'll have to run experiments to determine how accurate the model is... 2. Yeah, that wouldn't be a problem for isotropic materials. These simulations tend to be tricky for non-isotropic materials like cardboard or posterboard. For example, I published some comparisons between measurement and simulation here (acoustics.org/how-to-find-the-best-material-for-making-exciter-based-plate-speakers/) showing how weird posterboard acts. Posterboard simulations are very accurate at low frequencies, and very inaccurate at high frequencies. I'll have to do more research into how to best model that - maybe a frequency-dependent Young's modulus or something along those lines. 3. Yeah, I can generate impulse response or waterfall plots in this software. The weird part about doing that is that they are very, very location dependent - 1m away on-axis is very different from 1m away at 45 degrees. It's really different in that way from a traditional speaker. I can put that in, though, and maybe allow the user to select a measurement point. 4. Right now the output is being modeled with respect to a reference input force (0.1 J). So sensitivity is *kinda* being modeled, but just not with respect to the normal 1W electrical power input. You'd definitely see that posterboard has a higher average output than acrylic. It does make more sense to translate everything back through the exciters to a sensitivity, so I'll work on adding that in. 5. FSFS and FCFC are in there already! I've been thinking about how to model rounded edges, so I'll see if I can get that in there eventually as well.

Thanks! There are way too many publications to list, but my Google scholar account lists them all: scholar.google.com/citations?user=Dpw7u9IAAAAJ&hl=en&authuser=1

Pretty sure I used a Zoom R8 to record the guitar. I normally try to aim for 50-100 mV amplitude for "quiet" guitar playing and 200-400 mV amplitude for "loud" playing (e.g. chords). This will depend a lot on your pickups and such, though. If your voltage from the wav file is in the wrong range, you can boost it using a simple op amp circuit (inverting amplifier) or cut it using a voltage divider. You can also easily edit the amplitude of the wav file in a DAW like Audacity.

​@@earthtoneselectronics I plotted input and output impedance using a method from another video. It seems like it was done correctly. The input impedance seems too low at around 50K. The output impedance seems high at around 25K. I built the pedal and it works with my guitar and Fender Sidekick 10W amp. However it does not work with my test bench 12V car radio amp. I suspect the car radio amp is loading down the pedal. Here are the impedance measurements: ruclips.net/video/vTElvnFZGzA/видео.html

Figured it out, but thanks anyway. I would love to see more stuff like this from you!

Would you mind sharing what the solution was, in case anyone else encounters this? I haven't seen that error myself, unfortunately.

Not at all. I first used my DAW (Presonus Studio One 6) to record the DI guitar track and used it's mixdown function to write out a WAV file. I disabled all the extra options to try and get a standard PCM file as output. This file caused the input file error I cited above. I speculated that Studio One was not exporting a straight PCM format so I then used Audacity to record the DI guitar track and export a PCM file. This file inputted without error and worked perfectly. Therefore one should use Audacity to generate audio WAV files for LTspice. I was careful to make sure the output WAV file was in standard PCM MONO format.

Yah

Hey thanks! Glad to be of assistance!