Just go with the thinnest 5-layer you can find. Thin double sided tape was used for my experiments, but I would have used CA (super glue) if I was going to make it permanent.
I can't remember how the little carboard disk was attached to the black platic ring on the voice coil.
I took a look at those podium speakers. I see the whole panel is free floating at the edges, the panel being suspended down the middle by the array of exciters. That would be impossible to do with only one or two exciters and a large panel.
I can't remember how the little carboard disk was attached to the black platic ring on the voice coil.
I took a look at those podium speakers. I see the whole panel is free floating at the edges, the panel being suspended down the middle by the array of exciters. That would be impossible to do with only one or two exciters and a large panel.
O.K......will do.
I presume the plastic ring is attached with double sided tape also. We'll have to wait and see when I dismantle one.
I know what you mean about the way the PODIUM speakers are built altough I think you'll find that the corners are held by some kind of white gooey rubber like substance according to the review on 6 Moons where they watched as a panel was repaired by Shelly Katz, the designer.He mentions his never ending search for sticky materials before the right one was found(marketing hype?)
A floating panel is still what it is though and that's why I am intent on using multiple NXT motors to drive a large panel - it's the only way to approximate this design and get enough power handling and sensitivity.
Don't know where this will all lead to but I'll give it my best shot.
By the way, the other 4 pairs have arrived today, which will make it 6 drivers per panel, so, obtaining the panels cut to size will be the next step.
I live close by to a ''composite materials'' supplier and guess what.......he can supply NOMEX HONEYCOMB sheets and will laminate anything you want to it. Estimate so far is about $500 Aust. for (2X) 6 foot x 2 foot sheets. That's a lot to spend without much more experimentation though
Checked out a rubber goods supplier today - man!.........there is a multitude of rubber sheeting, strips tapes to choose from. There will surely be something there to suspend the panel with.
I presume the plastic ring is attached with double sided tape also. We'll have to wait and see when I dismantle one.
I know what you mean about the way the PODIUM speakers are built altough I think you'll find that the corners are held by some kind of white gooey rubber like substance according to the review on 6 Moons where they watched as a panel was repaired by Shelly Katz, the designer.He mentions his never ending search for sticky materials before the right one was found(marketing hype?)
A floating panel is still what it is though and that's why I am intent on using multiple NXT motors to drive a large panel - it's the only way to approximate this design and get enough power handling and sensitivity.
Don't know where this will all lead to but I'll give it my best shot.
By the way, the other 4 pairs have arrived today, which will make it 6 drivers per panel, so, obtaining the panels cut to size will be the next step.
I live close by to a ''composite materials'' supplier and guess what.......he can supply NOMEX HONEYCOMB sheets and will laminate anything you want to it. Estimate so far is about $500 Aust. for (2X) 6 foot x 2 foot sheets. That's a lot to spend without much more experimentation though
Checked out a rubber goods supplier today - man!.........there is a multitude of rubber sheeting, strips tapes to choose from. There will surely be something there to suspend the panel with.
Ziggy,
Thanks for keeping us posted I have a suggestion for panel material, but cannot find a trade name for the stuff. Anyhow, my wife came home the other day with some packing board from the post office. It seems to be a laminate styrofoam core faced by paper/cellulose. This is a very stiff material for its weight - semingly a good candidate for distributed mode projects.
Cheers,
Ed
Thanks for keeping us posted I have a suggestion for panel material, but cannot find a trade name for the stuff. Anyhow, my wife came home the other day with some packing board from the post office. It seems to be a laminate styrofoam core faced by paper/cellulose. This is a very stiff material for its weight - semingly a good candidate for distributed mode projects.
Cheers,
Ed
Update...........bought a plastic jar of SHELLAC FLAKES from the local hardware store (Bunnings for all you Aussies out there).
I will try the mix on some nomal 5mm thick corrugated cardboard scrap to see what happens.
The recipe for shellac ''varnish'' needs an 8 hour dissolving of the flakes in spirits.
Should be interesting as shellac is bug s**t (of all things !). It dries super fast and cures rock hard I believe.
This I presume will take the cardboard panels to a noticeably different performance level....it has to, as cardboard is essentially made from glued paper and is soft if anything - not ideal for NXT applications.
Here's an intersting fact : honeycomb nomex is also made of paper that's dipped in resin to harden and strengthen it so I think I'm on the right path with the shellac coated corrugated cardboard laminate.
The idea of using the honeycomb structure in DML's is due to the vibrations being able to travel in all directions due to the connections of the honeycomb cells........similar to the corrugated waves in cardboard laminates but maybe not as efficiently.
As many audiophiles believe that paper is the best sounding speaker driver material, being made of natural materials, the ''bug doo -doo'' infused card board is as natural as you can get I suppose
I will try the mix on some nomal 5mm thick corrugated cardboard scrap to see what happens.
The recipe for shellac ''varnish'' needs an 8 hour dissolving of the flakes in spirits.
Should be interesting as shellac is bug s**t (of all things !). It dries super fast and cures rock hard I believe.
This I presume will take the cardboard panels to a noticeably different performance level....it has to, as cardboard is essentially made from glued paper and is soft if anything - not ideal for NXT applications.
Here's an intersting fact : honeycomb nomex is also made of paper that's dipped in resin to harden and strengthen it so I think I'm on the right path with the shellac coated corrugated cardboard laminate.
The idea of using the honeycomb structure in DML's is due to the vibrations being able to travel in all directions due to the connections of the honeycomb cells........similar to the corrugated waves in cardboard laminates but maybe not as efficiently.
As many audiophiles believe that paper is the best sounding speaker driver material, being made of natural materials, the ''bug doo -doo'' infused card board is as natural as you can get I suppose
I just tried a piezo on cardboard and I find at higher levels it doesn´t differ much from what I have heard in stinking basement discos in my youth.
What I have to admit is that transparency is much better than the Podium Sound speaker I heard at the Highend in Munich this year. In fact together with Rethm (Lowther) it had the worst transparency I experienced at the show. It´s a shame that non of those NXT guys with their 1000 patents had the idea of using piezos for the top octave.
What I have to admit is that transparency is much better than the Podium Sound speaker I heard at the Highend in Munich this year. In fact together with Rethm (Lowther) it had the worst transparency I experienced at the show. It´s a shame that non of those NXT guys with their 1000 patents had the idea of using piezos for the top octave.
Must confess I haven't had much experience during my youth with ''stinking basement discos'' LOL !!
elOL, don't get confused between what is mainly high frequencies from a piezo on cardboard and transparency. The piezos can and will produce some good sounds in their limited range. Overdrive them and they will sound terrible.
I too have thought about using piezos as tweeters with the NXT panel drivers but don't feel that this is necessary in my listening room which is very large and live sounding. As a matter of fact, I have noticed some important facts that have emerged over the last few weeks of experimentation :
1. The NXT drivers are beginning to sound better and better each day and I can only (even though I'm not a great believer) attribute this to'' BREAK - IN '' which is at about 30 hours of use in total at the moment according to my rough calculations.
2. On the subject of transparency, this is what I have noticed more than anything else.........some recordings that have background shuffling, coughing and other noises are more pronounced now than ever. Sometimes they jump out at you quite unexpectedly. I have never experienced this as much with any other speaker over here , even with the large compression driver horns that I have at the moment.
I'm not trying to defend the Podium speakers and have never heard them (and probably never will), but I have heard some NXT small panels linked to small subs and can't say that their top end was anything to rave on about - quite the opposite in fact.
Some of these panels had METAL SHEETS on the fronts of the panel material
How in the hell is that going to assist in the high frequencies ? Sure it will stiffen the panel, but at what cost to the audio spectrum and sensitivity?
My purpose to this thread has been to demonstrate that DML's can and do work and by the looks of it, a ''podiumclone'' LOL is within our reach and cheap to build. No, you won't need a piezo as a tweeter, it will be a crossoverless true ''full range'' driver, I hope
elOL, if you found the Lowther based Rethm's lacked transparency, I suggest you have the wax removed from your ears.
With the Podium's sound, they are very contraversial in their high frequency delivery as I have discovered in my tests. As stated before, the high frequencies/transparency are all there in more than adequate amounts, it's just that they are presented to the listener in a different way.
I can move the one and only summed mono panel I have just a couple of feet in, out, left or right and the sound changes ( but not like a typical direct radiator speaker ).
What you heard at the show may well have sounded bad if the room acoustics and set up was not ideal. There is no doubt about that.
I can only hope that my continued experimentation ends up being a useable DIY product.
So far, it's a pure joy to listen to music through this prototype, even in mono, and not noticing driver material differences, crossover points, coloration etc. They just play music. Music you can listen to all day
elOL, don't get confused between what is mainly high frequencies from a piezo on cardboard and transparency. The piezos can and will produce some good sounds in their limited range. Overdrive them and they will sound terrible.
I too have thought about using piezos as tweeters with the NXT panel drivers but don't feel that this is necessary in my listening room which is very large and live sounding. As a matter of fact, I have noticed some important facts that have emerged over the last few weeks of experimentation :
1. The NXT drivers are beginning to sound better and better each day and I can only (even though I'm not a great believer) attribute this to'' BREAK - IN '' which is at about 30 hours of use in total at the moment according to my rough calculations.
2. On the subject of transparency, this is what I have noticed more than anything else.........some recordings that have background shuffling, coughing and other noises are more pronounced now than ever. Sometimes they jump out at you quite unexpectedly. I have never experienced this as much with any other speaker over here , even with the large compression driver horns that I have at the moment.
I'm not trying to defend the Podium speakers and have never heard them (and probably never will), but I have heard some NXT small panels linked to small subs and can't say that their top end was anything to rave on about - quite the opposite in fact.
Some of these panels had METAL SHEETS on the fronts of the panel material
How in the hell is that going to assist in the high frequencies ? Sure it will stiffen the panel, but at what cost to the audio spectrum and sensitivity?
My purpose to this thread has been to demonstrate that DML's can and do work and by the looks of it, a ''podiumclone'' LOL is within our reach and cheap to build. No, you won't need a piezo as a tweeter, it will be a crossoverless true ''full range'' driver, I hope
elOL, if you found the Lowther based Rethm's lacked transparency, I suggest you have the wax removed from your ears.
With the Podium's sound, they are very contraversial in their high frequency delivery as I have discovered in my tests. As stated before, the high frequencies/transparency are all there in more than adequate amounts, it's just that they are presented to the listener in a different way.
I can move the one and only summed mono panel I have just a couple of feet in, out, left or right and the sound changes ( but not like a typical direct radiator speaker ).
What you heard at the show may well have sounded bad if the room acoustics and set up was not ideal. There is no doubt about that.
I can only hope that my continued experimentation ends up being a useable DIY product.
So far, it's a pure joy to listen to music through this prototype, even in mono, and not noticing driver material differences, crossover points, coloration etc. They just play music. Music you can listen to all day
Ziggy said:
Maybe we are talking apples and oranges. With lacking tranparency I don´t mean the number of perceived events (the Lowthers are really good in this respect) but some kind of fog that lifts when you enter a room with conventional speakers. The Geobel NXT speaker is much better in this respect, as in others, but has limited SPL
Ok......I understand your point. Reading up on the Goebel, they are using a very small panel and a wooden one at that, augmented with a subwoofer and complex crossover. A recipe for disaster in my books.
It's much easier to make a small nxt panel than a large one. I have made both and they sound completely different. The smaller ones seem to be brighter or more ''airy'' but this is only an illusion because when you mount more drivers on a much larger sheet of anything (cardboard, plastic, whatever) the sound becomes more diffuse and less like a normal speaker.
Here's another thing - critical placement of the drivers to make the bending wave thing work is very debatable. In the free panel system I am playing around with, you can place the drivers virtually anywhere and there is no dramatic change in sound noticeable.
It's a weird effect and as I have mentioned many times before, everything is there only it's all around you not BLASTED AT YOU which is what conventional speakers do. This is not ''lifting a fog'' it's what we are used to hearing all these years with the same boxed in technology and multiple drivers with their damned crossovers.
It's much easier to make a small nxt panel than a large one. I have made both and they sound completely different. The smaller ones seem to be brighter or more ''airy'' but this is only an illusion because when you mount more drivers on a much larger sheet of anything (cardboard, plastic, whatever) the sound becomes more diffuse and less like a normal speaker.
Here's another thing - critical placement of the drivers to make the bending wave thing work is very debatable. In the free panel system I am playing around with, you can place the drivers virtually anywhere and there is no dramatic change in sound noticeable.
It's a weird effect and as I have mentioned many times before, everything is there only it's all around you not BLASTED AT YOU which is what conventional speakers do. This is not ''lifting a fog'' it's what we are used to hearing all these years with the same boxed in technology and multiple drivers with their damned crossovers.
Gave a scrap piece of 4 mm corrugated cardboard a few increasingly stronger coats of home made SHELLAC varnish.
The varnish does in fact stiffen and harden the cardboard, BUT................it does not penetrate in to the corrugations because of the glue that covers both interior sides and glues the sides to the corrugate.
The only way to achieve this is to squirt in the varnish in to the cavities using a sort of ketchup bottle.
Seems like more trouble than it's worth and I'm leaning more towards the corflute which is stronger for the given size and thickness when compared.
From my tests so far, there is a possibility that high frequencies are more prominant with the corflute but I can't be 100% certain of this. 5 layer cardboard corrugate is only effective in small panels and in small thicknesses. To get a large panel, you need to get 5mm thick stuff which just has too much paper in between the exciter and front of panel.
Corflute has much less material in 5mm thickness sheets - it's mainly air and vertical struts that form long, vertical square tubes, one next to the other. Corflute does not in any way sound inferior to the cardboard.
I have examined FOAMCORE. You've got to be kidding!.......this stuff is much too soft for DML's. I'm not even going anywhere near it.
I'll just have to bight the bullet and obtain a large sheet of Corflute and judge it's performance from there on. The large sheet of cardboard I have at the moment can really release some very low notes when required. I hope that the corflute can do the same.
The varnish does in fact stiffen and harden the cardboard, BUT................it does not penetrate in to the corrugations because of the glue that covers both interior sides and glues the sides to the corrugate.
The only way to achieve this is to squirt in the varnish in to the cavities using a sort of ketchup bottle.
Seems like more trouble than it's worth and I'm leaning more towards the corflute which is stronger for the given size and thickness when compared.
From my tests so far, there is a possibility that high frequencies are more prominant with the corflute but I can't be 100% certain of this. 5 layer cardboard corrugate is only effective in small panels and in small thicknesses. To get a large panel, you need to get 5mm thick stuff which just has too much paper in between the exciter and front of panel.
Corflute has much less material in 5mm thickness sheets - it's mainly air and vertical struts that form long, vertical square tubes, one next to the other. Corflute does not in any way sound inferior to the cardboard.
I have examined FOAMCORE. You've got to be kidding!.......this stuff is much too soft for DML's. I'm not even going anywhere near it.
I'll just have to bight the bullet and obtain a large sheet of Corflute and judge it's performance from there on. The large sheet of cardboard I have at the moment can really release some very low notes when required. I hope that the corflute can do the same.
UPDATE :After numerous side by side switching and testing between corflute and corrugated cardboard there is a clear winner and it's a surprise
CARDBOARD !!!!!!!!!!!!!
No matter how hard I tried to convince myself that corflute had to be better, it WAS NOT...........PERIOD!.......theAnonymous1 was right in his recommendation as per NXT's original panel material suggestion.
Cardboard, no matter what thickness or whether single or double ply(5 layer) still produced a more natural balanced sound and had a clearer top end.
Another revelation : the more exciters mounted on the panel(impedance taken in to account and wired appropriately) the greater the output in the high frequencies and midrange presence. There is no doubt in my mind that this is occurring and I have noticed this as each extra exciter was added to the mix during the course of experimentation.
The shellac coating is still in the works and a method of infusing the corrugations has not yet been solved - as previously mentioned, the only way that I can see this being done is to squirt in the shellac and that is where I am at in this point in time.
If this fails, it will not be a drama as I am only presuming that it will help in the sound reproduction but can't justify this for any certainty as yet.
The panels will be held in to the wooden frames by corner blocks and side blocks and will ''FLOAT'' on a highly flexible black silicone that is commonly available.
I have not tried to ''ground'' the exciters with their own separate mounting structure as yet but this will be looked at in due course.
Agreed, polypropylene/corflute just does not sound right. The highs are muted and voice takes on a dead character.
I have commenced in disassembling one of the sound pads.
The ''foot'' is held to the flimsy cardboard disk by a ring of double sided adhesive tape. The driver itself has a PTC resistor rated at around 1.0 amp.
Question is : if I use 6 of these drivers in a paralell/series configuration, can I increase the rating of the PTC? Can I only use one at the input terminal instead of replacing all six?
Your advise is much appreciated
I have commenced in disassembling one of the sound pads.
The ''foot'' is held to the flimsy cardboard disk by a ring of double sided adhesive tape. The driver itself has a PTC resistor rated at around 1.0 amp.
Question is : if I use 6 of these drivers in a paralell/series configuration, can I increase the rating of the PTC? Can I only use one at the input terminal instead of replacing all six?
Your advise is much appreciated
Hi Ed.
I guess that the honeycomb NOMEX would be the closest to the ideal material as used in the Podium speakers and some of the NXT variants.
At this point in time, I can view the NOMEX material and have a yarn with the supplier as the company is only a short distance from where I live (talk about luck!!).
Yes, it's bloody expensive, but as el'OL mentioned a while back, why beat around the bush with the poor man's version when the proper stuff can be used straight up.
The Podium speakers have Polyethylene foil bonded to both sides of the Nomex but I am not sure if this is available as a material through this supplier .
The fellow I talked to before Christmas stated that ''they can laminate anything you want to the nomex core''.
I will ring the company today or tomorrow to arrange for a visit.
Had a close look under strong light at a TEAC NXT speaker from one of their sub/sat. systems. By looking at the front of the grill, I could see that corners of the panel where cut off at 45 degrees and there were three round black ''dots'' placed in an irregular clump at one side of the panel. The two small ones were the same size and then there was the one large one. In relation to the panel size, these ''dots were considerably large and were obviously doing something to the dampening or perhaps tuning of the panel. Interesting???........hmmmmmm???.
Anyone have an opinion on the PTC resistor question??
I guess that the honeycomb NOMEX would be the closest to the ideal material as used in the Podium speakers and some of the NXT variants.
At this point in time, I can view the NOMEX material and have a yarn with the supplier as the company is only a short distance from where I live (talk about luck!!).
Yes, it's bloody expensive, but as el'OL mentioned a while back, why beat around the bush with the poor man's version when the proper stuff can be used straight up.
The Podium speakers have Polyethylene foil bonded to both sides of the Nomex but I am not sure if this is available as a material through this supplier .
The fellow I talked to before Christmas stated that ''they can laminate anything you want to the nomex core''.
I will ring the company today or tomorrow to arrange for a visit.
Had a close look under strong light at a TEAC NXT speaker from one of their sub/sat. systems. By looking at the front of the grill, I could see that corners of the panel where cut off at 45 degrees and there were three round black ''dots'' placed in an irregular clump at one side of the panel. The two small ones were the same size and then there was the one large one. In relation to the panel size, these ''dots were considerably large and were obviously doing something to the dampening or perhaps tuning of the panel. Interesting???........hmmmmmm???.
Anyone have an opinion on the PTC resistor question??
Ziggy,
Very interesting posts - looking around, I haven't found a lot of good information on DIY projects with transducers like these. I saw some of these NXT units for sale recently at Parts Express and bought a pair of these:
Dayton DAEX25 Sound Exciter Pair
They just arrived last night, but I only had about 15 minutes to try them out - primarily on some cardboard boxes. Its definitely a different sound than my main loudspeaker pair - and surprisingly good! (Though not a replacement quite yet!) I'm looking forward to more experimentation.
I've been wondering about a couple of things, though. One - it seems that musical instruments (think of a guitar, violin, or even piano) work in a similar fashion to a speaker made with these transducers - with the transducer replacing the string and possibly the bridge. But many of these instruments (guitars, for example) work like a ported loudspeaker, with a resonance of the air inside the instrument reinforcing bass frequencies. I haven't seen any examples so far, though, of enclosures for these kinds of drivers (apart from people putting them on boxes.) What's interesting idea is to make something like a guitar, with a side that radiates attached to a tuned enclosure to reinforce bass frequencies.
-Paul
Very interesting posts - looking around, I haven't found a lot of good information on DIY projects with transducers like these. I saw some of these NXT units for sale recently at Parts Express and bought a pair of these:
Dayton DAEX25 Sound Exciter Pair
They just arrived last night, but I only had about 15 minutes to try them out - primarily on some cardboard boxes. Its definitely a different sound than my main loudspeaker pair - and surprisingly good! (Though not a replacement quite yet!) I'm looking forward to more experimentation.
I've been wondering about a couple of things, though. One - it seems that musical instruments (think of a guitar, violin, or even piano) work in a similar fashion to a speaker made with these transducers - with the transducer replacing the string and possibly the bridge. But many of these instruments (guitars, for example) work like a ported loudspeaker, with a resonance of the air inside the instrument reinforcing bass frequencies. I haven't seen any examples so far, though, of enclosures for these kinds of drivers (apart from people putting them on boxes.) What's interesting idea is to make something like a guitar, with a side that radiates attached to a tuned enclosure to reinforce bass frequencies.
-Paul
About the dots:
The dots seem like they could serve two functions: one would be to damp out particular resonances. But the other is that by adding mass in the right places, you can probably slow down the oscillation for particular modes (at the expense of lower efficiency, I suppose) which may help to create more bass.
-Paul
The dots seem like they could serve two functions: one would be to damp out particular resonances. But the other is that by adding mass in the right places, you can probably slow down the oscillation for particular modes (at the expense of lower efficiency, I suppose) which may help to create more bass.
-Paul
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