[sedge]

Bobloblob

Oh dear, your right, I did forget to mention that the exciters are just glued onto the panels, with no spine, so far this is the easiest method to mount them.

I also just remembered something I did some months ago now.
I did try to mount an exciter on a 4 ft long 4inch wide cardboard core tube with a 3inch hole down the centre, this core was as solid as a rock.
I was thinking of filling it with sand.
The exciter was glued onto the side of the core and the panel stuck to the exciter with tape, the weight of the panel was supported by the mysterious disappearing kitchen sponge (sorry, dear).
The Idea was to have the exciters support the panel so as to leave the panel to vibrate freely (no damping of the panel at all!!!)
The experiment was going ok until the panel once again fell off.
But to my surprise the exciter kept on playing, the tube was now the speaker!
In the past, I have listened to the difference speaker stands can make to the sound of a small speaker, now I know why.
Just connect an exciter to you favorite speaker stand and listen to it sing along.
Podium say they tune the spine and frame like a piano sound board, make of that what you will.
Myself, I would rather not glue my very delicate panel onto something that is making almost as much sound, two speakers for the price of one.

I feel there is also another issue with mounting the exciter onto a solid spine.
The panel starts to act like a lf cone driver that is unloaded, rattling all over the place with loud lf.
I have noticed the panel without the spine is not moving at all,but the lf sounds the same.
This is with a single exciter ,not sure what happens with multiple exciters.
Until I know what’s going on with these things ,I‘d rather glue the exciter onto the panel and hang them up somehow.
The panel is not restricted and the exciter is only putting sound into the panel.
It’s so simple ,and pure.
If I change them from this, I have to know that I’m not spoiling the sound.
I have idea’s ,but not the time.
At the moment I’m more interested in what happens between the panel and exciter.

As for pure nxt panels…………….

sedge   

[pol_bct]

irishpatrick33  wrote

> I personally think the 3rd dimension has been completely ignored.


the main advantage of DML philosophy is it omnidirectionnal sound.
This is what makes the listener feeling "to be there".

If we play with 3rdD, we will kill this parameter and go back to cone and horn directivity,
I, personally, have zero interest into this.

The only positive exception I have tried is by setting two panels at 90°,  in order to get bass directivity,
to understand why and how,  have a look at the "Blumlein config"

POL

[pol_bct]

Naw....  I don't expect that, being NXT and all.  Really don't know what to expect.  But it might radiate OK all over the hemisphere with the exciter at the apex.  Did you actually try a hemisphere or sphere, or just the 2x2 panel?

Even if a 16" doesn't do much bass, it might make a fun mid/hi driver.

I am not sure of what you want to do with a sphere but I already did a try with a 76cm big sphere and an exciter at one side, it was terrible..., because the wave propagates from one side to the other and so on, and so on, I rediscovered the echo chamber

POL

[panomaniac]

Very interesting!  Thanks.

[sedge]

Panels and rooms

This weekend I moved the panels into the living room to see if the suck-out in the 100 to 250 Hz region was to do with the panels or my room.
In this room there were still cancelation between these frequancies, but were steeper and moved up and down within these two points, depending where the panels were placed.
I moved them all around the room but could not find the perfect place where there were no cancelations. I could get the panel to sound good but there was still a cancelation somewhere in this region 
So after a whole day of moving the panels around the room I now know what a pain in the butt panel speakers can be!
It is now Monday and I am back in my music room, and still moving panels about.

 I have found, while I was comparing near field and far field responses ,that when I moved the mic around to the side of the panel (max cancelation) suddenly, there was my 100 to 250 Hz suck-out!
I was a little surprised to see the 100Hz down to 25 Hz region only lowered by a few db.
On a 2ft panel with a cone speaker mounted, I would expect a constant roll-off bellow about 200 or so Hz.but in this position I would have expected an Lf dead spot.
In the past I think I have mentioned that I blend my12in Lf in with the panels, these run from 40Hz to 300Hz, this was done by ear (glad to see something still works).
Lately, when running the panel’s full range, I have used digital correction (about 6db) to fill this suck-out…….
Just had a thought!
On other speakers, that I have tried to correct suck-outs, I have used 15db of life and still not corrected it! That is why I don’t correct suck-outs, so why has this corrected it? And so easily!
My head is starting to hurt again; I’m going to have to sleep on this for a while.

Also just remembered that when I measured the panel from the side in my living room (about 3 meters away) the sound level had dropped but the Fr was good?
Any(sencible) Idea’s are welcomed.

sedge
   


 
 
     

[pol_bct]

Panels and rooms
.....
Any(sencible) Idea’s are welcomed.

sedge

we know from BassReflex studies, that in a given box/room, for a given loudspeaker, there is close to only one good tuning/position.
Transposing this to an 8 figure radiating panel, this lead to think that rear side of panels should face room corners, with an angle set at 45°, both panels are 90° from each other, and the only tuning is to shift both panels from and to the corners on this 45° diagonale to get the adequate level of bass&midbass.
Front waves will add, and back waves will be scattered equally by room corners.

POL

[bobloblob]

Sedge-

This will probably have no effect on the problem you are dealing with, but it might be an interesting experiment.

Assuming your panels are still suspended and not fixed anywhere, how about lightly clamping or restraining one panel emporarily in a few places, just to compare it with the suspended one?  This may not be the ideal way of mounting a panel, but it may be good enough to tell you how free vs. restrained sounds, and may give some valuable info for future use.

[irishpatrick33]

Results to follow.

Alright, so it appears as though my cone EPS speaker was producing surprising bass because of the driver--kinda think the cone EPS sucks now. The Dayton 25mm high shove variety is certainly more adept at delivering the bass. (1) high shove vs. (4) cheapies seems to be a fair comparison. The (4) cheapies can play a little louder/efficient, but the high shove seems to provide more potent bass.

Anyhow, experiments with the various perforated panels has been a disappointment. I haven't tried all of them yet, but they fail to deliver anything markedly different from a whole panel. Which gives me little hope for the tests with the last panel. I found the biggest differences to occur in the actual placement of the individual driver. As others have mentioned, mounting in the center of the panel results in reduced performance. I also found mounting near the top or bottom to be a poor performer. Two spots stood out a bit from the others, I will measure later and report. I will also try some horizontal variation. But I have little hope these tweaks will significantly improve performance. It always seems that these NXT speakers provide no soundstage whatsoever. They feel like they are stuck in the mud and slow. Hardly anything separates, especially the midrange. I was really hoping something could be done to transcend the typical NXT sound, but nothing has worked.

[sedge]

Irishpatrick33

your panels look a bit thin to be eps, are they foamcore?(paper coated)
could you give details please.

sedge

[irishpatrick33]

Yes they are foamcore. Cheap and easy to find. Great for an experiment like I have conducted. Still haven't finished yet. Kinda of smarting still from the disappointment that nothing changed sonically despite massive holes in the panels and such. I will also give the EPS cone a second shot with a modification.

[bobloblob]

FWIW, at least one brand of electric organ manufacturer (I think Yamaha) made some drivers with an EPS-like foam "cone".  The driver configuration was somewhat like standard drivers, but the "cone" was mounted to the frame and motor rigidly with no surround.  I don't remember if there was anything like a spider, though I don't think there was.  The "cone" was usually odd-shaped and four-sided, and had about the same surface area as a 15 inch driver.  Rather than flat, the "cone" sloped in from the frame to the motor, somewhat like a standard driver, but shallower.  Sounded quite good, from what I remember, and always surprised listeners when they saw the driver.

[irishpatrick33]

EPS cone mounted on top of exciter sucks.



While the LF was decent, the rest of the audio spectrum sounded like it was all bottled up. Not good at all.

I also tested the final perforated panel. Nothing. The designs had no impact on sonics, that I could discern.

Just a horrible set of results for both experiments. Complete waste of time except for two bits of info. The high shove 25mm Dayton exciters really seem to provide more/faster LF response. There were some spots with individual driver placement that performed better than others. Top, bottom, and middle were poor performers. I ended up having 7 vertical placements of the driver on the panel. The spot 30% from the top of the panel seemed to perform best, especially in a critical are such as bass. 60% down from the top also was a good performer. Now these experiments were simply my results. I suppose any combination of factors could influence the results. Regardless, those are my findings. Very disappointed.

[sedge]

Irishpatrick33
Quote
They feel like they are stuck in the mud and slow. Hardly  anything separates, especially the midrange.

This IS the sound of foamcore!!!!!

It has been said many times on this thread that this is a bad material.
Why torture yourself.

Zygadr has told you 10mm thick eps is fantastic.
If this is too expensive ,try my 25mm from the DIY store (£7 for a 8x4ft panel uk price)
You will only need one exciter for your size panel.(this will go very loud.)
You may need an Lf driver, depending on musical tastes .

sedge

[pol_bct]

...
The spot 30% from the top of the panel seemed to perform best, especially in a critical areA such as bass. 60% down from the top also was a good performer.
....

previous tests have already shown that 1/3 - 2/3 are good combinations
but only for single exciter.
If you want to put more exciters you will have to spread exciters + or -1/3 distance up and down from those positions.
this means 5/9 and 7/9  and/or  2/9 and 4/9 from top or bottom

POL

[j gale]

Pol,   All on a centre line?

[pol_bct]

> All on a centre line?

1/3 is not exactly on center...

POL

[panomaniac]

No, but it could be on a center vertical line...

[pol_bct]

ok,
if you do a "classical" stereo with 2 panels
nothing should be on the true center line
with my "special" coherent stero, all on a single big panel
the central L&R are on the center line around 1/3 from top,
and the L and R are around 1/3 of left & right zones,
also around 1/3 from top  (5/9 - 7/9 from bottom)

POL

[panomaniac]

I don't remember reading about your stereo panel - what did I miss?

[pol_bct]

I don't remember reading about your stereo panel - what did I miss?

http://img220.imageshack.us/img220/7687/ambionew.jpg

POL