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

Donka · « **Reply #280 on:** 25 Oct 2009, 05:56 pm »

Sedge,

I will say subjectively that the panel does sound brighter on the backside, definitely the one with the sheetmetal insert. Though the increase in HF may be due to boundary reflections.

sedge · « **Reply #281 on:** 26 Oct 2009, 03:02 pm »

Zygadr

It would be good to see the NXT frequency response, if you could dig out the graph.
Regarding the podiums:

A friend and I individually noticed that the high frequency notes appeared to be emanating from the back of the panel rather than the front. I did not feel I could suggest that Mr Podium turned them round! I have found that this is the case with all the panels I have tested. More on this later.

Zygadr

You might be interested in this, written a few days ago, but never got round to posting.

PROBLEMS WITH PANELS

The biggest problems with the sound of these panels is getting used to so much detail. If you have a natural recording in a church, lets say, the sound can be amazing! Astounding!! But if you put on one of your favourite studio recordings, you can end up listening to the studio engineer doing his job, for better or for worse. Sound effects such as echo, phasing, distortions to enhance a voice, are designed to sound acceptable on normal speakers. But on these panels one hears the machine making the sounds, sounds put in and removed - fascinating but Not Good. Consequently, may have to keep old speakers to listen to these recordings.

FullRangeMan · « **Reply #282 on:** 26 Oct 2009, 03:37 pm »

Quote from: sedge on 26 Oct 2009, 03:02 pm

PROBLEMS WITH PANELS
The biggest problems with the sound of these panels is getting used to so much detail. If you have a natural recording in a church, lets say, the sound can be amazing! Astounding!! But if you put on one of your favourite studio recordings, you can end up listening to the studio engineer doing his job, for better or for worse. Sound effects such as echo, phasing, distortions to enhance a voice, are designed to sound acceptable on normal speakers. But on these panels one hears the machine making the sounds, sounds put in and removed - fascinating but Not Good. Consequently, may have to keep old speakers to listen to these recordings.

Dear Sedge:
I never listen a such NXT panel, unless my Carver Amazing(ribbon) but I read some people said the same as you about the Podium, inclusive Mr.Ralph Werner in the 6Moons test of the Podium 0.5, http://www.6moons.com/audioreviews/podium2/model05.html He said:
# More appropriate for acoustic rather than electronic music
# Especially strong on live performances,
# albeit not from a front-row but far-field "deep space" perspective
My personal opinion this is not a problem, but a High Quality transparency feature, this is a speaker for well recorded SACDs etc...
Zygadr:
Why you are so so with the Visaton exciters?? Do you see any problem with them??
Looks to me all exciters are made in China, and Visaton have a reputation to made good drivers as the FR B200, 8 inches.
Seems to me the Visaton EX60 have all the moving power we need, 32mm VC, 25W, Neo magnet, accept glue or screws etc.
Neodymium magnet in cone speakers made a lot of treble in the freq. chart, maybe this is so with exciters. I see a shining future for this project...
Regards

FullRangeMan · « **Reply #283 on:** 26 Oct 2009, 09:34 pm »

Quote from: Donka on 25 Oct 2009, 05:56 pm

Sedge,
I will say subjectively that the panel does sound brighter on the backside, definitely the one with the sheetmetal insert. Though the increase in HF may be due to boundary reflections.

Maybe if you Invert the speaker cable connectors at the amp output may revert the hi freq to the front of the panel/room.
Just a idea...

sedge · « **Reply #284 on:** 26 Oct 2009, 11:27 pm »

Fullrangeman

I have not heard the 0.5s. I seem to remember Dr Katz saying that the ones at the show were probably prototypes of the model 1. In general I agree with most of what he says about panel speakers, but I was a little suprised when he concluded by saying:

"Ultrasonics are out of reach, but the midband is utterly transparent and clear."

What does this apparently throw-away comment mean? Does the frequency drop like a brick after the midrange? I would like to know more - is this a hint that something is missing?
last time I checked my hearing I could hear up to about 16k , If something is missing below this I will hear it, and when I say the panel reaches 20k, I only know this becaues the deq shows me on a screen.
should I use the deq to slice off the last 4k because I can not hear it ?.
also yesterday,I was listening to a cd of saxophone and gregorian chants rcorded in a church,this cd sounds fantastic but the frequancy response of the hole cd looks like a camels hump,drops off the scale below 300hz aprox and I think it did not even reach 10k.
could this be why live recordings sounds so good and full range rock and such like sound so bad .I would hope to build panels that reached fom 20hz to 20k .I know they do the highs now lets see about the lows .

sedge · « **Reply #285 on:** 26 Oct 2009, 11:37 pm »

fullrangeman
sorry
when I say I agree with most of what he says,I mean the moons review.

Donka · « **Reply #286 on:** 27 Oct 2009, 04:56 pm »

Zgadar,

I have seen that graph before, it's from a NXT technology/marketing paper. PDF found here: http://www.emgeton.com/manual_speakers/NXT%20Technology.pdf

However as noted in that paper they have compiled a database of material they've tested so therefore I expect they will show a graph of the most optimal material, and doubt very much that the panel modeled there is Gatorfoam. If you scroll down to the bottom where Mr. Azima briefly discuss' their Panel Designer software look at Figure C (the screen shot of the software running). Though it's a little blurry you can see that the measured response of the example test also has good HF however if you look at the panel material it is Plastic/Al Skins w/ Epoxy Resin Glue w/ Aluminum Honeycomb Core.

I did more digging and searching, primarily for companies that have licensed the technology and make installable units. They all seem to be using a honeycomb of varying degrees, from coated paper w/ paper honeycomb to mylar w/ aluminum honeycomb, the common denominator being honeycomb.

The other interesting comment I found re-iterated in a few places was NOT wanting the panel to ring like a bell as stated by others. That in fact panel materials with such property should be coated to dampen them. The reason being they stated panel that ring like a bell have increased distortion and color the sound.

Overall it looks like there are varying theories out there, I just wish we could find someone with access to the NXT Design software that could look up a few materials for us right quick. Anyhow I just want you to know I am not doing measurements to try to prove you wrong or anything, just trying to get the most out of these panels, as I have invested a lot of time and money in them. Having said that, others besides myself have heard and or measured the early HF roll-off of the GF w/ the PE exciters.

In all the papers I've read they describe the DML/NXT panels ability to replace pistonic speakers and reproduce sound better in basically every aspect, which would leave me to believe that these panel speakers should not be limited to certain types of music.

The other thing I found interesting was that most all the leading consumer/industrial electronics companies worldwide have licensed the technology. However, in the example NXT gives on it's own website regarding Philips tv's, they state Philips made their own exciters and were able to achieve the necessary HF using a less than optimal panel material vs.what NXT mocked up for them. So there are definitely other exciters out there besides the cheap Chinese, we just don't have access to them.

usp1 · « **Reply #287 on:** 27 Oct 2009, 05:02 pm »

Donka - In an earlier post you said that using a metal panel (panel insert) you were able to produce good HF response. What was the metal panel? For the LF it is clear that one needs a larger panel with lots of exciters. The HF seems to be a real challenge.

FullRangeMan · « **Reply #288 on:** 27 Oct 2009, 05:11 pm »

Quote from: sedge on 26 Oct 2009, 11:27 pm

"Ultrasonics are out of reach, but the midband is utterly transparent and clear."

Hi Sedge,
I sorry to know this statement. Literally ultrasonics start at 20Khz, but it do not help much.

Donka · « **Reply #289 on:** 28 Oct 2009, 04:05 am »

USP1,

Yes, I took the Oblong panel and cut a rectangular notch in one side of it so that I could fit a 8x20" sheetmetal panel in the void, I glued 2 exciters to the sheetmetal in opposing corners, and glued some GF strakes across the other 2 corners to hold the metal in the void. However, when I wired it in series with other exciters on the GF panel the dB output at the same input voltage was lower for the sheetmetal. So although it could produce the full HF range quite flat, it was dampened by having to overcome the magnetic attraction to the panel material itself at equal power level as the GF so it was barely adding anything to the party. I plan to order some thin aluminum and non-magnetic stainless from my industrial supplier next time I have an order in to test further.

However, I had some time finally to do some proper testing and playing with the DCX2496 this evening, actually still listening to my test panels while I write this. With the DCX I was able to separate the sheetmetal and the GF w/ exciters to individual channels. From there I added gain to the sheetmetal and crossed it over at 1kHz. Overall the result was quite good, though I had to tune the top end of the HF band and add some roll-off to 20k otherwise it would produce almost a hiss at high volume. Next I added some EQ to the GF channel and scaled back the gain on the sheetmetal and it gave a nice even sound w/ no anomalies, what was neat was the extra touch of realism/metallic sound the sheetmetal gave to cymbals etc.

Since the # of exciter's and configuration of the modded oblong is quite different from my other test panels I then setup the plain 4 exciter base panel as the Left channel w/ the framed base panel as right. I then proceeded to test various forms of EQ, and struck upon what I thought was good enough and started to do some listening at high volume to various genre's of music. The sound was good but seemed to be suffering in the LF all of sudden, at which point I remembered back to the reading I did over the last few evenings. What I remembered was that many papers stated you needed to set a high pass filter in the low-end. Not because the panel wasn't big enough, or that you didn't have enough exciters, but rather that the exciters start acting in a pistonic fashion at low frequency and is compounded by increased power/SPL, and therefore the panel is no longer randomly vibrating ultimately creating decreased output and increased distortion. So I added a Linkwitz-Riley 24dB/Oct high pass filter at 35Hz, and immediately as the settings updated from my laptop the depth of the midrange and LF immediately came back. Sweet!. Once I got that settled I went to fine tuning the top end, and after playing a multitude of songs I have found a simple low dB parametric correction in the HF band to bring the sound full circle. In my setup, this small correction brings the sound forward out of a diffuse hall echo to a broad yet defined sound-stage, with vocals center and present. Extra Sweet! Now I couldn't be happier with the sound, FOR ME it's there, detailed and encompassing, but w/o that shallow sound, and not genre limited.

As a side note, I played with panel placement in the room I have them setup, and at about 18" from the back wall, with the R channel in a corner, I found the HF to be noticeably louder due to rear reflections, this in a room with highly reflective materials nearly all around.

Edit to add: At this time I am quite satisfied with these test panels, and the SPL I was able to get out of them was enough for the room I had them setup in. However my ultimate goal was to build these panels as inserts into a sloped open beam ceiling, so the larger the better for that application. However when it comes to materials, though I would like to sample other panels, I think I am going to save the $100's for now and build out the Gatorboard panels, once combined with the DCX2496 it's really a thing of beauty.

One last thing I forgot to mention that I remembered reading, if you plan to use a framed/retained panel then it is ideal to place the exciters at varying distances from the corners, NOT down the centerline. When placed down the centerline it takes more power/excitation to bring the panel up to it's base modulation, therefore it is suggested to place them around the corners because the panel will be more responsive and efficient.

FullRangeMan · « **Reply #290 on:** 28 Oct 2009, 02:31 pm »

This ELAC exciter is the most powerfull I see!! Looks is have less bass response due the hi FS = 600 and 620Hz
http://www.elac.com/en/index.html maybe in a huge panel his bass can rise up??
Elac have a panel material too, I doubt it is soo light, just 0,125g per metre2 !! Anyone can inform the Elac material price??
The 12 ohms exciter is very good to parallel connection!With the VISATON and this ELAC we already have two top exciters to choose! Good News

FullRangeMan · « **Reply #291 on:** 28 Oct 2009, 03:32 pm »

Look at the ELAC exciter I can not figure out how to fit this ELAC exciter on the panel. . . Any Idea??
Seems there is various joint or indent etc on both sides... Maybe it do not accept tape or glue??

Donka · « **Reply #292 on:** 28 Oct 2009, 04:00 pm »

Fullrange,

When I came across that material chart the other day, I figured it must have been a misprint and is instead correctly Kg/m2.

Also I believe I read they suggest glue for mounting, the picture is a little deceiving because they have an integrated suspension/surround surrounding the exciter foot, howver the black plastic surround looks like it pops on/off but you would have to find out if they glue the exciter foot to it upon assembly. As shown you glue/tape the black surround shown I imagine.

FullRangeMan · « **Reply #293 on:** 28 Oct 2009, 04:16 pm »

Quote from: Donka on 28 Oct 2009, 04:00 pm

Fullrange,
When I came across that material chart the other day, I figured it must have been a misprint and is instead correctly Kg/m2.

Also I believe I read they suggest glue for mounting, the picture is a little deceiving because they have an integrated suspension/surround surrounding the exciter foot, howver the black plastic surround looks like it pops on/off but you would have to find out if they glue the exciter foot to it upon assembly. As shown you glue/tape the black surround shown I imagine.

Looks you are right Donka. Nevertheless this made the ELAC material incredible light, just 125 grams per square metre, wish it do not be expensive. (Gatorfoam 4,5mm weight 1120grams per M2). Maybe just is missing a exciter foot in this Elac image...

Donka · « **Reply #294 on:** 28 Oct 2009, 04:34 pm »

Fullrange,

I just looked up the weight of Perspex, and the listed 1.19 is the Specific Gravity or g/cm3. So you would have to multiply L x W (in meters) x Thickness (in mm) x 1.19 = Weight of sheet in Kg/m2.

Since we now know the correct units, the equivalent for Gatorboard would be 0.2488 g/cm3, basically double the weight of the Elac material.

The foot is behind that black surround spider, if you look at the 2 images you can see the black surround clips onto the magnet. If you look closely you can see the clear part of the foot behind the black surround. The question is whether the foot is glued to the surround when they snap it on, and whether it is removable at all, since they may not have a cloth suspension underneath, so it may be integral to base function.

FullRangeMan · « **Reply #295 on:** 28 Oct 2009, 06:24 pm »

Thanks Donka, So ELAC material weight over 500 grams per M2, this is really light. Elac seems much confident about it.
This is good news indeed...

FullRangeMan · « **Reply #296 on:** 29 Oct 2009, 02:29 am »

Quote from: zygadr on 29 Oct 2009, 02:15 am

My apologies..............as I got you guys very excired about the Elac exciter.
Unfortunately, the product (Imago loudspeaker) was discontinued and is no longer available.
Yet...............the manufacture date on the back of the exciter indicates it was made in 2008 ????

ZYGADR
Well, we can use the VISATON, also a nice exciter if not better. And the ELAC material, do you have any info about it?? Some images etc...

mkstat · « **Reply #297 on:** 29 Oct 2009, 10:32 am »

Donka · « **Reply #298 on:** 29 Oct 2009, 04:25 pm »

mkstat,

What Tymphany suggest there for a HP filter is very similar to what I read elsewhere and commented on in my post yesterday. It made a very noticeable positive difference in the sound by adding the filter I described.

You can definitely see the sinusoidal response they describe in the measurement graphs I posted for the free standing test panel. What I wonder is once you add a spine and some edge retention, which limits the exciter's possible extension, if it is then safe to run the panels full-range without detriment to the exciters. Maybe this is another reason for Podium's configuration.

mkstat · « **Reply #299 on:** 29 Oct 2009, 05:38 pm »