DIY Flat Panel Speaker Love

[Unbiasedsound]

Re: DIY Flat Panel Speaker Love

Dayton umm-6, calibration file is loaded to REW.

Forgot to mention there are substantial bass traps built and located in both corners targeting a large 120hz peak that I was getting with the NHT's and absorptive panels along the side walls targeted at a somewhat hot mid treble. Since these radiate differently than the NHT's I do not know what difference this made.

Speaking of bass traps I bought a 3/4inch yoga mat at ross for $8.00 put some under my Bertagni speakers and oh boy it made a big difference imo.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Haaa. bass traps and yoga mats?!? Where has our life gone???

Glad to hear you're tweaking away and making better sounds from your Bertagni Unbiasedsound! I am very interested in hearing a pair and may just have to pick up a pair on the bay if I can find one within a reasonable driving distance.

Are you considering building even a simple set of DML's??? A 24'x32' XPS panel with the Ultras would probably be a good place to start that will get you close to what you are listening to today. If you like the Bertagni's sound I think you will really enjoy building a set yourself...

[captainjack115]

Re: DIY Flat Panel Speaker Love

Hey Guys

I guess I'm just about the only one on here using corrugated plastic. My latest tinkering involves an 18"x24" panel that's been curved. No I wasn't trying for wide dispersion, we all know that's not a problem with DML's. Mounting the exciter on that sized board let things kind of floppy, especially on low frequencies. Last night while counting sheep, I thought about how I could make the panel more ridged, putting a curve in it seemed like it might work. Today I tried it and it does work, pretty well at that! I used packing tape to pull the sides in. I went from 18" to 17'. I'm guessing, but it looks like a 30 degree curve. Bass is flat to 50 hz and 4 db down at 40 hz. High frequencies on my preamp are set to roll of at 50hz, so this is pretty good.

I have a couple of photos. The panels are **** ugly, as I'm trying to prove my concept. So make sure all women and children avert their eyes from such ugliness. To get a nice smooth curve I need to mount the panel in some sort of frame that catches and compresses the sides from top to bottom.

I kinda cranked things up while listening and the exciters felt a little warm, then I started thinking. I know we all pretty much agree that using one exciter on a panel gives the best high frequency response and it's true. Since I'm using a Behringer 2496 for EQ anyway, why not put more exciters on the panel. The 2496 is an amazing device and will easily fix the loss.

Anyway, here's the photos:

Jack

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey Guys

I guess I'm just about the only one on here using corrugated plastic. My latest tinkering involves an 18"x24" panel that's been curved. No I wasn't trying for wide dispersion, we all know that's not a problem with DML's. Mounting the exciter on that sized board let things kind of floppy, especially on low frequencies. Last night while counting sheep, I thought about how I could make the panel more ridged, putting a curve in it seemed like it might work. Today I tried it and it does work, pretty well at that! I used packing tape to pull the sides in. I went from 18" to 17'. I'm guessing, but it looks like a 30 degree curve. Bass is flat to 50 hz and 4 db down at 40 hz. High frequencies on my preamp are set to roll of at 50hz, so this is pretty good.

I have a couple of photos. The panels are **** ugly, as I'm trying to prove my concept. So make sure all women and children avert their eyes from such ugliness. To get a nice smooth curve I need to mount the panel in some sort of frame that catches and compresses the sides from top to bottom.

I kinda cranked things up while listening and the exciters felt a little warm, then I started thinking. I know we all pretty much agree that using one exciter on a panel gives the best high frequency response and it's true. Since I'm using a Behringer 2496 for EQ anyway, why not put more exciters on the panel. The 2496 is an amazing device and will easily fix the loss.

Anyway, here's the photos:

Jack
[ATTACH=CONFIG]61629[/ATTACH][ATTACH=CONFIG]61630[/ATTACH]

Capin'! How ta h#ll are ya?!?

Yes... those ARE beautiful (not to overuse a quote...but beauty is always a light switch away)!!

This is a very cool test. How does it sound compared to your other panels? I know its not a direct comparison as the other are smaller and suspended differently but very curious to hear if the resonant/vibrational nature of the panel or "noise" (for the lack of another term) was reduced?? In other words... is the background "noise" under the music quieter?? If you get my line I'm trying to lay down here.

I have not listened to 2 exciters on a single panel but as you state... high freq. cancellation does occur... but those that used to listen to multi exciter panels also stated that some of the DML magic disappears?! But I think we really ought to try it. There are always tradeoff's and wonder what additional positive qualities may be exposed outside of high power handling and lowered failure rate of our exciters?!?

Think you might want to try an large panel if you have 2 exciters. That is a lot of exciter for not a large panel. Bass extension should be very good as you are already getting excellent extension with that small panel.

btw- How does that panel sound in the mid range compared to your Maggies? Still trying to determine how those corrugated plastic panels sound compared to XPS...

[Gary.M]

Re: DIY Flat Panel Speaker Love

This has been referred to elsewhere, but bears reposting. This NXT patent contains everything we need to know about optimising these DML panel designs..

http://www.google.com/patents/US6904154

Its a long read, and all in patent language which makes it a little challenging to read.

A few excerpts from it are as below:

"Interestingly, and valuably in practice, particular aspect ratios for side dimensions of a rectangular shape with isotropic bending stiffness emerged as being of usefully general application. One such preferred and highly effective aspect ratio is at about 13.4% from square (i.e. out of equality of sides), specifically at 0.882 or 1.134; and much of our early development work has used this value. However, another potentially valuable aspect ratio has been noted at about 37% out of square, though damping control of at least some of lowest resonant modes may be particularly advisable/valuable. There are others that can be viable, too, at least if lower efficacy is acceptable, whether or not comparably effective, or merely adjudged acceptably so for particular applications/devices and related desired operational frequency ranges, or (e.g. in specific loudspeaker implementations) utilised on a compromise basis including minimising contribution(s) to acoustic action/performance of unwanted frequencies of resonant modes, perhaps particularly below desired operational frequency range, see also further below regarding location of transducer means."

" we have further established that particular unwanted vibrations and/or vibrational reinforcements can be dealt with by said damping, i.e. as overall or selective edge damping and/or selective localised medial damping at relevant position(s) of said extent."

"There is, however, one effect that it has been found can be beneficial to take into specific account, at least as useful refinement, namely, for a substantially rectangular said member, the resonant modes associated with is diagonal dimension. Assuring at least mainly helpful contribution to desired distribution(s) of resonant modes can be aided by cropping or trimming or curving of corners, or forming to such shapes. Useful, though not essential, further refinement is seen in such corner cropping or trimming being differential, at least for corners of different diagonals, whether to different extents for each, say in a mutual relationship producing a similar “matching” (for diagonals-related resonant modes) to that above for the side dimensions, and perhaps further relative to or effectively continuing or complementing or usefully compounding the sides-dimension matching ratio.

Satisfactory shortening of only one diagonal of a said rectangular member, at least idealised for isotropy of bending stiffness, is seen at about 15% or about 10% short for above about 13.4% and about 37% aspect ratios, respectively."

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey Gary! A lot of the original direction over at AC was indeed extracted, over time, from the original patent.

"This NXT patent contains everything we need to know about optimising these DML panel designs.." I wish this were true. :-)

This has been great guidance and has formed (along with other papers) the basis of what we have been doing but making the best sounding flat panels is (at this time anyway) more about listening to different panel materials and making that material sound good then... choosing exciters that sound best on that specific panel material.

IMHO :o

[Gary.M]

Re: DIY Flat Panel Speaker Love

Hi rmeinke,

Yeah, I read all that. I can see a lot of empirical work going in to materials, and that seems to have settled on the extruded polystyrene. I didn't see so much methodical work done around the optimum dimensions though or the application of selective edge damping etc. Still, proof of the pudding is in the results... and I steer away from a dogmatic approach :-). I'm going to follow the NXT patent, and measure and listen. My reference is a pair of Quad ESL 57s and an open baffle project based on Martin King's work.

Time will tell :-)

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey Gary... didn't mean to sound uninterested and really happy that you posted it as this is one link that didn't get post here on PE TT. Thanks man!

Well, XPS is "fine". Its cheap, available and sounds good. If it were not for the PVA treatment we would probably still be listening to treated double cushioned cardboard or ply(there still is potential likely in both of these and more empirical research is needed ). Hoping to try curving XPS and only slighting tensioning the panel to reduce the underlying vibrational panel character that I am not totally in love with at the moment. No drastic change in direction... just a small tweak.

My personal take on panel dimensions and edge damping/suspension...

The dimensions/ratios in the patent, golden ratio, silver ratio and many others in between and beyond have been implemented. This is one specific variable of panel design that appears to have marginal value as there is no real difference in sound quality between these honestly... with XPS anyway. The guys at AC recommend large panels "to get the most from DML" and 2'x6' has been a popular dimension which is far from "optimal". On the other hand, rounding corners and edges is a much more prominent element that has a real impact on sound quality.

To panel/edge damping. A lot of work was done over at AC on double cushioned cardboard (adhesive backed thin foam and felt mainly) assuming this was done more on cardboard due to the fact that you can't easily round the edges for better edge termination(???) as easily as you can on XPS or ply. But this all depends on the panel material used. Professional panels use hard, rigid, high-tech honeycomb materials that are very stiff and ring. If we were listening to these panel materials you would see many discussions about edge termination, damping and suspension methods. Its the materials we are using... ply is way over damped IMHO and XPS is pretty well damped as well. At least on my smaller XPS panels, even slightly more damping impacts the sound quality... it really doesn't *need* more damping. Probably posted this a few times already, but I can hear a change in high frequencies and "air" disappears when I drape a kitchen towel over the top of the panel. Exciters can also play a small part. The Dayton Audio DAEX25FHE-4 Framed High Efficiency 25mm Exciter 24W 4 Ohm for instance seems to transfer more noise to the panel and find it needs more damping than the Ultra. So my personal stance on panel damping (at this time anyway) is damp only as much as needed to remove panel noise. If you damp the panel too much, it begins to negatively impact sound quality. These statements apply to XPS... the game would likely change with different panel materials.

Ramble, ramble, ramble... many thanks for listening in fellas... :-)

[rmeinke]

Re: DIY Flat Panel Speaker Love

one more thing...

One concept to kick around... what does everyone think about settling on a easy to build, simple, common "reference" panel and exciter so that we can begin to compare different designs?

We seem to go sideways more often than we go forward and we can not honestly say whether *this* design sounds better than *that* design, etc., etc.

Of course personal preference vary and there will be disagreement is what "sounds best" to each of us but have to think that we would at least get closer and help to continue to improve the sound quality of our flat panels.

Thoughts?

[Gary.M]

Re: DIY Flat Panel Speaker Love

Hi rmeinke,

Regarding damping I'm thinking more of the effect of it on the overall response of the panel. Particularly maybe at LF. I'll play like this... set up the panel as free as possible and a live rta out in the room. Then watch the rta while touching the panel here and there, both on the body of the panel and the edges. Note any changes in the rta peaks and troughs. Perhaps it may be possible to optimise the response by adding a touch of damping in one or two spots.

This is evident on the Podium design. Who knows...

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey Gary... I don't know bud. Had those thoughts at one time, others posted those thoughts and do think its possble to make some progress. But one of the guys who has been at this for some time now described that as roundabouts and switchbacks. IIRC, he was glueing quarters to panels, etc. to suppress peaks/resonances and his experience was that it just moved a problem to another area of the panel....roundabouts and switchbacks.

Don't know if this is a truly valid statement Gary, but I do tend to think we would likely be chasing squiggles but if we stay reasonable and look only to make small incremental improvements instead of approaching it as a panel cure all I can see how some improvements might be made?!?

Not the end all, but I still see EQ as a more practical method to create a panel that is smoother and better balanced.

Okay, I may be a bit cynical on the Podium approach. I find that large panels have more resonances than smaller panels and its hard to totally free a DML panel of resonances so those pads likely help control resonances across such a large, rigid panel that the Podiums use. :o

[Gary.M]

Re: DIY Flat Panel Speaker Love

All valid comments, but recall that the NXT theory has all of these resonances interleaved to create a wide bandwidth excitation that results in a full range output of reasonable flatness. That's why I think that starting with the patent's dimensions and exciter location stands the best chance of creating a panel that can be subtly tweaked to get an optimised response. We'll see, as only the results can speak for the theory.

Hey Gary... I don't know bud. Had those thoughts at one time, others posted those thoughts and do think its possble to make some progress. But one of the guys who has been at this for some time now described that as roundabouts and switchbacks. IIRC, he was glueing quarters to panels, etc. to suppress peaks/resonances and his experience was that it just moved a problem to another area of the panel....roundabouts and switchbacks.

Don't know if this is a truly valid statement Gary, but I do tend to think we would likely be chasing squiggles but if we stay reasonable and look only to make small incremental improvements instead of approaching it as a panel cure all I can see how some improvements might be made?!?

Not the end all, but I still see EQ as a more practical method to create a panel that is smoother and better balanced.

Okay, I may be a bit cynical on the Podium approach. I find that large panels have more resonances than smaller panels and its hard to totally free a DML panel of resonances so those pads likely help control resonances across such a large, rigid panel that the Podiums use. :o

[captainjack115]

Re: DIY Flat Panel Speaker Love

Hi rmeinke,

Yeah, I read all that. I can see a lot of empirical work going in to materials, and that seems to have settled on the extruded polystyrene. I didn't see so much methodical work done around the optimum dimensions though or the application of selective edge damping etc. Still, proof of the pudding is in the results... and I steer away from a dogmatic approach :-). I'm going to follow the NXT patent, and measure and listen. My reference is a pair of Quad ESL 57s and an open baffle project based on Martin King's work.

Time will tell :-)

Respectfully, "All" science begins with empiric endeavours, from cave men up to current times. Basic concept first, number crunching later. Certainly we would be foolish not to learn from the discovery of others.
The very reason for my quote from Ralph Waldo Emerson. I've always felt that we should learn the rules, then learn how to break them. This is why we don't build cars the way the Model T was made, we found better ways of doing it.

By all means use the NXT patent, measure and listen. But keep an open mind that their science is a set of parameters and there's always room to expand parameters to include new techniques.

Jack

[captainjack115]

Re: DIY Flat Panel Speaker Love

Capin'! How ta h#ll are ya?!?

Yes... those ARE beautiful (not to overuse a quote...but beauty is always a light switch away)!!

This is a very cool test. How does it sound compared to your other panels? I know its not a direct comparison as the other are smaller and suspended differently but very curious to hear if the resonant/vibrational nature of the panel or "noise" (for the lack of another term) was reduced?? In other words... is the background "noise" under the music quieter?? If you get my line I'm trying to lay down here.

I have not listened to 2 exciters on a single panel but as you state... high freq. cancellation does occur... but those that used to listen to multi exciter panels also stated that some of the DML magic disappears?! But I think we really ought to try it. There are always tradeoff's and wonder what additional positive qualities may be exposed outside of high power handling and lowered failure rate of our exciters?!?

Think you might want to try an large panel if you have 2 exciters. That is a lot of exciter for not a large panel. Bass extension should be very good as you are already getting excellent extension with that small panel.

btw- How does that panel sound in the mid range compared to your Maggies? Still trying to determine how those corrugated plastic panels sound compared to XPS...

Hey Rich,
In direct comparison, the bigger panels are louder and of course go lower. The EQ was a lot different as resonance was shifted in various areas. Quieter music never seemed to be that much of a problem for me with either size panel, there "is" noise though. Noise can be heard with the bigger panels on sine waves, but not noticeable on music, at least not to my old ears. I'm pretty sure that all or most of the noise is coming from those 3 strips of tape running around the back of the panels. They're being excited by the outer edges of the panels and sitting there like a couple of big wide banjo strings.
I really just used the tape to confirm my thoughts on finding a way of firming up the panel. It does just that and it's really a usable technique in my case, bass seems quite remarkable. Despite their smaller size I can honestly say that bass response is better and more listenable than my MMG's. The mids are good,not as neutral as the MMG's, but very listenable Let's put the brakes on right here for just a moment. These ugly things would have to be improved upon a whole lot just to shine the shoes of the MMG's. The Maggies are smoother, more neutral and far more dynamic. That being said, DML panels are a fun pastime for me and I want to see just how far they can be taken. There's still plenty of cool factor to enjoy.

The magic is the draw for me, they may not have complete neutrality or punch, but they really are very listenable.

I can't say for sure about using 2 exciters, highs will be effected, but I don't know about the magic that is DML. I can't see making really large panels in the near future because I have pretty small room that's already crowded. For several years now, I've considered building a set of John L. Murphy's corner line arrays. These things have a very small footprint and would fit very nicely in the corners of my small crowded room. As far as comparison to XPS, I'll have to make a set, and you'll have to make a set of corrugated plastic......... That's a pact!

Jack

[captainjack115]

Re: DIY Flat Panel Speaker Love

Hey Mike,
In direct comparison, the bigger panels are louder and of course go lower. The EQ was a lot different as resonance was shifted in various areas. Quieter music never seemed to be that much of a problem for me with either size panel, there "is" noise though. Noise can be heard with the bigger panels on sine waves, but not noticeable on music, at least not to my old ears. I'm pretty sure that all or most of the noise is coming from those 3 strips of tape running around the back of the panels. They're being excited by the outer edges of the panels and sitting there like a couple of big wide banjo strings.
I really just used the tape to confirm my thoughts on finding a way of firming up the panel. It does just that and it's really a usable technique in my case, bass seems quite remarkable. Despite their smaller size I can honestly say that bass response is better and more listenable than my MMG's. Let's put the brakes on right here for just a moment. These ugly things would have to be improved upon a whole lot just to shine the shoes of the MMG's. The Maggies are smoother, more neutral and far more dynamic. That being said, DML panels are a fun past time for me and I want to see just how far they can be taken. There's still plenty of cool factor to enjoy.

I can't say for sure about using 2 exciters, highs will be effected, but I don't know about the magic that is DML. I can't see making really large panels in the near future because I have pretty small room that's already crowded. For several years now, I've considered building a set of John L. Murphy's corner line arrays. These thing have a very small footprint and would fit very nicely in my small crowded room. As far as comparison to XPS, I'll have to make a set, and you'll have to make a set of corrugated plastic......... That's a pact!

Jack

Forgot to mention that I want to built a robust frame for the curved panels. I think that will cut down on noise by having the frame force the panels into a curve.