[sedge]

OB_NEWBIE
I've just come from the diy shop and was examining the low grade eps ,some worse than others .
They tend to have black bits in and gaps in the surface ,my main worry with this quality material is the contact with the exciter foot and unknown air gaps under the surface, a healthy amount of waterproof wood glue on the exciter foot and adjacent panel  area would be a good idea ,I think,thick wood glue does not shrink like the pva and would hopefully fill any gaps,good contact with the whole of the panel surface is essential,other than that I can't see why it shouldn't perform well,
 
Smaller panels like my 9x12inch 3mm xps panels don't really need supporting but do need a higher xo to be able the drive larger rooms .
Using different types of frame for mounting will increase the lower end performance and help drive the room allowing a lower xo,but the cost will be a not so open sounding panel but they can sound good.



This is a picture of the 9x12inch ,this is basically a base from a shop bought pizza,in fact all of my small panels were made from different sized and shaped pizza bases ,this was the only way I could get hold of the 3mm material,the only problem was the amount of weight I was putting on I a call them the pizza panels range
You can see some in the background of this picture

Mounting two on a single frame was good also, but does not exist anymore,the idea was to mount them in a large line array,I've still got all the panels,too many in fact
Steve

[OB_Newbie]

By smaller I meant smaller than the 2.5 x 5 ft. My favorite is 4 x 2ft but I got to say the square 2.5 x 2.5 is growing on me - especially after I made a free hanging stand. Took down some of the hot character of the 30 exciter, not to mention the better WAF amd living room factor... not to be discounted in my house  .

Since we are talking smaller, I have had some success with small Al and Cu looking plates. 3" x 4". Of course only for the upper frequencies. I havent had a chance to integrate them with bigger panels yet

YES Odal!!  Love the idea of a smaller panel.  I've been playing with multi panels and one of the issues is that larger multi panels don't position the exciters at listening height unless the panels are shorter which makes the overall size of the panels are small.

I have one speced to have a 24"x13" center panel with 32.5" panels(golden ratio sized) above and below the center panel (a 6 1/2 ft tall panel).  I wanted that center panel to run as full-range as possible but if you are reporting good results with Al I might have to try using a metal panel (though might have to make it smaller than that I have designed.  Though... I found a place in Wausau (near to me) that makes reasonable priced carbon fiber panels that I've been ready to pull the trigger on but have had too many different things to try.

Still waiting to pull the trigger on higher grade EPS... Sedge's framed ply panels may be the next I try so been hesitant.  Though the metal or carbon fiber panels aredifferent from what I've tried in the past and might be different and more interesting to try as you are reporting good results on Al and Cu      btw.. how thick are the metal panels you used? 

Thanks for the info Odal!     

[OB_Newbie]

OB_NEWBIE
I've just come from the diy shop and was examining the low grade eps ,some worse than others .
They tend to have black bits in and gaps in the surface ,my main worry with this quality material is the contact with the exciter foot and unknown air gaps under the surface, a healthy amount of waterproof wood glue on the exciter foot and adjacent panel  area would be a good idea ,I think,thick wood glue does not shrink like the pva and would hopefully fill any gaps,good contact with the whole of the panel surface is essential,other than that I can't see why it shouldn't perform well,
 
Smaller panels like my 9x12inch 3mm xps panels don't really need supporting but do need a higher xo to be able the drive larger rooms .
Using different types of frame for mounting will increase the lower end performance and help drive the room allowing a lower xo,but the cost will be a not so open sounding panel but they can sound good.



This is a picture of the 9x12inch ,this is basically a base from a shop bought pizza,in fact all of my small panels were made from different sized and shaped pizza bases ,this was the only way I could get hold of the 3mm material,the only problem was the amount of weight I was putting on I a call them the pizza panels range
You can see some in the background of this picture

Mounting two on a single frame was good also, but does not exist anymore,the idea was to mount them in a large line array,I've still got all the panels,too many in fact
Steve

Hey pizza man... seriously???  What material WON'T you mount an exciter too?      Pizza panels... good stuff... thin, thick... hand-tossed panels.  Yum.

Yeah, you have a few panels for sure.  I still question the fact that you are, indeed, married.  That is a lot of panels to still be married... a very understanding wife you have there Sedge.   

[sedge]

OB_NEWBIE
I should have pointed out that I do eat the pizza before mounting the exciter,there's a lot less mess that way
A very understanding wife  don't know we're that one came from!
You try sneaking a speaker more than 4inches into the front room ,or a led zeppelin cd ,you'd think world war three had started,I have to make a hasty retreat back to my bomb shelter(music room)

If I remember correctly,multiple panels or line arrays work best if listened to from a distance ,the cancellation affects between and in front of the speakers even out with distance.
This is why I probably prefer single panels with single exciters in the smallish rooms I have.
Steve

[sedge]

I should add that the cancellations that occur on the panel itself,from having two or more exciters on the same panel will not change with distance.
One Exciter will always be fighting the other at various points all over the panel.
Steve

[OB_Newbie]

I bough various router bits and will be routing a round groove between the 2 panels... likely at an smallish angle to vary the response of the panel along with different exciter locations for what I hope is a smoother combined response.  This should isolate those frequencies where cancellations would occur.

As for the array aspects.  In theory, a 2x6 panel with one exciter ought to operate the same as 2 - 2x3 panels assuming that the entire panel surfaces generate output.  Though I have to imagine that a single panel would not have even output over its entire surface?!?!  But there will be cancellation either way on both panels.  Likely more HF cancellation on the 2 panel array but that depends on the listening distance where they would sum.

I EQ the panels anyway so a slight drop in the HF won't be to much of an issue... hit the panels with a touch HF boost and I'm back in bidness. 

[OB_Newbie]

OB_NEWBIE
I should have pointed out that I do eat the pizza before mounting the exciter,there's a lot less mess that way
A very understanding wife  don't know we're that one came from!
You try sneaking a speaker more than 4inches into the front room ,or a led zeppelin cd ,you'd think world war three had started,I have to make a hasty retreat back to my bomb shelter(music room)

If I remember correctly,multiple panels or line arrays work best if listened to from a distance ,the cancellation affects between and in front of the speakers even out with distance.
This is why I probably prefer single panels with single exciters in the smallish rooms I have.
Steve

LOL! 

[sedge]

I bough various router bits and will be routing a round groove between the 2 panels... likely at an smallish angle to vary the response of the panel along with different exciter locations for what I hope is a smoother combined response.  This should isolate those frequencies where cancellations would occur.

As for the array aspects.  In theory, a 2x6 panel with one exciter ought to operate the same as 2 - 2x3 panels assuming that the entire panel surfaces generate output.  Though I have to imagine that a single panel would not have even output over its entire surface?!?!  But there will be cancellation either way on both panels.  Likely more HF cancellation on the 2 panel array but that depends on the listening distance where they would sum.

I EQ the panels anyway so a slight drop in the HF won't be to much of an issue... hit the panels with a touch HF boost and I'm back in bidness. 

Before you start to go routing everywhere,I think there are a few things you should know.
Years back now,I had two 12x12inch eps panels on a 12x24inch frame,with a small gap between the free floating edges between them,at the time I only had one of the panels with an exciter on it.
I then attached a small blob of bluetak about the size of a pea in the middle between the panels.
The output from the panel without an exciter on it was pretty much the same as the panel with the exciter on it two panels for the price of one exciter (I'm sure manufacturers would love this).
I might as well have straddled the two panels with the one exciter(now there's an idea)'
The only way to stop one exciter interfering with another on the same panel is to saw it totally in half .
You might change the modal pattern on the panel by routing because you have altered the rigidity,but you will not stop one side of the panel from exciting the other,it would be as if the routing was not there.

A 6x2ft panel with one exciter on would have one point source ,two 2x3ft panels would have two point source's,a 6x2ft panel with two exciters on would also have two point source's on.
Each exciter area in itself is nothing more than a flat cone speaker ,what happens to the panel after that first primary pulse is a bonus(dml)
As for EQing a mechanical cancellation on the panel ,once it's gone it's gone,you can only EQ what's left,better not to cancel in the first place.
I hope this helps.
Steve

[OB_Newbie]

Before you start to go routing everywhere,I think there are a few things you should know.
Years back now,I had two 12x12inch eps panels on a 12x24inch frame,with a small gap between the free floating edges between them,at the time I only had one of the panels with an exciter on it.
I then attached a small blob of bluetak about the size of a pea in the middle between the panels.
The output from the panel without an exciter on it was pretty much the same as the panel with the exciter on it two panels for the price of one exciter (I'm sure manufacturers would love this).
I might as well have straddled the two panels with the one exciter(now there's an idea)'
The only way to stop one exciter interfering with another on the same panel is to saw it totally in half .
You might change the modal pattern on the panel by routing because you have altered the rigidity,but you will not stop one side of the panel from exciting the other,it would be as if the routing was not there.

A 6x2ft panel with one exciter on would have one point source ,two 2x3ft panels would have two point source's,a 6x2ft panel with two exciters on would also have two point source's on.
Each exciter area in itself is nothing more than a flat cone speaker ,what happens to the panel after that first primary pulse is a bonus(dml)
As for EQing a mechanical cancellation on the panel ,once it's gone it's gone,you can only EQ what's left,better not to cancel in the first place.
I hope this helps.
Steve

Hey Steve,
Thanks for the info.  This will be a good test.  I am starting with a single 24"x64" low grade EPS with a light wood frame using 1/4" x 1-1/4" pine strips oriented with the 1/4" edge facing the front/back.  Panel solidly mounted to the panel. Intention is to have a 2 - 24x32" panels but wanted to capture some hard data along over the length of the build.

Progression:
A. 1 exciter in top panel position - measure.
B. Divide panel with routed groove on backside of panel - measure (assess the impact of the groove, lower panel output).
B. 2 exciters. 1 top panel and 1 lower panel.  Move exciter by hand to see if I can get a complimentary response so the combined response is smoother - measure, measure, measure.
C. Unless it sounds very good, continue to break down the panel and frame. Route grooves along the panel and frame to offer some isolation of the panel and frame... routing round corners or at least 45 degree angles in each panel corner.
D. Thoughts of purchasing a large diameter panel bit to route scallops to the front to help better terminate the panel edges.  Don't think that the delicate detail of a free mounted panel is obtainable with a framed panel but I'm interested to see what this does.
E. Bought a bowl router bit to thin the panel middle leaving a thick panel around the edges.  The low grade EPS I'm currently testing with is thin already so not part of this test but am ready to test for higher density EPS or XPS.

But to your experience with the energy transfer with bluetak, If I don't get proper separation, cutting all the way through the panel gets me back to where I would be if I just built the 2 panel from the start.

My thoughts are that there will be low freq. energy transfered absolutely no doubt but hope that the partial isolation will help add high frequency output.  Podium passively cross select exciters to prevent HF cancellation that would otherwise occur when mounting multiple exciters on a single panel.  Whether a 1/2 x 1/2 rounded groove will help... I hope to some extent...   

My take on learning more about framed panels.

oh, I forgot to post over the holidays as I was listening and retesting a bunch of my old panels.  An advantage (if even slight) of a larger panel.  The DAEX25FHE-4 mounted on a large 2'x4' had better extension than on the smaller 2'x2' panel??  I don't recall the exact frequencies but, roughly, the DAEX25FHE had 3-4kHz better extension on the large panel?!?

[Odal3]

Cool. Looking fwd to hear about your results.

 Btw rightly or wrongly, I have always gone for the principle to gradually thin the panels towards the edge on large panels. Idea is the "energy principle" to make it easier to propagate the wave the further away from the source. Exception is thin at exciter location

[sedge]

OB_NEWBIE
Looks like you've got a lot of fun ahead of you but it's the only way to get to understand how they work.
 About the thinning I do in the middle of the exciter foot area , on my 5mm xps ,the width is only about 3.5cm,you must make sure you leave plenty of meat for the exciter to firmly mount to,otherwise the exciter could tilt down under it's  own weight,plus would start flexing when driving the panel.
The same applies to the 1inch eps panel except the width of the cone area is more like 6.5 with a depth of about 1cm in the very centre,this helps you get closer to the sound the exciter is outputting,a more intimate and detailed sound, I would say.
Odal3
I'm not sure about thinning the panel with eps as it would probably loose some of its rigidity,plus I haven't noticed any problems with the sound moving through eps,quite the opposite in fact.
The 5mm xps I would describe as a lossy panel,heavily direct radiating with a not so high output dml mode,even more so when I sanded the outer 2inches or so,this helps soften the reflections I think.

I too am not keen on putting eps in frames ,but ply seems to benefit from it,there's more life and detail ,they are now more spacious sounding ,I'd go as far as saying these are the best nxt dml bmr panels I have ever heard (except for my poly +sub combo)and I have heard quite a few.
This is still early days yet,and I intend to do a few more mods so things should hopefully get even better.
Steve

[OB_Newbie]

Cool. Looking fwd to hear about your results.

 Btw rightly or wrongly, I have always gone for the principle to gradually thin the panels towards the edge on large panels. Idea is the "energy principle" to make it easier to propagate the wave the further away from the source. Exception is thin at exciter location

Probably sounds like I'm moving in different directions with - scalloping the edges for one approach for better edge termination.  The thinner inner panel area is taken from the Bertagni playbook.  It may have at least 1 advantage.  Using my 1 inch XPS, reducing the inner panel surface to 3/4" while keeping a thicker, more sturdy outer "frame" of XPS would make for a lmore ridged panel than a 3/4" XP alone. 

I was surprised by the 2+ dB loss in high frequency response on the 2'x2' XPS panel when I rounded rhe corners and edges.  The panel was VERY noticably less ridged after rounding.  The outer frame should act akin to and I beam.

I'm not as hot on this now as I want to better understand what the frame is doing a bit more and hear what they sound like. 

[OB_Newbie]

I'm not sure about thinning the panel with eps as it would probably loose some of its rigidity,plus I haven't noticed any problems with the sound moving through eps,quite the opposite in fact.
The 5mm xps I would describe as a lossy panel,heavily direct radiating with a not so high output dml mode,even more so when I sanded the outer 2inches or so,this helps soften the reflections I think.

+1 on the EPS.  The 3/4" low grade I'm testing with is incredibly light and likely UNDERDAMPED.  XPS I've also felt to be a little over damped but you realize this more clearly after using the low grade EPS.  I assume a higher density EPS will move closer to XPS but appears that it will have the upper hand over XPS... lighter and more resilient... more lively.

I too am not keen on putting eps in frames ,but ply seems to benefit from it,there's more life and detail ,they are now more spacious sounding ,I'd go as far as saying these are the best nxt dml bmr panels I have ever heard (except for my poly +sub combo

These framed ply panels have my attention.  Want to try these next if not leap frog the EPS frames.  What size panels have you built Sedge?

[sedge]

Zygadr liked the vh grade eps ,I only had a vh 40x40cm x10mm and 5mm test panel which performed well ,it put out a lot of energy ,lively and bright ,a larger panel would have been more controllable I think.

The 5mm xps has a very low coloration ,it has good self damping for it's thickness ,I have not heard 1inch xps but would be a little worried about it's thickness giving too much damping,the same thing would happen if you increased the eps from 1inch to 2inches let's say,ott I know but you get the idea.

This is a picture of the bog standard 10mmx40cmx40cm vh eps with the exciter in the centre  from my gallery at a distance of 2mtrs




This was the same panel after a few mods,that's as far as I went with this panel as getting more panels would have been expensive



This is how it looked.

I only have 3x2ft ply panels at the moment ,I'm going away for the week so will not get any further for awhile.
If you do decide to make a ply panel with frame,I would use at least 1 1/2x2 1/2 inch timbre,the more sturdy the better ,don't worry about losing db ,you won't,you'll gain db,and it won't rattle and buzz anymore,this is a very robust panel speaker,that's why I thought it would be good for pro work,I haven't decided how to mount the exciter yet as there are a few options,it would be interesting to see how a high powered exciter would perform with this panel.
Steve

[sedge]

When people come to this site ,that are new to dml ,they try and use the information gained from ordinary speakers ,that is not how they work!!! You need to forget about most of what you have learned ,the principal is simple really,but the implementation is very important ,if you want to get it right that is.
The good thing about the ply being solidly mounted in a frame is you don't have to know anything about it you just glue and screw it all together ,mount the exciter ,and it works  that's all I did.
Admittedly I was surprised when it worked so well,but that's the way it happens sometimes.
Steve

[sedge]

Just thought I'd better mention that you must make sure you apply plenty of wood glue to all of the joining surfaces as any gaps between the panel and frame will vibrate! Screwing and clamping is a must,I had thought of adding a strip of wood to the front to help clamp the panel down,but I'd gone too far by then,I'd used about 40 screws by then!
Steve

[mildperil]

I just received my new box from Parts Express yesterday and had a happy evening playing with the contents.

The big surprise was the Dayton Audio DAEX25TP-4, which had the the cleanest, most extended high frequencies of any exciter I have used to date. I bought the tripod version to use on my bike sound system, but there is a legless version here. I did A/B comparisons with the Dayton Ultra, the DAEX25FHE-4, and DAEX30HESF-4 on Re-Board, and it beat them all for high frequency clarity, although lacked the shove to do the bass, and couldn't go as loud (I remember further back in the thread some discussion of the smaller voice coiled exciters being better at high frequencies). I would say that for smaller, lighter panels, augmented by a subwoofer, it is a must try.It also set me thinking that if you were using 2 exciters on a panel, crossing over from a larger exciter to a smaller one to avoid cancelations, DEAX25TP might make a killer combination with the DAEX30HESF-4. I will have to get my MiniDSP out and try it.
Rewinding slightly to Sedge's comment concerning wind and my bike mounted panel, yes, I was worried about that too initially, but in practice the panel's area is not much bigger than a pannier bag. I cycled along the sea front in blustery weather and didn't notice much difference. If there was a force 10 gale, I might think twice about cycling with it, but I would probably bailed out on any cycling plans if I had seen the weather forecast anyway.[/color]It did get me thinking about the problems of using panels outdoors though. Beyond a certain size they are always going to be vulnerable to wind, so I started thinking about wind socks, and perhaps a solution could be to let the panel pivot and move along its leading edge, like a flag on a flag pole. You would want to get it above head height though, or else you might take someone's head off!

[mildperil]

I'm not sure what's going on with the formatting in the last comment. I can't seem to change it.

[sweenz27]

Hey guys, I've been away for a while, but looking for suggestions on a project I'm working on!
My wife is on board with this, so I'm excited!  I'm making a gallery wrapped canvas DML speaker in our bathroom.  I attached 2 Dayton exciters (with the 3 legs cutoff) and stuck on a piece of cardboard a little smaller than the canvas and glued to the back.  It actually sounds pretty darn good considering what it is, and I'm quite surprised with the bass response-not sure if it helps that the cardboard is almost suspended by the cavas, or if there is any detrimental effect. 
Now, the thing is that it sounds better off the wall, I'm guessing because the back wave is interfering.
Anyone have any recommendations to absorb the back wave?  Maybe cover the rear with cardboard sprayed with rubber material (flexseal), or fill with damping foam?  Here are some pics.  Thanks for your help!





Sorry for the orientation, not sure why they uploaded that way

[mildperil]

Hello Sweenz27,

I would try a few layers of foam, perhaps some of this sort of stuff - http://www.ebay.co.uk/itm/Black-Non-Slip-Mat-120x30cm-Roll-Hundreds-of-Uses-Anti-Slip-Grip-Mat-/290848255022?hash=item43b7e82c2e:m:mVFTGYvXND8EWngH8tH0U7Q.

Also, I see no reason why you can't take your cardboard panel a bit closer to the edge of the frame. I would have thought it would extend the low end a little further (unless the flex in the fabric is actually helping with the bass, its always better to try than to guess with DMLs it seems).

Ben