I believe those NXT speakers were manufactured in the early 2000s. I'm sure @spedge is quite knowledgeable about the NXT panels produced by those companies.
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By the way, these people (in the video) attempted to sell DMLs more than a decade ago, but now they are offering something quite different. Here’s what they aimed to sell around 2012...
I have no idea whether they sold anything. Perhaps those in the UK might have come across some of their products.
Thank you Christian for pointing out my preference for the round flueted panels.
I have compared the square fluted panel to the round flueted panel.
The problem with the square fluted panel, I believe, is shown quite well in the photos in lekha's post.
The flutes are never perfectly square.
They are always distorted and warped in some way.
The walls are very thin and usually bent, which will cause them to buckle and bend and probably vibrate under drive from an exciter.
The round flueted panel has very strong and rigid flutes that do not warp .
Smaller thinner round flueted panels could probably be 3D printed for better efficiency, as the panels I was given by JohnnoG only go down to about 6mm thickness which makes them about the same efficiency as a 3mm ply.
The sound from the 6mm round flueted panel is far cleaner than the sound from the square flutes.
But not as efficient.
Steve.
It is true that the round flutes contribute to the stiffness of the panel. Additionally, there is a certain amount of filling between the round flutes and the two surfaces, which could potentially distort the sound, someone said, indicating that it "might" have an effect.
Regarding those somewhat angled "flutes," someone mentioned that there are cells between the top and bottom layers, and that this emptiness contributes to the sound. Each cell (flute) has its own unique voice, and when they are all uniform, it creates a choir-like effect. Moreover, the larger the radiation area, the more pronounced the sound becomes.
It appears that, even in honeycomb panels, there are enclosed cells present, and these contribute to the overall sound emitted by the panel. We have been steadfastly ignoring those enclosed cells and the potential impact they may have.
Lekha.
I have mentioned the problems with flutes and cells over the years.
I would have thought it was pretty obvious.
I measured the response of the round flueted panels along the flutes and across the flutes and showed the different responses.
I have not tried a honeycomb panel, but have rejected cardboard, polycarbonate, and polypropylene square fluted panels.
The only one that I liked the sound of is the round flueted panel.
I do not talk much about the problems with cavities in the panels as I do not use them very much myself.
Steve.
I have mentioned the problems with flutes and cells over the years.
I would have thought it was pretty obvious.
I measured the response of the round flueted panels along the flutes and across the flutes and showed the different responses.
I have not tried a honeycomb panel, but have rejected cardboard, polycarbonate, and polypropylene square fluted panels.
The only one that I liked the sound of is the round flueted panel.
I do not talk much about the problems with cavities in the panels as I do not use them very much myself.
Steve.
But you have! An EPS panel is somewhat like a honeycomb.
Technically, your exciters are playing on air! You have treated the EPS surface with a 50-50 PVA solution, which blocks the tiny holes on the surface and also provides a more uniform surface. You've always maintained that EPS is the best material for a DML. I'm sure you are correct in this. I'm sure you've noticed that the EPS surface is never completely even, even after the PVA treatment. Your EPS panels contain enclosed cells, and those air cells possess their own "emptiness," which collectively creates the choir.
The expanded polystyrene beads in the EPS panel may resemble a honeycomb, but what is more important is the manner in which those air cells are formed within it. Perhaps that is the true reason you achieve quality sound from your EPS panels.
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Lekha.
I new you were going to pick me up on this point 😄
Yes eps does have trapped air inside its foam .
But not large cavities, depending on eps quality that is.
The problem as I mentioned with the square fluted polypropylene is the thin walls that bend and distort, they are not able wo withstand high pressure without bending.
The round flutes were designed to withstand large amounts of weight and used as protective floor panels.
They are very robust and are heavily damped by the round flutes , they are much stronger that the thin, bendy square walls that can vibrate and cause problems.
Steve.
I new you were going to pick me up on this point 😄
Yes eps does have trapped air inside its foam .
But not large cavities, depending on eps quality that is.
The problem as I mentioned with the square fluted polypropylene is the thin walls that bend and distort, they are not able wo withstand high pressure without bending.
The round flutes were designed to withstand large amounts of weight and used as protective floor panels.
They are very robust and are heavily damped by the round flutes , they are much stronger that the thin, bendy square walls that can vibrate and cause problems.
Steve.
I quoted Knauf in the earlier post regarding how EPS is made. Here’s another link. The fact is that even if we observe somewhat rounder polystyrene beads, if we break an EPS piece into beads, that bead still contains 40 to 50% air. This is why Knauf asserted that an EPS sheet is 98% air. You simply cannot drown an EPS sheet in water.
In any case, all those fluted panels have empty air channels in one direction, whereas EPS contains them throughout in a randomised manner, and they are exceedingly small. Perhaps this is why Dr. Bertagni chose to make his fortune from it, considering he was a Physics professor. As far as I understand, Dr. Bertagni utilised a very high-density EPS form. I read this somewhere.
Hello,
Here are 2 additional videos about directivity with an interesting discussion about the influence of the directivity on the sound stage. Omnidirectional speakers are considered among more standard designs. Strangely, no words about dipoles and open baffles (or open back).
What is loudspeaker directivity
Narrow vs Wide Dispersion Speakers: Which is Better?
Christian
Here are 2 additional videos about directivity with an interesting discussion about the influence of the directivity on the sound stage. Omnidirectional speakers are considered among more standard designs. Strangely, no words about dipoles and open baffles (or open back).
What is loudspeaker directivity
Narrow vs Wide Dispersion Speakers: Which is Better?
Christian
is a thin wall undamped box giving a DML like sound?
See:
See:
fun loudspeaker in 18 liter water bottle
with heavy eq
diy double cone after removing dustcap
works astonishingly well. like other thin wall speakers
with heavy eq
diy double cone after removing dustcap
works astonishingly well. like other thin wall speakers
Your speaker is essentially an upturned bass-reflex box. Perhaps the thin walls of the bottle are resonating and contributing to the overall sound output. I've been observing your experiments, particularly the aluminium foil damping of the diffuser and the damping of the basket with interest. Would you be interested in testing some flat panels as speaker diffusers?
Perhaps you would like to watch the Russian video and share your thoughts on it, particularly regarding how the simple corrugated aluminium foil resting on that flattened coil produces sound. There are magnets situated just a few millimetres beneath that coil.
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@lekha
sounds interesting.
you mean whizzer cones?
what kind of flat panels for what?
Would have to study your video to understand how the foil speaker works. You have a construction plan on this?
The bottle speaker is great in the mids, the bass is uneven and resonant. But the mids compensates for all. Nice listening experience.
Built it for a friend who wanted the box to be transparent.
sounds interesting.
you mean whizzer cones?
what kind of flat panels for what?
Would have to study your video to understand how the foil speaker works. You have a construction plan on this?
The bottle speaker is great in the mids, the bass is uneven and resonant. But the mids compensates for all. Nice listening experience.
Built it for a friend who wanted the box to be transparent.
Why do I get the impression that people who get banned from this forum continuously come back under different names?
Hello Freedom666,
Probably only experiments can answer to that. They have in common a wide radiation pattern. The bottle in the horizontal plane is an omni. A DML is a dipole (rear out of phase, null at the membrane plane). Omni vs dipole, does it make a difference in the listening experience. One difference might be in the impulse response and so the possibility to build a stereo picture (probably not needed for a garden speaker?). The IR of a DML is stable over a wide angle. In this bottle loudspeaker, I wonder how is the IR.
Christian
@homeswinghome
I associate with DML the unregular swinging pattern of any surface.
The bottle makes a decent sound in the mids and fails in the bass.
Maybe some more sophisticated DSP would cure the response.
But in the mids its vivid and spacious and tonally correct what I didn't expect as a result from such a random design.
And I understand much better how thin wall boxes work and why some people are fond of them
I associate with DML the unregular swinging pattern of any surface.
The bottle makes a decent sound in the mids and fails in the bass.
Maybe some more sophisticated DSP would cure the response.
But in the mids its vivid and spacious and tonally correct what I didn't expect as a result from such a random design.
And I understand much better how thin wall boxes work and why some people are fond of them
Please do.
I would be interested to hear your opinion on it. It’s not my video, but one I discovered on YouTube. I have a certain interest in this area. At the moment, I am observing others experiment with this concept. I’ve conducted a few tests myself, with quite intriguing results, although I don’t have any graphs or such. This is an old idea, dating back to the 1930s or even earlier. A great deal of experimentation was carried out by companies like Telefunken and Siemens during that time. Some of that work is archived in the Radiomuseum in Germany.
Which is precisely what audio engineers have been striving to eliminate in all those high-end speakers boxes. And, rarely succeeding in that endeavour.
It's quite fascinating to see how the equaliser in the macOS Music app can affect the sound of simple shop-bought speakers.
This was in the USA. At the same time, this type of "DML" was being produced and sold in Germany. Since there was no internet in those days, one can safely say that these experiments were conducted without knowledge of each other.
Apologies, I was a bit mistaken about the above video. It was a type of horn speaker.
However, the other videos demonstrate how the spike motor is constructed and how the vibrations are transmitted to the surfaces.
The DML seen here are based on plates, mainly rectangular. Some were non rectangular.
I don't have in mind tentative with a sphere. It looks like more than a variation of the Walsh driver (German Physics) or more of the MBL one which is not a full sphere but some slices (petals?) to get I guess flexibility (pulsating sphere)
Have a look around post #7447
Christian
I don't have in mind tentative with a sphere. It looks like more than a variation of the Walsh driver (German Physics) or more of the MBL one which is not a full sphere but some slices (petals?) to get I guess flexibility (pulsating sphere)
Have a look around post #7447
Christian