[sedge]

Sorry got cut short on last post.

I do have a 2x3ft  3mm ply panel that is very rigidly mounted in a solid frame ,the LF roll off is at about 40hz ,hf is above 20k,the efficiency is enough to fill a medium size room without overheating a 10watt exciter,24watts or more would be much better.
I use weights in certain places on this panel to fill in and increase output in certain areas ,these areas vibrate heavily,like a second or third LF drive unit (as an afterthought these places would not be a good place to put a second exciter ) My aim is to make the panel do the work,not the exciter .
Sorry again but have to go ,looking after a baby 
Steve

[sedge]

The silicone to support the exciter and to reduce buzzing from the spine was from an early patent ,maybe nxt ?
Large wood panels with a long spine will have a problem with bowing ,in and out ,all over the panel.
There are a few options for supporting the exciter ,one is a single mounting at the top of the panel ,this would support the exciter and allow some movement of panel and spine ,the spine would not necessarily have to be rigid ,it could be used just to support the exciter and not restrict the ,in and out movement, as long as you are not going down below 100hz or so,this should be ok.
Another possibility that I have in the past used on poly panels ,is placing the spine mounting on the panel closer to the exciter area ,this can be as simple as a small block of polystyrene glued to this panel for lightness ,or if there is an anti-resonance point that needs a weight applied maybe this could be a good mounting point(this last point is something I have thought of but not implemented) obviously you would need to be able to see the response to be able to do this.
Steve

[OZZIOZZI]

Odal3 said, "I found that the thinner ply warped and moved too much when playing loud." You are not wrong there. What was a almost flat sheet corkscrewed as the glue/water treatment dried. I guess that surface treatment applies surface tension and the sheet responds according to its weaknesses. Maybe I will try some thicker ply as Sedge suggests. Good to hear that my exciters are pretty rugged. I have been keeping the volume down--just in case of overdriving, but maybe I can crank them up a bit.

Re exciter mounting, I guess the best way is to pick the best spot and make sure they are firmly attached by the VHB adhesive pad. If they fall off then I can try other glue and/or spine. I remember an old trick with rubbing voice coils on vintage speakers is rotating the frame or enclosure 180 degrees so VC  sags the opposite way. The same principle should work with panels in the long term.

[pol_bct]

A thing I have noticed is that the vast majority of DML users agree that confortables sound levels are not difficult to reach even when using only one low power exciter per side. At the begining I made the assumption/calculation that I will need 4 to 8 exciters per side, I was wrong, when I reduced from 8 to 4, then 4 to 2, the sound level stayed very loud and gained in readability;  only the dimension of the panels is important,  small panel small sound, big panel big sound, huge panel huge sound.

POL

[j gale]

Well said.  I agree 100%. That is my experience exactly. I started with 8 exciters per panel and now use only one.

[pol_bct]

Well said.  I agree 100%. That is my experience exactly. I started with 8 exciters per panel and now use only one.

Tha name says it all: "Distributed Modes Loudspeaker", this is the proof of concept...

POL

[sedge]

I also agree 100% ,less is more.
Also large panel large sound.
But good sounding small panels are possible.

I am at the moment testing a 40mm30mm x 1mm phenolic panel a friend gave me ,he has larger panels and has just stuck them to a wooden frame with foam weather strip ,he said he read somewhere that it was a good idea,nxt probably .
I disagree with this statement ,damping a panel like this ,just sucks the life out of it.
I've glued a 10watt exciter to the panel and freely suspended it,the sound from the smaller panel is already an improvement .
This size and type material does have a bad resonance ,break up,problems ,around the 200hz region,but xo at about 250hz sorts this out.
The material is not as rigid as I hoped but the sound is quite good
When I have made up a second panel, I Will have to listen to them a lot more before I can say how good I think they are.
Although they are not very efficient ,xo ing them at 250hz allows the exciter to go a lot louder without overheating,it actually runs cold.
This could be another panel option .
We shall see.
Steve

[actonusa]

Was doing some research on Maggies, stumbled across exciters and it finally led me here.  Have read through most of the pages on this thread and have a couple questions regarding panel material.

Has anyone tried using thin aluminum sheet?  Most of the "Big Box" stores carry various sizes of 0.025" thick sheets for $10-$30.  Some of the sheet available is even perforated looking sorta like an ESL panel.

Another material that is commercially available is mylar or plastic sheeting.  I thought some of the thicker stuff like 20mil stretched over a wooden frame might give good results.  Planar and ESL speakers use mylar for their sound so I would think it would have merit.

[sedge]

Actonusa
The quick answer is.
Yes I have tried sheet aluminium ,and no I wouldn't us it.
Yes I have tried plastic sheeting ,and no I wouldn't use it.
Both have big problems.
Steve

[actonusa]

Thank you for your reply Sedge, I will scrap those materials for experimenting.

Will be ordering a couple exciters and an amp for parts express tonight.

[sedge]

Actonusa
Over on diy audio,under piezo nxt type panel,morray James explains the Mylar problems,he did a lot of work on the early nxt,a lot of money was spent on trying to get Mylar to work !!
The only trouble is you have to try and find it,unless someone can help.
Steve

[Gregory Roig]

Hey folks, Gregor here.  I haven't posted in a while.  I read an older post that someone was going to try "FALCONBOARD" for their dml panel.  Wondered if anyone has tried it and what the results are.

[pol_bct]

hi,
for those who think it's hard to move lots  of air with DML/NXT exciters

https://www.youtube.com/watch?v=FcYXznzHF2Q

 

[FullRangeMan]

Impressive. This NXT sound nice w/small power and a guitar>
https://www.youtube.com/watch?v=b_MNaEkDbF0#t=280.201

[Bendingwave]

Bumping up this awesome thread from Zygdar.......I have finally perfected my DML panel prototype as I am now satisfied with the sound after almost 2 and half years of hands on trial and error experiments.

Hopefully we can get this thread going and inspire more people into the unique sound of DML panel technology.

[Bendingwave]

When people first hear of DML flat panel speaker technology the first name that comes to mostly everyones mind is NXT.

Way before NXT developed there DML speakers in the 90's there was a man who developed his own form of DML loudspeakers during the 70's. This man's name was Dr. Jose Bertagni.

Dr. Jose Bertagni was a physics professor.. Working in his native Argentina, Bertagni experimented with materials including thin sheets of wood and plastic to produce diaphragms to accompany his omnidirectional Flat Panel loudspeaker designs. Ultimately, he discovered an expanded polystyrene-based formulation composed of individual beads which could be heat-formed into complex shapes while maintaining uniformity in structure and an even density. By 1970, he was granted his first U.S. patent, and subsequently was presented with 22 others in countries around the globe. Since then, 16 more patents have been granted worldwide for other Bertagni designs.

Bertagni began manufacturing his flat-panel loudspeaker designs in Buenos Aires, but by 1975, he moved his operations to the U.S. in Southern California to escape the increasingly hostile Argentinean political climate. Today, the company is based in the Southern California town of Santa Ana, where an engineering team led by Bertagni's sons, Alex and Eduardo, continues to devise new Flat Panel designs (the elder Bertagni died in 1992). Having operated under the names Bertagni Electroacoustic Systems (BES) and Bertagni Electronic Sound Transducers (B.E.S.T.) International for a number of years, the company is currently known as Sound Advance Systems.

While manufacturing under the BES name, the Bertagni family sold their products mainly to high-end consumer audiophiles. Their success with BES Geostatic loudspeakers in this market funded research to develop other applications of their Flat Panel technology, and by 1980, the company had expanded its marketing efforts to include commercial, pro sound, and residential applications.

All of my DML speaker designs are based of Bertagni speakers as that is what got me into DIY DML speakers as I own a pair of Bertagni SM 100's. My SM 100's is what I use to judge and compare the sound of my DML panels too when trying to find that perfect sound for my ears.

[Odal3]

Hi Bendingwave

Curious to learn more about your setup and especially the DML subwoofer you mentioned in the other thread. I'm currently matching my panels with OB sub.

[Bendingwave]

Hi, Odal3....Like Ive stated above my DML Panels mimic Bertagni speakers. I am currently using a 5.1 system of ALL DML panels including the sub. A DML panel sub is just a DML panel utilizing a sub amp.

Bertagni speakers technology are basically very similar to NXT's so called BMR technology which is basically just a exciter attached to a brace/spline which in turn is attached to a frame with some sort of surround (usually foam and or rubber) material holding the panel in place on the frame....Bertagni speakers just do it on a much larger scale panel.....Another design very similar to Exciter/BMR technology are the old school Sony APM square flat speakers.

One of the most common mistakes is that most DIY DML panel designs do not use a spline/brace attached to a frame. A spline attached to a frame is very important as the back of the exciter needs something to hold it place for it to actually push/move the panel material at higher excursions...it will also increase accuracy, clarity/treble.

Most people start of utilizing Rich M's designs on parts express gallery (aka OB newbie on this site) which is just a basic start up design into DML technology....Unless a DML panel is done right one wont ever experience a DML panels TRUE POTENTIAL.

Here is a review of Bertagnis flag ship DML speakers the SM 300 just so one can get a glimpse at there potential when perfected like Bertagni designs.

http://www.hifi-classic.net/review/bes-sm300-289.html

http://www.townwire.net/bes_d120%27s.htm

http://www.audioimprov.com/AudioImprov/Speakers/Entries/2012/6/15_Bertagni_SM-275_restoration.html

https://www.youtube.com/watch?v=r5eqcmHW3Vs&t=641s

On the youtube vid you can see Bertagnis design of using a frame/spline to hold the exciter in place.

[Bendingwave]

Another important info I want to add is that when using a exciter with those so called arms or how I like to call them legs for extra adhesive support, CUT THEM OFF as those legs actually HINDER some of the vibration of the exciter....I dont know why a lot of the Dayton audio exciters use those legs because it defeats the purpose of fully vibrating the panel, it seems that Dayton audio does not really understand exciter application.

Also the best panel material IMO is EPS EXPANDED POLYSTYRENE usually from high grade and up. Best all around thickness size is 1inch. There is like 5 different grades. Low, Medium, high, Extra high and Ultra high......low to medium density grades can be found almost anywhere at your local hard ware store or craft store while the other higher grades are harder to find and more expensive cost wise especially if shipping is required.....Bertagni speakers most likely use the high grade of EPS.

[Bendingwave]

One of the most common questions is what size panel to use.....Some will say the bigger the better but that is not always the case as panel size will depend on the type of exciter and the amount of exciters used on each panel.....a very small 13mm 3 watt exciter can be used on a smaller thinner sized panel even as small as 8 inches while a 32mm 40watt rms exciter will be over kill on the same size panel. On the other hand a 13mm 3 watt exciter on a 2ft.X4ft. panel is not enough to vibrate such a large panel while the 32mm 40 watt exciter should be enough. So like I said panel size is predicated on the type and the amount of exciters used per panel.

Bigger higher power exciters can be used on bigger and thicker panels.

Smaller less power exciters can be used on smaller and thinner panels.

Multiple exciters can be used on bigger panels.