[CLS]

Thanks for the insight. I understand better now.

This is what I thought, if I took 2 identical PS foam boards, one bare, the other is coated with paper, now which is more rigid?

I guess the one with paper should be better, no? If being bent, the paper on surface can provide stronger tension resistance, thus harder to bend. That translates to an overall stiffer character. No?

I thought, this is also like other types of sandwich boards -- the core provides resistance to pressure while the surface for tension. If the core was previously used alone, then adding paper on the surface could do good thing. Is that correct?

[zygadr]

If I recall, someone once posted that adding paper to a panel of some type as a form of laminate caused the H.F. to dissappear.

Once again, glue some paper on the foam and do the ''scratch test'' . Use another identical piece of plain foam as a neutral reference........... and see what happens.

[CLS]

Fair enough, will do the test.

OTOH, I'd like to add some observations about scratch test. As I try scratching here and there and give them a listen, their sounds are largely different. Among them, I found the characters of the surface alone can play an very important role.

I think the major factors could be the roughness and friction. These two contribute to the intensity and quality of the vibration generated between our fingers and those surfaces.

PS foam is rough and porous, it reacts the most to our scratching, thus the loudest in general. However, what if there's a kind of material which is as light and stiff as PS foam but with much smoother surface?

I found a fact that I can't predict the sound characters by scratch tests. Maybe OK for sensitivity, but not how it sounds. For exmaple, there's very little sound by scratching on glass, no HF to speak of, but the glass can deliver very bright and extended HF (that kind of HF can be obtained by a knife, I guess). Scratching the wooden ribs on my foam panel is also very quiet, again, not much HF to my ears. But excited by the transducers, it spits huge and broad peak in 10k~20kHz !

Oh well... 

[zygadr]

I found the scratch test to be helpful in both the sensitivity of the material and it's affect on High Frequency transmission.
However, the slightly rough surface does influence this test to a large degree. It's only a quick and dirty test.........that's all. There are no doubt many smoother light materials that may sound better in all areas....who knows?

The character of the sound does relate to the material used..........don't be fooled in to thinking otherwise The scratch test will not reveal the panel material's sound quality. I agree with this.

EPS sounds like poy foam, cardboard has a sound like hitting a cardboard box, some woods have a ''plank of wood'' like sound, Gatorfoam has a sound of it's own too, a sheet of glass sounds different again............and so on.

I think that the ability of the material to transmit higher frequencies efficiently depends on what lies within it's structure.
Something that is soft will not do the job............this is obvious(I have 68 exciters stuck to my pillow and can't hear a damn thing!!! )

Whatever the front and rear surfaces are, it all relies on what interconnects them.............that's why the honeycomb structure works so well. It has a high number of vertical and horizontal interconnecting bridges that transmit the exciter's vibration from the back to the front and carry the distributed modes accross the panel's entire surface with ease.
I regards to other materials that have a cell or cellular structure,(EPS, wood) these also act as bridges, but at a smaller or even microscopic level.

I have high hopes for Ultra Board which is as close as we can get to the Nomex brand used by Podium.
It's honeycomb interior is not coated in phenolic resin, but it may not have to be. We shall see?

[CLS]

Yes, the paper honeycomb board is very promising indeed.

I saw some of them before, very much lighter and more rigid than ordinary CC. But those were very thick and small in area. I'm still searching for thin ones with large area locally ...

Meantime, I've ordered some foamcore of 3mm thick. According to the seller, the core is identical to the 5mm bare board I used. Could be fun to experiment with...

[zygadr]

Let us know how you go with the 3mm foamcore.

[panomaniac]

Wow.  How long did it take you to figure that out? Or was it very obvious?

[CLS]

By the support of the feet, it stays in place without much stress on the VC (& this mounting ring). Under mid-low SPL, the loose part is still pressed on the panel without problem.

When the SPL gets higher (and usually coming with sustained high level LF), the excursion also gets larger, then the VC and mounting ring starts jumping, leaves thier related positions, so the noises begin.

I usually listen quietly, so this problem stayed unoticed for a few days. For the first time I found the cracking noise the other day was in a CD of chorous and pipe organ. And then I found sustained LF brought up the problem the most obviously. Interestingly, drums are pretty much OK.

It gets worse day by day. Finally I couldn't stand and pulled it off for checking.

[zygadr]

Sure I will 

---------

In the last few days, one of my little frogy gets noisy at higher SPL. I finally pulled it off last night and found it's because the mounting ring was off.













Did anyone encounter this? Is superglue good for this?

Superglue will be fine to fix this.

[mkstat]

Power rating : 50WMAX
Impedance : 8 Ohm
Frequency range : depending on the installation
Resonance frequency : 500Hz
Minimum mounting surface : Ø 80mm
Dimensions : Ø 90mm x 55mm
Weight : 0.95kg

regards
m

[zygadr]

mkstat................hmmmmm?.................haven't seen this one before.......good find!

[zygadr]

CLS, with the Monacor exciter you may be able to dispense with the bass shaker and small exciter all together....??????..........just place the Monacor where the bass shaker is now and you're in business!

[zygadr]

Bass shakers are designed to do just that...............shake bass and you with it. It is NOT designed to produce audio frequencies even though they still eminate from the unit some what.

We can not forget that this thread deals with ''AUDIO'' excitersnot bass shakers or anything resembling them (Clark Synthesis).

''NXT'' is where it all started and there are many working speakers out there that sound fantastic for a small amount of money and simple implementation of materials.

It seems to me that as we start to complicate the panel with sticks and braces (myself included), we encounter additional problems and resonances or lack of bandwidth????

[pol_bct]

....
It seems to me that as we start to complicate the panel with sticks and braces (myself included), we encounter additional problems and resonances or lack of bandwidth????

I have the feeling that by doing this we are farther from DML
and return close to pistonic

POL

[zygadr]

I have the feeling that by doing this we are farther from DML
and return close to pistonic

POL

Correct! 

[vaugi]

This looks good-
http://www.ultraboard.co.uk/
Quick quote is for two panels 2000mm x 600mm with-
6mm @ £12
10mm @ £15
18mm @ £18

Seems good, would the 6mm be too thin/bendy?

Do they need to be 'grounded', for example, the back of the magnet attached to a rigid support or just move in free air? Some people have a support, some dont. Will there be any cancellation going on if its just in free air?

I think i will just get a pair of the Visatons for the moment!

Interesting find inrank.  I have some cheapo parts express exciters in the UK, if you want to buy any PM me. I'd also be interested how this goes with the above panels, I've not got round to doing much yet, been trying to find a reasonable price for denser EPS, ends up expensive with delivery.

Vaugi

[zygadr]

Two email messages and two phone calls later, I still have had no satisfaction in obtaining the sample of Ultraboard I requested from the Australian supplier.

My phone call to the company last Friday was one of polite criticism that a potential customer should not be ignored due to the fact that he or she has only requested a sample and not a whole container's worth of board!

I was once again pomised that the information would be passed on. If I get no satisfaction by close of business tomorrow(Monday), I will be contacting them persistantly on a daily basis.
I will also use my place of work as reinforcement as we deal with posters and advertising boards during semester enrolment periods throughout the year.

I am hoping that I can convince them that they are potentially losing a customer due to their snobishness and lack of interest.

If I need to speak to the U.K. ''grand poobah'' and complain, then so be it!!

[el`Ol]

Mabe it's easier to get one from a printing service (could be hung on the wall after testing).

[zygadr]

Sample of ULTRA BOARD has landed in West Australia.

Should be in my posession soon!

[zygadr]

It has arrived this morning at my place of work. 

The piece is only a typical sample : 6 inches X 8 inches and 10mm thick.

Some pics:






As you can see, the internal honeycomb structure is quite evident and makes the whole panel INCREDIBLY strong yet lightweight.

Will test with similar sized corrugated cardboard and EPS to see how it performs.............standby!