[zygadr]

POL, .............correct............but as I said, I have only heard this effect with NXT technology.............no others(including other panel speakers).

[pol_bct]

> POL, .............correct............but as I said, I have only heard this effect with NXT technology.............no others(including other panel speakers

I think this comes from the conjonction of specifics quality of DML
wide range of frequency, no directivity over this range, surface of radiation
On usuals parameters , linearity and distorsion, DML are average to poor

POL

[sedge]

When using my 4ftx4ft panel (with  a single exciter) in my living room ,If I walked around the panel while playing music I could easily tell that the sound was coming from the exciter area on the panels, this is why I would call the panels point source.
I did read an article that stated that an nxt panel would radiate 50x50 nxt and point source.
As we are not rigidly mounting the panels in a frame, I thought that we were trying to minimise the nxt part, as this is a resonance in the panel?
Pol is using his panel as a stereo source (LxRx C) so the sound would, I expect, be spread across the panel.
 Podium state that the panels act like an acoustic horn, radiating from the centre.
They probably do all of these things, and more.
IN my long narrow listening room the sound bounces around the room, making the Hf sound hard sometimes, if I stand up close to the panel the hardness has gone.
This is why I am looking onto room treatment .to sort out Hf problems and the room suck-out  between 100 and 250 HZ(this last one is the biggest problem) .
I can easily sort this out by:-
1   digital EQ
2   blending in a 15inch unit
3   xover at 300HZ
But would prefer to sort the room first!

Interestingly, when I measured the 4x4 Ft panel in the centre of the living room ,I turned the panel facing the side wall and measured the FR from the side of the panel (3 mtrs away) the HF dropped like a brick above 10k ,but below this ,except for a drop of a few dbs, the response stayed  much the same .This would be impossible with a standard type of speaker.
Cls
I use single exciters (but I do have some 2 exciter panels)and LF down 30HZ  is very flat,but I would not like to over drive them with loud electronic music,I have done this and have enjoyed it ,but I know the panels are not at there best.
Also, if everyone remembers earlier in these threads I remarked on how the Hf above 10k is radiated (beamed )from the 1inch or so exciter foot ,this is easily measured by moving the test mic across the panel.
So below 10k the panel seems to radiate everywhere and above this they tend to beam ,but I must admit that when walking around the room I do not feel I am missing the sweet spot.
AS everyone has said ,these panels are special(in whatever form you use them).
It is the how and why that we are unsure of ,at least on this thread we have the chance to discus and probe and to try to understand what is really going on!
sedge.
 

[pol_bct]

sedge

with only one transducer, do you use standard el_cheapo
or something stronger like this kind of motor?
http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-861

> Podium state that the panels act like an acoustic horn, radiating from the centre.

I find this statement questionable, in the lower part of spectrum the panel edges radiate evenly, and sometimes much more than the exciter zone.
when going above 10kHz, this is no more the case, as you noticed.

POL

[CLS]

Hi Sedge,

It's amazing you got 30Hz from 4' by 4' panel !! 

On the bass of my panels, I got another strange impression. It sounds thin in the first half ~ one hour or so, then I hear more and more bass, eventually it's quite satisfying (down to about only 40Hz, though).  Or is it because I'm more and more getting used to the thin balance? However it starts over again like this every time.

I got tired of such long 'warming up', so I tried all those bass augmentation tricks. Cone woofers help a lot in my case. Now it maintains rich and full balance all the time, very stable. I managed to blend them well enough, at least for my own satisfaction.  (not bad at all I'd say, more coherent and tuneful than my previous systems... )

About the sound emitting source (spot), my observations are somewhat different. Within 1 ~ 1.5m of distance, I can detect the specific locations of the excitors (at lower 1/3 on panel). Further away (2~3m or even further), strange things happen. My panel is 6ft high. When seated, my head is at a height about half way of the panel where the images are mostly right at this same level (rise about 1ft from their 'actul' positions). Standing up, then most images also rise with me to my line of sight horizontally (another 2ft or so). It's self-adjusting !!  (er... my panels are very slightly tilted back, I'm not sure if it matters) Or, are they all illusions by my own imagination?

For the HF of the panel, I wouldn't say it's beaming. The loss at the side of panel, in my observation happens only at a narrow null area. So averagely the in room responses are still very smooth and even, much more omni than any other types of speakers.


Hi Pol,

I'm thinking about adding mass to my cheapo excitors... They are now supported by thin sticks with pretty free fore-aft movability. With larger mass on the exitor, it will become a bigger 'hammer', so the panel would be 'kicked' further away (more excursion, higher SPL). No?

OTOH, I have another interesting observation that the excitors stay almost dead still when playing ! How so? I don't get it.

If the excitors are mounted on a perfectly rigid spine and grounded, then the mass is coupled to the earth. But that won't happen. Instead, we got another set of mass-spring system, thus the requirement of damping etc.

I imagine the excitor should be 'riding' on the (chaotic) waves, giving only the initial 'excitment' and then let the panel do the rest. But I'm not sure if it's really the case. So I'll also try a (damped) spine in the near future...

As to the vibration of the panel, when playing loud bass, I've also seen larger excursion on the panel than at the VC of excitors, but it's not always like this. (random, indeed) Anyway, by naked eyes, it's hard to get a clear picture...

CLS

[zygadr]

NXT told me in an email that a ''free mounted'' exciter(no back support) LOWERS the resonant frequency of the panel dramatically..................more bass.

CLS, your panel is not very rigid...........much less than most............this would be a decrease in bass response also.

[pol_bct]

CLS wrote
....................................... ................................
Cone woofers help a lot in my case. Now it maintains rich and full balance all the time, very stable.
....................................... ................................

same situation by me,  I have a couple of 30cm who do the job under 100Hz quite nicely

....................................... ................................
About the sound emitting source (spot), my observations are somewhat different. Within 1 ~ 1.5m of distance, I can detect the specific locations of the excitors (at lower 1/3 on panel). Further away (2~3m or even further), strange things happen. My panel is 6ft high. When seated, my head is at a height about half way of the panel where the images are mostly right at this same level (rise about 1ft from their 'actul' positions). Standing up, then most images also rise with me to my line of sight horizontally (another 2ft or so). It's self-adjusting !!  (er... my panels are very slightly tilted back, I'm not sure if it matters) Or, are they all illusions by my own imagination?
....................................... ................................

yes, near field  - far field, in your case, near field goes to 6ft
farther you left near field, Hass effect comes strongly in play
the line of hearing follows you.

....................................... .................................
I'm thinking about adding mass to my cheapo excitors...
....................................... .................................

I am afraid this will kill the balance of the spider

....................................... .................................
OTOH, I have another interesting observation that the excitors stay almost
dead still when playing ! How so? I don't get it.
....................................... .................................

quite logical, above, say 200Hz you can't see anything, but it still moves

....................................... .................................
As to the vibration of the panel, when playing loud bass, I've also seen larger excursion on the panel than at the VC of excitors, but it's not always like this. (random, indeed) Anyway, by naked eyes, it's hard to get a clear picture...
....................................... .................................

I have tried as low as 10Hz, it's thrilling to see the panel edges warping and dancing like crazy

POL

[sedge]

Pol
Yes I use el-cheapo exciters ,they are not perfect but I do not think they are any worse than the others one the market ,we really need a new type of driver (piezo,planar,?)but for now these do the job fine.
Sorry
what I meant  when I said they radiated from the centre ,was that they radiate like ripples across the surface from the centre to the edge.
Cls
Foamcore  has problems producing hf over 8 or 9 k ,so I am wondering what the panel material you are using ?
Have you tested the fr response ?
When I was standing in front of my 4ftx4ft panels ,even with my ear practically on the panel,I still felt I could sea the sound stage,as if looking through a window.
I have mentioned before about these speakers being the biggest pair of headphones I have ever had !
It looks very odd sitting very close to the speakers but within the first meter or so you have no room problems screwing up the sound.
sedge

[CLS]

Hi Sedge,

Quoted from my first post:

...

The panel is some kind of PS foam, I'm not sure it's extruded or expanded. I'm lost in all those material names you guys mentioned. The material of my panel is usually seen as the base of various posters, or used as wings/bodies of those very light model planes...

It's 182 x 91 cm per panel, 5mm thick, very light and soft and can barely stand up straight by itself.....

As to the HF, I didn't get the picture of my EQ setting. Before EQ, it drops 3~4 dB above 10kHz and more or less keeps such level to the top (instead of rolling off). Applying EQ boost to counter that 3~4dB makes it flat to 20kHz (and it sounds that way, too). Eventually I turned down the boost a little. For pure tone, I can only hear up to 16kHz or so, but with music I can hear the difference above that.

In my earilier trails with CC, I needed more EQ boost in the HF. Even more so on the thicker one, so later I flipped it over to let the excitor face forward - the HF generated by excitor seemed not able to 'penetrate' that 2-layer of CC...   

[zygadr]

I have built another pair of VH grade EXPANDED POLYSTYRENE speakers.

Once again, they are 6 foot X 3 foot and 10mm thick.

However, I have discovered a method to stiffen the EPS so that the panel does not flop around and bend all over the place!!!
It now acts as a rigid, giant peice of EPS without gaining any significant mass..............still extremely light.

There are no wooden frames or support mechanisms at all............just a simple stand at the bottom of the panel to keep it upright and isolate it's vibrations from the floor and the stand itself.

With this design, the sound has entered a completely new realm of realism that has stunned me completely!!! 

[sedge]

Zygadr
To boldly go where no man has gone before 
CLS
Is the panel a sponge type foam with thick smooth paper each side ,If so its probably foamcore.

sedge

[sedge]

Cls
Just tested one of my old 2ft foamcore panels and the hf rolls off befoe 10k and is -20 to 25db down at say about 13k.
So I do not think your panels can be foamcore ?

sedge

[mzbrahce]

Sedge--

EPS is expanded polystyrene, or styrofoam as I know it.  VH grade is very dense.  I googled it and found 2 manufacturers in Michigan and emailed one to see if they're willing to sell me a few 3' x 6' sheets.  I've got a dozen of the cheapo PE exciters to play with.  I'll let you all know if I'm successful in getting the sheets and how much they cost.

--------------------------Mark

[sedge]

mz
ask for a sample first, styrofoam and styrene seem to get mixed up, it could be anything.
It must not be like the foam sponge.

sedge

[CLS]

Hi Sedge,

There's no paper surface on my panel. So I don't think it's "foamcore", either. It's not spongy, somewhat brittle instead. If bent to some degree, it'd just break.

I guess it's probably light enough and just rigid enough to make treble.

[CLS]

...

However, I have discovered a method to stiffen the EPS so that the panel does not flop around and bend all over the place!!!
It now acts as a rigid, giant peice of EPS without gaining any significant mass..............still extremely light.
...

Hi,

I sounds promising, and so intereting. Is it cambered surface? Like this?

http://www.teragaki-labo.co.jp/products/about_terra-sp3000.html

I found this on the web. 

[zygadr]

Hi,

I sounds promising, and so intereting. Is it cambered surface? Like this?

http://www.teragaki-labo.co.jp/products/about_terra-sp3000.html

I found this on the web. 

No 

[sedge]

cls
sounds like a panel zygdr tried some time back ,I think he said the panel had poor LF

sedge

[emailtooaj]

Hello Everyone,

Hey Zy, Does your new panel method involve anything like I tried with a thin coat of epoxy?
If so, I have had very little sound discolorization by using this method 

The panels still sound great after what?....8 months of use now!! Been very pleased, and exciters have not fallen off.
Also, the epoxy has not peeled off the panel itself. Has been a very strong bond!!!

Good to see everyone still up and running! 

[zygadr]

cls
sounds like a panel zygdr tried some time back ,I think he said the panel had poor LF

sedge

Those speakers in CLS's link must be the ugliest speakers of all time !!! ............I hope they sound better than they look!

Using wood as panel material results in a poor SPL usually............even Balsa wood.
On top of that is a lack of frequency extremes at both ends of the scale - bass and high frequencies.Controlling ''plank'' like resonances is virtually impossible unless you add great mass to certain spots which then reduces the SPL even further

You will notice that the specifications of the ''TERRA'' speaker  tells you absolutely nothing about frequency response or SPL.  It also uses subwoofers to get bass..............I rest my case

My new panels do  not have any epoxy coating or any other coating for that matter.
Bass is subterranean and high frequencies are spectacular.