Interestingly the cedia panel uses at least 9 weights for their panels.
I wonder if they take into account the mounting on the wall and how that would change the reflections?
Steve.
It just looks to me that they have stuck some black mastic inside the coil area, similar to what I did many years ago.
The frequency response on his computer shows no peak in the 10k area.
Steve.
The 3k peak could be the cavity resonance, try measuring the exciter from the back to see if it is still there.
Cupping your hand over the magnet area at the back usual makes the noise sound even worse.
I am only guessing as I have noticed this problem before.
Steve.
Hi aagas.
There are many grades of eps and how you treat them .
I have yet to see anyone copying my designs to the letter.
They usually deviate in ways I would not do.
Heavy panels can sound very good as do my round flueted polypropylene panels.
But only my eps can surprise me with their realism.
Obviously the eps needs subs for full range and must be blended in properly for this to happen.
Steve.
Yes I managed to find pretty good solutions to the problems on my panels .
Looking at the patent you show here, which I have not read yet, reminded me of my ply panel that I was trying to test different exciter mountings.
I did not finish or come to a conclusion about this.
Basically I was trying to get rid of as much of the coil foot as possible, to minimise the refractions going on in this area, which is causing bad distortions that are causing the frequency response deviations.
I practically gave up testing dml panels at this time, and at the moment am not intending to continue.
I have other priorities at the moment and have hardly been in my listening room.
Which more resembles a junk room at the moment.
Hopefully maybe next year I might try and start playing around again when I have cleared my room.
Steve.
Attachments
After reading about FAL driver and the need for high aspect ratio, can't we just use exciters in a line array configuration? A bit like sandasnickaren did on his panel but in a single line, arranged in a vertical pattern on a 1m long and 25cm wide eps column. In that way we will both get small distance between exciter and panel boundaries and high aspect ratio without resorting to custom made exciters
An Amina speaker from 10 years ago... and without any weights...
And a bit more elaboration on why the exciters are arranged in that manner.
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I just recalled the name of the other invisible flat panel speaker manufacturer from Germany. Everyone has their own theory and design. Here, of course, the manufacturer does not claim that they can achieve deep low frequencies without a sub.
And another speaker from China called EOGO features that exciter array, resembling a copy of Amina's design from 10 years ago—who knows...
It seems that this flat panel hidden speaker is available in Australia.
And another speaker from China called EOGO features that exciter array, resembling a copy of Amina's design from 10 years ago—who knows...
It seems that this flat panel hidden speaker is available in Australia.
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Here’s an eight-year-old video using 'conventional' speaker systems to excite the flat panel. This system is made in the USA, and most likely all the drivers and accessories are as well. His company has been doing this for the last 20 years and has been quite successful in business even today. As I mentioned before, you don’t need a shop-bought exciter to excite the flat panel; one can use the enclosed air (and some other methods) to get that flat panel to transform the music throughout the room. Note how shallow the 'conventional' drivers are in those speakers.
They can be quite easily used outdoors as well. An interesting fact is that the entire system is enclosed; nothing is visible, with no speaker grilles or similar components.
And a bit more elaboration on them...
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It's a study of a DML as a full-range speaker, and we automatically understand it as a flat panel functioning as a full-range speaker with distributed mode—whatever that entails—operating on that flat panel surface and producing music. The actuator can be anything, from a tiny exciter to a large cone speaker, or even a system of 'normal' speakers using 'compressed' air as the actuating agent. Even JBL has jumped on the bandwagon!
Even JBL has jumped on the bandwagon recently! There are numerous conventional speaker drivers available in the market, along with all sorts of crossovers, and one can create a standalone speaker without any 'ugly' WAF-unfriendly cone speakers or grilles. You can have a picture on that, and/or simply conceal it within the wall. All the while utilising that distributed mode! 👍🙂
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I've been considering this method of exciting the flat panel to transfer sound to the room at a much wider angle. I was thinking about Stanley Rich's patent from the 1960s. Perhaps someone else could have come up with that idea much earlier; who knows? The concept was to excite the trapped air in such a way that it would, in turn, excite the adjacent panel, using a standard cone speaker from that era. Stanley Rich aimed to create a low frequency speaker using that approach.
Bertagni, of course, utilised that idea by employing two areas of the same panel with different densities.
In any case, both Stealth Acoustics and Sonance utilise Stanley Rich's concept of using enclosed air to excite the flat panel before it produces sound for the room.
When looking at the back of Stealth Acoustics products in those YouTube videos, one might notice that they employ two (or more) areas to excite the panel. It appears that the conventional speaker driver excites the enclosed air to produce low frequencies—utilising pistonic motion—while the smaller speakers are used to generate high-frequency sound through bending wave technology.
Most likely, they are using two (or more) areas of the panel made from different materials. The lower part, featuring the conventional larger speaker driver, has a higher density material, with the air enclosed between that cone and the panel. That speaker's cone/baffle does not make direct contact with the panel. The high (or mid) frequency driver makes contact with the panel, and that area is composed of a lower density but much harder material. That section of the panel could be separated from the rest of the panel like a window, or it could be thinned around the area of the high (or mid) frequency driver. This area could be significantly smaller than the low frequency area or the rest of the panel, as a large area is not necessary for high (or mid) frequencies.
Interestingly, the perimeter of this flat panel is rigidly fixed to a frame, which is then securely attached to the wall (or studs). All of this is subsequently enclosed in a box cover. That cover contains some form of damping material to prevent the entire speaker from ringing or rattling.
One way or another, whether the flat panel features multiple areas with different materials, what occurs is the transfer of vibrations to that panel, exciting it to produce both pistonic motion and bending wave motions. This results in a wide soundstage in the room, where the listener cannot discern the source of the sound. And, of course, it is absolutely WAF-friendly.
Even JBL has jumped on the bandwagon recently! There are numerous conventional speaker drivers available in the market, along with all sorts of crossovers, and one can create a standalone speaker without any 'ugly' WAF-unfriendly cone speakers or grilles. You can have a picture on that, and/or simply conceal it within the wall. All the while utilising that distributed mode! 👍🙂
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I've been considering this method of exciting the flat panel to transfer sound to the room at a much wider angle. I was thinking about Stanley Rich's patent from the 1960s. Perhaps someone else could have come up with that idea much earlier; who knows? The concept was to excite the trapped air in such a way that it would, in turn, excite the adjacent panel, using a standard cone speaker from that era. Stanley Rich aimed to create a low frequency speaker using that approach.
Bertagni, of course, utilised that idea by employing two areas of the same panel with different densities.
In any case, both Stealth Acoustics and Sonance utilise Stanley Rich's concept of using enclosed air to excite the flat panel before it produces sound for the room.
When looking at the back of Stealth Acoustics products in those YouTube videos, one might notice that they employ two (or more) areas to excite the panel. It appears that the conventional speaker driver excites the enclosed air to produce low frequencies—utilising pistonic motion—while the smaller speakers are used to generate high-frequency sound through bending wave technology.
Most likely, they are using two (or more) areas of the panel made from different materials. The lower part, featuring the conventional larger speaker driver, has a higher density material, with the air enclosed between that cone and the panel. That speaker's cone/baffle does not make direct contact with the panel. The high (or mid) frequency driver makes contact with the panel, and that area is composed of a lower density but much harder material. That section of the panel could be separated from the rest of the panel like a window, or it could be thinned around the area of the high (or mid) frequency driver. This area could be significantly smaller than the low frequency area or the rest of the panel, as a large area is not necessary for high (or mid) frequencies.
Interestingly, the perimeter of this flat panel is rigidly fixed to a frame, which is then securely attached to the wall (or studs). All of this is subsequently enclosed in a box cover. That cover contains some form of damping material to prevent the entire speaker from ringing or rattling.
One way or another, whether the flat panel features multiple areas with different materials, what occurs is the transfer of vibrations to that panel, exciting it to produce both pistonic motion and bending wave motions. This results in a wide soundstage in the room, where the listener cannot discern the source of the sound. And, of course, it is absolutely WAF-friendly.
Lekha.
I have posted Rich's patent many times over the years.
This patent still interests me and one day I do hope to do my version of this system.
It is very similar to an ABR except it is driven directly by the front of the cone driver and not by back cavity resonances.
Although back cavity resonances could still be used as well, I would think.
It is also cited by NXT for some reason using a tube to pump air from the cone to the panel and with an exciter attached to the panel.
A piezo unit might be a better option.
Steve.
I have posted Rich's patent many times over the years.
This patent still interests me and one day I do hope to do my version of this system.
It is very similar to an ABR except it is driven directly by the front of the cone driver and not by back cavity resonances.
Although back cavity resonances could still be used as well, I would think.
It is also cited by NXT for some reason using a tube to pump air from the cone to the panel and with an exciter attached to the panel.
A piezo unit might be a better option.
Steve.
I've been off the boil with the want to build audio devices using Forum guidance for a while.
The Holiday Period has created time to revisit past interests.
The link may be showing a Panel Material that could be of interest, as I have seen Aluminium Composite as a structure has become a used material in recent posts.
This is intended as a Cladding Material to be used in Construction, which usually means a large amount of Waste Material in attractive dimensions can be discovered towards the end of a project when it is known to be a used material.
Samples may be able to be found for trials that are not with too much cost.
https://www.husk-architectural.co.uk/wp-content/uploads/2019/06/Technical-Manual.pdf
The Holiday Period has created time to revisit past interests.
The link may be showing a Panel Material that could be of interest, as I have seen Aluminium Composite as a structure has become a used material in recent posts.
This is intended as a Cladding Material to be used in Construction, which usually means a large amount of Waste Material in attractive dimensions can be discovered towards the end of a project when it is known to be a used material.
Samples may be able to be found for trials that are not with too much cost.
https://www.husk-architectural.co.uk/wp-content/uploads/2019/06/Technical-Manual.pdf
The Rich patent is utilised in these invisible speakers solely for the low frequency portion of their flat panel, while the high and mid frequencies employ the bending wave model. In this case, the coil former makes contact with the membrane to convey the vibrations -- one can use standard commercial exciters for that purpose.
You might also like to read this patent.
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Hello Steve,
I have tested also this kind of solution... maybe not deeply enough. The peak from the rear side is clearly visible in the directivity plots (update of my paper coming in the next days?... I have to include measurements from Thomas and from Eric).
At that frequency, the emission from the rear is higher than from the front. It is radiated to almost all the directions of the rear while the front shows 3 lobes. Any idea to have a better understanding and so solutions is welcome.
Christian
lekha,
I'm kind of hoping that was a joke. But I'm afraid it wasn't and that you still misunderstand my question.
I understand that when a wire has a electrical current, and is in a magnet field, there is a resulting force on the wire.
But your post (below) seemed to be saying that in a typical driver/exciter design, that the electromagnetic force causes a "vibration" of the coil in addition to the pistonic vibration of the coil that we are all aware of. My question was simply, what is the nature of these other vibrations that occur "on both sides of the wound coil"?
Are you really speaking of some other vibration of the coil? And if so, what? Or did you simply mean that the pistonic motion of the coil results in vibrations of the panel in all directions, both inside and outside of the coil foot?
Eric
That video really was interesting. He's really getting some good lows!
But I don't think it's a dome or mastic that is on the apparent exciter positions. Below is a close up of one of those panels. There's an obvious "pattern". Does that look like anything familiar to anyone? (and I don't mean that like some kind of riddle where I think I know the answer, I really don't know).
But this seems like a decent guess to me:
Another curious thing I noticed was that the more central exciter doesn't appear to be located at the "magic" spot defined in the DPK patents. According to their patents the exciter should be at about 41% across the width of the panel, but is appears to be located at closer to 34%. I wonder why that is.
Eric
lekha,
I was wondering about that. That is, about how the drivers are coupled to the panel in the Stealth speakers. But I didn't see that discussed in the videos. Do you know that for sure? Has Stealth confirmed that at some point?
Thanks
Eric
JohnnoG,
Thanks for the link. It might have some good damping properties. But from an efficiency/sensitivity perspective it doesn't look like a great candidate, as it is only very slightly lighter than solid aluminum, at equal stiffness. So I think from the efficiency perspective the aluminum honeycomb is more promising, If you can find it.
Eric