NXT.......rubbish??....THINK AGAIN!

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Lynx_TWO

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New to this whole thing - Building 5'x10' Gaterfoam panel LCR
« Reply #3060 on: 23 Dec 2017, 04:47 pm »
Good Morning!

So, I'm new to this whole DML panel thing but have been reading up on it.  I have three Dayton Audio DAEX32U-4 Ultra exciters coming, and purchased a 5'x10'x3/16" oversized panel of Gaterfoam https://graphicdisplayusa.com/products/gator/   I will be mounting the three exciters in a LCR configuration.  Now, as far as placement goes, I was originally going to simply divide the panel in three equal parts mathematically, then go down 2/5 (24") draw a line lengthwise, then mount L and R 16" from each edge, and the third right in the middle at 60" from the edge, 24" down.  I'm seeing other ratios here like 4/9 and 3/7, so does that mean I should mount the exciters, say, 26.7" from the top and 17.14" from each edge?

I'm currently sticking with three exciters, but want to also leave room for multiples if I feel the need in the future.

Still trying to figure out the best way to mount such a beast of a panel, so expertise would be welcome :D  If this work really well it'll be my projector screen.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3061 on: 24 Dec 2017, 12:09 am »
Welcome Lynx_TWO......the ultra exciters seem to have some quality control issues so make sure you test them out to see if each one is working.

The best most uniform and accurate sound reproduction comes from using 1 exciter per panel....when using more then one exciter per panel the sound waves will interrupt and disrupt each other to certain degrees...its like throwing a single pebble into a pond making a uniform ripple but when thrown more then one pebble at the same time the waves disrupt each other which could have both good and bad effects...The goal is to reduce the bad effects while increasing the good as there are so many factors involved.

There are two main ways to prevent this..The simplest one is to use separate panels for each exciter, this is also the most accurate uniform method as there is no other waves interfering and disrupting with each other..........The other way is very very complicated which utilizes different size/thicknesses of grooves and channels in ones panel to help block some of the waves from interfering with each other by reducing the level of cross talk cancellations. Plus the proper placement between exciters can also help aid/boost in certain frequencies.

Its hard to explain it in words, its best for you to experiment and experience it for your self to get the gist of what I am talking about.

Good luck in your experiments and have fun.




Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3062 on: 24 Dec 2017, 12:12 am »
double post my bad.

Lynx_TWO

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3063 on: 24 Dec 2017, 05:42 am »
Interesting... I did notice the exciters I chose have some quality control issues, so I'll definitely test before mounting them.  The reason I was going to use one exciter for the Left, Center and Right (3 total) was due to using the panel as a projection screen, and also due to the fact from what I've read, you'll still have LCR imaging on one panel.  I've also notice some TV manufactures doing this on their screen, and I believe they are on the same panel (could be wrong though).

Couple things I've learned from reading through multiple threads:

  • I currently plan on rounding the corners, probably around a 4" radius due to (edge refraction?)  Not sure if there is a formula for the radius or not...
  • Mount the panel itself in a frame.  To do this, I was thinking of making a simple oak frame about 1/2" larger than the panel to keep 1/4" gap all around.  Was planning on then using a 1/4" bead of clear Lexel http://www.sashco.com/hi/pdfs/Lexel_TechData.pdf to adhere the panel edges to the frame and keep an elastic bond on the sides of the panel since the stuff is super-stretchy.  Only downside is it takes 1-2 weeks to fully cure.  Am open to other / better options.
  • After all the reading, it seems it's better to NOT use a spline in the back of the panel and to keep the panel as free from interferance as possible, aside for attaching the edges to minimize distortion.  I suspect loss of bass should not be an issue since it's a 5'x10' panel (haven't seen anyone use this large a panel yet)
  • Since this will be wall-mounted, it seems I'll need to get some acoustic foam to place between the panel and the wall.





Thoughts?

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3064 on: 25 Dec 2017, 12:42 am »
Yeah, one can still  have LCR imaging on a single panel, its just the sound quality wont be as accurate due to 3 different waves intertwining with each other....For home theater applications I suppose its alright but for listening to music (be it 2 channel or multi channels) I would assume one would opt for the most accurate reproduction in sound quality as that is what most audiophiles strive for.

. Rounding the corners seems to help improve sound quality.....I dont know if there is a set formula but I just use a 2-3 inch circle as the radius.

. For me a frame is a must due to my designs but not everyone uses one....as for that Lexel, its says not to be used on polystyrene, although I dont know for sure if Gator board is polystyrene... a lot of types of corrosive adhesives will eat through and corrode polystyrene so one has to be very careful of which ones to use....I would use just plain old silicone the type used in Aquariums as a sealant.

. Actually using a spline IMO is better as it supports the exciter and keeps it tightly in place to reduce "DISTORTION", and in turn enhances the sound quality making the bass, mids and highs sound more pronounced and accurate.....This is most likely the same reason why Shelly Kats designed the "PODIUMS", utilizing a spline....but dont take my word for it, try it your self and see which one you prefer.



« Last Edit: 25 Dec 2017, 02:04 am by Bendingwave »

Lynx_TWO

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3065 on: 25 Dec 2017, 03:45 pm »
Oh yea, I just looked at the specs and Gaterfoam is polystyrene core, glad you said something before I melted the edges!  :oops:

I've been looking around for modeling software to calculate optimum placement for the exciters and so far have found nothing.  There's gotta be an excel spreadsheet or something out there right?

I thought about cutting a kerf in the back of the panel to divide it into 3 equal parts, but I imagine the front face would likely then crack due to flex, yes?

I will be sure to experiment with and without a spline.  It does make sense to support the back of the exciter with a rigid piece and give it something to 'push' off of.  I feel like a 1"x2" or 1"x3" T-slot extruded aluminum would be the stiffest option, and it's pretty inexpensive.  https://f-l-8020-store.myshopify.com/collections/10-series-bars/products/1020  It would be fun to make the frame from that stuff, but 8' is the longest I've found.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3066 on: 26 Dec 2017, 12:21 am »
I dont think there is any modeling software for the placement of exciters out there right now for the general public.....the big companies could have there own software like NXT but I doubt they would openly share it with the public.

It would depend on the thickness of your panel and 3/16 is pretty thin to begin with so most likely it will be to fragile and crack due to flex especially for such a huge sized panel.....This is the reason I prefer panels 1/2 inch thick and over as its easier to carve thicker panels without the worries of it breaking.

Yes, the spline is also used for the exciter to push off of and to keep it in place from voice coil sagging due to the weight of magnet....The frame holding the panel also helps support the weight of the panel material as one will need both a frame and a spline for the most balanced sturdy support.....When most people think of exciters the first thing that comes into there mind is a free floating panel with a free floating exciter meaning there is no frame support holding the panel nor a spline support holding the exciter.....without the support of a frame and spline there is bound to be voice coil sag due to the weight of the exciters magnet and or the panel material....voice coil sag is a result of unbalanced sound and or distortion due to not having any type of support....Using a frame and spline will solve the sagging problem of the voice coil and reduce distortion .....Ever heard of the BMR driver developed by NXT? Its basically a exciter utilizing a frame and a spline support like a conventional cone driver.


Lynx_TWO

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3067 on: 26 Dec 2017, 03:26 am »
Whoa, now those speakers are interesting.... I wonder how they'd sound replacing the stock 2" BOSE headrest speakers in my ND miata?  Too bad they don't seem to make a 6.5" driver for the door!

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3068 on: 2 Feb 2018, 09:22 pm »
Today I want to talk about what to use when mounting a DML panel to a frame.....I personally would never mount the DML panel directly on to a frame because the resonance of the panel will also vibrate the frame creating distortion....What I use is the FrostKing (3/4X7/16) rubber foam weatherstrip tape to adhere them to a frame that can be bought at most hard ware stores including Home Depot.....To adhere the foam to the panel and frame you can use plain old wood glue like tite bond etc.

The rubber foam greatly reduces the resonance of the frame therefore reducing distortion for a cleaner sounding panel.

actonusa

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3069 on: 5 Feb 2018, 05:03 am »
Bendingwave.....would one be better off going in the direction of Magnepan and the many that mod their speakers?  Why not make a frame of an acoustically inert material like MDF and secure the panel directly to the frame?  So instead of the frame resonating it is absorbed and/or deadened.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3070 on: 5 Feb 2018, 09:50 am »
I don't know much about Magnepans designs and there modifications so I cant comment if it would be better.......For DML panels I will say it wont be better because when two solid objects touch each other with one of the objects vibrating there is bound to be distortion between the two solid objects touching as well as resonace. The rubber foam for the DML panel is basically used like the surround on a conventional cone speaker used to attached the cone material to the basket.

DML panel= cone material

Frame with spline=basket

Rubber foam=surround (be it foam, buytl rubber, cloth etc.)

For better understanding think BMR.

Although MDF can help with reducing resonance one will still need some type of rubber, foam or cloth material to attach the panel to the frame for dampening to reduce vibration distortion and resonance.







Jamneb

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3071 on: 1 Mar 2018, 04:24 pm »
Here are a couple of white papers on using audio exciters - sorry if they have been mentioned before:

https://www.mouser.co.uk/pdfdocs/PUIExciter_White_Paper.pdf

http://www.visaton.de/downloads/pdf/visaton_exciter_principles.pdf

There comparison and data on different panel materials are interesting.

Has anyone used Phenolic sheet or Dibond?

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3072 on: 27 Mar 2018, 05:28 am »
Here is a interesting video on DML panels for beginners and start off intro.

https://www.youtube.com/watch?v=zdkyGDqU7xA

captainjack115

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3073 on: 5 Apr 2018, 02:59 pm »
I watched that video several times over the past few days. The presenter went to great lengths to illustrate his findings.

I started playing with DML's after reading the late Zygadr's original post in 2009.
He had such enthusiasm for his new found project, I couldn't help but get involved and became a believer.
So, 9 years later and I'm still messing with these things on and off. I still don't have them figured out, but I did accumulate some observations over the years.

First of all, one exciter on one panel seems to give the most predictable results.
My first pair of working prototypes consisted of cheap, low power exciters I bought in bulk from Parts Express.
I constructed frames with 4 sections, the panels were 12x12 inches and mounted into each section with duct tape.
So, with one 5 watt exciter per panel, I had a 20 watt power handling speaker.
I crossed them over at 150 hz 4th order hp filter and used a subwoofer. If you're hoping to get tactile bass with a very large panel driven by multiple exciters, forget it. It's not going to happen!

Getting back to that video.
In the second half he shows resonant nodes with suger and how the pattern changes with frequency.
I recently ran pink noise through a panel and observed it with a spectrum analyzer.
At one meter the spectrum analyzer shows a fairly predictable pattern. What I found interesting was that bringing the test mic within an inch of the panel, and moving it around the surface, showed definate signs of considerable comb filtering.
1/6 per octave looked like the teeth on a saw as the mic was moved around.
Here's the thing about that. Do the nodes and comb filtering combine in a predictable caos as distance increases?
I don't know, I'm not a physics expert.
Demonstrations have shown that DML's are nearly immune to feedback and stereo imaging can be heard and appreciated in very large venues.Tonewise they done sound as good as my Magnepans, but they can be very listenable. They seem to shake off inter-aural crosstalk and display a certain headphone kind of separation.
As for a sweet spot, it seem to be there the minute you walk in to the room where the DML's are playing.

Still, very interesting!

Nickolay V

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3074 on: 6 Apr 2018, 01:28 am »
New NXT diaphragm material & results
Russian forum
http://www.tornadoacoustics.ru/forum/25-1026-2

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3075 on: 6 Apr 2018, 10:35 am »
I watched that video several times over the past few days. The presenter went to great lengths to illustrate his findings.

I started playing with DML's after reading the late Zygadr's original post in 2009.
He had such enthusiasm for his new found project, I couldn't help but get involved and became a believer.
So, 9 years later and I'm still messing with these things on and off. I still don't have them figured out, but I did accumulate some observations over the years.

First of all, one exciter on one panel seems to give the most predictable results.
My first pair of working prototypes consisted of cheap, low power exciters I bought in bulk from Parts Express.
I constructed frames with 4 sections, the panels were 12x12 inches and mounted into each section with duct tape.
So, with one 5 watt exciter per panel, I had a 20 watt power handling speaker.
I crossed them over at 150 hz 4th order hp filter and used a subwoofer. If you're hoping to get tactile bass with a very large panel driven by multiple exciters, forget it. It's not going to happen!

Getting back to that video.
In the second half he shows resonant nodes with suger and how the pattern changes with frequency.
I recently ran pink noise through a panel and observed it with a spectrum analyzer.
At one meter the spectrum analyzer shows a fairly predictable pattern. What I found interesting was that bringing the test mic within an inch of the panel, and moving it around the surface, showed definate signs of considerable comb filtering.
1/6 per octave looked like the teeth on a saw as the mic was moved around.
Here's the thing about that. Do the nodes and comb filtering combine in a predictable caos as distance increases?
I don't know, I'm not a physics expert.
Demonstrations have shown that DML's are nearly immune to feedback and stereo imaging can be heard and appreciated in very large venues.Tonewise they done sound as good as my Magnepans, but they can be very listenable. They seem to shake off inter-aural crosstalk and display a certain headphone kind of separation.
As for a sweet spot, it seem to be there the minute you walk in to the room where the DML's are playing.

Still, very interesting!

Not sure if you have read this article on Bertagni speakers but it is very interesting as this is the reason I got into DML technology and how my designs are built on. Dr.Jose Bertagni was well ahead of his time when it came to DML technology.

How Sound Advance Loudspeakers Work
In a most basic sense, here's how the current generation of Sound Advance Flat Panel loudspeakers work: Instead of propagating sound by passing it through a cone or dome-shaped structure, an electrical signal is sent through a copper-wire coil, which produces a magnetic field causing vibrations. This coil is attached to the back of a specially fabricated diaphragm made of polystyrene. Vibrating back and forth, the diaphragm bends like an archer's bow to produce a wide variety of pitches which vary according to where it's struck by the coil. As previously mentioned, the sound itself then emanates from the entire surface of the diaphragm. When paint or wallpaper is applied over these loudspeakers, it merely becomes part of the vibrating surface.
Within this entire operating scenario, it is important to remember that the diaphragm is what sets this transducer technology apart from all other types of radiating sources. During the manufacturing process, special additives are added to the raw polystyrene bead material used by Sound Advance which enables it to meet ASTM E84 flame-spread and smoke-density ratings. Then the material is formed under heat and pressure via a wet molding process which also provides the shaping needed to create grooves and channels called IM traps which reflect return energy from the diaphragm edges away from the coil.
An environmentally-controlled curing period follows, during which the diaphragm is stretched and bonded to its supporting frame with proper amounts of tension. Dampening weights are added at this point in time as well, at a number of points in each system to tune the motional response of the entire motor structure.
Upon completion of this process, the motor structure houses a variable-thickness diaphragm which rigidly complies to lower frequencies while allowing a carefully-controlled, progressive decoupling of the diaphragm's surface from the driver to reproduce higher frequencies.
Given its very nature, the entire diaphragm assembly radiates energy at lower frequencies while a controlled and tailored reduction in effective diaphragm surface area occurs as the frequency increases. This produces exceptionally wide angular coverage at higher frequencies as a result.
Conversely, low frequencies move the diaphragm backwards and forwards from a central position in a motion dampened completely at the edges. Mid and high frequencies travel from within the composite material toward the outer edges, where they are extinguished inside the IM traps.
Collectively, all of this activity energizes a large number of the individual polystyrene beads comprising the diaphragm's base material. When each bead comes into contact with an adjoining bead, it radiates just like a miniature point source.
Over the years and through the various name changes, the company which is now Sound Advance Systems has seen their Flat Panel loudspeakers installed in the White House, King Fahd's palace in Saudi Arabia, the Greek Theater in Los Angeles, the Mirage Hotel in Las Vegas, the Hard Rock Cafe in New York City, the Hotel de Coronado in San Diego, the Ritz-Carlton in Dana Point, California, the Hollywood Bowl, and private residences of great distinction and celebrity. Privately held, the company is given direction today by President Donald J. Taffi.

Other Manufacturers Involved in Flat Panel Technology
Other manufacturers currently involved in the flat-panel loudspeaker race in the U.K. include New Transducers Limited (NTL) and NCT. Designers of the well-hyped NXT line of components, NTL promises to bring their first flat-panel products to market in the very near future.
As for the future of flat-panel loudspeakers in general, based upon all evidence, the technology has matured to the point where it is here to stay. In addition to the applications described thus far, those imbued with the entrepreneurial spirit are already aglow with an abundance of ideas. Projection TV screens could easily double as a loudspeaker, for instance. Or how about having the headliner of your automobile serve as a loudspeaker system too? Then there's the notebook PC equipped with sound panels that slide out of the sides next to the display screen. And don't forget a talking microwave oven, combination solar-powered toaster/portable stereo, and, well, let's just say the possibilities are endless for now, and leave it at that.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3076 on: 7 Apr 2018, 11:19 am »
I have found some new videos of Bertagni speakers playing so those that have never heard them can get some what of an idea of how they sort of sound like to get a glimpse into the DML panel speaker sound...The first vid is of the DIY video of free floating DML panels and the second vid is Bertagni DML speakers. See if you can hear the differences in the free floating panels vs. Bertagni speakers and see which sound you prefer better.

https://www.youtube.com/watch?v=zdkyGDqU7xA DIY free floating DML panels utilizing (XPS) (pink) Extruded Polystyrene (29 min. music starts)

https://www.youtube.com/watch?v=tU4JiqE9GIY  Bertagni DML speakers uses High density (EPS) (white) Expanded Polystyrene.

Free floating panels do not use any spline or frame, while Bertagni speakers utilizes a spline and frame for a more accurate all around sound.

The difference in sound between EPS and XPS is that EPS has warmer tones with less shoutyness and more bass......XPS has a little better clarity but very shouty in the mid frequencies with less bass.

captainjack115

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3077 on: 7 Apr 2018, 10:08 pm »
About 50 years ago, (Yes, I'm that old) I bought a speaker made of what appeared to be styrofoam. From the back, a magnet was embedded into the styrofoam. The front had a circular metal disc, about 1.5 inches.
I recall high sensitivity and extended high frequency response. Not very big as I remember, maybe 8x10 inches.
It was a long time ago, I wish I could remember more details.Somehow this seems more like conventional speaker, well not so conventional since it is flat. More like a point source, and not modal like a bending wave DML.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3078 on: 8 Apr 2018, 01:55 am »
Ive seen those disc shaped speakers only online as they seem to be like the first prototypes into DML technology with a combination of BMR. Technology that came out around the 60's-70's.....BMR technology basically comes from DML technology...Bertagni speakers are actually BMR's but on a way larger scale, that's why in my other post I said BMR technology is nothing new nor were NXT or tectonics the first to discover it, they just made it popular.

Not sure if you seen this article on Bertagni speakers but it has the pictures of the small disc shaped speaker I believe very similar to what you were talking about and it goes to show you how Bertagni went way above and beyond all other plastic planar designs.

http://www.audioimprov.com/AudioImprov/Speakers/Entries/2012/6/15_Bertagni_SM-275_restoration.html

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3079 on: 9 Apr 2018, 10:04 pm »
Another video of Bertagni speakers this time playing a song with vocals.  https://www.youtube.com/watch?v=T_Ixuxq-zgk

These Speakers would of sounded much better if they were placed on the floor, instead of on top another pair of speakers. Plus like I stated many post before using some type of aurlex pads or even yoga mats on the bottom of the speakers will help tighten up the sound.