DML arrays are called "Multi Actuator Panels" which helps google the research papers.
At one time Tech Ingredients had a DML panel calculator on their web site. You could change the dimensions and see the frequency range. Length in one dimension was all that was necessary to lower frequency. Long and thin was fine if you didn't want a wide panel.
The only reason I went with tall and narrow was to copy Don Keele's ground plane CBT array. Or ceiling plane CBT if you hang them. The advantage turned out to be a good vertical sound field. I dont know if they perform any better than a good DML because I've never built a good DML to compare. It may be overkill.
One advantage of DML low frequency subs might be that you can more easily position them like Earl Geddes recommends. You could hang one in the middle of your wall or on your ceiling unlike a traditional subwoofer enclosure.
At one time Tech Ingredients had a DML panel calculator on their web site. You could change the dimensions and see the frequency range. Length in one dimension was all that was necessary to lower frequency. Long and thin was fine if you didn't want a wide panel.
The only reason I went with tall and narrow was to copy Don Keele's ground plane CBT array. Or ceiling plane CBT if you hang them. The advantage turned out to be a good vertical sound field. I dont know if they perform any better than a good DML because I've never built a good DML to compare. It may be overkill.
One advantage of DML low frequency subs might be that you can more easily position them like Earl Geddes recommends. You could hang one in the middle of your wall or on your ceiling unlike a traditional subwoofer enclosure.
Lf panel
Hi burntcoil.
I think I already have some of the answers you are looking for.
Last night I quickly knocked up a 1.5m by about 40 cm 5mm thick,I did notice some interesting things while playing about with them,but as for the low frequency rumblings they seemed quite normal to me.
If you look at my gallery on audiocircle and click on the round cardboard panels pic you will see a selection of panel measurements ,the 40cm vh grade eps and the large 5ftx2ft eps all have the same rumblings even when you move the mic further away into the room notice how the 100hz to 200hz region drops away leaving the lf below 100hz still rumbling,this is pretty much on all my panels even my rigidly mounted panels on the dml for pro use forum although you are using them slightly differently to enhance the effect.
I can dig out the 40cm panel and post some new pics here if it helps ,just let me know.
Bang goes my royalties from that patent
thanks a bunch!!
Think I'll pm you to discuss this further and see what you think.
Steve
Hi burntcoil.
I think I already have some of the answers you are looking for.
Last night I quickly knocked up a 1.5m by about 40 cm 5mm thick,I did notice some interesting things while playing about with them,but as for the low frequency rumblings they seemed quite normal to me.
If you look at my gallery on audiocircle and click on the round cardboard panels pic you will see a selection of panel measurements ,the 40cm vh grade eps and the large 5ftx2ft eps all have the same rumblings even when you move the mic further away into the room notice how the 100hz to 200hz region drops away leaving the lf below 100hz still rumbling,this is pretty much on all my panels even my rigidly mounted panels on the dml for pro use forum although you are using them slightly differently to enhance the effect.
I can dig out the 40cm panel and post some new pics here if it helps ,just let me know.
Bang goes my royalties from that patent
thanks a bunch!!Think I'll pm you to discuss this further and see what you think.
Steve
@Spedge, sorry about those royalties, you just gonna have to cancel that yacht : ) Great information thank you and yes I would like to see/hear about the other panel. PM me whenever you want!
@bradleypnw yes that’s a great build, Geddes work is very pertinent here thank you for reminding me of it.
@bradleypnw yes that’s a great build, Geddes work is very pertinent here thank you for reminding me of it.
Resonance
Hi burntcoil
So basically I think you are tapping into a major panel resonance in that exciter area but it is not just the panel that is resonating.
You have the exciter freely mounted on the panel and as shown in my pics of my panel responses on audio circle ,they go very low with a trademark m shape usually below 100hz .
Now I believe this is where the exciter transitions from a panel exciter to a panel shaker, exactly the same as a bass shaker ,to me this has been pretty obvious for some years but has not to my knowledge been disused except in a should we clamp the exciter on a spine or leave it to support itself argument.
I should say if you do clamp the exciter usually the response drops off heavily after about 40hz or so,you would need a very powerful exciter or a smaller panel to drive it into piston mode.
Using the exciter as a bass shaker is to me like reflex loading a speaker ,I have no problem with it,I just didn't have any use for it at the moment.
Better leave it there for the moment,and see what you think.
Steve
Hi burntcoil
So basically I think you are tapping into a major panel resonance in that exciter area but it is not just the panel that is resonating.
You have the exciter freely mounted on the panel and as shown in my pics of my panel responses on audio circle ,they go very low with a trademark m shape usually below 100hz .
Now I believe this is where the exciter transitions from a panel exciter to a panel shaker, exactly the same as a bass shaker ,to me this has been pretty obvious for some years but has not to my knowledge been disused except in a should we clamp the exciter on a spine or leave it to support itself argument.
I should say if you do clamp the exciter usually the response drops off heavily after about 40hz or so,you would need a very powerful exciter or a smaller panel to drive it into piston mode.
Using the exciter as a bass shaker is to me like reflex loading a speaker ,I have no problem with it,I just didn't have any use for it at the moment.
Better leave it there for the moment,and see what you think.
Steve
Tall panels
I tried to upload pics of my measurements of the tall panel to this post but failed , I'm used to using audiocircle .
Anyway not only does it measure slightly better but to me sounds better too.
When the exciter is at the bottom I noticed that at the top in the last 6inches or so the LF practically disappeared which didn't happen when turned over,there was full LF top and bottom.
The 5mms panel I was using was very inefficient ,I had to turn the volume up about 8db to match my rigid framed 3mm ply panels
As an after thought I should have taken measurements with the exciter in my usual 4/9 and 3/7 position to make a comparison,but as I couldn't post the pics anyway it's no big deal.
But before I put them away I will measure this.
Steve
I tried to upload pics of my measurements of the tall panel to this post but failed , I'm used to using audiocircle .
Anyway not only does it measure slightly better but to me sounds better too.
When the exciter is at the bottom I noticed that at the top in the last 6inches or so the LF practically disappeared which didn't happen when turned over,there was full LF top and bottom.
The 5mms panel I was using was very inefficient ,I had to turn the volume up about 8db to match my rigid framed 3mm ply panels
As an after thought I should have taken measurements with the exciter in my usual 4/9 and 3/7 position to make a comparison,but as I couldn't post the pics anyway it's no big deal.
But before I put them away I will measure this.
Steve
A very substantial spine would be needed and a way of aligning the coil ,plus finding a material that didn't warp with time and with temperature,large panels would be a problem,with small panels you would end up with something like a large bmr .
For me this was just too much work,and the frequency response I was getting from my test panel wasn't good plus I realised just how awkward moving around a large magnet was!!
I thought in the end it would be easier to just buy a bmr .
Steve
For me this was just too much work,and the frequency response I was getting from my test panel wasn't good plus I realised just how awkward moving around a large magnet was!!
I thought in the end it would be easier to just buy a bmr .
Steve
I've thought about this for a few years as well and the only references I can find for extending base, that make sense to me, is simply increasing the panel dimensions to increase the modal densities for lower freq's. In fact that appears to be why lower freq's (in a dml, not from pistonic motion) have reduced smoothness and SPL's in the lower end. Now most of what I've read seem to indicate that shape itself was not so important for bass, but rather total panel area (as in it didn't seem to matter if you were using a square shape or long rectangular shape as long as the total area was the same.) Now as a side effect of using larger total area for a panel, you are not just increasing the modal density for bass, but increasing it for ALL frequencies across the spectrum. And we know that increasing the modal density smooths out the peak and valleys, especially in the high end and overall increases the SPL's (though I suspect there's a limit to this as you only have so much driving force in an exciter, so you will reach a point of diminishing returns on panel size in terms of exciter used and overall SPL's. And of course what size panel per exciter wattage might achieve that max SPL before diminishing returns sets in is unknown).
So the latest design I've been thinking about is thus (and keep in mind my designs are about max frugality with respect to sound quality, i.e., those of us poor HAVE to be cheap in this game
)At any rate, I'm looking to build a free standing system that would be 2.1 system. The panel material I'll leave a mystery for now, but it comes in 4' x 8' sheets at any local hardware store ;-). Why is that demensions important? Because then I only have to make 2 cuts on the sheet to create the 2.1 scenario. I would make a cut down the middle, vertically, of the sheet to create 2 sheets of 2' x 8' and then take one of those and again cut it down the middle vertically to create 2 sheets of 1' x 8'. Those would be used for "full range panels" hoping to acheive responce down to 40-50 hz and then use the larger 2 x 8' sheet as the center "sub" panel to cover the last octave or so.
So why use this shape? Well 2 reasons 1. its cheap and easy to cut from a standard size, easily available product sheet. 2. I think the 1' wide panels will have much better WAF
Now there is a 3rd reason...the mystical/magical reason...the 1' x 8' panels are the equivalent of having 5 - 1' x 1.618' panels stacked on top of each other...i.e., the golden ratio...now I don't take much stock in all the golden ration crap but hey you never know and its there in the panel design for the taking lol.So on the 1' panels I would use a series/parallel arrangement of exciters down the middle and off-set. The sub panel would use several bass shakers to max out the potential low bass.
And of course, because it will be free standing it will be framed and splined in some way...
I look forward to see what your able to achieve with long panels...
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Aaaaa
Aaaaaa!
I presume that a picture will be separate from this post at the bottom .?
Just testing
It should be a picture of the response from the exciter area at the bottom of the tall panel at about 6 or seven inches moving the mic up and down the lower half .
Steve
Aaaaaa!
I presume that a picture will be separate from this post at the bottom .?
Just testing
It should be a picture of the response from the exciter area at the bottom of the tall panel at about 6 or seven inches moving the mic up and down the lower half .
Steve
Attachments
Pics tall panel
Ok good,the first pic on the left is the same as before but the top half only,the half without the exciter on,I haven't shown it but after The last let say about 6inches The LF below 100hz disappeared off The screen!!
The second pic in the middle is the panel turned over so the exciter is at the top,the mic as before up and down the bottom half.notice the increase response
Now the last pic on the right,same as before ,a nice looking response and the response below 100hz held up all the way to the top edge of the panel !!
I hope this isn't as confusing to you as it is to me,I'm used to putting my notes with the pics,hope I've got it right
Steve
Ok good,the first pic on the left is the same as before but the top half only,the half without the exciter on,I haven't shown it but after The last let say about 6inches The LF below 100hz disappeared off The screen!!
The second pic in the middle is the panel turned over so the exciter is at the top,the mic as before up and down the bottom half.notice the increase response
Now the last pic on the right,same as before ,a nice looking response and the response below 100hz held up all the way to the top edge of the panel !!
I hope this isn't as confusing to you as it is to me,I'm used to putting my notes with the pics,hope I've got it right
Steve
Attachments
Tall panel
I also tried my usual 4/9x3/7 positioning on the tall panel ,this made them sound rather anaemic ,a sub would have to be used or eq.
I have to remind everyone that this was a 5mmm panel with a 10watt exciter held on with double sided tape,I am in the other room posting this and wouldn't be surprised if the exciter has fallen off!
Not bad considering.
Steve
I also tried my usual 4/9x3/7 positioning on the tall panel ,this made them sound rather anaemic ,a sub would have to be used or eq.
I have to remind everyone that this was a 5mmm panel with a 10watt exciter held on with double sided tape,I am in the other room posting this and wouldn't be surprised if the exciter has fallen off!
Not bad considering.
Steve
@geosand
That is a very solid plan and I look forward to hearing about how it turns out. I am going to continue with my obsession with long panels for the time being as I am puzzled by the big difference I experienced between the tall panels and the same material used in a golden section ratio. It may be something to do with the panel geometry, e.g. the increased flexibility you get with the long ratio, it might just be there were material differences I was not aware of, but until I get to the bottom of it it is going to bug me.
I agree for a floor stander a frame is essential. Spines I only use if trying to get bass from a panel, in my experience to date anything from 100 hz and up doesn’t need one and if you are using multiple exciters, e.g. 4, I am agnostic about them above 50hz and don’t like fighting the additional problems they bring.
Good luck with the build
Burnt
That is a very solid plan and I look forward to hearing about how it turns out. I am going to continue with my obsession with long panels for the time being as I am puzzled by the big difference I experienced between the tall panels and the same material used in a golden section ratio. It may be something to do with the panel geometry, e.g. the increased flexibility you get with the long ratio, it might just be there were material differences I was not aware of, but until I get to the bottom of it it is going to bug me.
I agree for a floor stander a frame is essential. Spines I only use if trying to get bass from a panel, in my experience to date anything from 100 hz and up doesn’t need one and if you are using multiple exciters, e.g. 4, I am agnostic about them above 50hz and don’t like fighting the additional problems they bring.
Good luck with the build
Burnt
I agree with gro sand that fr response on the right is excellent. Considering the panel size and the exciter you are using that’s a remarkably even response.
I am sure I have not understood you but in your first image did you sweep the frequency? If it’s not too much bother a low frequency sweep on your big panel from say 30 to 100 would be very interesting.
Burnt
Phew, just finished reading this thread and the audio circle one, really nice info, in both. I want to thank everyone for putting in the effort to chart this somewhat unknown technology.
I am happy to say I made my first xps(1000mmX500mmX8mm) dampened with 34/66 PVA glue:water solution dml panels driven by DAEX32EP-4, 1/panel placed in the Monacor 1 position. They sound ridiculously good. They are currently freestanding with no frame or spline to hold the exciter. However I will try framed dmls in the near future, make tests on my own and share the results.
One candidate panel material that I didn't see mentioned is wood fibre panels, like this one:
https://www.steico.com/en/products/wood-fibre-insulation/steicounderfloor/overview/
Well, I tried them, they suck bad), but can't help but wonder if they would be a good choice after some treatment, like applying a coat or two of lacquer/epoxy/[insert rigidising solution here]. If anyone tried this please let me know so that I won't waste my time going towards the same dead and.
I also noticed that in both dml megathreads about dmls I've read(this one and the audio circle one) there is a member(same person in both forums) that does more harm than good to the discussion, he did contribute somewhat to the topic(although he is mostly repeats 3-4 things useful things), info for which I too am grateful, but the bulk of his interactions are constituted by useless drama generating posts. For anyone wanting to completely ignore his posts here is a solution:
1. install the ublock origin addon for your browser
2. open the addon's dashboard
3. click on the My Filters tab
4. paste this in the texbox below
5. click on Apply changes
6. focus on dml diy development
I am happy to say I made my first xps(1000mmX500mmX8mm) dampened with 34/66 PVA glue:water solution dml panels driven by DAEX32EP-4, 1/panel placed in the Monacor 1 position. They sound ridiculously good. They are currently freestanding with no frame or spline to hold the exciter. However I will try framed dmls in the near future, make tests on my own and share the results.
One candidate panel material that I didn't see mentioned is wood fibre panels, like this one:
https://www.steico.com/en/products/wood-fibre-insulation/steicounderfloor/overview/
Well, I tried them, they suck bad
), but can't help but wonder if they would be a good choice after some treatment, like applying a coat or two of lacquer/epoxy/[insert rigidising solution here]. If anyone tried this please let me know so that I won't waste my time going towards the same dead and.I also noticed that in both dml megathreads about dmls I've read(this one and the audio circle one) there is a member(same person in both forums) that does more harm than good to the discussion, he did contribute somewhat to the topic(although he is mostly repeats 3-4 things useful things), info for which I too am grateful, but the bulk of his interactions are constituted by useless drama generating posts. For anyone wanting to completely ignore his posts here is a solution:
1. install the ublock origin addon for your browser
2. open the addon's dashboard
3. click on the My Filters tab
4. paste this in the texbox below
Code:
www.diyaudio.com##tbody:-abp-has(>tr>td>div>a:has-text(DMLBES))6. focus on dml diy development
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Near field
Gazza
The pic on the right just shows the total response output of the top half of the panel ,it is not a fixed point measurement,if you moved a fixed point mic (usually placed in the middle of the exciter position) to the left or right by a few inches the response would change considerably,so where should you place your mic to find the real output?
For me it is around the room and best of all your seating position.
You could have a very good near field response but when you move out into the room it all falls apart! ,Also different panels (eps ,xps,ply, carbon, whatever,size shape,you name it) will have a different in room response ,the worst usually happens below about 300hz or so ,in my experience anyway.
This is why I usually have my LF speaker,not sub, running up to the 300HZ region no matter what panel I am using ,this smooths out the suck outs dips in the room response.
How low I let the panel go is all dependent on size (4inch up to 5ft) and how well it can cope with usually very loud music, including close mic recordings and electronic music,my exciters can get very hot with heavy panels,small panels will tend to vibrate heavily and buzz if used too low.
I must go ,I can hear my wife beckoning (shouting)to me.
Those sweet tones.
Steve
Gazza
The pic on the right just shows the total response output of the top half of the panel ,it is not a fixed point measurement,if you moved a fixed point mic (usually placed in the middle of the exciter position) to the left or right by a few inches the response would change considerably,so where should you place your mic to find the real output?
For me it is around the room and best of all your seating position.
You could have a very good near field response but when you move out into the room it all falls apart! ,Also different panels (eps ,xps,ply, carbon, whatever,size shape,you name it) will have a different in room response ,the worst usually happens below about 300hz or so ,in my experience anyway.
This is why I usually have my LF speaker,not sub, running up to the 300HZ region no matter what panel I am using ,this smooths out the suck outs dips in the room response.
How low I let the panel go is all dependent on size (4inch up to 5ft) and how well it can cope with usually very loud music, including close mic recordings and electronic music,my exciters can get very hot with heavy panels,small panels will tend to vibrate heavily and buzz if used too low.
I must go ,I can hear my wife beckoning (shouting)to me.
Those sweet tones.
Steve