No, the ideal would be a nice very large green area falling down gently to the blue with the angle.
This is the link to Directivity measurements applied to DML (directivity plots). Ed4. I posted it here some weeks ago. The plots of the previous post are from it. Maybe you will find more explanations of what are directivity plots. There are some links in the paper to different sources.
From the work of F Toole and others, the general requirements for a loudspeaker (independently of its technology) is in anechoic conditions to have a flat on axis response and a directivity so that the reflections from the room (= sound coming from other angles) have the same general response with a lower level. The idea is the reflections have the same tonal balance as the direct sound.
For DML, we can think to use EQ to correct some FR imperfections. All the directions will be corrected.
So the most important is to avoid peaks or dips that could occur in a specific angle ranges. For DML, This is my opinion as directivity tests and plots are not of general use... not to say I am the alone doing them.
What I saw from those directivity tests are mainly peaks (red or orange areas) out of axis
Christian
lay the panel in a horizontal position and run some krazy glue into those cracks that ought to solve the buzz.
Twocents.
I am happy to share.
I prefer the sound of a more central mounting for my exciters.
The NXT positions are 3/7 x 4/9 which suits me fine.
On very small panels I like to place the exciter in the centre of the panel to keep the ballance, with less panel wobbling going on.
Unless I am not using low frequencies on the panel.
With panels that flex differently in different directions, placing the exciter in the centre of a square seems to be OK,for a 2ft proplex panel anyway, but I have not tested other panel materials, only proplex, and the square fluted panels ( I did not quite like the sound of the square fluted panels ).
I suppose I could try a 2ft square 1.5mm 2ply panel and see what happens 🤔
But not at the moment.
Actually, with the 1.5mm panel in the video I just stuck the exciter near the middle somewhere, my wife had popped out ,so I was in a hurry, the exciter was a new one which had the sticky tape mounting .
I quickly slapped on the exciter and wired it up to a digital amp, and that was it 🫣
Steve.
I am happy to share.
I prefer the sound of a more central mounting for my exciters.
The NXT positions are 3/7 x 4/9 which suits me fine.
On very small panels I like to place the exciter in the centre of the panel to keep the ballance, with less panel wobbling going on.
Unless I am not using low frequencies on the panel.
With panels that flex differently in different directions, placing the exciter in the centre of a square seems to be OK,for a 2ft proplex panel anyway, but I have not tested other panel materials, only proplex, and the square fluted panels ( I did not quite like the sound of the square fluted panels ).
I suppose I could try a 2ft square 1.5mm 2ply panel and see what happens 🤔
But not at the moment.
Actually, with the 1.5mm panel in the video I just stuck the exciter near the middle somewhere, my wife had popped out ,so I was in a hurry, the exciter was a new one which had the sticky tape mounting .
I quickly slapped on the exciter and wired it up to a digital amp, and that was it 🫣
Steve.
Delignified Wood used to create a Translucent Wood has been a development for quite some years.
About Seven Years ago the Maryland University discovered a much improved environmentally friendly method, where Chemicals used are not so damaging.
Today things have moved even further, as there are very high quality Plant Based Phenolic Resins / Fibres being produced, that substitute Petrochemical Industry Phenolics being Impregnated into Petrochemical Industry Fibres .
Cutting Edge Products are now being produced using Grass Fibres (Pampas Grass Cellulose Fibres are a Match for other commonly used Fibres at the same surface area dimension.
New Plant Based Phenolic Resins, are possibly able to become Translucent or Clear if exposed to other treatments.
Formula 1 Chassis are a full structure / composite Structure using the new Organic Structure Forms now able to be produced.
https://www.goodnewsnetwork.org/transparent-wood-nearly-as-clear-as-glass-from-umd/
About Seven Years ago the Maryland University discovered a much improved environmentally friendly method, where Chemicals used are not so damaging.
Today things have moved even further, as there are very high quality Plant Based Phenolic Resins / Fibres being produced, that substitute Petrochemical Industry Phenolics being Impregnated into Petrochemical Industry Fibres .
Cutting Edge Products are now being produced using Grass Fibres (Pampas Grass Cellulose Fibres are a Match for other commonly used Fibres at the same surface area dimension.
New Plant Based Phenolic Resins, are possibly able to become Translucent or Clear if exposed to other treatments.
Formula 1 Chassis are a full structure / composite Structure using the new Organic Structure Forms now able to be produced.
https://www.goodnewsnetwork.org/transparent-wood-nearly-as-clear-as-glass-from-umd/
Hello JohnnoG.
These new wood materials might sound promising but until we know what they sound like, I'm not holding my breath.
Hopefully they will sound good 🤔
There are a few good materials out there already that are ready to use and are cheap.
I was going to go to the Whittlebury audio show this weekend but I am still recovering from a bad cough and cold .
I like to keep my head in the real world of Audio, just to remind myself how far I have come with DML.
I missed the Bristol show also.
Hopefully I will make it to the other shows later in the year, health permitting.
Steve.
These new wood materials might sound promising but until we know what they sound like, I'm not holding my breath.
Hopefully they will sound good 🤔
There are a few good materials out there already that are ready to use and are cheap.
I was going to go to the Whittlebury audio show this weekend but I am still recovering from a bad cough and cold .
I like to keep my head in the real world of Audio, just to remind myself how far I have come with DML.
I missed the Bristol show also.
Hopefully I will make it to the other shows later in the year, health permitting.
Steve.
Christian.
Are there any of the videos of me using my various panels for PA work , that you think could be of interest to others.
Preferably not ones with me singing, I am not ready for stardom yet 🤣
Steve.
Are there any of the videos of me using my various panels for PA work , that you think could be of interest to others.
Preferably not ones with me singing, I am not ready for stardom yet 🤣
Steve.
Thank you Steve. The same as the Monacor exciter positions.
Steve, you make it look so simple. Here I am trying to keep up with this thread, trying to understand the technical discussions and jargon, trying to figure out the ultimate sounding panel material, trying to figure out the ideal size and ratios and how to mount or suspend them, trying to figure out which exciter to use and where to stick it, trying to figure out PETTaLS and how to simmulate it, trying to figure out REW and how to measure it, ....
And then here comes spedge - picks up a discarded piece of plywood for free, slaps on a cheap 10W exciter somewhere near the middle, hangs the panel with a piece of tape and it sounds truly amazing! At this point, I really envy you.
Hello Steve,
Among the last ones, there the ones where you shown the clamped version with a "thick" plywood. They show how a panel works with a wall just behind. And for this panel, it works not badly. It shows also at a moment the low level of feedback when you used your mic. It might be also a warning with the buzzing sound maybe due some little piece of wood not well glued into the plywood.
Maybe the sound of those panels are not as good as the one with the 1.5mm plywood... It could be also my memory...
Christian
Twocents.
Sometimes it is just that simple.
Over the years I have made so many panels from different materials shapes and sizes.
The best panels would be the ones that you do not have to do anything to, to make it them sound good.
But all, need just a little help to take them up to the next level or two.
Yes, I do find it easy nowadays to build good sounding panels.
Some may call it luck or maybe I actually know what I am doing.
Maybe it is just knowing what not to do.
My rigid ply panels had the most effort put into them as my skills at woodwork are very limited.
Strange that the easiest ones to make , sound the best.
I do not get caught up in measurement techniques for design purposes but measuring afterwards is helpful.
The sound of the panel is all I worry about, isn't that what this is all about.
The only thing I worry about is having a low frequency driver that can match and do justice to the panels, without that the sound of a DML can fall on its face, and sound lacking.
Steve.
Sometimes it is just that simple.
Over the years I have made so many panels from different materials shapes and sizes.
The best panels would be the ones that you do not have to do anything to, to make it them sound good.
But all, need just a little help to take them up to the next level or two.
Yes, I do find it easy nowadays to build good sounding panels.
Some may call it luck or maybe I actually know what I am doing.
Maybe it is just knowing what not to do.
My rigid ply panels had the most effort put into them as my skills at woodwork are very limited.
Strange that the easiest ones to make , sound the best.
I do not get caught up in measurement techniques for design purposes but measuring afterwards is helpful.
The sound of the panel is all I worry about, isn't that what this is all about.
The only thing I worry about is having a low frequency driver that can match and do justice to the panels, without that the sound of a DML can fall on its face, and sound lacking.
Steve.
In one way: terrible. In an other: encouraging.
What I have been trying to do for some months now, is to link Steve's experience to measurements or to some design rules. I would say I am happy to see for example the directivity measurements draw a similar set of materials than the one Steve is happy with.
Even if not finished, the "noise" of the central area and the from the rear side have been also explored.
One think remarkable is Steve with his phone can make good recording. To get something acceptable with mine, I have to use external mics, an external mic preamp and an application able to use the unprocessed sound.
One think we have also notice is the reverberation time of Steve's rooms is quite low while mine is quite high. It might explain why I have an interest in response at different angles.
Christian
Yes, it's all about the sound, for me too. But your years of experience obviously helps to get the sound you want.
It is very interesting for me - that you worry about low frequency drivers? Most builders here are concerned about getting the high frequencies right. Which exciters are your favorite ones for light plywood panels then?
Twocents.
I bought a large batch of sell-off 10watt exciters about 15 years ago.
The idea was to have at least 8 exciters to a panel similar to a podium panel.
Hence all the tall panels in those days, which was supposedly needed for the low frequencies.
It didn't take too long to realise that the last thing I wanted was very low frequencies on my panels.
In the past I have gone into great detail on how to achieve good high frequencies on panels using similar 25mm exciters
The new 25watt exciter I used on the 1.5 flexible ply is pretty similar to my 10watt exciters, I could not tell any difference, they even overheated the same.
The 25mm exciters I use have no trouble reaching 20k and above, it is the panels that have the problems.
That is as long as you remove the horrible sticky tape rings that come with the exciters, which rolls off the hf above around 10k.
They may actually use them to get rid of the 10k peak on most materials, if the panels can go that high that is.
I cannot stress enough that if you want clean clear treble from an exciter, you need to sort out the problems associated within the central coil area.
Having a strong plot up to 20k isn't much good if it sound crap!
Steve.
I bought a large batch of sell-off 10watt exciters about 15 years ago.
The idea was to have at least 8 exciters to a panel similar to a podium panel.
Hence all the tall panels in those days, which was supposedly needed for the low frequencies.
It didn't take too long to realise that the last thing I wanted was very low frequencies on my panels.
In the past I have gone into great detail on how to achieve good high frequencies on panels using similar 25mm exciters
The new 25watt exciter I used on the 1.5 flexible ply is pretty similar to my 10watt exciters, I could not tell any difference, they even overheated the same.
The 25mm exciters I use have no trouble reaching 20k and above, it is the panels that have the problems.
That is as long as you remove the horrible sticky tape rings that come with the exciters, which rolls off the hf above around 10k.
They may actually use them to get rid of the 10k peak on most materials, if the panels can go that high that is.
I cannot stress enough that if you want clean clear treble from an exciter, you need to sort out the problems associated within the central coil area.
Having a strong plot up to 20k isn't much good if it sound crap!
Steve.
two cents,
I think by "low frequency driver", Steve meant "an accompanying woofer" (probably a conventional pistonic driver) for the lows that sounds as good as the panel for the highs.
But he will have to say for sure.
Eric
Eric.
That sounds good for the lower midrange.
My transmission line speakers were designed to XO at near 400hz but they start to sound boxy above about 250hz.
I could get away with XO to say the proplex panel for the lower midrange and XO of about 60hz for the subs.
This all depends on the main panel used.
Steve.
That sounds good for the lower midrange.
My transmission line speakers were designed to XO at near 400hz but they start to sound boxy above about 250hz.
I could get away with XO to say the proplex panel for the lower midrange and XO of about 60hz for the subs.
This all depends on the main panel used.
Steve.
I decided some months ago to look at DML in details starting from the highs. It comes from that the coincidence frequency measurements, the directivity plots, the investigations around the drum effect and the rear SPL with the influence of the exciter itself and of the spine. I am now coming to the mid to low frequencies and typically the question of the crossover point.
It is a range where a DML starts to suffer of a lack of modes (more dips). It is a range also where the distortion increases which is expected as the excursion increases when the frequency decreases.
It seems also that a panel in the lows needs a too long time to stop. Or in other words, as Steve shared, a panel damped enough for the bass might be too damped for the mids to highs.
So with that I was wondering if there are reasons to go below let say 200Hz or even 300Hz except the technical beauty of a full range.
With these cut off frequencies, the woofer can't be too far from the DML.
Has somebody already experimented an open baffle woofer with a DML?
Christian
It is a range where a DML starts to suffer of a lack of modes (more dips). It is a range also where the distortion increases which is expected as the excursion increases when the frequency decreases.
It seems also that a panel in the lows needs a too long time to stop. Or in other words, as Steve shared, a panel damped enough for the bass might be too damped for the mids to highs.
So with that I was wondering if there are reasons to go below let say 200Hz or even 300Hz except the technical beauty of a full range.
With these cut off frequencies, the woofer can't be too far from the DML.
Has somebody already experimented an open baffle woofer with a DML?
Christian
Christian.
I have my cone drivers about 30cm behind and to the side of the panels.
I use time delay on the panels to match with the panels.
I believe this also helps with room modes as they both cover frequencies somewhere between 80hz and 300hz but in different positions in the room.
The low frequency drivers are also against the back wall, so no reflections from the rear wall.
This works very well, and maybe I could make a drawing of this too , to demonstrate what I believe is happening and why it works so well with a DML panel.
Eric will have an apoplexy, I'm sure.
Steve.
I have my cone drivers about 30cm behind and to the side of the panels.
I use time delay on the panels to match with the panels.
I believe this also helps with room modes as they both cover frequencies somewhere between 80hz and 300hz but in different positions in the room.
The low frequency drivers are also against the back wall, so no reflections from the rear wall.
This works very well, and maybe I could make a drawing of this too , to demonstrate what I believe is happening and why it works so well with a DML panel.
Eric will have an apoplexy, I'm sure.
Steve.
Christian, OB with dml crossed at 160 Hz is my system for a long time, double 15" per channel with 15" sub below 40Hz.
After many experiments with several materials and some exciters to couple the bass region panels with the mid/high panels i did make a stop just to listen to music, nevertheless the excite exciters were promising in that two different materials panel approach but only if we listen at moderate levels (which is more than appropriated for most of the living rooms in Europe).
With time i will still pursuit the dml full range.
Steve,
I think this approach makes sense. I can't find anything to disagree with.
Your drawings never make me apoplectic. I rather enjoy them.
Eric
Yes this is a very good configuration as your woofer are close to the walls so don't suffer from cancellation in this range as you say and there are also not so far from the panels. The wave length at 300Hz is about 1.1m so you are almost in the quarter wave length distance. With in addition the the time delay to compensate.
If I remember you adjust the filters to have a common frequency range between the DML and the woofer.
I don't see reasons to have an apoplexy ;-)
Christian