[Tinnitus]

I tried putting the cheap $5 exciters one on either side (both in and out of phase) on a cardboard panel and in both cases the results were terrible. It seems there is a lot of cancellation when one does that.

Damn, that's a shame, thanks for letting me know, I doubt that results with stretched fabric would be any better in that case.
I'll have to try the fabric idea first anyway as it may be a complete dead end for all I know.
I've only managed to read about half way through the 50 pages of this forum so far so I apologise if I'm repeating approaches that you've already rejected.
Has anyone reading this tried fabric?
Has anyone tried sticking one to a drum?, skin or shell?

I wonder of these exciters could be shipped in a padded envelope, as a personal letter, and whether it would speed the transit?  I might be willing to assist, contact me with a PM

Your offer of possible help is very generous John, thank you.
I'll pm you shortly

[Tinnitus]

Well, it turns out silk is fairly expensive.
Too expensive for me to use for experimental panels.
So I've bought some taffeta instead at about half the price, it seems good and strong and while it's not as thin as the silk I saw it's still pretty darn thin.
This stuff is cheap enough that I can try different approaches with stiffening/damping finishes without breaking the bank.
I'm also considering cutting up an old paragliding wing that I have lying around, but that would only be if the taffeta shows some sort of promise.
It's occured to me that finished fabric panels may be 'postable' if I make the stretching frame so it can be dismantled.
If my eventual results are listenable perhaps I could send them to one of you to compare/measure against your board type panels?, I can't afford the exciters to take more than one type of approach myself so I'll be in the dark as far as comparison goes.

[DanTheMan]

What about a stretched fabric like denim and then apply fiberglass resin to the center portion?  It should make it suitably stiff and it will hold itself in place as it dries.  If you want to stick with the mother of tone principle, paper mache in the same fashion.  Hmm, that sounds interesting.

Dan

[ondesx]

Hi Guys,

This thread is now going long isn't ?

Have anybody tried some expensive but powerful exciters from like say the Clark Synthesis TST429 Platinum Transducer ?

I mean instead of installing several little exciters everywhere the panels, is there any interest in using only one, but powerful unit instead ?

[Tinnitus]

Have anybody tried some expensive but powerful exciters from Dayton like say the 427 ?

I mean instead of installing several little exciters everywhere the panels, is there any interest in using only one, but powerful unit instead ?

Yes there definately is, see the last few pages of this thread.
I'm intruiged by the idea of making my own exciters, but I know voice-coil winding isn't especially easy.
I also don't know how different exciter 'architecture' is to typical drive units.
Does anyone think it might be possible to butcher a mid or full range drive unit and re-build it to suit our needs?
If I find fabric makes an acceptable resonator I could attempt to build a voice-coil into a hole in the membrane (tube piercing membrane) with a magnet fixed to a spline (or other basket substitute).
Cooling might be problematic, but silk impregnated with phenolic would probably be pretty heat resistant, and some sort of lightweight heatsink could be installed around the voice-coil on either side of the membrane.
Constructing something like this would not be 'pie in the sky', finding the time for it might be though.
Maybe I should spend less time on the internet?
Naahhh.

[ondesx]

I look to the opportunity of build my own motor... It isn't an easy task indeed... Magnets of Neodymium are expensive and are very strong : there is some caution to deal with. Then, the form and the type of steel, the rectification of it, etc... Not to speak about FEMM simulations of the magnetic field to be done if you want to go into the right direction !

Really, this is the hard way to go.

This is the reason that I follow the present thread since I hope we can do a good speaker with already existing exciters, drivers or whatever industry can offer for at least an affordable price.

[BowerR64]

What i dont understand is why is everyone stuck on a panel? why not try other shapes? why does it have to be flat? forget the flat crap its not working lets try other things i tried but i dont know enough about this to really design anything that would work.

Success???...................this is totally insane...........on a small scale it can be done............large scale..............forget it!!........the CC wants to bloat, bend and warp............you can't fight this fact.

For those that have nerves of steel and endless patience.............use something else or use nothing and save yourself a lot of frustrating effort.

I got two matching CC panels up and running on my main system last night(untreated.......of course).

Played what is probablY the greatest percussion CD on this planet(I can post details is you like)...........weird label, one off find.

Results?, ...............after 5 minutes the backs of the exciter casings were uncomfortably warm to hot. After 20 minutes..............I was concerned that they would start to glow RED.

On top of this, the adhesive exciter mounting rings (the proper ones supplied by NXT) were softened by the heat and looked like they were beginning to release their adhesion.

Further to that, with two identical panel materials playing, I noticed that they have a sonic signature.............cardboard........ ....what else?

You can now openly accuse me of constantly changing my opinion on this technology, breaking out in over excited, premature enthusiasm(and you would be 100% correct!), but it is a known fact that the choice of panel material will greatly influence the final tonal output........and this is the most deceptive and annoying part of all!!
At first impression, CC sounded much better than all other materials tried so far, and it does...............but, they have a sound that reflects what they're made of.............as does everything else.This is without doubt the most unpredictable, fussy, temperamental speaker technology I have ever encountered...........and I'm fed up with it.

''Mother of tone''?.........yes it's there, it's more real than foam boards but it's not the ultimate..............I don't know what is.

Frustrated, I connected up the Gatorfoam panels that had 6 exciters and repeated the tracks at the same volume setting, noting the temperature...........same thing..........2 extra exciters won't provide the necessary power handling for any music with severe transients.On top of that, the Gator has it's own sound............muffled and weird tonality..........go figure.

I can conclude that if you listen to ''tame'' music at soft to medium levels with a ''medium'' powered amp, you can live with these speakers and enjoy them for what they are. Use CC as it's the best sounding.

Beware though, that these cheap(and even the expensive more powerful ones - 15watt ....?? ............yeah..........impressive!) exciters have VERY LOW power handling capability and are inefficient..........VERY.

Now,............here comes the dilemna..........you add more exciters to increase power handling...............which it does, to a point.............with NORMAL levels/music.........BUT!............as we have found, more exciters is not allways good and in most cases leads to a detrimental effect on vibrational modes.In other words, it kills and confuses them.
So, .............we reduce the number of exciters...............REVELATION...... ............NOT! (power handling goes to shit!)

Some may say that this is a balancing act.................yes it is.

In my case and I know there are others out there who will agree, there comes a time when you wan't to hear a full symphony orchestra at live levels for an extended period of time (I mean ''LIVE'' not just loud.....however you gauge that) or a closely miked percussion one or something similar because you wan't to blast yourself to the back wall..........just for fun and the adrenalin rush!.............without having to worry that your exciters are going to melt or get damaged due to over excursion and going ''pistonic''..........which they WILL!!

It's o.k for the reviewers at 6 moons to say that the Podiums can reach ear damaging levels. Maybe they can............but for how long?..........and............ they have the luxury of using a panel material that is half the weight of our lightest diy offerings and consequently, they will sound at least twice as loud..........NXT advised me of this fact when I enquired on how and where to get the Nomex panels and what the result would be.

We all know that the cost factor prohibits any practical efforts to obtain this stuff and that Podium have a single company specially manufacture their panels to their specifications..............great

I leave this with you for comment if you like. I've been factual and honest with all here.
I believe that we have come as far as we can go within the limits of a diy panel.
To me it's a speaker that can be used for some music, but fails on a good chunk of others and is dependant on transient severity and power input to survive.

Where to from here?....................................... ....................................... ....

[sedge]

zygadr, I understand your problem,you have a very large room [I have been to concerts in smaller venues ]a high power version exciter would help you a lot but for some reason nxt and such do not seem keen on the idea?
thick cc is not very efficient so I use quite thin cc single layer and have just shellacked one side first to sea what happens .
the most efficient so far has been 15x 12 x1 polystyrene [very loud ] mmmm needs a bit of work though but it did give some very interesting sounds ,must try a bigger panel . AS to fabric and polythene panels I have dabbled some years ago using them as a baffle for my drive units ,they sounded quite good at low volume but at higher levels they just went to pieces.I wonder how many electrostatics would do  the same If used with a test tone?[buzzing along with the music as they reach their limit].

[ondesx]

@ Sedge : How do attach the foam to the frame ?

[doug s.]

i think pol_bct's idea of running exciters horizontally, close together, with, maybe one off to the side for increased treble, needs to be explored further.  even if done on two separate panels.  along the lines of what he posted here:

http://www.audiocircle.com/index.php?topic=70541.msg727581#msg727581


if i had the room, i would be doing this now.  meanwhile, i simply lurk, waiting for the future appropriate living enwironment; by then, y'all will have it figured out.  so, i need to point y'all in the right direction.   

doug s.

[ondesx]

This is a comment found elsewhere on the Net (from amina website I believe...) :

The problem of creating LF is not just size, rather the problem is that in order to create amplitude at lower frequencies, simple vibrations of the common exciter used in this technology would not be enough. Large movement would have to be created, which will take a device with long enough Xmax (the distance from 0 Volt or rest to full forward excursion of the coil at Max power) and a less rigid surface, and lots of power. The material would have to be flexible enough to allow the required movement to create the amplitude. By nature of the vibrational technology that is being used one can create devices using specially designed surfaces that are extremely rigid and lightweight, and therefore can produce very high frequencies. Properly designed, these can be completely hidden from the eye by building them into wals and ceilings, plaster and paint them over, without degradation of audio quality, even up well beyond our highest hearing capabilities. Making them flexible for low frequency reproduction would render them unusable for high frequencies, and they would sound muddy. Furthermore, the low frequencies would end up vibrating the devices, rattling everything loose, resonating with other spring-like structures at sympathetic frequencies (drone) and cracking the wallplaster or any other compound if it were build into the wall. Besides that, who wants to put vibration like that in any device, unless it was a massage chair. In most sound systems nowadays, we use subs for LF reproduction anyway. The combination of conventional technology for subs that can be hidden in furniture, and NXT allows us to create speakers that we can hear but not see, no cluttering and cables as they can hide behind the paint and wallpaper in walls and ceilings, be build into devices and furniture, and no longer be the eyesore of the interior decorator. Both the Audio enthousiast and the designers are happy campers that way.

[pol_bct]

Hello all DML fans!

>> The problem of creating LF is not just size, rather the problem is that in order to create amplitude at lower frequencies, simple vibrations of the common exciter used in this technology would not be enough. Large movement would have to be created, which will take a device with long enough Xmax


I desagree completely with this opinion, this analysis could be true about piston drivers
or If we had exciters with very large Xmax, but we are talking about DML modes and we only get
low power exciters.

Producing LF is not only a matter of excursion but of surface of radiation
If we move one inch² by one foot, we will NEVER get LowFrq
but if we move 1 meter² only by 1 millimeter we will have serious BASS

regards

POL

[j gale]

I agree totally with POL on this,because that is my experience. As long as the panels are large bass is not a problem. With my large panels I don't bother with a sub. Don't need it.

[jeffac]

jeffac has access to what I believe may be the ultimate CC..........XITEX.

Guys, been away again for a few days but before leaving got to pick up some freebie 4 mm Xitex CC, 4 x 1840 mm x 715 mm sheets in fact, 
Also picked up 2 x 1800 mm x 750 mm and 2 x 1200 mm x 750 mm sheets of the very high quality 6 mm dual-flute CC as shown in the pic I posted. 

And I got them home intact, so past base 1.

The XCC is very rigid across the flute orientation but prone to warping along it as its only 4 mm wide. Flutes are quite tight and surfaces very hard, both flutes and surfaces appear to be made of premium kraft paper. Indeed I might bring home some scales to prove this, but it feels very similar in weight to the 6 mm DFCC sheets of essential the same dimensions. Scratching and fingernail pinging gives an almost brittle dynamic sound. Native frequency of these tests seems somewhat higher than the DFCC. Impressions, I think the XCC might make a dynamite panel material when treated with Floorguard Tung Oil, and used with a spine, and with a multiple panel decoupling idea I have in mind that hopefully will work.

The DFCC is structurally very rigid in both directions with a piece 1800 x 750 mm in dimensions and could be used easily without a spine and sound very good I think… as jgale and zygadr have already proven. Treatment with Floorguard or similar might take it to another level … but will need to experiment with trying to do this successfully with a very large panel, and as zygadr has found, this is not straight forward. That said, the flutes of the DFCC run in the 750 mm width direction so just maybe this will help avoid warping during the treatment process.. but testing will be required. 

General comments on the latest discussions, all out there and very interesting ideas …..

However, jgale's and bobloblob's Replys #977 Reply #978 sum up some of my thinking for the time being at least.

Bass is deep and tuneful on large panels… but it will be very difficult to ever get that outright low down slam of pressurized BOX bass, same as for most OB bass though…  so of no real concern I believe in what we’re trying to achieve here.

Percussion dynamics.. I think some of this can be solved by adding HF dynamics as I've tried with the use of a piezo tweeter cone, which in my current panels, is added to a small panel on top of the NXT panel, now elevated slightly so the panels are more decoupled as I'm enjoying this. And based on my enjoyment of the sound of my dinky single exciter panels, just maybe more of that dynamic attack of percussion instruments can be rescued by avoiding multiple exciter interactions and expanding on the one exciter per panel theme.

Better get off and earn some brownie points with my valentine.. seeing its that special day and all.

cheers..jeffac

[sedge]

Ondesx
At the moment I am just using masking tape to hang the panels from some up lighters I have in my room,it is easy to change the panels quickly  for comparisons .
My friend eventually came over the other day [work and family seem to get in the way of audio heaven] so I ran through all of my panels so far all  in that one evening .
He made some very interesting comments .
1 -He felt that the presentation of the sound was very different  from ordinary speakers.
 2 he was hearing new sounds from music that he has been listening to for the last 30 odd years .
3 Because he is a bit of an artist [piss artist ?] he describes sound in art terms such as pencil sketches  and colour paintings , he could hear coloration’s and distortions but because the picture was so beautiful you just ignore them.
This was listening to the first set of polystyrene panels I had knocked up the night before as an experiment ,they were rattling and buzzing lick mad if you turned the volume up or had a sustained horn note.so when I changed to the better panels things improved .
The upshot of all this is he wants at least three pairs of my exciters .
Two pairs for his main speakers and one pair for his computer room.
At the moment he is using 2 inch bandor units and 15 inch Lf divers in an open baffle arrangement .
Now he has heard them he must have them[he is hooked and will soon be pulling all his hair out trying to get them perfect]hee hee haa haa.What are friends for.
If they did not sound soooo damned good you could just walk away and give up,but that’s not going to happen, no matter what, I am not loosing this sound and I am going to stick with it .Ok if I hear something that sounds better then that would be the way I would probably go,but I do not see anything out there at the moment that is going to do the job better even with their problems[which can be solved with subs and tweeters very easily if that is the way you wish to go].
But I must say that even though the thought of a full range panel is very exciting ,I do have problems with the thought of one exciter producing high level sound from say 5 hz to 20 k and beyond ,I can not see it at its best ,it may sound good but is probably going to end in a bang.
Even if I do end up with a large full range panel I would probably roll off the low fs to a sub ,I do not know the answers for everyone but I do know what is best for me.
But that does not stop us from trying!

[ondesx]

Well, could we try to summarize the info on panels, first the definite points :

- for LF efficiency then we need large panels at least 1 m^2 or 4' squared.
- the stiffness is the important factor for HF range.
- the sensitivity is better for lighter panels (i. e. the lighter the louder)
- there is no box needed, since the bipolar radiation improves the overall output about 3 to 6 dB compared to dipolar speakers.
- the exciter(s) must not be centered...
- several materials will do... at least with a low weight and a high stiffness.

But several points remain unclear :

- first the shape of the panel : square, circular or rectangular?
- is one high powered exciter better than several low powered exciters regarding audio quality (frequency range, loudness, overall distortion, coherence and depth of soundstage, musicality and truth of the instruments and voices, etc.).
- must the panel be free or firmly attached to the frame, in the later case is the shape important or not?
- most exciters are to be used horizontally (i. e. facing floor or sky), would they have a shortened life when used vertically ?
- which is definitely the "best" material for the panels ? And the best exciter ?

I hope somebody will synthesize the situation yet...

[ondesx]

But I must say that even though the thought of a full range panel is very exciting ,I do have problems with the thought of one exciter producing high level sound from say 5 hz to 20 k and beyond ,I can not see it at its best ,it may sound good but is probably going to end in a bang.
Even if I do end up with a large full range panel I would probably roll off the low fs to a sub ,I do not know the answers for everyone but I do know what is best for me.
But that does not stop us from trying!

As far as I know, some exciters have a frequency range of 5 Hz to 17 kHz! I think the LF range wouldn't be a problem. HF will roll-off more or less faster and I'm afraid that a tweeter will probably help much more than a sub... But I didn't any experiment yet, my very high power exciter was ordered recently and I'll have it in the next week probably (hope so...).

[usp1]

 wonder if it would make sense to have more than one panel for each channel. A large panel for the LF and a smaller perhaps more rigid panel for the HF. From my experience with the few panels I tried the problem if the HF rolloff.

[ondesx]

wonder if it would make sense to have more than one panel for each channel. A large panel for the LF and a smaller perhaps more rigid panel for the HF. From my experience with the few panels I tried the problem if the HF rolloff.

If you read the comment from POL few pages ago, he suggested even for stereo listening only... one panel !

I really like very much this idea for (at least...) the theoretical time and space "coherence" of the resulting wave !...

[Tinnitus]

Well, could we try to summarize the info on panels, first the definite points :
- most exciters are to be used horizontally (i. e. facing floor or sky), would they have a shortened life when used vertically ?

Thanks for rounding up the main points here ondesx.

Couple of questions and Ideas:
Has anyone tried hanging their panels flat ( as they would be if installed in a ceiling)?, if so how does it sound?.

How about combining your 'Single panel for stereo' approach with the 'Seperate bass panels' idea?.
This would result in two panels, one hung below the other, treble and bass driver style, but each panel radiating both stereo channels.
If we have panels optimised for frequency requirements purists who hate crossovers may not even need an electronic crossover to seperate freq's as we might have a 'physical x-over'.

A further possibility might be to use one panel for both stereo channels, but change it's physical properties over it's surface by treating the bass portion of the panel so that it's suitable for lower freq's, and treating the treble portion to respond to the higher freq's( or changing the thickness/density of the panel ).
This change in panel properties could be gradual or immediate, and exciters could be grouped as needed.
Not easy perhaps, but with what you guys already know from your experiments it might be possible?

my very high power exciter was ordered recently

This sounds promising, looking forward to hearing your opinion/results.