+ @Veleric
Hello Steve,
Still with us ?
I found in my files those measurements : mic @2cm from my plywood panel at the exciter and then 20, 40, 60cm. 60cm is close to the edge. I think I already posted them. I found also in my files a comparison at 18cm for EPS based on your measurements (not easy to transform in a table your pictures!).
Below 1st is 1/12oct smoothing, 2nd is 1/3oct showing a constant increasing attenuation with distance and frequency.
In your mearsurements, in HF I don't understand why after being attenuated, the level increases again.
@BurntCoil and/or @spedge and et. al. I have been scanning through the posts from both of you and am impressed with what you both have come up with. I want to build some DMLs and could use some input. I have read through a lot of this thread and will continue to do so, as well as seen several DML vids including the ones from Tech Ingredients. Love that guy.
Background (for context)
Firstly, though I am not a pro speaker builder, I have DIYed a lot of home and car audio setups over decades, have fabrication skills, and a large shop with tools to work in. This is just an 'I'm not a total noob' disclaimer
I have a large space without much sound treatment and hard walls that I have speakers set up in, two PA speakers and a large sealed sub. The room is 30' x 40' x 12' (9.1m x 12.2m x 3.7m) and does not reverberate nearly as much as one would think.
However the room modes are rampant, so I want to try DMLs. Call it an excuse. SAF and size are not restrictions. A shot of what I have in this space is down below... Two self powered PA speakers (two way with 15" and a horn) and a sealed sonosub (two Dayton UM15-22) powered with a large Class-D amp. It was some work but the speakers are all hung to keep the floor space clear (very important). I have tuned the delays and the EQ for a particular sweet spot in the room but would like to open that up. It sounds pretty good but not AL headphone or studio monitor great.
Questions:
1. I want to build a framed panel setup similar to what BurntCoil did with the tall blonde build. My hope is that starting with this as a successful baseline will answer a lot of the initial questions (like aspect ratio of the panel). Any strong reasons to deviate from this?
2. These panels will be hung so that changes the dynamics a bit. However I would not expect the intertial effects to be dominant compared to a floor standing design. Do you agree? I have seen frameless hanging DMLs work, but do not know the tradeoffs in terms of say SQ.
3. These could potentially be very large panels, at least up to the size of US paneling sizes, like 4'x8' (~1220mm x 1440mm) for example. The wall space where the current PA speakers are hung could accommodate panels as large as 6'x9'. Would you go larger given this opportunity?
4. What would you change due to the context of this use environment? Or does it really not matter much?
Perhaps once could consider this a chance for DML experimentation with my time and money, and to point me in the right direction. Thanks in advance.
Background (for context)
Firstly, though I am not a pro speaker builder, I have DIYed a lot of home and car audio setups over decades, have fabrication skills, and a large shop with tools to work in. This is just an 'I'm not a total noob' disclaimer
I have a large space without much sound treatment and hard walls that I have speakers set up in, two PA speakers and a large sealed sub. The room is 30' x 40' x 12' (9.1m x 12.2m x 3.7m) and does not reverberate nearly as much as one would think.
However the room modes are rampant, so I want to try DMLs. Call it an excuse. SAF and size are not restrictions. A shot of what I have in this space is down below... Two self powered PA speakers (two way with 15" and a horn) and a sealed sonosub (two Dayton UM15-22) powered with a large Class-D amp. It was some work but the speakers are all hung to keep the floor space clear (very important). I have tuned the delays and the EQ for a particular sweet spot in the room but would like to open that up. It sounds pretty good but not AL headphone or studio monitor great.
Questions:
1. I want to build a framed panel setup similar to what BurntCoil did with the tall blonde build. My hope is that starting with this as a successful baseline will answer a lot of the initial questions (like aspect ratio of the panel). Any strong reasons to deviate from this?
2. These panels will be hung so that changes the dynamics a bit. However I would not expect the intertial effects to be dominant compared to a floor standing design. Do you agree? I have seen frameless hanging DMLs work, but do not know the tradeoffs in terms of say SQ.
3. These could potentially be very large panels, at least up to the size of US paneling sizes, like 4'x8' (~1220mm x 1440mm) for example. The wall space where the current PA speakers are hung could accommodate panels as large as 6'x9'. Would you go larger given this opportunity?
4. What would you change due to the context of this use environment? Or does it really not matter much?
Perhaps once could consider this a chance for DML experimentation with my time and money, and to point me in the right direction. Thanks in advance.
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I am also reading a lot of what @Veleric has done as well, particularly in the successful use of RevolutionPly (lauan like) since that is a material I was wondering about. Also your point on the use of frames to prevent warping is a good one. I had not considered that.
Thanks to @homeswinghome for his comparison of materials for panel selection here
and the summary of design selection trends in the overall thread here
Thanks to @homeswinghome for his comparison of materials for panel selection here
and the summary of design selection trends in the overall thread here
@Deude_Mann
That would be quite large panels.
I would use smaller panels with separate subs because I don't think DML offers advantages in the sub regions, but if you really like the sound of DML for sub I would probably use separate bass panels.
DML speakers have much wider useable range than regular speakers, but is still has limitations where you have to start making tradeoffs when it comes to coil and plate size. To handle lots of bass you want a big coil to handle lots of power, but a big coil means more impedance and less treble.
And to handle bass well you need a big plate that has very loose suspension, while for mid and treble you probably want a smaller plate with more firm suspension for tighter sound.
That would be quite large panels.
I would use smaller panels with separate subs because I don't think DML offers advantages in the sub regions, but if you really like the sound of DML for sub I would probably use separate bass panels.
DML speakers have much wider useable range than regular speakers, but is still has limitations where you have to start making tradeoffs when it comes to coil and plate size. To handle lots of bass you want a big coil to handle lots of power, but a big coil means more impedance and less treble.
And to handle bass well you need a big plate that has very loose suspension, while for mid and treble you probably want a smaller plate with more firm suspension for tighter sound.
Back in the early 70s, Bose did a demonstration in a small auditorium at their labs of an experimental system they were working on. On the stage they had a single pair of 901s and were playing a recording of the Morman Tabernacle Choir singing. In the beginning it sounded as though the whole choir was singing. As the demonstration continued it sounded like each member was still singing as they walked off stage one by one until it was just a single person singing. They then opened the curtains, showing that the sound was coming from only the two 901s on the stage. Their future vice president of marketing was giving a demonstration at the military audio club retail outlet. I had just bought a set of 901s and was having a problem setting them up. After business hours, he brought his computer and went out to my house off base and spent at least an hour setting up my system! It was he who told me about the demonstration (he was there). Unfortunately, Bose did not market the unit, as they would have cost $25,000 at the time. No telling what they would cost now!
Thanks. I should have mentioned I am going to keep the subwoofer and can cross it over actively with a 4th order (LR) filter on both sides. That is what I am doing now at 100 Hz.
I was guessing based on what I have read here that a large part (see what I did there) of the sound of the DML is due to their large effective size. Since I have a large space, would a larger panel (in a larger room) not be more desirable? The listening position is up to 40 feet from where the panel would be hung so in that sense it is more like an outdoor setting (minus the walls) and not so much a media room or near field setting.
Alternatively I can read up on this thread as my application might bear some similarities.
https://www.diyaudio.com/community/threads/dml-pa-systems.390363/
https://www.diyaudio.com/community/threads/dml-pa-systems.390363/
Hello @Veleric did you mean the thought about larger panel size making the source less point-like and more distributed? Or reading the PA thread? Or both
I did read through the whole PA thread and I did not see a lot on panel size specific to larger areas. I did see however that in at least one experimenter's experience that at higher SPL they had to pay more attention to how well the edges of the panel were supported compared to lower levels for personal use. One of the experimenters in that thread also raved about how good the DMLs sounded (when crossed with subs) in a couple of PA system deployments when compared back-to-back with a standard PA setup. They also got a lot of compliments from casual and audiophile listeners. So that was encouraging.
I did read through the whole PA thread and I did not see a lot on panel size specific to larger areas. I did see however that in at least one experimenter's experience that at higher SPL they had to pay more attention to how well the edges of the panel were supported compared to lower levels for personal use. One of the experimenters in that thread also raved about how good the DMLs sounded (when crossed with subs) in a couple of PA system deployments when compared back-to-back with a standard PA setup. They also got a lot of compliments from casual and audiophile listeners. So that was encouraging.
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Also I want to mention that there is a difference in sound when using a rigid spine than without a spine. I am not saying that one sounds better then the other as its personal preference but there is a discernible difference.
There is also two types of spine. The rigid one that I use and the flexible one that Veleric uses.
There is also two types of spine. The rigid one that I use and the flexible one that Veleric uses.
I think that larger plates will sound and act a bit more like DML, including a longer decay in the response. So as long as it is large enough to give the required bass response, it is a matter of finding balance between how tight or large you want it to sound. Even a tiny plate has an enormous effective size compared to a tweeter though, and you don't need a big plate to get the benefits of DML. I do want a tight a punchy sound, and try to get them big enough to get smooth response down to desired XO, but not bigger. Even if you are on the other side of the spectrum and want a extra pronounced DML effect, I would say a 1220mm x 1440mm plate is very large. I would split it in four for power density and tightness, but half size could be ok.
I'm currently using two 1,400 x 450mm panels for semi-outdoor live PA. Each panel has 4 x 20W DAEX25Q-4's in a crescent cluster. The panels cross over at 200Hz to a sub, and are plenty loud enough, and when I wire them for stereo, you can get a pristine sound stage even at 20m away (65ft?). For more laid-back indoor performance I use them as-is without cross-overs or subs.
I sometimes use them at home as hi-fi to play background music when entertaining guests. I've been through a few decent hi-fi systems in my past, and none of them would deliver the sound or experience I get from these.
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To be sure I understand it, by spines you are referring to the support for the back of the exciter, and not panel bracing correct? I saw some discussions about trying to tune the panel response with classical guitar style bracing but I don't think that is what you are referring to.
Hello Deude_Mann
You can refer also to the documents I stored in github audioDIY DML. Among the documents an history file collecting different realizations and links to posts of this thread and also the pdf from Burnt about the tall blonde.
Christian
Hello
Yes "spine" is the wording for the bck support. There were some posts about a bracing technique of the panel (membrane) similar to the one in guitar but I think there was only one realization like that and I don't remember the "final" results were published.
Christian
Hello André,
Which material is it?
Have you already shared FR and spectrogram?
+ @Deude_Mann
The panel dimensions are I think generally limited in size by the use in room like a living room. The living room dimensions allowing to reach the targeted bass, it is not a problem.
The "pioneers" of DML threads could relate better than I could the time where increasing the dimension of a panel was a target.
I have in memory the posts of a DML builder writing that he took advantages to move to Madagascar to build very large panels.
It is not clear for me what we could get from very large panels :
- better bass extension? probably no need as the 100/200Hz can be reached with medium size.
- higher mode density so a smoother FR?
- less edge reflections. Is it an advantage?
- there is the risk to increase the time to stop the vibration...
- effect on the efficiency? André, do you have experience on that?
With your large room, if you have the possibility to start by experiment with very large panels and then the possibility to test smaller one, why not.
Christian
The same principles that apply to the SIZE of a diaphragm in conventional cone drivers apply to DML as well.
The main reason for a larger sized panel is low end frequency extension and a little more output in certain frequencies.
In conventional cone drivers bass is produced by moving air and the larger the diaphragm/cone area the more air it moves. DML's produce bass by bending the panel and the larger the diaphragm the easier it is to bend the panel.
To many people are overthinking DML's. I will say it again when it comes to physics of a conventional cone drivers DML's arent much different. This is why NXT/Tectonic built the BMR driver. This is why the physical structure of a DML should be built like a BMR.
Also the BMR concept is nothing new as this is basically similar to Bertagni's design.
The main reason for a larger sized panel is low end frequency extension and a little more output in certain frequencies.
In conventional cone drivers bass is produced by moving air and the larger the diaphragm/cone area the more air it moves. DML's produce bass by bending the panel and the larger the diaphragm the easier it is to bend the panel.
To many people are overthinking DML's. I will say it again when it comes to physics of a conventional cone drivers DML's arent much different. This is why NXT/Tectonic built the BMR driver. This is why the physical structure of a DML should be built like a BMR.
Also the BMR concept is nothing new as this is basically similar to Bertagni's design.
I haven't tried really large panels since I have been focused on power density and use a 100Hz HPF.
But using small to medium size plates I would say that when it comes to bass you don't need a big plate at all to extend to 100Hz. However, the response inte the low and mid is less smooth with very small plates. Also, you have to keep in mind that DML will both work with the waves bending the plate and as a piston element. This means that for a big plate you get bass even when having stiff suspension, and for smaller plates you need looser suspension to get good bass response.
I don't think edge reflections are a problem really, and in any case you have to weight it against the response time. With a very large plate the waves will travel for a longer time, but since the edges both reflect and dampen the waves, smaller plates will have a tighter response.
When it comes to efficiency it doesn't seem to make much different with size either. Again, the difference in the larger plate will be that waves are not dampened as quickly as on a smaller plate, but the amplitude of the initial waves will be the same. I would speculate that with a larger plate the amplitude might diminish slightly less with distance since you will get a broader front of waves, so can be that more of them that reaches your ear.
But indeed for a permanent installation like that I would experiment and decide what sounds best. Can be a bit tricky to test though due to suspension requirements changing depending on plate size.
I spent $$ working out which exciters i shouldn't be using.
My first ones were with DAEX30HESF-4 , they overheated and the membrane diaphram sagged causing a pretty crap sound , i thought Dayton would have stopped making these because i can see on the newer designs they addressed the issue , yet DAEX30's are still being sold
I will be buying either DAEX32EP-4 , or EX32EP2-4 to replace the first ones because they both have a steel spider that prevents sagging of the body versus the axis of the voice coil.
I wish Dayton had the honesty to withdraw the first product , thats $ 160 AUD for four of them i wasted.
I also tried using XPS panel from our "big box store" in Australia (Bunnings) but their XPS foam is about 1/3 of the density of the foam used by the guys you see on American Youtube Channels and its not as good , the sound is doughy .
After testing a few materials my final product is 3 mm thick MDF laminex coated board , the sound is crystal clear , i didnt do any tests but at a guess i think they would cover 100 Hz up to around 12,000 - 15,000 Hz that i can hear.
The frames are 90 x 19 Pine with an LPG heating torch waved over them for effect , with 2 coats of Polyurethane , The 3 mm MDF is attached with double sided VHB tape , and two 40 watt exciters mounted at 2/5th , diagonally almost opposite each other on each panel.
Hopefully you get the optimum setup with your canvas first time ?
Some guys didnt like the exciters that have the plastic stabiliser arms , they cut theirs off stating the arms damped the sound too much.
That is interesting. For example @Andre Bellwood posted above that he uses the DAEX25Q-4 which is an arm design and based on his reports they work well. However he is using four of them on a large panel so perhaps some damping is not an issue; this is assuming the damping is across the response and not localized.
Right now I am leaning towards a lightweight plywood panel 3mm in thickness. I think I will use a simple frame around the perimeter with the panels attached via adhesive backed foam tape since I want the ability to suspend these in a non-vertical position.
Some engineering, because I am one
- As an option it might be interesting to try a 5mm plywood panel since the mass goes up linearly with thickness, but the stiffness goes up to the 3rd power. So for example increasing thickness from 3mm to 5mm would increase mass by ~1.67 but increase stiffness by almost 5 times. So in terms of the importance of the mass to stiffness ratio it is a winning battle. I know this neglects some things like the importance of flexibility for wave propigation and overall mass for the exciter. This could be an interesting theoretical exercise but I think build and test might be the way to go.