Has anyone seen any hints about the details of the Amina aluminum honeycomb panels? Like their thickness (total), skin thickness, and areal density? From the videos they look to be about 4-5 mm thick I would guess, but any more is hard to tell.
Eric
Here’s an old, charming patent, written in an era when there were no computers, personal or otherwise, nor smartphones and such. It’s fascinating to observe the level of thought that went into drafting that patent. While he didn’t mention bending waves, he certainly had an understanding of resonating flat panels.
Are the patterns identical on the other panels ?
I presume that if this is some sort of mastic or even a more rigid structure, it is used to break up the strong standing waves in the central area.
Similar to the amina patent and my technique for various panel materials.
But you still have the cavity resonance to worry about.
Steve.
I was wandering if this material (end grain balsa) is a suitable candidate. The thinniest option seems to be 5mm.
https://www.ebay.com.au/itm/1533459...-8fcb-ca8aeec9dbee|iid:1|vlpname:vlp_homepage
@ Veleric I have got myself once more tuned in to the needs of the Panel and attached a link with a large range of materials with very low Kg/M3 weights.
The Honeycomb in the opening page of the Link is lighter than Aluminium and looks to be a product that comes with a lesser width dimension to enable a thinner panel to be produced.
https://www.easycomposites.co.uk/3mm-29kg-aerospace-nomex-honeycomb
I wonder if using this material to externally clad the Round Flute Panel that @ Spedge uses would benefit from the treatment, even if only used as a Rosette as a mounting base where the exciter is attached.
The Honeycomb in the opening page of the Link is lighter than Aluminium and looks to be a product that comes with a lesser width dimension to enable a thinner panel to be produced.
https://www.easycomposites.co.uk/3mm-29kg-aerospace-nomex-honeycomb
I wonder if using this material to externally clad the Round Flute Panel that @ Spedge uses would benefit from the treatment, even if only used as a Rosette as a mounting base where the exciter is attached.
The concepts from those old patents remain relevant even today; what has changed are primarily the drivers and the materials used for the front resonating flat panel. There are several methods to make that flat panel resonate, whether through enclosed air (gas), air in front striking the panel at a close distance, or the actuator, or the coil former being connected directly to the panel itself.
I must say that I was quite pleased to read this old patent from Willard A. Murray. It describes a sound production apparatus that, if constructed nicely, would look lovely with nice pictures hanging on the wall, with wires embedded in the wall. There are plenty of shallow speaker drivers available, so the entire enclosure can be quite thin. Additionally, there’s no need to dismantle the cone or the basket. All one needs to do is select the material for the front resonating panel and adjust it on those spacers until the optimal configuration is found.
There are two apertures, 21a, also concealed behind the front resonating panel, but they do not function exactly as bass-reflex holes. One might consider adding two short tubes and even incorporating some damping material on the back wall. An interesting aspect here is the stiffening of the front and back panels of the box with that screw, which can cause the front and back faces to bend slightly inward, thereby adding tension to them. Additionally, the opening for the speaker is smaller and positioned off-centre. Or, would the damping material be necessary?
I remember, at an audio show many years ago listening to a speaker which used bolts through the panels to tune the speaker to sound how you wished.
It was quite large and very expensive.
I never saw it again at following audio shows.
I have doubts as to how the patent speaker would sound.
But I do wish patents were shown and written as they used to be back then.
I actually enjoy reading them, even when I think they are a little odd 🤔
Steve.
It all revolves around the resonating front panel, and sometimes even the back panel. Stanley Rich's concept of trapped air (gas) transferring vibrations to the front flat panel to create an omnidirectional scattered sound in the room has been employed by the well-known Dr. Bertagni and is still utilised today by prominent invisible speaker manufacturers such as Stealth Acoustics and Sonance, among others.
Hiding the speakers in the wall is practically impossible, as the walls are made of solid brick. However, hanging some fairly flat boxes on the wall and pasting attractive images on them can certainly be done, and there would be no WAF resistance to that. There is absolutely no need to pay exorbitant prices for good old ideas. Not much carpentry knowledge is required either, provided one can cover any flaws with the image. 🙂
Both Rich's and Murray's ideas are quite excellent!
Hiding the speakers in the wall is practically impossible, as the walls are made of solid brick. However, hanging some fairly flat boxes on the wall and pasting attractive images on them can certainly be done, and there would be no WAF resistance to that. There is absolutely no need to pay exorbitant prices for good old ideas. Not much carpentry knowledge is required either, provided one can cover any flaws with the image. 🙂
Both Rich's and Murray's ideas are quite excellent!
Sonnar,
My browser wouldn't let me follow your link, but I did a search on ebay and found this:
https://www.ebay.com/itm/1533459422...tE1McHGn+A05pdsvewY/5SlA==|tkp:Bk9SR9Di9NKBZQ
Is it the same?
On that page 5 mm is the thinnest you can select to purchase,, but in the description at the bottom it says that down to 3 mm is possible. I think that is getting close to what would work best. If I recall, @Sandasnickaren was making his own about 2 mm thick, and Oliver Goebel was using slightly thinner yet.
Eric
lekha,
I never had the impression that Bertagni used trapped air to drive the panel. What makes you think so? Was it in any of his patents?
ric
JohnnoG,
That nomex honeycomb is a very good candidate as a panel core material. I have tried it myself, but have not yet mastered the art of constructing a composite with it. I'll probably try again eventually.
I'm not sure I understand what you are suggesting with respect to using it in combination with the flute panel. The way I would think of using the honeycomb is as a central core between a top and bottom skins of a very thin (say < 0.5 mm) but high modulus material like carbon fiber/epoxy or fiberglass/epoxy, or wood veneer, or even paper or Mylar. The honeycomb alone has effectively no bending stiffness at all. It only becomes useful as a panel when it is part of a composite structure.
Eric
Thank you Eric.
The link is correct. I haven't noticed the 3mm option. Great find.
I will try to get in touch with them and order two panels sometime in the new year.
Valeriu
Sonance has acquired the patent rights of Sound Advance Systems, which was Bertagni's company, and Bertagni had referenced Rich's patent at some point.
But referencing Rich's patent may simply have been part of his review of prior art. It doesn't mean he was using the technique in his own designs.
Eric
Well, Bertagni company and its rights were sold to Sonance in 2005, and Bertagni is out of the picture. Now, the importance had moved to Sonance, and their invisible speakers. Here’s a lengthy video I just found while searching for an answer to your question, which mentions that Sonance uses trapped air to disperse low frequency sound, a concept that originates from Stanley Rich's patent. It aligns with what I speculated about Stealth Acoustics' invisible speakers.
The high (and mid) frequencies are produced by the small driver that makes complete contact with the specially designated area of the flat panel. It could simply be the coil former with a footing but featuring a stiffer spider, or even an exciter as we know them. Just ignore their fancy names for speaker drivers and the like.
Interesting information can be uncovered when you start digging on the internet. This pertains to Bertagni and his flat speakers. Take note of the dates; they are prior to the NXT developments.
https://www.latimes.com/archives/la-xpm-1993-06-01-fi-42176-story.html
https://www.newscientist.com/article/mg15621051-200-patents-speak-up/
How it looked ...
How it looked and sounded ...
Here, Bertagni had used the 'standard' pistonic idea...
It resembles a cone from the back, but the front is flat and in one piece, so where is that cone-like dispersion of air? Suddenly, is it a flat dispersion of air, or what?
(It's in Brazilian Portuguese, so you'll need to use subtitles.)
https://www.latimes.com/archives/la-xpm-1993-06-01-fi-42176-story.html
https://www.newscientist.com/article/mg15621051-200-patents-speak-up/
How it looked ...
How it looked and sounded ...
Here, Bertagni had used the 'standard' pistonic idea...
It resembles a cone from the back, but the front is flat and in one piece, so where is that cone-like dispersion of air? Suddenly, is it a flat dispersion of air, or what?
(It's in Brazilian Portuguese, so you'll need to use subtitles.)
Regarding the video about the Sonance Invisible speakers. Interesting implementation. Looks like a WAW (woofer assisted wide band) setup combining bending wave technology for the wide band section, and pistonic action for the bass, with a crossover. Much like a two-way speaker.
Using their IS8T model as an example:
The woofer section looks like they use a conventional type 6.5” woofer and a large (roughly 40cm x 30cm) passive radiator.
The flat panel section is used from around 300Hz upwards and looks like a very small (around 15cm x 12cm) panel using a relatively large (44mm voice coil) driver/exciter. No indication of what material is used for the panel, or how it is mounted.
They really try hard to be invisible. Important technical details (for us) are also invisible. Nowhere DML is mentioned, although they do mention the speaker has 170 degree dispersion.
Using their IS8T model as an example:
The woofer section looks like they use a conventional type 6.5” woofer and a large (roughly 40cm x 30cm) passive radiator.
The flat panel section is used from around 300Hz upwards and looks like a very small (around 15cm x 12cm) panel using a relatively large (44mm voice coil) driver/exciter. No indication of what material is used for the panel, or how it is mounted.
They really try hard to be invisible. Important technical details (for us) are also invisible. Nowhere DML is mentioned, although they do mention the speaker has 170 degree dispersion.
Thanks for the video. It is long, but I think the truly interesting part is only about 10 minutes long, so not so bad (from about 5 minutes until 15 minutes).
Nope, not much. At 11:47 they talk about the panel. I had to listen several times to figure out that all he says (I think!) is "fiber reinforced composite", which is obviously quite vague. Apparently they have moved away from Bertagni's PS foam, but of course it could be PS foam with fiberglass skins, or some other core, or who knows what.
In the clip below that lekha posted, they talk about "IM traps". Where those described in any of the early Bertagni patents?
Eric
Well, whether or not it acts like a DML they would never use the term "DML", because "DML" is what NXT called their design. As lehka pointed out, Bertagni was ahead of NXT (Verity) by decades. So there's no way Sonance is going to be calling their own panels "DML" when they own the Bertagni patents (but not the NXT ones).
Eric