[bobloblob]

While you are doing this, have you thought of trying POL's format?  Might be fun to compare while you are doing all this too, especially since it would be easier (not to mention cheaper) to test out on CC.  For test purposes, it could even be done before you treat the CC, just to compare the separate panels with the one large stereo one.

This has been some journey for you, hasn't it?  Sounds like the results have really been worth it for you - and for the others, too.

[zygadr]

While you are doing this, have you thought of trying POL's format?  Might be fun to compare while you are doing all this too, especially since it would be easier (not to mention cheaper) to test out on CC.  For test purposes, it could even be done before you treat the CC, just to compare the separate panels with the one large stereo one.

This has been some journey for you, hasn't it?  Sounds like the results have really been worth it for you - and for the others, too.

I may try POL's idea but not at this stage..........maybe later on some time.

Yes, bob.  it has been a journey and I have mostly intentionally forgotten the not so nice parts and kept up with the fact that these panels are true panel speakers and should be included in the same school as Magnepans, Ribbons and Electrostats..................yes...... ....they ARE that good

[hblester3]

To everyone that has helped with this thread thank you! Just a few days ago I got the cheap exciters and some 1" EPS foam low density all I could get quick. I am using the little DTA-1 from Parts Express and these are great. First made a 2 X 4 ft panel with 4 exciters two channels on one panel at 8 ohms. was impressed enough to make 2 6 x 2 ft panels 6 exciters measured 2.5 ohms wired parallel. They sound good if not pushed too hard. I then took the 2 x 4 panel to my brothers house and pushed them with his 200 watt Onkyo had great sound lots of bass and clear just had to damp the edges. Now Zygadr's post will have looking for some good cardboard and rounding up some shellac and enjoying the foam panels till I can treat the CC can't wait to get them done. A quick question looking for a better amp would the Dayton Audio DTA-100a be a good choice as that would be about the limit of the funds I have now or maybe the Sure 2 x 100 or 4 x 100 boards as I have good power supply.

Thanks Hubert   

[irishpatrick33]

Are we supposed to tape both sides of the panel... or just one?

[pol_bct]

> Are we supposed to tape both sides of the panel... or just one?

I have the feeling, but it's only my feeling ,
that doing only listening side could be a good compromise

POL

[zygadr]

Tape just the front/ listening end. That is all that is required.

Allow enough room so that the edges of the panel material do not touch the wooden frame's opening.
The actual width of the gap does not matter.

[mkstat]

I tried this stuff:

http://www.busch-model.com/katalog/e/artikel/7207-h0.htm

For worldwide distributors - just look here:

http://www.busch-model.com/online/?rubrik=8&sprach_id=en

It's a bit on the heavy side - about 0,9kg/m² but it's cheap and incredibly stiff.
There is just one size available - 90 x 60cm.
I coated these panels a few months ago with quite good results.
Good bass response - HF response up to about 14kHz.

-m

[hblester3]

 Quick question how is the best wat for the cores of cardboard to run lengthwise or with the width with like a 6 x 2 foot panel?

[zygadr]

Looks like great stuff indeed!

I wonder if it can be glued together?

[pol_bct]

> There is just one size available - 90 x 60cm.

nice, but small,
it's a very different experience to listen to a medium size panel
and to listen to a big one, surface of radiation is everything...
http://img218.imageshack.us/img218/7919/p261010alainltc.jpg

POL

[zygadr]

> There is just one size available - 90 x 60cm.

nice, but small,
it's a very different experience to listen to a medium size panel
and to listen to a big one, surface of radiation is everything...
http://img218.imageshack.us/img218/7919/p261010alainltc.jpg

POL

Amen!!!

[mkstat]

This could be an alternative:

http://www.kohlschein.de/de/material/pdf/falconboard.pdf

Standard size:
244cm x 122cm (and larger up to 366cm x 152.4cm)
Mass of a 6mm Board: 1123g/m²

Costs are €22.- for one Board excluding shipping, sold in packs of 15 (€330.-)


http://www.falconboard.com/FindFalconboard/tabid/88/language/en-US/Default.aspx

-m

[bobloblob]

Just checked Falconboard and it also comes in 10 & 15 mm thicknesses.  The 15 is for what is called "Falconboard build" and may be structurally more rigid.  Looks like Nomex, except Falconboard isn't resin impregnated, so the honeycomb core will be softer than the Nomex core and will absorb more energy before producing sound.  Because of the honeycomb structure, there is no way to get shellac or other hardening media into the guts of the panel.  Nonetheless, it sure looks like it may be worth trying.  Wish these finds were easier to source, though Falconboard may not be so difficult to find as VH grade EPS panels are, since it has more common uses.  Standard corrugated cardboard is the easiest of all.

Falconboard looks like a good find.

[Running Martin]

Hello together,
I am new here and I am very impressed by the effort and progress of the members here in optimizing materials for the use in exciter technology. I could find  a supplier for High Grade EPS 30kg/m³ in Germany:

http://sansys.de/warmedammungen/dammplatten/raumgewicht-30-kg.html

This stuff is working good. Nevertheless I want to try some others also.
In another forum end grain balsawood was mentioned. Perhaps I order some 3mm sheets and laminate them with glasfiber and epoxy. Another try could be:

http://shop.strato.de/epages/15452660.sf/de_DE/?ObjectPath=/Shops/15452660/Products/902190_11/SubProducts/902194&ChangeAction=SelectSubProduct

Martin

[zygadr]

I would definitely give the Falconboard a try.
It may sound good........ it may not...........only one way is to try it if you can get a reasonable sized sample?

bobloblob is correct in the fact that the internal composition of the panel needs to be able to transfer the highs as easily as possible. EPS does this very well, and so does C.C. when fully treated.

If you are cutting the cardboard(C.C.), the flutes of corrugations should run VERTICALLY up the board.

Balsa wood is something that ''should work'' but I am concerned about self panel noise coming in to the picture. In other words, the balsa may introduce a sound of it's own unless carefully damped at strategic spots.
Also, it seems to suppress high frequencies a bit too much from my experience.

[mkstat]

Another try could be:

http://shop.strato.de/epages/15452660.sf/de_DE/?ObjectPath=/Shops/15452660/Products/902190_11/SubProducts/902194&ChangeAction=SelectSubProduct

Hi Martin,

i have used exactly this material (from this supplier) in a custom invisible ceiling mount loudspeaker system with very good results. 
Very high efficency but needs some damping. Frequency response up to 18kHz is no problem with the 4.3mm stuff. I've tried similar gfk/aramid honeycomb sandwich materials from other suppliers but this one is the best so far.  I can recomend - btw it's possible to get larger sheets than posted in the webshop on request. 

regards
-m

[Running Martin]

Hi Markus,
thank You for telling us Your experience with this material. Which kind of damping did You use ? With my EPS panels I use the cloth tape recommended by zygadr.

Martin

[mkstat]

Which kind of damping did You use ?

A combination of surface damping in form of a very thin self adhesive PE-foil (actually the glue is the damping element), a 1.5mm double sided soft foam tape around the perimeter and mass loading on the panel. But i'm using comparably small panels in a different loading condition (infinite baffle) - so be carefull when comparing this approach to the large size panels discussed here in this thread. Large panels certainly have different pros and cons.

-m

[CLS]

Hello there,

This is my first post here, and I'm glad it's in this wonderful thread.

First of all I'd like to thank all your contributions. I've learned a lot. Here are my recent experiments about these little excitors and big panels:

My 2nd trial with CC (in front of my previous system):

I flipped the panels over to make the excitors on the front side. It was becuase the HF would be largely attenuated by the too thick and heavy CC. (what about the 1st? It was a single layer smaller CC, single panel for 2 excitors... no picture left)

This is the 3rd trial:

10 stripped excitors (the cheapo):


I took Pol's advice, placing the excitors on 1/3 positions, 2 groups of excitors in horinzontal alignment:


The excitors are supported by 2 thin sticks. It's like a cantilever, or upside down pendulum. Without panel, the 'resonant' frequency of the one with single excitor is about 2Hz, and the one with 4-unit group is well under 1Hz. Should be far enough from any resonances of the panel.

I'm hoping such device can support the weight of excitors without interference with for-aft movement.

Close-up:


The panel is some kind of PS foam, I'm not sure it's extruded or expanded. I'm lost in all those material names you guys mentioned. The material of my panel is usually seen as the base of various posters, or used as wings/bodies of those very light model planes...

It's 182 x 91 cm per panel, 5mm thick, very light and soft and can barely stand up straight by itself. And it's slightly curvy on both ends, not very flat. The support is a minimal build, and the upper portion of the panel is suspended by a thin cotton string. A strip of foam is bent as a loop of 'spring', supporting at the upper 1/3 to maintain the fore-aft position.



The overall looks of the system:


Larger toe-in:


Already long, more later....

[CLS]

I don't know how you guys got satisfied bass from these little excitors. Up to now I've tried 3 panels - single layer small CC, double layer larger CC, 5mm PS foam big one... They all need a lot of EQ (boost) on LF to make it reasonably flat (down to about 40Hz, very little under that.... )

On the 3rd trial I made it 2 groups of excitors - 1 & 4. I wired them all in series and with a cap across the 4-unit group (so this group is bypassed when in mid-high frequencies... ) By some simple RC filter calculation (and of course some more trial and error), I took 47uF, 100uF, 160uF for the experiements.

This is the impedance plot:


As can be seen, because the LF section is bypassed in mid-high, they 'appear' only in the LF (as expected).

But I need more power feeding into the LF section (4-unit group), while high impedance is not a good load for high power with ordinary amps. Hehe... guess what !  I got my 3886-based chip amp configured as high output impedance (20 Ohm). With some current feedback, it delivers more power into the high impedance zone.

It works to some extent, but not enough. I still need some more EQ upstream (digitally, I got a DEQ2496).

Again, per Pol's advice, maybe it needs 1:9 ~ 1:10 to make a proper proportion. Or, also driven by a even higher impendance source.

OTOH, at this stage I'm not sure it's the limitation of the drivers, or the intrinsic character of the panel, or the entire setup (my minimal support system), it can play pretty loud to a level (beautifully), but above a certain point, the sound would be thickened, somewhat compressed and fuzzy... (oh, that's VERY loud indeed, enough to be painful, and bothering the neighbors... )

If the limit is not in the drivers, then it'd be a waste to use more. And the larger group might be a drawback considering its physical size on the panel - too large of the contact patch to make proper excitement... (?)

So, later I tried 2-way actively crossed at 160Hz or so. The brief impression was good, but it still needs some more fine tunings and evaluations.

Now I'm facing the bad old dilemma - to make it as perfect as possible, or stay simple?

....