[mightym]

Sedge,

What kind of Polystyrene are you using?  Is it white in color, usually known as expanded polystyrene ( if examined closely, you can see the little beads in the structure ).  Or is it pink/blue extruded polystyrene?

How are you attaching the exciters?

As soon as I receive my exciters I plan to experiment with the Extruded Polystyrene, as well as Corrugated.

The thicknesses I have available are 1/2" and larger in 1/2' increments, I planned to start with the 1/2" stuff.

John

[Tinnitus]

Im glad someone thought it was funny

There's clearly extreme sports applications for NXT technology which we haven't yet considered!.
Good luck with your shellacing.
I'm guessing that you feel 25mm thickness is a good bet for thickness after trying the  1/4 inch, 1 inch and 2 inch?

What kind of Polystyrene are you using?

I'm curious re' this too.

[sedge]

Sorry I was dragged away to Ely for the weekend [good concert at the cathedral though,loved the acoustics]  and visited a bird reserve on  sedge FEN.
 tinnitus and mightym
I was hoping to get high impact polystyrene but all I could get was the low-density stuff used for insulation.
The high impact is very fast sounding and is probably ok as is  ,will have to see if shellacing or coating with paper will improve the low- density stuff.
Playing at very high volume the metal panels do get hot [single exciters only]but the poly panels are cold to the touch ,the volume control is a good 15 db lower.
If anyone knows how to got hold of  high impact polystyrene sheets  please let me know.
The hf above 10k with these panels will still have to be sorted somehow ,I have a few ideas but will have to wait and see if they work?
Zegadr,
I hope you do not mind me asking but In your last post you mentioned another type of panel ,is there any chance you could let us know what it is as I would be happy to give it a go,that is if I can get hold of it.
 It is not easy getting hold  of the material you want ,you would think that in this day and age  it would be .

sedge

[zygadr]

sedge, you have been on the right track all along. The ''other'' material is VH expanded polystyrene.
The VH refers to it's grade/quality and hardness.

It has great potential as a panel material...............extremely light, therefore very LOUD 
However, it is not that rigid compared to say.........Gatorfoam, and some other composites which are a lot heavier due to the rigidity aspect.Normal expanded poly is NOT ''solvent resistant'' so be careful with what you coat it with!

VH expanded poly foam is NOT the same as the expanded poly foam core found in between the faces of FOREX smart

I showed the foam supplier a piece of Forex and he clearly said that he had not come across anything like it in the foam industry.I have not seen anything like it either and I have looked at many varieties of expanded foam.
This is not surprising, because FOREX smart is a specially fabricated product for the signage industry and I believe it's made in Europe somewhere (Switzerland?)

The only panel materials worth considering as an upgrade to Gatorfoam or plain corrugated cardboard is XITEX which Jeffac will be experimenting with in the near future, or IMHO.........FOREX smart in a 5mm thickness.

Both of the above materials are considerably heavier than expanded polystyrene foam, so there will be a big difference in SPL ...........for the worse
However, I believe the performance level will be higher.

The fact still remains that there is one serious issue with DML exciters............ ..................

Their sensitivity/efficiency and power handling is very low ..........this correlates with the facts below:

I will, for the last time, state the  facts as I see them, of what we are dealing with ..................

1. unless you want to strap two small pieces of panel material with exciters to your head/ears as headphones, you will need to use more than one pair of exciters and God knows what panel material!??????

2. two single exciters, for most people, on standard panels, in a resonably sized listening area, is just NOT loud enough unless you listen to elevator music levels or sit 3 feet away from them

3. No problem.....we'll just turn the volume up.................NO!!!!..... ..........the exciter will be getting way too much power than it's designed for and will get hot..............so hot that it can melt expanded polystyrene............. as I have experienced
Hang on!.............. ............we'll cross them over to a subwoofer..that's it!.................if you think this way, you're better off building a hybrid ELS or ribbon loudspeaker..............lots of posts on that crap

4. O.K..............we'll use a bunch of them.......paralelled and series configured for increased power handling/output................MORE PROBLEMS .............I'm not going there again..........we all know this gray area

5. High frequencies, although satisfactory, are FAR from the ''high resolution'' catagory unless complemented with an additional high frequency unit, .................which defeats the purpose in my view (although a rear mounted raw piezo cone seems to work wonders ).

There we have it.............short and sweet and more importantly...........the way it is as I see it after all the testing, researching and experimenting over this large period of time.

I'm sure many of you will secretly admit that every now and again, you want to listen to your choice of music at ''REALISTIC'' levels...........I know you do.
I also know that you'll come back and say that for a small sized room, you have plenty of volume............maybe you have.........but remember that these exciters have strict guidelines to their xmax being stretched and consequently their performance deterioration and life expectancy is dramatically compromised/reduced..............far from a ''reliable'' technology?

Yes, they can be easily replaced(well, not allways) with more cheap one's if they fail, but, ONCE AGAIN, the same rules apply : they are extremely low efficiency, low power,delicate devices(including the more classy expensive ones) that are not suited for loud or heavily dynamic musical passages over an extended period of time. ...........so forget your large scale symphonic works, up front closely miked,but low recording level jazz or heavy metal head banging stuff...........these puny vibrators won't cut the mustard

It's a technology for a range of certain music, not a technology for all sorts of music and without question, musical fidelity is questionable with the exciters/panel materials available to us.............and that is the problem........... and will probably be that way for a very long time.

[mikadosan]

Zygadr,

Have you tried the new 32mm balanced exciters or 25mm SFH exciters? Regarding to your comments on the limitations of the exciters I think that you have not... Am I right with this?

I have been using the both above models for a while and for me there is no turning back to the "Daytons" anymore... There´s a HUGE difference between the standard generation 1 exciter and for example the new 25mm SFH exciters then.

-M

[zobsky]

I will, for the last time, state the  facts as I see them, of what we are dealing with ..................

...
3. No problem.....we'll just turn the volume up.................NO!!!!..... ..........the exciter will be getting way too much power than it's designed for and will get hot..............so hot that it can melt expanded polystyrene............. as I have experienced
Hang on!.............. ............we'll cross them over to a subwoofer..that's it!.................if you think this way, you're better off building a hybrid ELS or ribbon loudspeaker..............lots of posts on that crap

I agree with most of these points. However, regarding point 3...

Nothing wrong with a well executed subwoofer to augument the first octave or so. At least that was my conclusion after playing with a pair of 6' x 2' gator foam panels (before the exciters fell off).
a. Let's face it, not everyone can accommodate giant panels in their rooms.  And then, there is the issue of power handling at higher volumes, as you pointed out.
b. The Fletcher Munson effect, . .where at low levels, the ear requires the bass to be at somewhat higher volume in relation to the rest of the spectrum in order to perceive the sound as balanced. At least in my panel  implementation, the midbass was punchy and easier to integrate with a (horn) sub. Sometimes, I feel that midbass is harder to get right (can't really use a sub for this), and once it sounds right, easier to integrate with a true subwoofer.

Full range is a noble objective, but let's face it. In many cases, augmented wide range (where I consider wide range to cover the midbass and midrange ie. 80 Hz to 4000 Hz or above)  is a more practical idea. I still dabble in both camps, for what it's worth. Multi-way is another beast that I've never been truly satisfied with

[captainjack115]

Hey guys,


I have 28 of those PE exciters, that's 14 pair.

If anyone in the U.S. wants them, I'll let them go for $35.00 plus shipping.

Jack

[sedge]

Zygadr
Just did a quick test on my hi impact styrene panels [12x 16 inch the largest I have ]  they are a t least  12db louder than my metal panels.
so they are not even ticking over when the ones on the metal panel are bouncing all over the place[this is at a very loud volume!!!!].
The fr response very good from aprox 100hz to 12.5k and is about 10db down at 16k and stays about that up to 20k .
This panel did have shellac on the driver side and gave it the extra 2 to 3k hf over the untreated panel.
As you have already found ,if you use  a panel that is too stiff you will loose Lf ,the exciter is too week to move the whole panel as one ,my metal panels seem to put sound out in waves along the panel surface even at very low Lf .
These  panels go all the way down to 20hz but at minus 10 or more db .
If we had a vastly more powerful exciter and a very stiff panel would we not  be back to a piston motion of a cone driver ?,and do we really want our panels moving back and fourth as one at these very low fr? [I am thinking of all the problems this might cause in the mid and hi Fr. let alone the stresses on the panel itself].
By the way ,the thin metal panel is 30x 39 inch in size .and the fr is very good[the best I have seen on any single driver] from 100hz to 20k [can not measure above this that’s as far as my equipment goes ].
The lf rolls off below the 100hz but can be heard and felt, but if I want powerful lf for electronic or rock music then a lf unit is a must .
 Yes ,I am still looking for a more efficient panel, but it must have as good a tone as the metal panel ,this I have not found yet but live in hope!
Zygadr what are your thoughts on stacking panels as they do with ELS panels [quads]
There would be no cancellation effects on the panel itself only in the air as in line arrays .
You could have three panels per side ,one exciter per panel,4ft wide x by 2ft high,a  total of 6x4ft panel or more if wanted.
I only throw  this in as a way of getting around  the low efficiency problem ,has anyone got any ideas on this?are there other benefits of doing this?
More questions than answers I think .
I wanted to say more but have run out of time again.
sedge

[doug s.]

sedge, go back and read pol's suggestion for mounting exciters - three or four closely spaced exciters mounted horizontally across a wertically oriented panel, w/another exciter mounted along the same horizontal line, but away from the close-mounted group, towards an edge.  the line should be ~2/3-1/3 from the bottom-top of the panel.  based on what pol says re: how the exciters react due to spacing, this may give you the bass and treble extension you are looking for.  if it gives decent treble extension, then no reason why one shouldn't use subwoofers crossed over at 100hz or lower - this is something that benefits all speaker systems, imo...

doug s.

[zygadr]

mikadosan, no, I have not used the SFH exciters..........why?...because I have the full driver list and specifications/parameters from ''BILLIONSOUND'', the manufacturer.

From that, there is a definate improvement between the standard exciter and SFH........but not as much to warrant the extra expense.

For a start, the SFH  is only a 3db increase in sensitivity/spl...........but that is dependant on panel material used.
Secondly, it's ''shove factor'' is not that much more as people are led to think due to Parts Express's product information description...........had a good laugh at that one.
It's stated power rating is 5 watts( ) more than a standard exciter..........impressive .........what Billionsound also specify, is that to get that extra 5 watts, the exciter needs ''adequate heat sinking''.............say what??????!!

I also know the differences are not that great because of NXT's back and forth emails in the past where I asked a lot of relevant and probing questions(and they answered honestly I believe).

They stated that there will be an improvement, but without the proper honeycomb panel material, the improvement will be noticeable but not ''life changing''.

If you have discovered otherwise, then good on ya!...........I feel happy for you.

I personally, don't have the inclination to waste my money on these drivers as I know you still need at least 4 or more to get a sensible and respectful power rating/SPL for your panels .............for that matter, we may as well stick to the cheap one's.

sedge, as you have found, the high impact(VH) grade foam is an obvious ''dark horse'' that has been overlooked in my opinion.
Yes, .........people have used foam boards in the past, but the foam cores in these panels is absolute shit. Some, like the Gatorfoam black core is VERY soft and is probably why there is no HF performance

I am at the point now where I believe that due to experimentation with the high impact poly, that EXTREME LIGHT WEIGHT has more significance than : ''rigidity'', ''internal dampening'', ''mother of tone'' etc., etc.

There is no way out of using multiple exciters..............this HAS to be done..........no buts about it.
Also, the exciters MUST be held/fixed tightly to a brace at the back of the frame that holds the panel. Otherwise, the low weight of the poly will be negated.

Of equal importance is that the polystyrene needs to be attached or held to a frame with rubberised silicone compound in at least 6 places around the perimeter of the panel/frame.This is critical to avoid resonances due to the panel's low weight/mass.

As you can see, I'm suggesting that the panel will sit ON TOP of the frame.........not inside it. The opening in the frame work will be slightly smaller than the panel dimensions.

I have tried a rear mounted piezo raw cone, paralelled with one of the exciters and the high frequency problem is non existant.
the piezo does NOT have an opening through the panel..........it's simply mounted at the rear but off to one side compared to the exciters.

This is all experimental at the moment, but looks very promising. The Forex is still under consideration, but due to it's far grater weight/mass and high expense, it will be a last resort at this stage.

Also under consideration is coating the poly with light weight KRAFT PAPER or something along those lines?.........just a thought.

So, ..with VH POLYSTYRENE...........we have VERY HIGH OUTPUT(about bloody time! ), VERY LOW MASS (great!), VERY LOW COST(you bet!), AND GOOD SOUND(even with multiple exciters............fingers crossed )

[sedge]

Zygadr the high impact polystyrene that  I have is like the stuff you get you washing machine delivered in,the surface is smooth and hard-ish,Is yours the same or are we talking of something different ?
What size panels are you using ?where did you get them? Did you look at the weather report before picking them up?
I used sticky paper to cover one of the soft poly panels and ended up with 2x4ft midrange unit !!!
doug s
I have tried this and I feel it is not for me ,although I may try 2 or 4 exciters grouped in the centre of the panel,and as I have said before, my metal panels do not have hf problems .
this panel stay within a 5db band from 100hz to 20k and beyond.
sedge

[zygadr]

sedge, it's impossible to say whether you have the high impact stuff or not.The high impact version is noticeably harder than standard poly..........especially if sqeezed at the edges.It's surface is not really super smooth....sort of slightly rough. The scratch test reveals a very loud transmissive quality and the edges look more dense with smaller/finer ''cells''.

Did I check the weather report?..........no..........these bits fit in to my car .........and gets parked in an enclosed area connected to the house....................no wind

I have noticed that the polystyrene foam used to pack electronic equipment(moulded to shape etc) and various other items is not ''high impact, high quality''..........it's shit, and is not useable. This is the same garbage found in Art supply shops covered in black paper(both sides).

When you say you covered it with sticky paper( ) and ended up with a 2X4 ''midrrange'', are you saying you lost bass AND highs ?................more information please.

My sample panels are about the same size, but more square....sort of.

There is plenty of bass and lots of SPL ..........tonality(and resonance control) is GREATLY DEPENDANTon dampening the perimeter of the sheet!

Remember Podium's ''SOUND BRIDGES'' at the sides of the panel, used to ''TUNE'' the panel to Shelly Katz's liking?............well the same applies here due to an extremely light material............the way I see it

[j gale]

Zygadr, What's the thickness of this stuff? I see ads for hi impact polystyrene in several thicknesses. Seems easy to be talking about different products while thinking they are the same.

[zygadr]

j gale, the the thickness I am experimenting with is 10mm thick : VH grade

http://www.foamsales.com.au/products/polystyrene/polystyrenesheets/

[zygadr]

Just had an idea........................I have at home some adhesive aluminium tape - 2 inches wide.

Wonder what would happen if I lay a strip of the aluminium down vertically along the height of the rear of the poly, then stick the exciters to this strip???

[sedge]

Zygadr
Warning
If you have not found out already, if you try to remove anything stuck to polystyrene it will pull off the little beads on the surface .
I was lucky with the midrange  panel as all the sticky paper  fell off over night .
When I tried to peel off my exciter from my hi impact styrene it stripped the shellac and some of the beads came off and left little holes on the surface ,so swapping exciters around is a problem .
The 12x16ins hi impact panel is 2cm deep and gave a far better fr response[100hz to 12k or so and pretty flat !!! ] than the 6x2ft  Ld which is one inch thick and can only manage to 8k or so [with sticky paper only 4k,the response looked like the dome shape of a mid cone unit]
As an experiment I stuck another exciter on my metal panel ,if you move the mic up and down or side to side in front of the panel you can clearly see a large suck-out wave running up and down the frequency bands ,this does not happen with a single exciter!
I will have to see if having them as close together as possible is any better?
sedge

[zygadr]

sedge, yes, I know what you mean. Once youve stuck something on the poly, it's got to stay there

Interstingly,I tried the aluminium tape last night................no improvement in sound..........then,............ it became worse!......why?...........because the foil did not want to stick to the poly..........kept falling away from it(nothing wrong with the tape.......just doesn't like the poly surface ).

You will find that 2 cm thick is TOO THICK..............10mm is the maximum thickness before H.F. is affected.

On single versus multiple exciters, raw poly seems to behave differently in my case. I found that close together was not as good as far apart as possible........SPL wise that is........measurement wise may be a different story.
I know that with the first 6 exciter Gatorfoam panels, as you moved your ear down the panel, you could easily hear the separate loudness increase opposite the individually spaced exciters.
Maybe that is what you are measuring?

In practice though...........the whole panel becomes one cohesive source from a short distance onwards.

[sedge]

Zygadr
With 2 exciters close together on the panel there is a 5 dB or so increase in volume [I was switching one exciter on and off to see if I could hear and see any difference on the analyser] I had a quick listen to some music from my 3m seating position and could not hear any bad affects [so far anyway]
Moving the mic up and down close to the panel once again showed a [ suck-out ] wave which moves up and down the frequency band but this time only in the region between about 10kto 20k.
When I moved the mic away from the panel the fr response settled down to normal again [moving the mic around the room did not show up any bad responses] which seems to correspond with your listening tests.
On axis from 1inch to 10 ft the response seemed identical to a single exciter.

Looking again at the efficiency of the styrene panel it is more like 18db more efficient than the metal panel ! and this is from a 12x16 inch hi impact styrene panel with an fr from 100hz to 12.5k[rolling off above this, not falling like a brick]
The exciter is  literally just [ticking over] and is not being strained at all ,but is putting out vast amounts of sound [we are talking about pain thresh-hold here ],which makes me have to ask the question,do you still really need more exciters on your panels  ??

I have looked on the net but have not yet found a supplier of hi impact sheet styrene,lower grades are not good for full range drivers but these are the only types readily available  .
If anyone knows of a supplier in the uk, please could they let me  know ?
 You would think it would be easy
sedge

[jonners]

I have looked on the net but have not yet found a supplier of hi impact sheet styrene,lower grades are not good for full range drivers but these are the only types readily available  .
If anyone knows of a supplier in the uk, please could they let me  know ?
 You would think it would be easy
sedge

sedge -

Is this the stuff you are looking for? Max thickness seems to be 6mm.  http://www.plasticstockist.com/index.cfm?Page=cHJvZHVjdHM=&sector=MTE=&Group=NzA=&SubGroup=NzA0MQ==&jump=31

Also on eBay, but only up to 4mm:  http://cgi.ebay.co.uk/4-0-x-1372-x-660mm-White-High-Impact-Polystyrene-sheet_W0QQitemZ180478891468QQcmdZViewItemQQptZLH_DefaultDomain_3?hash=item2a056155cc#ht_500wt_754

[sedge]

jonners
thanks for the info but it looks like high impact polystyrene could be all sorts of products such as a clear sheet  or something with a gloss coating ?