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

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Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3100 on: 10 Sep 2018, 03:18 pm »

If you look at all the professional manufacturers of DML/BMR loudspeakers from Bertagnis, Sony's APM's, Technics SB flat driver series, Yamahas Ear speakers to Podiums you will notice they ALL use some sort of frame and spline....There is a reason why all of these professional loudspeaker manufacturers utilize a frame and spline.

The spline is needed to support the magnet on higher excursions as it needs something to push against....with nothing to push against to support the magnet on higher excursions the magnet will rattle and make a lot of noise and also some percentage of energy will be lost resulting in lesser/weaker vibrations going all into the panel....not sure if that made sense but oh well. LOL



I don't wanted to disagree. I just do not have the experience to say something about the sound quality with or without a spline. In my little experiment I noticed no difference. That's neither for nor against it.
Though, as I explained, I can imagine that it might improve bass when the mass of the magnet is not enough to withstand the force pushing against the panel.
But what I see is that it is a good idea to take the burden from the light plate. So I support your statement to use a spline. Just more from the technical part where I have more experience with.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3101 on: 11 Sep 2018, 12:46 am »
In doing many side by side A/B comparisons of DML panels with a spline and panels without a spline I have noticed this difference.

Panels with a spline tend to sound a tad more tighter/accurate and pronounced in all frequencies with a more forward like sound effect.


Panels without a spline tend to sound more diffused and less pronounced with a more (recessed) laid back like sound effect.


DML panels have a very diffused sound to begin with especially the "Free Floating Panel designs", so it can sound unnatural when compared to the conventional cone type of drivers. Which sound one prefers is personal preference but it seems that the high end speaker manufactureres choose the one with the spline and a frame.


Free floating panels sound very diffused.


Panels utilizing some type of Frame and Spline sound less diffused.



« Last Edit: 11 Sep 2018, 09:07 pm by Bendingwave »

Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3102 on: 13 Sep 2018, 03:28 pm »
Ok, note to myself: When building the next panel, save one measurement without a spline and one with and compare the direct sound components.

Next topic: Maybe if I have enough prototypes I try DMLs for a home theater installation. But that requires direct wall mounting for the surround speakers which kills the sound. I tested a bit with 5 mm sound insulation (XPS, the thing you put underneath laminate) as panel and noticed an improvement when bending it (looks a bit like the plywood panel someone constructed for wall mounting). Thinking about this I come to the conclusion that the non uniform distance to the wall prevents destructive interference with reflected waves. So it might be a good idea in general to (slightly) bend a panel to reduce negative effects of walls nearby. What do you think?

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3103 on: 14 Sep 2018, 12:12 am »
It depends on how one mounts there surround speakers...I use the 9 inch L-brackets to mount my surround DML panels so there is about 7 inches from the speakers to the back wall.


I haven't experimented with bending of the panels so I cant really comment on it but JMC does bend there panels since there panels are (if I am not mistaken) mounted close to or directly on the wall.....So you could be right in bending a panel slightly if mounting it directly to the wall.



koko007

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3104 on: 17 Sep 2018, 02:16 pm »
Hi Bending and Kame,

did you see:

http://www.tornadoacoustics.ru/forum/25-1026-4

koko007

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3105 on: 17 Sep 2018, 02:29 pm »
and this:

http://www.tornadoacoustics.ru/forum/25-1026-3

Sorry for 2 posts, i cant find way to edit first.  :duh:

Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3106 on: 17 Sep 2018, 02:46 pm »
I tried my best with google translater. What was the most interesting for me was the panel material discussed on page 2. It is on my todo list to try to laminate thin XPS with fabric. Mainly for protection. My test-panels all have notches from my wife and the kids. For whatever reason no cat has harmed the panels so far...

Odal3

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3107 on: 18 Sep 2018, 02:13 am »
Thanks for the historical article Odal3.

Someone on Audiokarma said that Yamaha licensed the technology from Bertagni/BES....which is probably why its shaped that way like an ear. If you look at bertagnis design its shaped very similar.

https://img.usaudiomart.com/uploads/large/1096124-bertagni-electroacoustic-systems-bes-sm100-speakers.jpg

Thanks for sharing too - I had never seen those before, so had to do some googling. Fun to see that the thread is still going on!

koko007

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3108 on: 18 Sep 2018, 09:19 am »
On the third page there are links (now broken) with the movie of the speaker in the work. I can tell you, that the panels look quite flexible and that the bass panel has a great extrusion (they made their own exciters). Panels, seem to me, were made of thin xps with laminated fabric, something like 2-5 mm sound insulation. Also, i think bending  panels is good way to go like in this case (what i did with antinox like material):


https://www.youtube.com/watch?v=FNugB9DZzK0&frags=pl%2Cwn

and

https://www.youtube.com/watch?v=Kdz4A0Ibg9A&frags=pl%2Cwn

I was tried material like antinox but in my country i cant find 2mm thick material so i used 3 mm which is to much for my exciter (much quieter than xps), although the sound was more natural than xps.

And this is measurement of Russian speaker:



Impressive!

Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3109 on: 23 Sep 2018, 04:21 pm »
Let me give you a small update on my experiments. First I added a small exciter to my panel and take a frequency response for each:

Next I will order some components for a simple crossover at about 6 kHz.

Additionally I started the construction of an wall-mounted dml-speaker with a curved panel. As I read on another forum that someone made enclosures for dml-speakers out of foam board I thought I test some paper honeycomb board. I bought it for my dml experiments but it sounds not good enough.

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3110 on: 23 Sep 2018, 10:01 pm »
Paper honeycomb does NOT vibrate like foam as that is one of the main reasons why EPS is my choice of panel material as well as XRK's foam speaker enclosures.


When EPS/XPS foam is used as an enclosure (or DML panel) it vibrates like a instrument especially in the lower frequencies......I made a DML panel sub using T.E. frog exciter (incorporating XRK's foam enclosure) and compared it against the conventional cone type of subwoofer (polk psw10) using the same sub amp and my DML sub sounds better with better detail, accuracy and it actually plays deeper/lower....The only thing the polk psw10 did better was it hit harder with more punch due to the conventional pistonic movements of conventional cone type of drivers. Sure the polk sub is a entry level sub at only $100.00 but my DML sub cost me only $35.00 to build.

Also a DML sub blends better with DML panels then with a conventional cone type of sub.

Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3111 on: 24 Sep 2018, 03:49 am »
Paper honeycomb does NOT vibrate like foam as that is one of the main reasons why EPS is my choice of panel material as well as XRK's foam speaker enclosures.
So you suggest to use the same material for enclosure as for the panel?

When EPS/XPS foam is used as an enclosure (or DML panel) it vibrates like a instrument especially in the lower frequencies......I made a DML panel sub using T.E. frog exciter (incorporating XRK's foam enclosure) and compared it against the conventional cone type of subwoofer (polk psw10) using the same sub amp and my DML sub sounds better with better detail, accuracy and it actually plays deeper/lower....The only thing the polk psw10 did better was it hit harder with more punch due to the conventional pistonic movements of conventional cone type of drivers. Sure the polk sub is a entry level sub at only $100.00 but my DML sub cost me only $35.00 to build.

Also a DML sub blends better with DML panels then with a conventional cone type of sub.
A DML sub is interesting! Do you have any pictures to share? Which dimensions do you use and how deep does it go?

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3112 on: 24 Sep 2018, 11:29 am »
Yes....Even I wouldn't have thunk it until I read XRK's foam core speaker enclosure on the DIY forum.


A DML sub is just a panel utilizing a sub amp so that only the low frequencies saturate the panel....sorry don't have any pics....panel size is around 16inchX24inch.....I cant tell you exactly how low it goes as I don't have the means to measure it accurately but the polk psw10 states it can go as low as 40hz so I am guessing my DML subs are lower like in the 30hz range.

Right now I am tweeking my DML satellite panels that are only 10inchX16inchs. Which uses only a single Dayton 13mm exciter which is around the size of a nickel....Currently am using the receivers high pass cross over at 100hz for the DML sats…..I could later on just put a non polarized electrolytic 250uf capacitor directly to the DML sats.




Kame2

Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3113 on: 24 Sep 2018, 06:24 pm »
Do you think a single 3W exciter is enough to handle a moderate playback volume?

How thick are your panels? And how thick are the walls of your enclosures? What material do you use for the spline? Do you take any care to secure your foam from damage? Or do you just don't allow kids and pets (and the wife) to get in the same room? ;)

Bendingwave

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Re: NXT.......rubbish??....THINK AGAIN!
« Reply #3114 on: 24 Sep 2018, 08:31 pm »
It would depend on how big ones room is and how loud you like to listen to music.....In my small 10ft.X12ft. room it can play at sufficient moderate levels as I don't listen to music at very loud levels but you will need at least a 100hz high pass crossover for the Sats.


This is just my prototype DML satellites as I can make them have greater SPL by utilizing a higher power handling bigger/larger exciter....With these panels you can custom tailor every aspect of it.

My DML satellite panels are 1/2 thick high density EPS......enclosure is the same 1/2inch thick....Material for spline is wood.


I dont have to worry about damage of the foam as no one touches my panels, not even my chihuahua. lol