Hello Eric
The substitute to the original 3M VHB tape haven't been a topic for me up to no!
Just to have an idea of the availability of the 3M product you found, I checked on Amazon : only one proposal about 650€ for 6!
To put more money in the tape than in exciters or panel material is a problem.
I made some research on the forum to find and see it was already discuss (of course! everything seems discuss several time!)
- #2624 : specification of the original 3M VHB 9473 used by Dayton audio
- #2699 : proposal of a Tesa 64621 "alternative"... at least for testing
So I am going to be more attentive to the gluing possibility for testing. I think Spedge says to use PVA.
As I would like to make measurements from my first XPS panel, I will glue one exciter on it with this Tesa and see how it stays or not.
Completely different :
At random of the posts, I found a thread about plinth building for turntable. The goal is probably at the opposite of what is needed for a DML but it gives information about plate material characteristic : damping factor, critical frequency (not coincidence) and the frequency area where stiffness, mass or damping drive the behavior of the plate. Link to web site. Do you know that?
Christian
Leob.
I was not intending to infer that a polystyrene panel could not handle more than 10watts.
it's more that my ears would start bleeding if I actually tried to use the whole 10watts 😄
I like listening to my music at very realistic sound levels ,rock, classical,jazz , electronic, Japanese drums, you name it.
my 10watt exciters do not even get warm.
even though the house is moving ,the exciters are only ticking over.
the ply on the others hand will get very hot and will self destruct .
huge power amps are not needed ,unless you are using a very inefficient panel with many powerful exciters.
I think what tectonic are trying to show is that you do not need massive banks of speakers to drive a large venue.
because of the intelligibility and clean spread of sound even in a very reverberant hall.
On the tectonic site on YouTube you will find large concert halls with only three panels per side, filling the whole venue even to the far corners !!
This is the difference dml can make to pro sound, but I think it is a bit of an up hill struggle trying to get the died in the wall massive pa system lovers to understand this ?
A correctly designed dml panel will go excessively loud without compression.
I found this out very early on ,when I played machine gun fire over my eps panels, I could feel the pressure on my chest pounding my lungs, I was shocked to hear a real machine gun being fired in my room, and so was a friend who was visiting at the time, he said he could feel his teeth rattling in his head 😂
Cone speakers would sound like a wet fart in comparison !
Pardon my language.
Steve.
I was not intending to infer that a polystyrene panel could not handle more than 10watts.
it's more that my ears would start bleeding if I actually tried to use the whole 10watts 😄
I like listening to my music at very realistic sound levels ,rock, classical,jazz , electronic, Japanese drums, you name it.
my 10watt exciters do not even get warm.
even though the house is moving ,the exciters are only ticking over.
the ply on the others hand will get very hot and will self destruct .
huge power amps are not needed ,unless you are using a very inefficient panel with many powerful exciters.
I think what tectonic are trying to show is that you do not need massive banks of speakers to drive a large venue.
because of the intelligibility and clean spread of sound even in a very reverberant hall.
On the tectonic site on YouTube you will find large concert halls with only three panels per side, filling the whole venue even to the far corners !!
This is the difference dml can make to pro sound, but I think it is a bit of an up hill struggle trying to get the died in the wall massive pa system lovers to understand this ?
A correctly designed dml panel will go excessively loud without compression.
I found this out very early on ,when I played machine gun fire over my eps panels, I could feel the pressure on my chest pounding my lungs, I was shocked to hear a real machine gun being fired in my room, and so was a friend who was visiting at the time, he said he could feel his teeth rattling in his head 😂
Cone speakers would sound like a wet fart in comparison !
Pardon my language.
Steve.
Following #4561about tape alternative...
For my last tests I used a Tesa 05690.
Typing that on tesa.com leads to Tesa 05681.
Let me first answer to the second part of your reply (thank you for reply).
About the 3k foll off, it is also what it reminds me; not by experience but what I read on the threads. Those materials (XPS 9mm and XPS 5mm) really look like those foam between paper skins except they are sold as XPS. My knowledge about those materials is to thin. Maybe somebody could explain where is the trap but I really feel it is an other sort of material or process.
What is more curious is the behavior of the EPS which is much more easy to recognize as material.
About the frame, I took the option to support the membrane at its lower edge by 2 small foam pad in order to test more heavy material (I have question about what makes the efficiency) and in addition for pads to press the membrane against the foam pads glued on the frame. The position of those pads is similar to Tectonic fixation position. The foam is the one I used tor my plywood panel. A 17x17mm foam from 3M for a garage door sealing.
In my view, 2 or 3cm long pad was supposed not to applied an important strength... my balance says when the pad is about half pressed, the equivalent needed weight is somewhere between 150 to 180g; Is it too much?
In an other hand, when the membrane is kept in position in this way, it remains completely flat even at the pad. The outside pad is pressed but the one (same size) between the membrane and frame not.
As the dimensions are quite large (60cm wide for 80cm high), I thought it would be ok; probably modifying the low end but not let say above 100 or 200Hz.
Christian
For my last tests I used a Tesa 05690.
Typing that on tesa.com leads to Tesa 05681.
Hello Steve,
Let me first answer to the second part of your reply (thank you for reply).
About the 3k foll off, it is also what it reminds me; not by experience but what I read on the threads. Those materials (XPS 9mm and XPS 5mm) really look like those foam between paper skins except they are sold as XPS. My knowledge about those materials is to thin. Maybe somebody could explain where is the trap but I really feel it is an other sort of material or process.
What is more curious is the behavior of the EPS which is much more easy to recognize as material.
About the frame, I took the option to support the membrane at its lower edge by 2 small foam pad in order to test more heavy material (I have question about what makes the efficiency) and in addition for pads to press the membrane against the foam pads glued on the frame. The position of those pads is similar to Tectonic fixation position. The foam is the one I used tor my plywood panel. A 17x17mm foam from 3M for a garage door sealing.
In my view, 2 or 3cm long pad was supposed not to applied an important strength... my balance says when the pad is about half pressed, the equivalent needed weight is somewhere between 150 to 180g; Is it too much?
In an other hand, when the membrane is kept in position in this way, it remains completely flat even at the pad. The outside pad is pressed but the one (same size) between the membrane and frame not.
As the dimensions are quite large (60cm wide for 80cm high), I thought it would be ok; probably modifying the low end but not let say above 100 or 200Hz.
Christian
Attachments
Steve,
Below the 2 FR on the same graph.
Frankly speaking I can't explain the differences except by invoking the role of the room.
So yes it is the same panel in both. No change. It is also the same electric chain (laptop, DAC, amp, mic, setting of REW). I am in a phase I keep my panels, canvas and plywood, as they are before deciding what to change.
The main big difference is one is outdoor in my garden (I posted some pictures), the other indoor. In indoor condition, I can't say I keep the mic position between the different records but it isn't the point here.
I already observe with the plywood panel that the low end is higher outdoor than indoor. Which make sense because of the possibility of combining earlier the rear wave indoor.
In our living room (indoor), the canvas has a wall (painted one, no damping or diffusor) 30cm behind it.
In the spectrogram below, we see that the dot line which shows the position of the maximum for each frequency (which is hidden in a pure FR without windowing) is far to be at t=0 which says there are strong reflections.
Precision : if there is no change in the panels, it might be one measure is with one panel, an other with the second one explaining some change in the location of the peaks.
Consider also one is indoor around 20°C, the other outdoor around 5 to 7°C
REW offers options for windowing, one is frequency dependent window. When applying it, the differences are more limited. For now I don't use it because I have found no detailled explanation of how it works.
Before that, I limit my use of REW to compare FR coming from the same test cession (ie test of central mass). I started with outdoor last August in order to try to explain "local" differences (ie the bass level or what is a reason of a peak : from the panel or a reflection)
All advice for a better measurement quality welcome!
Christian
Indoor :
Christian.
what you need to do is freely suspend an eps panel and gently hold the panel between two fingers, using both hands on each side of the panel ,if necessary.
as you slide your hands around the panel while you look at the RTA response ,you will see the frequency response constantly changing ,and also by increasing the pressure between your fingers, I have in the past used this method on certain panels for finding the places to apply small weights to fill in dips in the response,which can be useful.
Heavier force is needed for ply panels , but the same applies.
Tectonic use 5 weights on their panels , I used 4 weights on my rigid ply panels although One has fallen off.
I do remember applying about 6 weights to a 30cm eps panel once, which increased the frequency response below 500hz, which made it pretty much full range, but it did not sound like an eps panel anymore, it sounded more like a cone driver.
DML is no different to a cone driver when it comes to gluing the coil rigidly to the cone, sticky tape will eventually come loose, and long before the exciter falls oft the HF will start to droop .
I know this from experience.
Steve.
what you need to do is freely suspend an eps panel and gently hold the panel between two fingers, using both hands on each side of the panel ,if necessary.
as you slide your hands around the panel while you look at the RTA response ,you will see the frequency response constantly changing ,and also by increasing the pressure between your fingers, I have in the past used this method on certain panels for finding the places to apply small weights to fill in dips in the response,which can be useful.
Heavier force is needed for ply panels , but the same applies.
Tectonic use 5 weights on their panels , I used 4 weights on my rigid ply panels although One has fallen off.
I do remember applying about 6 weights to a 30cm eps panel once, which increased the frequency response below 500hz, which made it pretty much full range, but it did not sound like an eps panel anymore, it sounded more like a cone driver.
DML is no different to a cone driver when it comes to gluing the coil rigidly to the cone, sticky tape will eventually come loose, and long before the exciter falls oft the HF will start to droop .
I know this from experience.
Steve.
Christian.
30cm is far too close to the rear wall for panel measurements, the panel is already showing signs of low end cancellations from the wall, this will also change the higher frequencies also.
Maybe when out side again you could see what happens if you paced the panel 30cm from an outside wall, and even experiment having the panel at varying angles from the wall ,to minimise standing waves reflections ?
it's just a thought ?
Steve.
30cm is far too close to the rear wall for panel measurements, the panel is already showing signs of low end cancellations from the wall, this will also change the higher frequencies also.
Maybe when out side again you could see what happens if you paced the panel 30cm from an outside wall, and even experiment having the panel at varying angles from the wall ,to minimise standing waves reflections ?
it's just a thought ?
Steve.
Thinking about it, when trying to compare a line array speaker and a DML, using the often specified sensitivity rating is of course misleading since it is measured 1m on axis. You don't want extremely loud sound just in front of the speakers, actually the opposite to avoid ear damage. The important thing is the average loudness experienced by the audience, so the total efficiency of the speaker. Sound emitted to the back will usually be wasted, but wide off axis dispersion will be very valuable.
What is excessively loud of course depends on context a lot. My 100w active speakers can play louder than I need at home indoors, and I can have a party in the garden with people dancing to them if I push them to the max. But for this party I need something that will beat a efficient and great sounding 25kw system for the exercise to be successful, otherwise I will not end up using it.
SPL is not everything, and especially not 1m on axis, but it has to be felt extremely loud over an 20x20m area, and like everything with sound level things escalate exponentially, so if you want to double the level with double the area covered the 100wpc easily becomes 10kw.
I think it will be hard for DML to be come popular for PA systems. Look at the JBL VFX I linked to. Small, sturdy and easy to handle, and probably need 6-8 Techtronic panels to replace one of those. It could catch on if the audiences really enjoy it, but rental firms wont start buying and recommending DML.
For me it is a just a personal passion to throw an annual party, and it seems like DML could deliver a really spectacular and unique experience in a quite cost efficient way (one VFX speaker is around €2600, so that is quite a few exciters, panels and amps).
Leob .
polycarbonate does tend to have a very harsh sound , because of its rigidity and probably the large cavities ,it has a very high resonance, or ringing ,a bit like glass.
To be honest I did not like the sound ,so never took it any further,it was also pretty heavy for my exciter.
I did wonder if the much thinner polycarbonate panel used for greenhouses would be better, but as usual I did not want to buy in bulk .
so that was the end of that.
Steve.
polycarbonate does tend to have a very harsh sound , because of its rigidity and probably the large cavities ,it has a very high resonance, or ringing ,a bit like glass.
To be honest I did not like the sound ,so never took it any further,it was also pretty heavy for my exciter.
I did wonder if the much thinner polycarbonate panel used for greenhouses would be better, but as usual I did not want to buy in bulk .
so that was the end of that.
Steve.
Thank you Steve
30cm is the distance that is ok for our living room... unfortunately not from the loudspeaker point of view. Some weeks ago, before our exchanges and outdoor measurements, I thought the main problems where from reflections so I started to think about absorber or diffuser on the back of the panel and make measurement from this position. I see now it is more complex. By facility for test as the additional mass, I have let the panel in its standard position. Not good or at least confusing for our exchanges. Outdoor measurements are weather dependent and a bit longer to set. Our living room is less than 5m by 5m with many things... I will thing what is the best option.
Christian
Leob.
easy to handle ? 21kg each you must be a strong lad 😁 and 2600 eu each !
6 to 8 tectonic panels to replace one of those ?
you are vastly underestimating DML panels .
in one of their YouTube videos they use 6 tectonic panels ,3each side to fill a 5000 seat concert hall with no beaming,no central sweet spot to worry about ,and no mic feedback.
Plus subs of course.
the organisers were amazed.
you wouldn't take the panels down any lower than about 150hz I would think.
There are lots more videos
Steve.
easy to handle ? 21kg each you must be a strong lad 😁 and 2600 eu each !
6 to 8 tectonic panels to replace one of those ?
you are vastly underestimating DML panels .
in one of their YouTube videos they use 6 tectonic panels ,3each side to fill a 5000 seat concert hall with no beaming,no central sweet spot to worry about ,and no mic feedback.
Plus subs of course.
the organisers were amazed.
you wouldn't take the panels down any lower than about 150hz I would think.
There are lots more videos
Steve.
Steve,
I am not sure there is a simple answer to that question or a least, I am not sure we can have conditions free of boundary conditions enough to answer.
By the end of December, I made some tests with the mic at 75cm from the canvas with different back wall distances. The 1m or even 50cm FR show the same tendency than the outdoor FR but locally difference up to 5dB can be found.
Using a frequency dependent window limit the differences by rejecting the reflections. I will try to check if there is a "consensus" on its use.
The FR at 2m with the back wall at 30cm is very different from what i got in December at 75cm with a back wall at 30cm or 20cm.
Here also using the frequency dependent window reduce the difference.
There are few possibilities to reduce boundary interference : decrease the source to mic distance, increase the source to mic distance, use of some absorber or diffuser...
I have perhaps to go back to previous post where we discussed about distances.
What about your conditions from boundaries?
Christian
Steve,
I understand the edge conditions change the low frequency behavior. For the EPS, I am first surprised by the high frequency roll off. The panel is quite large. Do you think the way to suspend the panel change the response above some kHz?
Christian
This is plain sheets, so no cavities:
https://www.amazon.se/gp/product/B09DXFZRX9/ref=ppx_yo_dt_b_asin_title_o01_s00?ie=UTF8&th=1
Actually I was ordering acrylic, and though that was what I still was looking at when I finally found the right size and thickness...but later realized it was actually polycarbonate.
Indeed they are a bit ringy without any damping, but when damped they sound great and not harsh at all...but that could be the 50mm exciter not giving great high frequency response. They can produce quite a lot of bass, but unless I cut below 150hz they get quickly saturated and starts wobbling uncontrollably. I do like the look and durability or clear acrylic and PC, and very happy with the sound I can get from them, but for a large system I already suspected that it will not be efficient enough.
Some interesting claims in the Tectonic videos. I get that you cannot really compare watt to watt, or even SPL to SPL, but I have problem understanding how DML could be that much more efficient. I will have to try some more sensitive materials so I can get an idea what it is capable of, but I hope you right and that one can get away with a lot less area and watts than I have expected!
@spedge
Steve,
I just played a little bit with REW options after reading quickly around the frequency dependent window. There are posts from Bob Katz about that. A good reference even not recent.
So on the same records than before, I applied a 10 cycles window with a psychoacoustic averaging. Not sure it is exactly the best settings but it remove part of the reflections and the method seems said to be more close of what we hear (window to be between 6 to 15 cycles)
Below the result for :
up
2 - orange : outdoor mic @1.5m
3 - purple : indoor mic @0.75m back wall 1m
4 - green : indoor mic @0.75m back wall 0.5m
down
1 - red : indoor (an other room) mic @2.2m, back wall 0.3m => usual listening situation
5 - blue : indoor (same as 3 and 4) mic@0.75m back wall @0.2m
Is it less confusing? A better reading of the panel characteristics?
@All : I'ld appreciate help to know more about the "last" or "most common" REW used in this forum.
Christian
Steve,
I just played a little bit with REW options after reading quickly around the frequency dependent window. There are posts from Bob Katz about that. A good reference even not recent.
So on the same records than before, I applied a 10 cycles window with a psychoacoustic averaging. Not sure it is exactly the best settings but it remove part of the reflections and the method seems said to be more close of what we hear (window to be between 6 to 15 cycles)
Below the result for :
up
2 - orange : outdoor mic @1.5m
3 - purple : indoor mic @0.75m back wall 1m
4 - green : indoor mic @0.75m back wall 0.5m
down
1 - red : indoor (an other room) mic @2.2m, back wall 0.3m => usual listening situation
5 - blue : indoor (same as 3 and 4) mic@0.75m back wall @0.2m
Is it less confusing? A better reading of the panel characteristics?
@All : I'ld appreciate help to know more about the "last" or "most common" REW used in this forum.
Christian
Christian.
The idea for recording measurements outside that would match the inside wall reflections would hopefully give some sort of consistency.
If there is a similarity between the two without all the other reflections ,then you know how much the back wall is affecting the plots.
at the moment you have a lot of plots of the art panel, all showing different results and the other poly panels all showing very similar responses ? When I know they are very different.
It is very confusing .
I usually concentrate on one panel only(that's the idea anyway) and if I like the sound I see how I can improve it, swapping between many panels and not understanding what is happening in and outside would give me a headache.
You need some consistency, measuring in the best sounding position in the room .
Even in my overcrowded junk room I can still get good measurements.
I just took this measurement in my room, this is the normal panel position in my room,shown in the other picture .
There is also a second panel showing another type of panel suspension using an old sponge,
It is far from perfect but it matches the near field response quit well.
Giving me something to work with that I understand.
Steve.
The idea for recording measurements outside that would match the inside wall reflections would hopefully give some sort of consistency.
If there is a similarity between the two without all the other reflections ,then you know how much the back wall is affecting the plots.
at the moment you have a lot of plots of the art panel, all showing different results and the other poly panels all showing very similar responses ? When I know they are very different.
It is very confusing .
I usually concentrate on one panel only(that's the idea anyway) and if I like the sound I see how I can improve it, swapping between many panels and not understanding what is happening in and outside would give me a headache.
You need some consistency, measuring in the best sounding position in the room .
Even in my overcrowded junk room I can still get good measurements.
I just took this measurement in my room, this is the normal panel position in my room,shown in the other picture .
There is also a second panel showing another type of panel suspension using an old sponge,
It is far from perfect but it matches the near field response quit well.
Giving me something to work with that I understand.
Steve.
Attachments
Leob.
Sorry , I just saw the 6mm and just presumed it was fluted, that is a very thick heavy panel and will take a lot to drive.
I really wished I could have found a clear panel that worked for me , they look so cool.
In some of those tectonic videos they show installing 4 DML panels,to cover very large venues, which replace 15 standard pa speakers .
So quite the opposite to what you are a expecting.
Steve.
Sorry , I just saw the 6mm and just presumed it was fluted, that is a very thick heavy panel and will take a lot to drive.
I really wished I could have found a clear panel that worked for me , they look so cool.
In some of those tectonic videos they show installing 4 DML panels,to cover very large venues, which replace 15 standard pa speakers .
So quite the opposite to what you are a expecting.
Steve.
Christian.
ok so the lower traces are very close to the back wall which is causing a large hump In the response at 300hz to 400hz .
And a rolling off of the frequencies below this hump, which makes sense.
When you are playing the pink noise ,do you listen to the harsh tinny sound that is produced , the closer to the wall the panel gets ?
I described this hollow tinny noise, as I would call it ,in the recording I made ,when I moved the art panel closer to the wall.
Steve
ok so the lower traces are very close to the back wall which is causing a large hump In the response at 300hz to 400hz .
And a rolling off of the frequencies below this hump, which makes sense.
When you are playing the pink noise ,do you listen to the harsh tinny sound that is produced , the closer to the wall the panel gets ?
I described this hollow tinny noise, as I would call it ,in the recording I made ,when I moved the art panel closer to the wall.
Steve
That sounds very encouraging Steve!
Being my first foray into DML, I might have no clue how good they can sound, but using the 8ohm 50-100w exciter they can go loud and sounds great. Have to measure the output of my amp (Aiyima A08). It claims to do 150w into 8ohm, but doubt that is true. At full power with a really strong input signal I start to get distortion, but not sure yet what is from the amp, exciter or panel.
These panels was really to see if I like how I think electronic dance music sounds on DML at all, and to serve as living room speakers together with a sub eventually, even if I decide not to go ahead with the plans for a large system.
Next step will be attempting to make efficient and good sounding composites and get more different exciters to try on them. I think the ones I'm using is a winner for the application since they are cheap, can handle lots of power and sound really good to my ears, but will try different sizes and perhaps make separate panels for treble with smaller exciters.
Being my first foray into DML, I might have no clue how good they can sound, but using the 8ohm 50-100w exciter they can go loud and sounds great. Have to measure the output of my amp (Aiyima A08). It claims to do 150w into 8ohm, but doubt that is true. At full power with a really strong input signal I start to get distortion, but not sure yet what is from the amp, exciter or panel.
These panels was really to see if I like how I think electronic dance music sounds on DML at all, and to serve as living room speakers together with a sub eventually, even if I decide not to go ahead with the plans for a large system.
Next step will be attempting to make efficient and good sounding composites and get more different exciters to try on them. I think the ones I'm using is a winner for the application since they are cheap, can handle lots of power and sound really good to my ears, but will try different sizes and perhaps make separate panels for treble with smaller exciters.