Yes, that's usually the way it works. The people who ignore math and science typically understand things better than those that apply it, right?
Eric
@spedge "all the technical people on this site have not a clue as to what they are doing" is a far from accurate or justifiable claim. There is room for subjective opinion on performance and room for analysis and technical debate. Its not a binary option. Veleric is right, as this is such a new field there is a need for careful measurement based enquiry.
Several posts deleted because once a subject gets mentioned then threads get dragged off course as more and more chime in.
In this instance it is talk of anti vaxers.
If your post got caught up in that then it too has been deleted.
From the rules:
Not Allowed:
2. Discussions of politics, ethnicity, religion, medical or other divisive issues of any sort.
In this instance it is talk of anti vaxers.
If your post got caught up in that then it too has been deleted.
From the rules:
Not Allowed:
2. Discussions of politics, ethnicity, religion, medical or other divisive issues of any sort.
Burntcoil.
I have stated clearly how to do the measurements.
But instead Eric makes a fixed point measurement at one metre ?
now he is making measurements only below 5k ?
does he want to find the problems ?
If I was giving directions and I said turn right at the roundabout then take the second left, but he turns left at the roundabout and takes the fifth right , is that my falt?
was I wrong ?
Steve.
I have stated clearly how to do the measurements.
But instead Eric makes a fixed point measurement at one metre ?
now he is making measurements only below 5k ?
does he want to find the problems ?
If I was giving directions and I said turn right at the roundabout then take the second left, but he turns left at the roundabout and takes the fifth right , is that my falt?
was I wrong ?
Steve.
Burntcoil.
I was responding to this post by andre in response to Eric's post.
I was not saying everyone technically minded person was talking rubbish.
If everyone thinks you can add another exciter on a panel without the two exciters interfering (impinging) on each other in a bad way, you are in cloud cuckoo land.
You can only hope to get the best of a bad idea, by moving the exciters around to minimise the problems so that you can try to increase wattage and and power handling
Nothing to do with the quality of the sound produced by the panel.
Steve.
Here is the answer for you 
a bit tongue in cheek
https://www.researchgate.net/public...f_multi-exciter_distributed_mode_loudspeakers
The site allowed me to just download it. It often does
I came across a very decent run down on how and where DML fits in compared with other forms
https://medium.com/@ResearchFeature...-for-invisible-sound-integration-576f751d9f73
Suppose it fits in with my own thoughts even though I haven't done anything on them. Big slabs of foam - no. Something just of adequate size to cover the spectrum that they can cover.
a bit tongue in cheekhttps://www.researchgate.net/public...f_multi-exciter_distributed_mode_loudspeakers
The site allowed me to just download it. It often does
I came across a very decent run down on how and where DML fits in compared with other forms
https://medium.com/@ResearchFeature...-for-invisible-sound-integration-576f751d9f73
Suppose it fits in with my own thoughts even though I haven't done anything on them. Big slabs of foam - no. Something just of adequate size to cover the spectrum that they can cover.Another. Some interesting general aspects in it. Edge effects and panel suspension. Those apply to all??
https://riunet.upv.es/bitstream/handle/10251/3347/tesisUPV2873.pdf
https://riunet.upv.es/bitstream/handle/10251/3347/tesisUPV2873.pdf
So I've re-visited these wood+poly panels I made a while back. I cut them down to 1 x 1 1/2 feet to center the wood section a little better. I super glued the window foam around the rear of the exciter to block the holes that run around the frame of the 24FHE's. The thickness of foam was also perfect to glue to the wood spine for support adding flex that I feel can't hurt when dealing with thin wood panel material to help quall harshness. The outer "arm" foam pieces are the last install that I like to use for support over time (I'll take the hit on damping).
The center "buttons" on the front are stuck on there with a double sided tape that I stuck to my pants first so they would be easier to remove later. They are made of the same poly foam as the outer panel and are there for more harshness nasties coming from the voice coil area, per Steve, I hope?. If you zoom in on the side shot you can see how I use the silver tape on the board and on the exciter mounting circle so that 5 minute epoxy can be used between the two and the entirety can be removed later. Remember to scuff both faces before epoxy.
I did an A-B test beside my pair of straight poly foam panels that I have been enamoured with for the past few months. I used those panels as a template for re-sizing these wood+foam panels so testing is pretty much equal except for the rear holes being covered which is a first for me.
My go to song for A-B testing is Eric Claptons, Change The World. Well, this just changed my world because I can hear what I've been missing in the clearness of his voice, the guitar twings, and all of the different percussion instruments used. The symbols when they come around are cleaner.
For sure the exciter being placed on the rear of the pure foam panel lost some clarity having to travel through that 1/2" of softer foam compared to the thin hard wood. I guess more "bright" is the term, nothing wrong with the poly's, these are just cleaner in my book. May get tired of them, who knows?
I haven't tried my wood-canvas panels with some of these 24FHE's yet, but this seems to be the same principle just not much bass as people seem to be getting from those (seems to be the canvas being attached all around to the frame has a lot to do with that). Now off to listen to Howard Jones , No One Is To Blame for starters ahhhh David Essex, Rock On yeah!!!!!
The center "buttons" on the front are stuck on there with a double sided tape that I stuck to my pants first so they would be easier to remove later. They are made of the same poly foam as the outer panel and are there for more harshness nasties coming from the voice coil area, per Steve, I hope?. If you zoom in on the side shot you can see how I use the silver tape on the board and on the exciter mounting circle so that 5 minute epoxy can be used between the two and the entirety can be removed later. Remember to scuff both faces before epoxy.
I did an A-B test beside my pair of straight poly foam panels that I have been enamoured with for the past few months. I used those panels as a template for re-sizing these wood+foam panels so testing is pretty much equal except for the rear holes being covered which is a first for me.
My go to song for A-B testing is Eric Claptons, Change The World. Well, this just changed my world because I can hear what I've been missing in the clearness of his voice, the guitar twings, and all of the different percussion instruments used. The symbols when they come around are cleaner.
For sure the exciter being placed on the rear of the pure foam panel lost some clarity having to travel through that 1/2" of softer foam compared to the thin hard wood. I guess more "bright" is the term, nothing wrong with the poly's, these are just cleaner in my book. May get tired of them, who knows?
I haven't tried my wood-canvas panels with some of these 24FHE's yet, but this seems to be the same principle just not much bass as people seem to be getting from those (seems to be the canvas being attached all around to the frame has a lot to do with that). Now off to listen to Howard Jones , No One Is To Blame for starters ahhhh David Essex, Rock On yeah!!!!!
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Steve,
The measurements at 1 meter were not intended to reproduce your observation. Rather, those where in response to the video posted by Audio Frenzy, and intended to look for any comb filtering of the sound waves in the air, rather than "on" the panel.
Regarding the previous videos of the close mic'd measurements across the whole panel, I limited those to max 5 kHz only because I thought the results were not well enough resolved above 5k to provide good information. I had not recalled that you were specifically interested in the region close to 20k, sorry.
I took another look and the results from 5k to 20k are really not so bad, especially if I used a faster (shorter) FFT. At the very high end, the natural frequencies are really close together, so they overlap a lot more than at lower frequencies, but are still sometimes distinguishable.
The videos below repeat the previous tests, but show the results from 1k to 20k, using an 8k FFT with 1/48 smoothing and no averaging.
First is the result for the single exciter. I suggest watching at 0.25 speed, otherwise everything happens too fast. One interesting thing, that was not visible when the frequency was limited to 5k, is that the exciter position is obvious, because the hf response really jumps. In this video, it happens at about 4 to 5 seconds, and the output from about 8k to 15k is much stronger than other at any other time/position.
This next video is with 2 exciters, as close to each other as possible, about 5 cm. You can see the jump in hf output as the mic passes over each exciter, but as they are close, it's pretty quick, even at 1/4 speed. The jump in response at the 2nd exciter is weaker, I don't know why.
and finally with the exciters spaced 15 cm apart. Again the increase in hf response at the second exciter is weaker than the first, but clearly visible.
Eric
Here is the answer for you
https://www.researchgate.net/public...f_multi-exciter_distributed_mode_loudspeakers
The site allowed me to just download it. It often does
Those are for WFS applications, so using multiple exciters arranged in a line to play different signals.
Quite interesting, but cannot find anything that would apply to using a cluster with the same signal.
Have you even read his patents? He talks about "intermodulation between the low frequency and high frequency regions of the speaker" not intermodulation between two exciters next to each other playing back the same signal. If you for some reason want to do that kind of outdated design, there might be some useful info in his patents.
This is what I mean about Gurus thinking they know it all. SMDH Low frequency and high frequency of a speaker means there is TWO (2) EXCITERS per panel one exciter for the low frequency and one exciter for the high frequency which is 2 exciters on the same panel.
How do I know this for a fact? I own a pair of Bertagni SM100 speakers.
Have you ever heard Bertagni speaker in person?
Out dated? Bertagni was way ahead of his time he is one of the pioneers of DML that sold his products in hifi retailers around the world. What did you accomplish Leob? LMAO
I bet Bertagnis speakers sound better then anything you have ever built which is probably not much. LOL
Like I said to much talk not enough walk.
How do I know this for a fact? I own a pair of Bertagni SM100 speakers.
Have you ever heard Bertagni speaker in person?
Out dated? Bertagni was way ahead of his time he is one of the pioneers of DML that sold his products in hifi retailers around the world. What did you accomplish Leob? LMAO
I bet Bertagnis speakers sound better then anything you have ever built which is probably not much. LOL
Like I said to much talk not enough walk.
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That isn't as I read it. He was using digital filters to smooth the response measured with a swept frequency. This however isn't the same as playing say music that contains a whole load of frequencies however he did listening tests. There are other similar papers. Once commercial use thought is using projection screens as a speaker.
Bertagnis Flagship model the SM300 is featured in this article.
https://www.hifi-classic.net/review/bes-sm300-289.html
https://www.hifi-classic.net/review/bes-sm300-289.html
Eric .
I am surprised that you found the increase in the response in the area of the exciter interesting, especially as I have been banging on about it for some years now ?
The pistonic ( primary drive ) area of the exciter act's as a full range driver, similar to having a 2inch full range driver on a baffle.
This area will always be louder than the rest of the panel, as it is the first pulse that produces the wave that moves out from the coil in circular waves.
If two coils are on the same panel surface these outward waves will collide , interfering with each other's natural flow.
Your videos apart from being very fast for some reason ?
Does not seem to show much at all ?
as you cannot find the problem using your methods, You will just have to wait until I do my video on YouTube, watching me move the microphone around the panel slowly in real time, as the waves move up and down in frequency as the microphone is moved away from and inbetween the exciters.
I have just got back from Iceland and have caught a bad cold ( did you know it is cold in Iceland , something to do with the name maybe ?) ,so am in no hurry at the moment to do tests,
Still time for you to find it yourself , and save me the effort.
Steve.
I am surprised that you found the increase in the response in the area of the exciter interesting, especially as I have been banging on about it for some years now ?
The pistonic ( primary drive ) area of the exciter act's as a full range driver, similar to having a 2inch full range driver on a baffle.
This area will always be louder than the rest of the panel, as it is the first pulse that produces the wave that moves out from the coil in circular waves.
If two coils are on the same panel surface these outward waves will collide , interfering with each other's natural flow.
Your videos apart from being very fast for some reason ?
Does not seem to show much at all ?
as you cannot find the problem using your methods, You will just have to wait until I do my video on YouTube, watching me move the microphone around the panel slowly in real time, as the waves move up and down in frequency as the microphone is moved away from and inbetween the exciters.
I have just got back from Iceland and have caught a bad cold ( did you know it is cold in Iceland , something to do with the name maybe ?) ,so am in no hurry at the moment to do tests,
Still time for you to find it yourself , and save me the effort.
Steve.