DIY Flat Panel Speaker Love

[Kornbread]

Re: DIY Flat Panel Speaker Love

Should be able to finish homework this afternoon. May have time to get some pics and a short write-up or take some measurements. Using REW what kind of measurements would you guys like to see?

[rmeinke]

Re: DIY Flat Panel Speaker Love

Hey UBS... sup?

Why Bertagni did what he did with his designs is speculation on our part but looking at the speaker design trends from the 70's... lots of drivers, 4-5 way speakers... big and loud... a single panel and low power handling "exciter" would not *look* like a favorable or exciting design choice at that time. To me, the huge, wide, room filling soundscape is due to the nearly omni-directional output of Bertagni's DML panels. It is this output, along with the detail and "speed" of the panels are what makes these flat panels addictive to listen too... despite their shortcomings (uneven response, slight coloration of the panel material and the bit of low-level underlying but constant vibrational character, which, you do adjust to quickly). Its hard to turn off the music and have had far to many late night listening sessions when I should have gone up to bed. Bertagni was on to something early for sure...

I can live with and enjoy the performance of XPS panel if it was the only and last material available to build flat panels but switching from the KEFs to the panels have sparked my interest again in panel materials. The "Hhhhhhhaaa" coloration is the basic signature of XPS. I've been listening to open baffle speakers for a few years and enjoy the more open dipole presentation... its not the diffused sound of DML that I initially reacted to. It doesn't detract from the performance... just one aspect that I want to improve to make even better flat panels.

May go back and try to improve cardboard. Shellaced cardboard was popular for sometime and was smooth and natural but rolled off around 10K on axis. I think folks stepped away from it given the high freq. response but at that time I saw no one discussing the power response of the DML panels which the freq. balance in the room would not sound rolled off as much as the on-axis measurements suggest and the reason why they the guys didn't feel like they sounded rolled off. EQing panels were not in vogue either at the time so a slight bit of EQ may be able to make treated cardboard a worthy performer again. Cardboard is an overdamped material but wonder if the water:PVA treatment if applied heavily to the cardboard panel (allowed soak into the inner flutes) will be enough to make the cardboard more solid, less damped and of course rigid enough. 2 layers of cardboard would be needed for panels in the 24" x 30+" panel sizes but given higher power handling exciters I'd give up some sensitivity for a more natural sounding panel. Everyone was building large panels at the time and its hard to believe that these large treated cardboard panels would perform as well as they did given the lack of rigidity. I don't expect treated cardboard will be good for large panels but smaller panels I really hope so.

Cheap foam core boards don't sound good by themselves but treated and layered may be interesting too. Will be more dense than straight XPS but will it be overdamped is the question. Once I finish up the current project I think its time to go back and test materials again now that we all know a little more about DML performance.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Thanks for the pics and description. Measurements are good but the aspect we are dealing with won't necessarily be identified or be assisted by measurements. After seeing these, my feelings are the same as my initial response... some dampening material between the panel and frames is where I would start... can't imagine this sounding good.

As a matter of fact, for my current project I have speaker stand that has a 1 1/4" board running horizontally that the (near) top of panel rests on. Resting on this board alone, the panel is *very* shouty with my original 24"x24" panels. Rubber bands on each corner was an improvement but still not optimal. Finally, soft cloth doubled and laying across the entire board finally cleaned up the midrange and am now enjoying their magic again. Not the same situation as yours naturally but I was *surprised* by the impact this thin piece of wood had on the sound. Next iteration will not have this board unless a panel/exciter combination needs more dampening(adding dampening material). This particular panel has the "Dayton Audio DAEX25FHE-4 Framed High Efficiency 25mm Exciter 24W 4 Ohm" attached. This is definitely "hot" sounding through the midrange and can quickly hear why I thought that these panels were very detailed sounding initially... very sharp and detailed even on square project panels with no rounded corners or edges. The panel construction might also contribute to the hard(er) sounding midrange... will be validating this as I finish the design.

To your project more specifically, cheaper pine is not usually very straight, true or uniform so there is plenty cause for concern here. Glueing to the frame is another option but I'd still think that you will have considerable panel noise yet and the sound quality will improve more with some dampening in this specific design. Looking more closely at the frame, thicker cloth seems the easiest to test with... even having some stick out of the frame which could later be cut off carefully with a utility knife. If you troubleshoot like I do, I'd grab anything I have around to see how the panels react. I'd fold paper toweling, cut up an old bath towel or ?? and put it between the frame. This is fun to troubleshoot and can't wait to hear the results of some dampening material added.

[rmeinke]

Re: DIY Flat Panel Speaker Love

Oh, and thinking about this more... use a *thicker* cloth material like felt or synthetic fleece used for cheap fleece blankets you see everywhere. This will provide significant amount dampening. I know a thinner cloth might be easier to retrofit into the existing frame but afraid a normal weight cloth may not be completely adequate... would hate to have you take it apart and not get the results we are looking for! :(

Good luck with the rebuild!!!

[Fshow]

Re: DIY Flat Panel Speaker Love

1" xps sanded and glue coated, 48x35~1.37 which is near the preferred dimensions,
1 dayton daex32ep-4 per panel placed at 3/5 IIRC,
Lightweight pine frame from 1x2's and 3's, screws can be adjusted to tighten or loosen the panel to some degree
Panel held into place from all sides, frame lightly clamps onto panel edges

One panel is missing it's exciter as the thing stb after a few minutes. PE quickly sent a replacement but the panel has some damage from removing the dead exciter.

Maybe a few pics would help. Roughed the frames in, if I can get them singing the frames will be disassembled, sanded, stained, and rebuilt to look a lot better than they do now. Never mind the dirty shop.:D



What kind of measurements would you guys like to see, I'd being using REW. Would like to get a baseline before doing any mods but that's going to take more time and my laptop which is tied up most of the time.

Hi Kornbread
don't give up on attaching your panel solidly around the entire perimeter. My panels are very similar to yours and yes they don't sound right until they are equalized. Basically you need to lower the center frequencies. (iTunes has an equalizer you could use)
Attaching the panel solidly solves The problem of panel rattle at lower frequencies. It may also damp the panel ring because I don't hear it on these panels. I have my panels running side br side to a pair of double stacked Advent speakers. The panels don't have the powerful bass that the adverts have, but you will be amazed how deep the panels can go.
As far as the tone and detail the panels you will be pleased,,,,,but we are never satisfied that's part of the fun.
p.S. You don't have to solidly mount the panels to the frame, you can support the entire perimeter with some sort of flexible membrane but it has to be stiff enough to stop the rattle.
Fred

[Fshow]

Re: DIY Flat Panel Speaker Love

Kornbread. One more thing , I just noticed you don't support your exciter. I think you need to add this to make it work
Fred

[Kornbread]

Re: DIY Flat Panel Speaker Love

This was my initial thought, but when I supported the exciter with a cross-member the panel sounded as if you just tried to suffocate it with a pillow. Didn't make sense to me, but it sounded much better without support.

My plans are to take a router and remove parts of the panel along the edge where it joins the frame. Remove a section then listen, then repeat the process until I reach some kind of sweet spot or have just a few small tangs supporting the entire panel. This should free up the panel to oscillate. The sound they produce does fill the room and for the most part there is no sweet spot you have to sit in, on the flip side they sound nothing like my Apogee Calipers (planar, magnetic) but do very loosely sound like my Carver Amazings.(hybrid) YMMV

The panels do sound better with better amplification, still nowhere near hi-fi, but better. May eventually cut the entire panel out then use some 5" wide duct tape to hold it to the frame, aka speaker surround.

These panels put out a lot of energy in the midrange/upper midrange, eq'ing would help. Surprisingly, they have some deep bass, not much, but there is some there and that's with them in the middle of the room, with some boundary reinforcement they should fill out better in the bottom. The treble really isn't that rolled off either but they definitely radiate more treble energy from the side the exciter is on.

[Fshow]

Re: DIY Flat Panel Speaker Love

This was my initial thought, but when I supported the exciter with a cross-member the panel sounded as if you just tried to suffocate it with a pillow. Didn't make sense to me, but it sounded much better without support.

My plans are to take a router and remove parts of the panel along the edge where it joins the frame. Remove a section then listen, then repeat the process until I reach some kind of sweet spot or have just a few small tangs supporting the entire panel. This should free up the panel to oscillate. The sound they produce does fill the room and for the most part there is no sweet spot you have to sit in, on the flip side they sound nothing like my Apogee Calipers (planar, magnetic) but do very loosely sound like my Carver Amazings.(hybrid) YMMV

The panels do sound better with better amplification, still nowhere near hi-fi, but better. May eventually cut the entire panel out then use some 5" wide duct tape to hold it to the frame, aka speaker surround.

These panels put out a lot of energy in the midrange/upper midrange, eq'ing would help. Surprisingly, they have some deep bass, not much, but there is some there and that's with them in the middle of the room, with some boundary reinforcement they should fill out better in the bottom. The treble really isn't that rolled off either but they definitely radiate more treble energy from the side the exciter is on.

Hi Kornbread

Ok, I can't explain why it didn't work for you. Was the exciter mounted in a neutral position so that the exciter wasn't offset at rest. I used the thruster exciter but I can't imagine that being the problem. All I can say is my panels sound airy and detailed, (after equalization).
Keep up the hard work there are many roads to success.

Fred

[rmeinke]

Re: DIY Flat Panel Speaker Love

This was my initial thought, but when I supported the exciter with a cross-member the panel sounded as if you just tried to suffocate it with a pillow. Didn't make sense to me, but it sounded much better without support.

My plans are to take a router and remove parts of the panel along the edge where it joins the frame. Remove a section then listen, then repeat the process until I reach some kind of sweet spot or have just a few small tangs supporting the entire panel. This should free up the panel to oscillate. The sound they produce does fill the room and for the most part there is no sweet spot you have to sit in, on the flip side they sound nothing like my Apogee Calipers (planar, magnetic) but do very loosely sound like my Carver Amazings.(hybrid) YMMV

The panels do sound better with better amplification, still nowhere near hi-fi, but better. May eventually cut the entire panel out then use some 5" wide duct tape to hold it to the frame, aka speaker surround.

These panels put out a lot of energy in the midrange/upper midrange, eq'ing would help. Surprisingly, they have some deep bass, not much, but there is some there and that's with them in the middle of the room, with some boundary reinforcement they should fill out better in the bottom. The treble really isn't that rolled off either but they definitely radiate more treble energy from the side the exciter is on.

Hello Kornbread,
To get decent results from these panels, you would have to remove almost all of the panel and leave only very small "tabs" on the middle of the top, bottom and each side. This will certainly help improve the sound quality and is a quick test. Still might want to put some type of material between the frame and panel if you decide to go that route... it will still add some level of panel noise if left alone.

If you want the best possible sound quality a better solution would be to use felt of some other thicker/damped material to hang the panels from the frame. Lighter suspension improves high frequency output. If I just place a folded kitchen towel and drape it over the top if the panel I hear a reduction in high frequency output and a loss of "air". Further, with a lighter suspended panel both sides of the panel will produce very comparable output... with no more high freq. output exciter side. You are likely getting more HF output exciter side due to the solid mounting to the frame. It's reducing panel output pretty significantly so you are hearing more from the exciter directly instead of the panel... that surprises me that exciter output is that noticeably higher... especially with the Thuster as it is not vented. Even with a vented exciter like the DAEX25FHE-4... I really don't hear any more output if only a *really* small difference. But I'm not solid on that either... output very, very close.

The light felt suspension should be pretty easy to implement and might be less time overall then messing with cutting away and tweaking the panels. Kinda like this:



Glue a 6.5" x 2" (roughly) wide pieces felt to both sides of the panel to create a loop. A wood block fits inside the loop and will be held in place in the existing frame slot by a screw. I would put 2 on top 6-8 inches from each side. 2 in the middle of each side and 2 again on the bottom all about 6-8 inches from each corner (I only show 1 tab on the sides... I'd start with 2 per side). You can add more if you needed and can also probably tune the panel somewhat by either loosening or tightening the suspension blocks.

I would not use duct tape except for testing to see what a lightly suspended panel sounds like. Duct tape is a bit more stiff and not very damped... consider that only a quick solution and I would not go around the entire perimeter of the panel. XPS as a material is already overly damped. It doesn't need much more help from the mounting method.

If you go with the softer suspension, much of the mid-range resonances/edginess will go away. I still cut the mid-range but that isn't an attempt to suppress panel resonances (which i have found to be an issue with the DAEX25FHE-4 exciter) but simply a smoother freq. resp. and better tonal balance.

One last thing... I would round the corner and edges. This helps to smoothly terminate the nodes as they leave the panel and reflects less waves back into the panel.

Let me know if you have any questions about the above sketch.

Good luck!
Rich

[rmeinke]

Re: DIY Flat Panel Speaker Love

Was going to say as well. DML's don't operate under the same principals as conventional drivers. Moving them closer to the walls will not improve bass response and actually the reflected rear output makes them more shouty overall.

Once you get the suspension dialed in you will have strong bass output down in the 40Hz range... not as much as your Amazing's but will sound more full compared to the Apogees. The Calipers used to sound a bit thin to me from the bottom to the upper bass region (200-300Hz)... loved them... but just not enough bass output and slam for me.

[rmeinke]

Re: DIY Flat Panel Speaker Love

For anyone following this thread and considering building a set of DMLs...

For a recent project, I added black inkjet ink to the water:PVA mixture and found that it doesn't dry as hard or may just take longer to cure. The mixture I used was 1/4 cup ink, 1/3 cup water and 1/4+1/3 cups water. For future panels, I would include more glue or reduce the amount of ink in the mixture or both. Not knowing how black the mixture would be I went a little overboard. It was almost black enough after the first treatment... I could have lived with the color after a single coat.

I also made the mistake of attaching the exciters shortly after the panels were dry. I use a hair dryer to make the treatment process go quicker and it was dry to the touch but the both exciters eventually fell off the panels. The adhesion of the treatment to panel failed for half of the exciters surface area; on the other half some foam also came off so was close. Changing the mixture and/or the drying time will take care of it.

On the positive side, the panel finish turns out to be between a flat and satin... really nice and happy with the results. If the treatment was a bit more durable you could almost get away with no frame and grill cloth and leave the panels entirely exposed as is. They sure do look nice treated this way...

Just wanted to caution anyone who might want color the panels black.

[Kornbread]

Re: DIY Flat Panel Speaker Love

Was going to say as well. DML's don't operate under the same principals as conventional drivers. Moving them closer to the walls will not improve bass response and actually the reflected rear output makes them more shouty overall.

Once you get the suspension dialed in you will have strong bass output down in the 40Hz range... not as much as your Amazing's but will sound more full compared to the Apogees. The Calipers used to sound a bit thin to me from the bottom to the upper bass region (200-300Hz)... loved them... but just not enough bass output and slam for me.

rmeinke,

Give me some time brother, I'll get around to experimenting with them. Due to my serious lack of free time I'd love to just tear into them and mod the ╖ell out of em' cause all this reading I've been doing makes me think they have much more to offer ... but, I really want to do something that seems to be lacking on this and the AC thread ... take base-line measurements, mod, then retake measurements and that's going to take time, considerable amounts of time. Everyone can say this or that, but with measurements we have some kind of basis to verify what is happening. Now, if I can just get a couple free days .......

Using REW, what kind of measurements does everyone need to see?

... and haven't read much about using a bass shaker on a large panel instead of a conventional sub. Anyone?

[rmeinke]

Re: DIY Flat Panel Speaker Love

Lol... all good kornbread... not pushing ya brah.

Considering you have OB/ribbons, your tastes are tilted to the DML direction. DML's don't have the refinement that electrostats or ribbons have... at least on XPS. Being kind to XPS...response is not very smooth. Still listenable el natural but if you want an audiophile grade panel, EQ is a must. The bass to upper base is ragged and mid-range from 700-2500Hz or so is somewhat elevated. There are sharp peaks and dip in that range but they are narrow and not terribly noticeable. To me, the panels near omni-directional radiation pattern and randomly generated nodes across the panel seems to mask the freq. resp. anomalies. Put this way, if you were listening to a conventional speaker with such a freq. resp. it would be objectionable.

On the other hand, the sound stage is absolutely huge thanks to being nearly omni-directional... it sounds "live". Even a small 14.5"x12" panel FILLS the room... a real treat to listen to... hard to believe such a tiny a$$ panel can perform such an act. I bought a pair of KEF Q500s a few months ago to have a well reviewed commercial speaker to compare designs to and while I really like them a lot and not disappointed with the purchase but after listening to them on and off for a few week stints, they are upstairs in my smaller listening room covered up. Just really enjoy listening to the magic panels more... they keep my interest for hours and hours and find it hard to turn them off and go to sleep. I have never had so much fun just listening to the music. I've always LOVED listening to speakers, comparing the best from Focal(still my fav), Dynaudio, Eton, Seas, Vifa, Peerless, etc. always looking forward to what speaker I'm going to build next (usually before the current build is done)... how will this tweeter sound with this woofer and on and on. But with these panels I stop analyzing and just listen to the music. I've wanted too build a 2 panel DML array for months and months and still seem to chose to use my limited time to listen to the panels I've already built.

Yeah man... you are right, they do have a lot more to offer.

I would considered building a simple 24"x30" panel with the Ultra's and smoothed with EQ kornbread... once you know you like the presentation of a DML or certain aspects of them, build a set of panels that best meet your needs or specific goals.

Funny you mention bass shakers. Someone over at DIYAudio has a 4'x8' 2 inch XPS panel and seemed to like it but he hasn't responded to the thread for months and months so no real details there. CLS over at AC used shakers and thought they produced drum work better than anything he has listened to but there were other aspects that he wasn't as happy with. He has some massive OB H frames so can see why a shaker and foam board is not the ultimate low freq. producer. But I'd like to go at it to see what can be done with less on the cheap and not compete directly with a traditional sub woofer but a quality system taking advantage of what it does do best and try not to extract performance or those characteristics it's not as well suited to do. We shall see. I still think OB bass bins are the best solution to mate with the panels. But still fun to see what can be done...

As for measurements... what is it that you want to measure and improve? I only measure basic frequency with Omnimic to EQ them "flat". I'm not sure what other measurements would tell me honestly.

Its been proposed that you measure a certain panel size, thickness, exciter placement and see what the affects are. That is a perfectly legit proposal. That would take incredible amounts of both time and materials and would tell you nearly exactly what the NXT Design Studio models would tell you assuming you enter all of the variables needed to model the exciter, material and placement of the exciter/exciters on the panel correctly.. it will predict the freq. response accurately. I think we are at a different place... a more interesting and fun stage. We need to listen to different exciters and panel materials to see what *sounds* the best. What measurements are going to tell us what materials *sound* the best?

After listening to the KEFs I was annoyed by the vibrational smearing I hear with XPS. I can still hear it on some music more than others even weeks after switching back to the panels. So I will be spending some time in the future trying different panel materials and treatments that may have less of that vibrational signature.

Later...

[Kornbread]

Re: DIY Flat Panel Speaker Love

rmeinke,

Seen you refer to the nxt? (brain now working yet) design software several times but haven't seen a link. Is it free and where is it at?

[Kornbread]

Re: DIY Flat Panel Speaker Love

No time for mods, was able to get a few measurements.

1 meter from front of panel, panel in middle of room, REW;