[exspec]

I have long lurked in this thread and posted a few comments here and there. My friend and I just each purchased 8 of these drivers for our own experimentation. While he is a long way off, I am getting eager to begin on mine. Here are some new brain droppings:

I have four 18" H frame woofers, so I am covered below 150hz easily by those. The plan is to use the panels for Mid-High sections of my speakers.

That said - The Tectonic Panels use a XO to a ribbon Tweeter at approximately 6000hz. I have a BG Neo 3 Tweeter that is dipole, and was hoping to use it in a three way driver with an 8" Full ranger. Since the transducers have arrived, the idea of incorporating the tweeter and the DML "mid panel" has had the hamster running on the wheel a fair bit. Tectonic uses a tall narrow ribbon, whereas I would be utilizing a more rectangular and smaller ribbon. I haven't thought about orientation etc, but was curious as to what your thoughts would be on making a panel very similar to the Tectonic in Orientation, but with a Neo3 in the centre of the panel instead of the Heil tweeter Tectonic uses.

Utilizing a crossover out of the vocal range need not be explained, but the ability to get out at a certain frequency would really open up the possibilities of other panel materials as they need only produce a limited range. The panel at a given size and shape has a fixed resonant frequency, no? Wouldn't it be best to work with/around this and factor it into the design and selection of panel material? I am new to this so forgive me if I am mistaken. My friend has XPS in his basement, about 1/2" or 3/4" and at first I discounted it and moved past it, but rereading some of this makes me think that it could be an ideal panel material - especially if only used in a portion of the frequency range - such as mids.

The materials to use is a tricky one. Ideally the honeycomb sheets would be not so expensive, but we cannot get that lucky. I had thought about various sources. There are honeycomb core cardboards IIRC. I would love to try taking the core and placing veneer over it, but the cardboard would probably collapse once the resin is applied and any force is introduced…. This lead me to wondering whether or not a canvas in a frame would work if one applied some type of resin or something to build up/stiffen the canvas in the centre of the frame, leaving an untreated border around the centre, which would allow the untreated canvas to act as a suspension of sorts.

The Monacor placement was always what I had assumed the defacto placement would be depending on the amount of exciters per panel. Does anyone have any direct comparison between the Monacor placement and the "Four in line" placement pattern found a few pages ago in the thread? If so, what were the pros/cons of these two techniques?

Anyone still treating the edges to handle diffraction etc? If so, any new tips? I haven't seen much mention of it, nor have I spotted it in many recent photos.

Suspension - I am contemplating the use of elastics or o rings on the four corners to hold each panel within a frame. One reason is that I was assuming the tension of the elastic or o ring could be altered to "tune" the panel, somewhat akin to a drum head.

Sorry for all the random thoughts, so many Ideas to try. These get your brain working in overdrive with the possibilities, but the transducers look like they can only be removed and reapplied once or twice before having to decide on one :S

[sedge]

hi all
25mm thick xps is a good all round panel material  as long as you minimise the self noise and the room suckouts you will have in the 100 to 300 or so hz  region  probably caused by the strong rear wave.
this seems to depend on panel size and room size and can either be a shallow  dip from 100 to 300 or so hz or a sharpe dip anywhere in that region say 150 to 200 hz or even multiple dips.       
I think this is why some music sounds odd on some panels which can sound a bit thin  in the lower midrang ,the problem is easy to see with an RTA and a mic .
the near field responce will look good up to a few ft from the  panel and then the room will do its worst the more you move the mic into the room,I can not stress this point enough that the panel could sound good in one room and bad in another if this problem is not sorted.
i would not use anything thicker than 25mm poly
panel sizes from 8ft to 10inch
i have used ps foam (not foam core!)from 3 to 5mm and xps hard and soft from 5mm up and i only use one exciter per panel ,if more output was needed  i would stack them as quad do,but usually the problem is trying to get the Lf unit to go as loud as the panel without stress or strain,my TL s do a good job but the cones now need refoamimg .
exspec you say you have purchased 8 of these drivers.which drivers are they ? .I only ask as the panel material in my opinion would have to match the exciter.also you should get up to 20k without a tweeter.
steve

[zygadr]

sedge, I have wondered about using thicker VH XPS but have not yet tried it.
I too have settled on only one exciter with XPS and find the volume of sound sufficient.......BUT sound is a bit thin.
Do you have any comments on this?

[sedge]

hello zygadr hope you are well.
not sure what you hope will happen to the sound with a thicker heavier vh panel,I think the 25mm poly works as a full range panel because of the combination of lightness and stiffness (and size )if you used a 50mm panel it would be twice as heavy and very rigid for its weight ,the exciters we use would have a lot of trouble driving this,the panel would be over damped and too rigid,better to have a light panel with a bit of flex in it and if your panel is already producing full range its probably in the right area.but it might need a bit of adjusting to get it to sound better.
as for the suckouts in 100 to 300Hz region causing the panels to sound thin in the lower midrange i usually run my tls from 300Hz down and blend the sound with the panels,this i do by ear and then check with the RTA,this gives me LF power I want and fills in the suckouts.
my tls are a few ft behind the panels and are time aligned .the thing is ,am I canceling the rear wave(so that I can hear the panel),enforcing the front wave or both,I have no way of measuring this but to me it sounds as if the panel is producing the sound,which ever it is I am happy as long as it sounds good.
at sometime I should take some RTA photos to show the problem and the cure but I must go to bed as its late and getting hard to see the screen.
steve

[zygadr]

Thanks sedge.
I have 10mm VH XPS at the moment and will try 20mm which will have just the right amount of rigidity increase that I am looking for in a large panel.

As regards the exciter's drive ability, P.E. has some high powered ''thruster'' exciters recently added to their range of products that should be excellent for the task............hopefully?

As mentioned before, I will be using only one exciter per panel. These exciters will not need to be supported at the rear as they do not suffer from ''voice coil droop'' which has been a problem in the past. Placement of the exciters will be in ''position 1'' as per the Monacor system.

[sedge]

I have spent all day doing this and its mixed up all the caption and pictures  :duh:so if you want to sea the correct pic with its caption you will have to go to my gallery as I am going to hang myself :banghead:this shows the dip between 80 and 300HZ.

this pic shows the dip between 80 300HZ at 12FT into room.peak hold

now it has lost other pics ,I give up !

[xit]

hi Zygadr and all


i'm new in this forum this is my first post and i'm very interested in this project
and wanted to get involved in, try some designs ... but i'm not sure i've got it all
i've tried to read all the pages and can summarize a bit what is the "today's ideal config"
of panel/drivers to begin in the right way ... ok, for what i see:


PANELS:

- for a general rule of thumb, panel has to be stiff, thin, light and as free floating as it can be with a minimum suspension points
- core stiffness is important for the transfer of the sound and give more highs
- panel material gives the tonality of the sound, also it's self damping is important for smoothing out SPL response
  synthetic materials have poor self damping in general, they are bright and coloured, natural materials have good self damping

CARDBOARD shellac treated, was the winner, have a natural sound but lacks of a bit of highs ->good but not hi fi
PLYWOOD got highs and natural sound but too heavy, lack of efficency ->not enought spl or exiters need to be more powerful
REBOARD seems make muffled sound, too much self damping (because of the honey comb absorbing energy or weight?)->not hi fi
EPS has a harsh plastic sound -> not hi fi
XPS (coated) has air and micro dynamics -> hi fi ? (warfedale used this kind of matter but not coated, paper sandwiched)
BALSA not yet reported (solid spurce and other instrument wood maybe suitable also)
HONEYCOMB not yet reported exept in reboard, the honeycomb seems to absorb the energy (honeycomb should be treated...?)

amina: aluminium honeycomb, kraft paper sandwich
tectonic: kevlar honeycomb, carbon fiber sandwich, use of little weights on the panel
podium: nomex honeycomb, mylar sandwich with some bridges to the frame to "tune the panel"
göbel DML speakers: wood with special treatment
warfedale DML speakers: XPS sandwich panel (white gatorboard?)



DIMENTIONS:

golden ratio (seems to be tectonic's one also) is 1.134:1
silver ratio (from patent) is 1.37:1
ratio from tech notes is 1.41:1
zygadr ratio is 1.33:1
j gale ratio is 3:1

- experimented good results with 4ftx3ft (zygadr) and with 2ftx6ft (j gale), maybe some other dimentions are ok ?
- the bigger the better: more bending modes=more lows, smoother SPL response (dimentions not less 4ftx3ft for good results)
- ratio seems very important for the amount of modes generated but which one to choose ?
  (some people experimented good results with also 2ftx6ft or other dimentions than the recommended ones, which one to choose?)



EXITERS:

- placed ala Monacor seems to be the best, original 3M and 3M double sided tape is ok for experiments
  but glues like Glfex epoxy glue are better, more highs and energy transmitted
- drivers placement: lengh of the side from the corner intersection lines 4/9, 3/7 (preferable) and 5/13
- 4 per panel is ok to give good music volume but one big would be better in sound
- reducing slightly the driving point seems to give more highs
- in commercial solutions certain models seems to have a power limit circuit protection

TECTONIC ELEMENTS (=HIWAVE=NXT)
- not the one used atm because too weak in power ?
- conception problems exepted the balanced ones
  (voice coil droop -> need to be held by a back spine)
- previoulsy used: (HIAX= Hiwave, TEAX= Tectonic Elements)
  TEAX 32C20-8
  TEAX 32C30-4
  HIAX 32C20-8 (or could be TEAX...)
  HIAX 32C30-4/B (or could be TEAX...)

don't know why really they are not used anymore, maybe sound quality also ?
don't know if a audio quality comparaison has been made ...

DAYTON
- the one used atm:
  DAEX 25 SHF4 (4 ohms) = flagship product (BL=4.29)
  DAEX 58 FP = people's favourite (BL=5)
  DAEX FH E4 = the "dark horse" (BL=3.65)
- they need also back spine helding because they are too heavy and gives weight to the panel
- amina and podium sound use HIAX 25C15-8/SF (but for some shady reasons it's not obtanaible for the public ?)
  http://www.tectonicelements.com/downloads/datasheets/DS-HIAX25C15-8SF.pdf
  in this one the BL factor is 6.56 and it's high value is important for efficency in large panels


i hope these infos are correct and help others to understand something
what i think is i need to get some honeycomb material panels and some exiters and begin to play with asap !
i'm considering using a ribbon or planar tweeter because dml seems to have some spl problems in the highs
and also a subwoofer crossed around 250 to make a hi fi full range 2.1, 2.2 or 2.0 (3 way assembled speaker) stereo system
i'll keep you in touch about this ...


cheers

[zygadr]

Sedge, still can't see what your conclusions are?
Are we on the right track with VH XPS  ???????

[zygadr]

 Went to the local hardware store and grabbed (did not purchase)6   915x100x2.5mm balsa wood planks and held them in my hand to check on weight in respect to a possible home made balsa plywood.
Forget it!!!!!....... Way too heavy........ and this is only a small amount compared to what would be required for a full size panel.
So far VH XPS is the winner by a long shot, and I do not even have any large pieces that are properly mounted at the moment!.... .........very rough experimental set up, yet sound is clear, if a little thin due to the dimensions of the panel.
I guess it's up to me again to purchase some large panels?
This time I am considering curving the panels!

 

[j gale]

Hi zygadr,  I would like to try some VH XPS but haven't been able to find any. can you tell me what it is generally used for? if I knew that I might find some. Thanks for keeping this investigation going.   Jim

[sedge]

hi zygadr
what I was trying to say was if you make the perfect panel with a flat response from 20HZ to 20KH and put it in the  living room ,it would probably have a big hole in the lower mid range,I say probably because I have no way of predicting the room response, as the size of the panel and the room and also where the mic is in the room will change the response shape .I would think other panel speakers such as quad would have the same problem.
I have had large panels playing in my front room and they sounded very thin in the lower mids but when I went to make a cup of tea in the kitchen next door it sounded  fantastic ,as if there was a real jazz band in the front room.

I use a low frequency driver in tandem with the panel to  run from 300HZ down ,this fills in the suck outs and takes the pressure of the exciters in the LF ,rolling them off at say 30 to 50 HZ  or so saves your mid and HF from being stressed .

do you treat your panels to stop self noise and other probs.

if there was anything lighter than poly I would try it,the exciters we use are best suited to light panels ,I have tried hard heavier panels but they need to be driven by powerful shakers such as monacor or drayton hn8 I think its called?
 I have in the past  rum my  exciters hot and they will sag very quickly and burn the voice coils I know this from experience.
mostly I use ordinary xps or foam panels as I like the sound I can get from them.

steve

[zygadr]

Hi sedge. Thanks for the explanation, I understand now.
I have not as yet tried any coatings on the XPS but have been thinking constantly on this subject.
I truly believe that some sort of coating will benefit the material's sound but need to research and experiment on this problem.
Also, I am almost certain that the use of rubber disks or something similar can be used to ''tune'' the XPS. Podium do it as does some mini hi fi manufacturers that use medium sized NXT speakers. I have seen these ''disks'' through the front metal perforated mesh of the speaker fronts 
Experimentation is about to begin at home here, so it will be interesting.

Hi j gale, VH (very hard) XPS is primarily used in the building industry as insulating foam. It is noticeably harder than standard XPS and has a smaller bead size with greater density, yet is still very light. It is also used in the signage business I believe?.

Now, here is the weird thing..............WHITE ''GATORBOARD'' is TOTALLY DIFFERENT to the black Gatorboard that I originally started with. White Gatorboard is VH XPS sandwiched between a thin white clay/paper substance.
I recall having two identical small samples of both the black and white Gator. The infamous ''scratch test'' had the white Gatorboard clearly superior to the black version. Highs were far more prominent and the sound was noticeably louder.
I never tried the white Gatorboard as I had already invested in the black. Looking back now, I realise that there would have been a great difference in sound quality if I used the white stuff instead.

Where to get VH XPS???..............any foam supplier should be able to help. They need to know that it is the harder, high quality XPS, and it comes in 10mm thickness (minimum).

I will try to post some links and info if possible.

[zygadr]

Here is a link to where I got mine from. I think we should go back to calling it ''VH EPS''.

http://www.foamsales.com.au/shop/p-polystyrene-sheet-10mm.html

[zygadr]

I have a local distributor for Gatorfoam,(NOT ''GATORBOARD''....sorry  ) Re-Board etc., etc., only 5 minutes from my home.
 They owe me !!!! (due to non delivery and no communication after ordering Re- Board over 18 months ago!!!! )

I will be paying them a visit and will be performing some serious (but gentlemanly  ) complaint and sample requesting tactics (which  I am well known for  ).

Hopefully these inefficient drones will arrange for a supply of largish samples of white Gatorfoam after I am finished with them!!! 

I have a positive feeling that this may be the way to go with a suitable panel material that is already coated, only 5mm in thickness and can be tuned?................The black Gatorfoam was well damped and did not need tuning. However, it did affect the transmission of highs which will not be a problem at all with the white version.
Trust me, if you look up the website, you will find that they state that both the black and white is ''extruded polystyrene''.................it is NOT!!!!. The black interior was soft and spongy, the white was hard and ''crisp'' when you depressed it  with your thumbnail..........BIG DIFFERENCE!!)

Wish me luck guys...................we could be on to something (that we may have seriously overlooked  ) if memory serves me right 

[sedge]

hi zygadr

I have used coins stuck to the panels in certain places to increase the output in the lower end of some of my smaller to medium size panels but not for cancellation purposes.

steve

[sedge]

hi zygadr
you can vastly improve the sound of your panels with a very light coating of pva but it has to be done in a certain way.I mentioned this some years back on this forum but no one seems to have given it much thought,I have an old 40 cm vh xps testpanel in my loft ,I could get it down and test it for you,or do you have any scrap panels you can test yourself and compair with the untreated panels ,the test panel does not have to be the same size as the db output and sound  will be very similar above say at least 200HZ if a 40cm panel is used if my memory serves me well.
using any poly panel or foam panel without a light coating will have a lot of self noise will tend to be over bright and have a tendency to sound hard at times,vh xps is no exception.
Steve

[zygadr]

Guys, I have noticed the harshness with the panels I am using at the moment.
However, we must remember that this is raw, VH EPS.
Yes..........adding coins or extra exciters(if freely mounted)will lower the resonant frequency of the material and produce lower bass response (at an efficiency loss).

At present, the potential of VH EPS is promising,but I have no intention of paying big bucks for white Gatorfoam if it's going to present the same old problems!!.

I have a worrying feeling that even if we obtained the infamous Nomex honeycomb stuff with Mylar skin will cause serious problems as does EPS without being tuned............by what for God sake ...........????????????

There is a way to make our own honeycombed paper/cardboard laminate, but is this worth the effort??

[zygadr]

There is a two pack lacquer that had a sample board at my hardware store.
Amongst the test panels was EPS. The lacquer, which is generally used on furniture, created a rock hard coating for the XPS that was quite impressive.

Is this perhaps the final death rattle of this thread as we approach 100 pages?

[oldschoolVlad]

Thanks for your input, xit. Didn't know about Göbel.
Just look at that hi-end panels in HD:

http://www.youtube.com/watch?v=mc3eZcgltJk

Now ask me what is that hi-end up to 30 kHz. The answer is "the right wood, the right thickness and final bending rigidity".

[sedge]

oldschoolvlad

and don't forget the carbon webbing that is glued to the panel.

steve