Subjectivity
So here is a funny thing. One mans open fast but demanding speaker is another mans vibrating plastic bag. Yet another mans impactful, exciting energetic speaker is another mans shouty compressed box. To an ESL lover no boxed speaker ever sounds right, to a lover of cones an ESL will never match a properly engineered monitor.
And both parties are right. To them
It is highly unlikely we will ever be able to agree on subjective issues, there are fundamental neurological reasons for this and loads of mitigation factors such as the room, the source, the amplification.
I am well aware there are specific responses to specific regions of the frequency spectrum, there is no denying that, but material preferences with DML’s do seem to be a matter of personal taste rather than some absolute correctness.
I find this guide useful The Only EQ Chart You'll Ever Need For Separation in Your Tracks : Audio Issues
To those that love their foam panels I am happy they bring you a great deal of pleasure. I am another one who prefers 3mm Birch Ply. Infinite baffle v reflex, horn loading V open baffle, fans will never be in complete agreement.
So here is a funny thing. One mans open fast but demanding speaker is another mans vibrating plastic bag. Yet another mans impactful, exciting energetic speaker is another mans shouty compressed box. To an ESL lover no boxed speaker ever sounds right, to a lover of cones an ESL will never match a properly engineered monitor.
And both parties are right. To them
It is highly unlikely we will ever be able to agree on subjective issues, there are fundamental neurological reasons for this and loads of mitigation factors such as the room, the source, the amplification.
I am well aware there are specific responses to specific regions of the frequency spectrum, there is no denying that, but material preferences with DML’s do seem to be a matter of personal taste rather than some absolute correctness.
I find this guide useful The Only EQ Chart You'll Ever Need For Separation in Your Tracks : Audio Issues
To those that love their foam panels I am happy they bring you a great deal of pleasure. I am another one who prefers 3mm Birch Ply. Infinite baffle v reflex, horn loading V open baffle, fans will never be in complete agreement.
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Steve,
I'm not sure I follow you. But I gather you think the frame and foam surround is a problem. Below is a measurement I made on a 1" XPS panel (Foamular 250) some time ago, with no frame. It shows a similar lack of HF response as the 1/2" XPS. Maybe not quite as bad, but still fading above about 3 kHz.
And it also shows the issue that I have seen often when much or all of the panel edges are free. That issue is a big dip, followed by a sharp spike in the response at the low frequency end. Note below the dip at about 110 Hz with sharp peak at maybe 160 Hz. This low frequency end dip/spike thing is not just with PS foam. I've seen it with other panels too, so I believe it has more to do with the panel mounting (or rather, lack thereof) than it has to do with the panel material. And that's the reason I consider mounting the panels to a frame via foam, around much or all of the perimeter, to be my "default" mounting.
Eric
I don't understand what you mean. Is it that if FR isn't flat between 200 and 500 it sounds muddy? Or if you only get 200-500Hz it sounds muddy? Or something else?
I didn't mean to imply that my plywood panels are anything particularly wonderful, I just meant that they provide decent response all the way up to 10 kHz or better, while my attempts at PS foam panels all start fading above 2 to 3 kHz or thereabouts. Others may have had better luck, I have no doubt.
Not sure exactly which panels you're talking about. To my wife's dismay, I tend not to throw my panels away, no matter how bad they sound, just in case someone has a brilliant idea that I have not already tried that might fix them. But I agree with your suggestion about experimenting with other materials. I'd have to count to be sure, but I think I've tried close to 30 different panel materials so far.
Eric
Frequency response
Burntcoil.
It's not about subjectivity it's about the frequency response in the measurement of the xps panel rolling off after 2k,I'm trying to point out that there is a serious problem with the panel or exciter,I would expect at least a good performance up to 10k,as with the Ply panel .
I have a collection of vintage radios from the 1920s and even they would out perform this.
I mean no disrespect or bad will but surely it must be pointed out.
Steve
Burntcoil.
It's not about subjectivity it's about the frequency response in the measurement of the xps panel rolling off after 2k,I'm trying to point out that there is a serious problem with the panel or exciter,I would expect at least a good performance up to 10k,as with the Ply panel .
I have a collection of vintage radios from the 1920s and even they would out perform this.
I mean no disrespect or bad will but surely it must be pointed out.
Steve
Hi Steve, do you care to share more details on your setup, especially the low end driver side?
?
Burntcoil.
Sorry I'm a little confused ,I don't remember stating a preference for foam or ply,I do have some 5mm xps foam panels and of course ply I also have various other materials, I am happy to listen to all of them and often do,except the ones I have thrown away of course,some materials don't do dml well.
As far as I'm concerned if a panel measures well and it sounds good you are on to a winner,and if it measures not so well but stil! sounds good that's fine too, but if it measures badly and sounds bad ,what do you do?
I have been a keen audio enthusiasts since the early 70s and making dml panels for about 10 years now ,I am very happy with the various panels I have but it is very hard to stop investigating new ideas.
One day.
Steve
Burntcoil.
Sorry I'm a little confused ,I don't remember stating a preference for foam or ply,I do have some 5mm xps foam panels and of course ply I also have various other materials, I am happy to listen to all of them and often do,except the ones I have thrown away of course,some materials don't do dml well.
As far as I'm concerned if a panel measures well and it sounds good you are on to a winner,and if it measures not so well but stil! sounds good that's fine too, but if it measures badly and sounds bad ,what do you do?
I have been a keen audio enthusiasts since the early 70s and making dml panels for about 10 years now ,I am very happy with the various panels I have but it is very hard to stop investigating new ideas.
One day.
Steve
Through my adventures.. Entirely My Opinion(s)..
Rectangle/Square panels that are directly connected to the exciter isn't good. Corners reflect weird resonances back into the driven material, hence.. Distortion.. **Remember the Pebble in the Pond**
The thickness/density of the material has a definite impact on the frequency response and SPL, especially in the mid/high frequency spectrum. The Tweeter region likes thin, non ferrous metals, like Brass, Aluminum, or even Copper. The Mids like wood ~3mm in thickness. The mid bass.. Well.. Is still somewhat of a mystery BUT I Do Know the unit doesn't need to be huge to get some decent bass..
I built a set of "Throw Together" units using 2-9"x9" pictures constructed with plastic canvas and computer printed artwork. A pair of economy drivers from Parts Express with the 3 sticky feet cut off and rear supported via a wooden spline, A 3.25" wooden circle @ 3mm in thickness as a mount of the v.c. to the center of the canvas. First fire up.. They sounded like crap! (Buzzy.. Flappy.. Nasty!!) Not having a lot to lose, I got the hot glue gun out. I glued the inside parameter of the frame to the canvas.. It helped.. Ran a bead of hot glue from the corners to the round disc, like an X.. Somewhat better.. Made circles around the disc towards the outside frame, just eyeballing the distance of the glue circle to the disc, two separate loops around and trying to evenly divide the space between the disc and the frame and WOW!! They went from.. "Oh, well.. If I mess 'um up, I'll salvage what I can" to "These are epic! Try to figure what you did!!" This set is the best overall sounding units that I have constructed! A simple "Hail Mary" that became a jewel! I'll compare them to the $30 4.5" 2-way bookshelf speakers sold by Parts Express..
Foam panels sound hollow to me. Constructed several. The ElCheepo 1/8" foam board material that is faced with paper on both sides gives the best sound in that category..
And.. A question to ponder.. "Why do these panels always sound better on the side that the exciter is mounted on?" The side the exciter is mounted to and the intended listening side always sounds different. Anyone else notice that..?
Rectangle/Square panels that are directly connected to the exciter isn't good. Corners reflect weird resonances back into the driven material, hence.. Distortion.. **Remember the Pebble in the Pond**
The thickness/density of the material has a definite impact on the frequency response and SPL, especially in the mid/high frequency spectrum. The Tweeter region likes thin, non ferrous metals, like Brass, Aluminum, or even Copper. The Mids like wood ~3mm in thickness. The mid bass.. Well.. Is still somewhat of a mystery BUT I Do Know the unit doesn't need to be huge to get some decent bass..
I built a set of "Throw Together" units using 2-9"x9" pictures constructed with plastic canvas and computer printed artwork. A pair of economy drivers from Parts Express with the 3 sticky feet cut off and rear supported via a wooden spline, A 3.25" wooden circle @ 3mm in thickness as a mount of the v.c. to the center of the canvas. First fire up.. They sounded like crap! (Buzzy.. Flappy.. Nasty!!) Not having a lot to lose, I got the hot glue gun out. I glued the inside parameter of the frame to the canvas.. It helped.. Ran a bead of hot glue from the corners to the round disc, like an X.. Somewhat better.. Made circles around the disc towards the outside frame, just eyeballing the distance of the glue circle to the disc, two separate loops around and trying to evenly divide the space between the disc and the frame and WOW!! They went from.. "Oh, well.. If I mess 'um up, I'll salvage what I can" to "These are epic! Try to figure what you did!!" This set is the best overall sounding units that I have constructed! A simple "Hail Mary" that became a jewel! I'll compare them to the $30 4.5" 2-way bookshelf speakers sold by Parts Express..
Foam panels sound hollow to me. Constructed several. The ElCheepo 1/8" foam board material that is faced with paper on both sides gives the best sound in that category..
And.. A question to ponder.. "Why do these panels always sound better on the side that the exciter is mounted on?" The side the exciter is mounted to and the intended listening side always sounds different. Anyone else notice that..?
@Spedge
This thread moves quickly. I wasn’t replying to you directly, just offering a view on why people have materials preferences. Still digesting the data you shared so will reply when I have got some sort of idea what is going on with long panels. That may take a while.
For now I think it is safe to say that for above 100hz tall panels are fine and if they are more domestically suitable I don’t think you will lose any of the DML magic when combined with a sub.
P.s. I agree about the experimentation bug. I came across DML’s for the first time last June and have built 4 sets and run a stack of experiments since then. They are addictive to listen to and the experimentation is great fun as it’s so cheap and easy to do.
This thread moves quickly. I wasn’t replying to you directly, just offering a view on why people have materials preferences. Still digesting the data you shared so will reply when I have got some sort of idea what is going on with long panels. That may take a while.
For now I think it is safe to say that for above 100hz tall panels are fine and if they are more domestically suitable I don’t think you will lose any of the DML magic when combined with a sub.
P.s. I agree about the experimentation bug. I came across DML’s for the first time last June and have built 4 sets and run a stack of experiments since then. They are addictive to listen to and the experimentation is great fun as it’s so cheap and easy to do.
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If you have any spike in that region, it could contribute to the muddiness. Your panels are flat in that region, but it's also the region that is the loudest in all your FR, so basically, the most forward frequencies from your panels are from that region.
Like here:
My remark about better response was aimed at the scale you showed your graphs, in 20dB increments... there is no resolution. I see that your next post had a graph with 10dB resolution... better but still compressed curve. Again, try 5dB increments on the vertical scale.
I was referring to the XPS panels that had 20dB drops higher up.
Your best attempt was reasonably flat (again, the scale!) but drops 20dBs from 2kHz up. That'd be a lifeless piece of board to me.
Either it's the board, or your exciter.
Low end
Hi twocents
I still have some IMF TSL 50 transmission line speakers I purchased in the mid 70s ,since I started building dml (or nxt as we called them)panels they mainly do low end duties ,before I got hooked on dml panels I took out the midrange units and placed them on top in a open panel setup,I've liked open baffle ever since,they go very low,lower than most subs and very powerful to boot,they were designed to xo at about 400hz ,so this gives me a lot to play around with.
I have tried open panel bass with 15inch units they sounded a lot more punchy with more slam ,but I missed the powerful low end,and of course the slam I can get from dml panels.
Steve
Hi twocents
I still have some IMF TSL 50 transmission line speakers I purchased in the mid 70s ,since I started building dml (or nxt as we called them)panels they mainly do low end duties ,before I got hooked on dml panels I took out the midrange units and placed them on top in a open panel setup,I've liked open baffle ever since,they go very low,lower than most subs and very powerful to boot,they were designed to xo at about 400hz ,so this gives me a lot to play around with.
I have tried open panel bass with 15inch units they sounded a lot more punchy with more slam ,but I missed the powerful low end,and of course the slam I can get from dml panels.
Steve
I really like that comment! It pretty much sums up what I think most of us are pursuing. We like the DML sound better than what decades of cone and planar technology have produced - and we do it despite aesthetics, placement limitations, etc. and what critics and our own previous assumptions and biases tell us.
Piezo
Offgrid.
Tectonic call this side the primary drive side and yes to an extent they do sound better ,the down side to this is the exciter itself ,a great chunk of vibrating metal and spider which causes massive disruption of the response in the 10k region and a phasey sound.
When podium first launched their panel at an audio show in the UK ,can't remember which ,you could walk around the back and at the time i thought they sounded better that way.
When I did the same (turned them round)to my panels yes they sounded great,but after a short time I could hear something wasn't right ,it was then after measuring that i found the problem.
The only other option I can think of is piezoelectric drivers ,rs in UK sell sonitron flat panel speakers and piezoelectric amplifiers ,I have been looking at these for a couple of years but for some reason can't get my wallet open!!! It would only cost about £35 for one channel but worrying if it didn't work to well on a panel ,just remembered I've ordered 5 50mmm piezo exciters on ebay couldn't stop myself ,I think ziggy started with piezo units on this site years back but they were not powerful enough to drive the panels then.
Well we'll see maybe it I get around to it?
Steve
Offgrid.
Tectonic call this side the primary drive side and yes to an extent they do sound better ,the down side to this is the exciter itself ,a great chunk of vibrating metal and spider which causes massive disruption of the response in the 10k region and a phasey sound.
When podium first launched their panel at an audio show in the UK ,can't remember which ,you could walk around the back and at the time i thought they sounded better that way.
When I did the same (turned them round)to my panels yes they sounded great,but after a short time I could hear something wasn't right ,it was then after measuring that i found the problem.
The only other option I can think of is piezoelectric drivers ,rs in UK sell sonitron flat panel speakers and piezoelectric amplifiers ,I have been looking at these for a couple of years but for some reason can't get my wallet open!!! It would only cost about £35 for one channel but worrying if it didn't work to well on a panel ,just remembered I've ordered 5 50mmm piezo exciters on ebay couldn't stop myself ,I think ziggy started with piezo units on this site years back but they were not powerful enough to drive the panels then.
Well we'll see maybe it I get around to it?
Steve
Patent
Burntcoil.
I don't know if you've seen this patent from 1961 but thought you would find it very interesting ,I had to dig around to re-find this again ,I had it on my tablet some years ago but my wife deleted it!! My audio habit annoys her .
It is us323695A Abraham B Cohen electrical res associates inc.
Filed 1961-04-25.
It's a good read not like nxt 's nonsensical gibberish.
I know some early valve radio's used sound boards ,ply basically, so dml speakers have been around a long time,if I ,we,had known about this patent
The world of audio could have been so different.
Steve
Burntcoil.
I don't know if you've seen this patent from 1961 but thought you would find it very interesting ,I had to dig around to re-find this again ,I had it on my tablet some years ago but my wife deleted it!! My audio habit annoys her .
It is us323695A Abraham B Cohen electrical res associates inc.
Filed 1961-04-25.
It's a good read not like nxt 's nonsensical gibberish.
I know some early valve radio's used sound boards ,ply basically, so dml speakers have been around a long time,if I ,we,had known about this patent
The world of audio could have been so different.
Steve
Spedge
Wow! Very nice find!
For those interested note
"A still further object of this invention is to provide means of control over the modal vibrations of flat pistons to insure uniform vibrations of all parts of the flat plane of the piston"
Available here US3236958A - Loudspeaker system
- Google Patents
I agree that the loudspeaker world took a serious wrong turn when Kellogg and Rice's theory began dominating.
I also think this prior art should have invalidated the NXT patent. Patents are getting very sloppy.
Thank you Spedge!
Wow! Very nice find!
For those interested note
"A still further object of this invention is to provide means of control over the modal vibrations of flat pistons to insure uniform vibrations of all parts of the flat plane of the piston"
Available here US3236958A - Loudspeaker system
- Google Patents
I agree that the loudspeaker world took a serious wrong turn when Kellogg and Rice's theory began dominating.
I also think this prior art should have invalidated the NXT patent. Patents are getting very sloppy.
Thank you Spedge!