[fivestring]

Forget about Kapa, no good at all.
Today I listened to a pair of Dibond panels, on the left channel 2mm thick, 23x90cm, on the right channel 3mm thick, 30x90cm, the 2mm thick Dibond was noticeably more transparent and the highs were crystal clear. I used only one exciter per channel, but I also measured and listened to a 2mm Dibond panel fitted with two exciters and found out it measures and sounds the best when two exciters are mounted either very close or far (70cm) apart, at the recommended 8" distance the highs were lacking. All measurements and listening were done at the cca 2,5m distance.
Since I posted my findings at our Slovenian forum, someone posted very good results with a 2m tall panel where he used six exciters in a vertical line, very close to each other and said everything was much better, the bass as well as the highs, but I need to verify this.
I was also thinking for a taller panel, to spread the exciters progressively from each other, for example between first and second exciter there would be 10cm distance, between second and third there would be 20cm distance and so forth.
Listening to 2mm Dibond panel fitted with one or two exciters there is no lack of high frequencies at all, actually from the cca 500Hz up everything sounds very clear and transparent.

[captainjack115]

But in the end I wouldn't be surprised if we end up with Gatorfoam. Then to me it is mainly a task to see how bass could be improved by subs or perhaps OB-bass.
For the high treble I would easily suggest some omnidirectional super tweeter solution. And that certainly will exsist.

I was very pleased to know that someone on this forum actually heard Ziggy's speakers. "That's evidence"!

I can't stress enough that's it's very important to round the corners of these panels. Additionally, the mounting of the panels has a big impact on bass response. The panels must "not" sit on the floor, doing so will upset the balance of resonance distribution. The panels must sit in a spring-like suspension. I'm getting bass well into the low 30 hertz range.

Jack  [/size]

[tincalifornia]

I would like to thank all the posters to this topic.

I am very pleased with what I now have and look forward to where this topic might be headed.

I went lo fi cheap for some garage speakers and like them so much I'm now thinking about how to replace my baby magnapans and monster amp.

I ended up with 32 x 40 x 0.125 foamcore art board.
I coated the foamcore board with lacquer on both sides.
1 pair of the $5/pair parts express exciters for each foamcore board.
I left the white basket/feet on the exciters.
I left the high pass cap and thermal limit on as the units come from parts express.
I ca/super/ glued them to the foam board.
hung them from the ceiling by pushing wire through the corners of the foamboard.
they are 1 foot from the back wall.
driven by a 30wrms t-amp.

if they come unglued I'll reglue them or try the 3m tape.
I don't have the foamcore corners rounded, but will try that if they develop sounds I don't like.

some could argue that the bass is lacking or the highs fall off, but I can say that I'm very happy with them as they are.

I hear bass. I hear highs.

It all sounds very natural and very clear without beaming or hotspots.
they sound better than my magnapans. I am amazed. they definitely have more bass than the baby magnapans.

I am very happy with them and have this thread to thank.
details of part numbers are up on my website if anyone is interested in more info.
  http://pov.us/index.php/Main/Other-audio-portNXTspeakers

[scorpion]

That's interesting Captainjack, Bob's panels just rested on the floor and no corners were specially rounded. But  how should we get them into the air ?

/Erling

[jeffac]

I have heard Ziggy's Black Monsters not for a very long time but long enough to say that his Gatorfoam finds are great. He may very well sit on one of the best high bass, midrange, low/mid treble speakers there is. And that's no small business.

Hi Erling,

Its a real pity I didn't get a chance to listen to Ziggys monster panels too whilst in the neighbourhood on holidays a couple of weeks back as if as good as both you and he say, additional good impressions posted here then might just have avoided the "where's the EVIDENCE" sideshow.

Anyway, its good to see additional impressions arriving now that he indeed is on to something quite special in the use of a very large panel that no one here has yet replicated as well as good ideas flowing again.    I've also had the same thought of 'fivestring' in progressively increasing the spacing of multiple exciters upward/downward from the central pair to potentially spread any resonant nodes and plan to experiment with exciter magnet-magnet mounting to a spin. I also have an idea for panel floor support that should be non-destructive to bass, but its a little wacky to throw in yet until I've checked its potential. 

cheers.. jeffac

[cometarossa]

Hello,
i'm new and i'm really interested in the project.
I've a question, why don't use a honey-comb core Nomex panel as the original Podium Sound model 1?
There is something wrong with that kind of material?

I found something like this:
http://www.plascore.com/pn1-nomex-aramid-fiber-honeycomb.htm

or

http://www.imatec.it/flash/pdfs/NOMEXeng.pdf


thanks

[captainjack115]

That's interesting Captainjack, Bob's panels just rested on the floor and no corners were specially rounded. But  how should we get them into the air ?

/Erling

[/b]

Hi Erling,

I'm using a self supporting frame and suspending the panels with elastic bands at the moment.
I punched several holes around the outer perimeter, the elastic bands are looped through the holes, the other end of the of the bands are attached to small hooks inside the frame. The sides and top require stronger bands, the bands at the bottom more or less are there to stabilize.

This is a temporary solution, the bands will eventually stretch and move things out of position. Gravity is most unkind. Springs may work, but they need to be dampened with foam or silicone.

The main thing is that the panels should be acoustically isolated from the frame. Hanging the panels from the top edge simply won't do, bass notes would have them swinging around uncontrollably. The panels need to move in a predictable manner, if they aren't sufficiently dampened there will be Doppler shift.

Another matter has just occurred to me!

Pistonic woofers generate counter E.M.F., mostly due to their large excursions.
My instincts tell me that several exciters would still generate less counter E.M.F. than it's pistonic counterpart.
"If" this should be the case, the damping factor of the driving amplifier should be of less importance.

Jack

[captainjack115]

Hello,
i'm new and i'm really interested in the project.
I've a question, why don't use a honey-comb core Nomex panel as the original Podium Sound model 1?
There is something wrong with that kind of material?


Hello and welcome!

There's nothing much wrong with Nomex, in fact most people on this forum would love to use it. Nomex is not inexpensive and carving it up for DIY experiments can be costly.

I'm working on an idea that may negate the use of Nomex, if it works I'll let everyone know what I did. There's no sense in several contributors of this forum duplicating my futility.

Jack

[captainjack115]

This is not an easy decision for me to make after the events of the last few days.

Due to so many kind and supporting personal emails received, from considerate and thoughtful people, pleading with me to return (some from people that I have not heard of or known about, some from all parts of the world and even phone calls from within West Australia and the Eastern States of Australia!),I will come back if you still wish me to do so on this forum , as it now seems very obvious that the NXT panel project has such great significance apparently..........to more people than I could have ever imagined.

Welcome BAck!!!!!

Jack

[j gale]

Zygadr,  I am so pleased to see you back. I hoped a quiet day or two would do it. I'm all for the idea of hunting for another panel material in the hope that it will better gatorfoam. If we don't have that result, the gatorfoam is good enough. If exciter parameters exciter positions, numbers of exciters, panel size, mounting strategies etc could be optimized the gator would be fabulous. I agree with Scorpion when he says "He may well sit on one of the best high bass, mid range, low/mid treble speakers there is." I believe that even foamcore or similar can be greatly improved by lacquer or other coatings. I think the possibilities are endless. I also think that the critics will remain unmoved until like it or not they hear one of our big panels for themselves. When it comes to audio I have never been able to determine if I like something or not any other way. Now some more info about those piezos. Do the smaller ones work too?

[usp1]

Welcome back Zygadr...and don't let the critics get to you.

By the way has anyone thought about Mod Podge...the stuff crafts people use for paper and cardboard. Maybe Mod podge on corrugated cardboard might do the trick since it supposedly does not get absorbed into the cardboard like more liquid coatings like varnish do.

[DanTheMan]

Firstly, I am not an unkind or malicious person despite my last outburst, which I sincerely apologize for............that was just plain stupid and I reacted impulsively.......again!

It seems very clear to me now that we need to accept measurement techniques, whether they are 100% effective or not. We need to be decisive and analytical of panel materials, mounting methods and ALL aspects of this project.

No offense taken Ziggy.  I assume you are apologizing to me? or perhaps Fivestring? or perhaps to all?   I do think to make incredible panels, measurements will help us get there one way or another.  I can't recall any successful engineering projects that didn't involve measuring.  Of course listening matters as well!   All in perspective.

It's good to have you back.  You are the person who got me interested in taking a stab at this technology.  I feel like I can return now as well--though I'm sure my welcome will be less warm.
The only time I ever heard an exciter panel was in a Brookstone's (I think that what it is called) store.  It was just a little cheap (as far as build is concerned) device, but it did manage to sound good in the MR and had a crazy depth of field like an electrostatic driver.  I think they were trying to market it as one in a shady sorta manner.   

So it seems like there is a general consensus that foam board for art projects is a good material on the cheap?  I'd like to experiment with something cheap to find the best placement for the exciter(s) by measurement(s) and also see if we can't find a pattern for placement in the response graphs.  Any other dirt cheap material I should be interested in readily available in the US?

Thanks,

Dan

[DanTheMan]

BTW, 2 posts happened while I was writing my previous post.  For what it's worth, I wasn't trying to say this whole thing is a bad idea (I hope that not what people actually thought ), just that it seemed the design process wasn't going well.  IOW it didn't seem to be progressing in the right direction.  Just sort stabbing in the dark and the prevailing attitudes were not going to help it progress.

I'd like to pursue a more systematic approach and I'll need a little help getting up to speed.

Has there been an optimal size, and/or shape determined?

Is there any reason why the same placement(s) on different materials of the same size/shape would effect the sound in specific ways other than what involves the intrinsic properties of the panels?  Boy, that's poorly worded. In other words, shouldn't the placement that yields the best treble response on a foam core board transfer over to the best response on re-board?  Thoughts?  Experimental Data already available?

What again are the properties of the material we are looking for?  I know light and rigid, but isn't there something else that needs to be included here?  I thought it was mentioned before, but I can't seem to find it.

Thanks,

Dan

[Kludden]

I thought we had mist Zygadr. Welcome back. We DIY needs guys like Zygadr.

Regards
Kludden

[cometarossa]

Anyone know how to find out this software?

http://www.vxm.com/NXT.html#Heading7 

 

[mkstat]

It seems to be a proprietary skript (by NXT) for AkAbak speaker simulation software.
Akabak is free for private users.
http://www.randteam.de/_Software/AkAbak/Download-AkAbak.html

To get access to the DML skript you will need a NXT licence.

-m

[cometarossa]

It seems to be a proprietary skript (by NXT) for AkAbak speaker simulation software.
Akabak is free for private users.
http://www.randteam.de/_Software/AkAbak/Download-AkAbak.html

To get access to the DML skript you will need a NXT licence.

-m

Hmm.. this is really unpleasant.
I'm dreaming a software like that to play with...
I understand that the measurements are not so important with this tecnology, but as they wrote:

"NXT is a highly deterministic technology: the acoustic performance of an NXT panel can be very accurately predicted once a few key parameters are specified relating to the size and shape of the panel, the positioning and electromechanical properties of the exciter(s), and the material properties of the panel material itself. "

So i think there are a lot of mathematical formula out there
Obviously they (NXT) have a stand alone loudspeaker software. I don't belive they create a custom software for any licensed companies...
I want that software! 

[mkstat]

I've found more info about the DML prediction software on the R&D Team Software (Joerg Panzer) homepage and in the AkAbak manual:


Quote from www.randteam.de:

"AFR-Designer simulates the radiation and motor parameter of a fully coupled motor-plate-acoustic loudspeaker driver. The model is based on modal-analysis and axis-symmetry. AFR-Designer makes use of Vacs as output device. This approach dramatically reduced the cost of development because the design concentrates only on the implementation of the mathematics and on the input part. AFR-Designer was designed after specification for Nxt (2003).

PanSys This software simulates the fully coupled system: Lumped elements for the exciter and electronics, modal analysis for the plate, the enclosure and the radiation. PanSys is very powerful in prediction and a particularly useful tool for the design of rectangular plate speakers. The code-base of PanSys is huge and it took us several years to develop (1997).

AkAbak for DMLs This special implementation of AkAbak is able to simulate the response of multiple exciters on a plate. The plate was assumed to be infinite and some assumption about the radiation were made. This project was done for Mission UK (1996)."

Quote from AkAbak Manual:

"In 1998 the developer of AkAbak joined the NXT-Distributed Mode Loudspeaker project at
New Transducers. NXT has selected AkAbak to be the base for its software front end 'NXT
Designer'. The latter is part of the NXT licensee package and incorporates the DML
components and tools for panel design. AkAbak is developed in parallel with the NXT
Designer, i.e. both packages are compatible. The only differences are the DML components."

-m

[DanTheMan]

Thanks for getting me a bit more up to speed here Ziggy!

Man I'd love to have that software!  Anyone good with modal analysis?   It seems to me that placement should be independent of material, but I of course could be off.  No one's done that experiment?

So what do we know about building a good panel?

1) we need a suspension that allows the panel to vibrate as freely as possible w/o swinging
2) the material needs to be stiff and light for the panel
3) in-line, off-center exciter placement seems to work best
4) anything else?
Dan

[captainjack115]

1. Panel suspension needs to be stabilized so that there is no further stretching downwards due to the effects of gravity.

Consider using a low mass compliant brace, with just enough lift to neutralize gravity. Something that would loop around and under the magnet and fasten to the panel just an inch or two above each exciter. I'm not trying to be humorous, but it would act something like a bra. Yes I know, I'm thinking about a rubber band, but we need something that won't lose elasticity over time.
It would be simple and we wouldn't look like we were trying to copy the Podium's to the last detail. Using a spine also means connecting it the frame and suspension system.

Just a little something to think about.

Jack