https://www.linkedin.com/in/marcelo-vercelli-547b174/
Here, I found a video about him. I haven't watched it before.
You can search for him on YouTube; there are a few more videos available.
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Well, the British Defence Ministry was more or less the starting point of this saga, and since it is connected to that ministry, it would be quite difficult to find any information. He and another individual were the key figures behind the patent. Those were the Cold War times, with a lot of hush-hush activities. I wonder why Carl Pinfold speaker seemingly disappeared, leaving behind neither a patent nor any notes.
Those were the Cold War times, with a lot of hush-hush activities. I wonder why Carl Pinfold seemingly disappeared, leaving behind neither a patent nor any notes. But not so small as Pinfold's, or else it would resemble computer speakers.
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Here is an interesting speech about omnidirectional sound and generally on how sound reflects and spatiality, etc. The DMLs are more or less omnidirectional or undirected, so this speech might be of interest to everyone. Dr. Johann Ablinger is the owner of Quell.
Here is a patent by Graham Banks and Julian Fordham in 1999 regarding the creation of a tweeter at the voice coil area of an exciter.
Hello Lekha,
This video is about omnidirectional loudspeaker. A source that radiates 360° (at least horizontally), all the direction with the same phase. There are few loudspeakers in this category. The DML are dipoles with a rear radiation in phase opposition to the front. A consequence in an open baffle configuration is a null in the plate plane (90° out off axis). This is clearly visible in the directivity measurements. With that comes the nice figure of eight... but only up to a certain frequency. Above as for the open baffle with a standard driver, peaks and dips occur on axis and lobes appear at angles like 45° then 60° (for the main ones). We can think to correct the on axis FR thanks to some DSP, there are good solutions like CamillaDSP for that. The challenge in my opinion, at least to make the DML acceptable by the audio community which is widely referring to the CTA2034 (spinorama), is to make the directivity smoother which can be done only by the loudspeaker design.
There are 2 options of pattern to target : the figure of eight over a wider frequency range for the ones having their loudspeakers away from their walls (1m?) and some cardioid with no radiation to the back for a close to wall placement.
Where the brainstorming should be is in the solutions to control the directivity in the mids of those configuration, without loosing the quality of openess already reported and without introducing a boxy sound as also reported.
Christian
Steve (@spedge ) is our specialist of such construction! To have 2 mechanical devices matching is probably a nightmare for a DIYer. When a DSP correction is available, Is there a need?
Christian
I found that patent while looking at another one related to "normal" cone speakers, which aimed to use that area to create a tweeter point within the internal side of the voice coil. It seems they have been attempting that in the 1980s, and before.It's not about trying to use two devices, but rather one device—one voice coil for two functions.
By the way, what about trying a slightly curved panel instead of a flat panel for the DML? Slightly convex panel with the exciter on the concave side. Just a thought.
Inventors seem to constantly come up with new ideas to find solutions for creating music from a flat panel, sometimes even quite unusual ones. Here is an interesting idea from around 2006. WO2006078247A1
Here, the inventor is attempting to eliminate the action or interference from the inner area of the voice coil.
Here, the inventor is attempting to eliminate the action or interference from the inner area of the voice coil.
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When we consider a voice coil, we typically think of its pistonic motion, often overlooking the fact that a coil carrying an electrical current vibrates within a magnetic field. We are so accustomed to viewing it solely in terms of pistonic motion that we tend to forget that in a 'normal' cone speaker, the lateral movement of the coil is constrained, meaning only the visible pistonic motion is apparent. This was advantageous for speaker manufacturers in the past, and it remains the case today. However, the coil actually vibrates within that magnetic field. These vibrations occur on both sides of the wound coil, indeed in all 360°. Nevertheless, the coil is confined to a coil former to somewhat limit these vibrations.
Those vibrations occur on both sides of the coil former—and they move in at least two opposite directions. Thus, the issue lies within that area inside the coil former. In a 'normal' cone speaker driver, that area is somewhat open, and the cover is referred to as a dust cap, allowing for heat dissipation and so forth. People are often inclined to cover up the problem, but some are seeking solutions. (These few patents, and even @spedge, address this.)
In a flat panel, the area inside the coil former is the one that presents the most audio problems—vibrations move away from the coil former throughout the rest of the panel, while they interact with each other within that area. One could, of course, create a hole in that region to alleviate the issue, but it wouldn't be aesthetically pleasing.
Thus, the concept of a damper within that area, as described in the aforementioned patent, is noteworthy. There may be additional patents and implementations that have emerged since then as well.
To achieve the desired results, we cannot rely on the exciters currently available on the market; instead, we essentially need to construct our own exciter or dismantle an existing one to access the voice coil. The larger issue is that the exciters available commercially are generally quite weak, featuring small or tiny voice coils and weaker magnets. To obtain a well-made actuator, one might consider that jolly Brit's idea: dismantle a high-quality standard speaker driver, remove the cone and the basket, add a foot to the coil former, incorporate a damper on the inner side of the coil former, and secure the coil former to the flat membrane via a foot (bobbin). There may be additional ideas to explore as well.
Those vibrations occur on both sides of the coil former—and they move in at least two opposite directions. Thus, the issue lies within that area inside the coil former. In a 'normal' cone speaker driver, that area is somewhat open, and the cover is referred to as a dust cap, allowing for heat dissipation and so forth. People are often inclined to cover up the problem, but some are seeking solutions. (These few patents, and even @spedge, address this.)
In a flat panel, the area inside the coil former is the one that presents the most audio problems—vibrations move away from the coil former throughout the rest of the panel, while they interact with each other within that area. One could, of course, create a hole in that region to alleviate the issue, but it wouldn't be aesthetically pleasing.
Thus, the concept of a damper within that area, as described in the aforementioned patent, is noteworthy. There may be additional patents and implementations that have emerged since then as well.
To achieve the desired results, we cannot rely on the exciters currently available on the market; instead, we essentially need to construct our own exciter or dismantle an existing one to access the voice coil. The larger issue is that the exciters available commercially are generally quite weak, featuring small or tiny voice coils and weaker magnets. To obtain a well-made actuator, one might consider that jolly Brit's idea: dismantle a high-quality standard speaker driver, remove the cone and the basket, add a foot to the coil former, incorporate a damper on the inner side of the coil former, and secure the coil former to the flat membrane via a foot (bobbin). There may be additional ideas to explore as well.
Hello Lekha,
I think you already know I disagree with your way to describe all those mechanisms and how thinks are mixed here. No time today to reply in detail.. I am still in the opinion alternative exciter is not a priority.
Please come back with convincing results of trials.
Christian
I think you already know I disagree with your way to describe all those mechanisms and how thinks are mixed here. No time today to reply in detail.. I am still in the opinion alternative exciter is not a priority.
Please come back with convincing results of trials.
Christian
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Everyone has the right to disagree. That does not mean what I mentioned was incorrect.
To incorporate a damper, you need to create your own actuator. A company that has been successful for the past 25 years (doesn't matter the name of the company) is using a modified damper and produces its own exciters. What is available on the market are merely hobbyist models. Everyone who aims to be successful in the flat panel speaker industry creates their own exciters. We can do the same, but it is much easier to dismantle a well-known 'normal' speaker driver.
As I mentioned earlier, there may be additional patents and implementations that have emerged since then as well. It is always better to read the patents alongside the images that accompany the text. The essence of the matter is always contained in one or two sentences; the rest is just the icing on the cake. By the way, I don't need to convince anyone.
This might be true, but since this is a diy thread - please share details and pictures of how you would do this. Which 'normal' speaker driver will work well, and which ones have you tried?
Take a look at the patent mentioned here. Of course, the inventor won't reveal how the exciter is constructed, but he addresses a significant issue. Since this is a DIY thread, the rest is up to you. I can only inform you that some embodiment of that idea is being used commercially. I'm not mentioning the names of people or companies, not to get into any unnecessary argument.
Sorry for late answer.
I’ve measured them today 1m, 2,8 volt resulted in 83dB.
The exciter is TEAX25C05-8 Classic Audio Exciter 8 ohm impedance.
Thomas
The main problem with these omnidirectional speakers is they use conventional driver units and boxes.
Would I like them , probably not.
But one thing he said in the video did strike a chord with me.
At the 5 minutes point he mentions the touch ability or emotionality of a speaker.
This is very important to me, and so far my eps panels are the only panels that excel at this, bringing out the detail and emotion of a performance.
Other materials can come close, but not close enough.
Heavy panels struggle the most.
Heavy panels can sound very good , but ultimately they sound lacking in emotionality to me.
Steve.
Hello Christian.
I suppose the obvious answer would be to have a separate tweet in the centre of the coil area something like the tannoy concentric drive unit with its separate crossover.
This could then be easily blended in with the different panel materials.
The patent shown does not deal with the problems of the cavity resonance which is just as big a problem.
Although a very light fabric dome material could reduce that significantly if done properly , similar to my roughly made domes.
But as you say, matching the dome output to the panel material is a major problem.
My domes were designed to reduce cavity resonance and oil can resonance not to produce significant hf.
But on certain panels they did help the hf output by preventing peaks and hf suckout cancellations.
Steve.
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I believe you were good at identifying the problem and making a concerted effort to find a solution. Have a look at this patent as well.