[Odal3]

Hi Sedge, Thanks for sharing the measurements. Can you help explain how to interprete the reading such as the units on the Y scale, etc.  Is it correct understanding that your smaller but thicker 10mm panel plays louder all accross?

[sedge]

as you can see from the pics I also setup an old large panel to see the room response ,12ins was good but 2mtrs was bad it sounded like I had a subwoofer up to 100hz  and a ribbon tweeter from 300 up to 20k(big hole 100 to 300hz).credit to the panel the air in the room was pulsating in the LF ,even more so in the next room, overall sound was better to, but the in room was thin and over bright.
the panels sounded a lot better in my small music room but still not perfect, only when I switch on the tls do they start to sing.
as I'm using the panels full range but using tls to cancel room modes , does that mean they are full range panels or not?
steve

[sedge]

odal3
I use a 30db scale (each dotted line is 5db)yes the 40cm panel is louder but not that loud ,I was running back and forth to the next room where the rta was and obviously didn't have the same volume on the amp when changing the panels
I think that's what you wanted ?
steve

[Odal3]

Thanks for the clarification.

[Odal3]

Did this thread come to a conclusion on the shape and size of the panel (ignoring material for now)? I remember reading something about it here but can't find it, so sorry if this is duplicate. Anyway, it seems like most use rectangular/square panels with rounded (?) corners, but is that just because of ease of constructions since they are pre-cut like that or is there an advantage with it? I guess one advantage is that it make it easier to duplicate exact exciter placements (monacor, etc.), but most instruments use large smooth curves around on all edges. What comes closest to mind is a sound board in a grand piano, which was discussed back in 2011 on this thread.

BTW: check out some of the latest Piano hybrid pianos using transducers on the the soundboard - for example the $17000 Yamaha U1TA that was recently introduced. Looks like it is two transducers - one in the bass section and one in the treble area of the soundboard: http://data.yamaha.jp/sdb/local/products/images/43327/12075/43327_12075_1.jpg

Pic of transducer: http://fresnopianogallery.com/news/wp-content/uploads/2014/07/Transducer.jpg

Kawai have had some pianos as well with transducers (but they had to complement with speakers for the higher frequencies)

Of course, I'm not suggesting to build a piano (or a real soundboard), but what if making  a large area with gradually thinned edges for better low-end (just like the bass area of the piano soundboard) and a smaller "treble" area with a reverse curve radius and edge treatment for stiffness (shellac?).

Has anyone tried this shape?

Maybe even playing around with high pass /low pass filters for the different areas (or mini-dsp if one wants to be really fancy). Wouldn't this also help avoiding what looks like a type of comb filtering effects that cancel out the higher frequencies? There was a recent example of this in one of  the GR research threads where 4 LGK drivers were full range on the same baffle. http://www.audiocircle.com/index.php?topic=126112.0

[sedge]

odal3
this is why I only use one exciter per panel, although line array cancellations should even out with distance from speaker as in a hall or church, they would not measure well up too close.

the cone Idea came to me because someone said that panels didn't have up front cosy sound  , everything sounded distant ,so I put the cone on the 25mm panel to give it more presence and detail which worked well I think, obviously very thin panels don't need this, we must not forget that the inch or so around the centre of the exciter works as a piston and a lot of the hf above 10k comes from here.
steve

[sedge]

a lot of the harshness in the sound comes from the centre of the exciter area, I used to use blu-tack to tame this noise .I have tried other damping but blu-tack was cheep and easy to remove and change size and shape. then I stumbled on the next mod
which I'm sorry I will have to go I'm being call to get off the computer

steve

[Odal3]

The only harshness I have heard has been due to which amp and power supply I use. I hear no "harshness" with a Tpa3116 powered with an Astron. A non modded tpa3110 amp with a laptop brick on the other hand doesn't come across as nicely (but still good).

[sedge]

what type of panel are you using 'I would not use this on a hard panel such as ply wood,I don't think anyway?
I think oldschool vlad talked about this problem on page 98 with pics.
If you have no problems then obviously this is not for you but it works for my panels and could help other peoples  panels.

steve

[oldschoolVlad]

we must not forget that the inch or so around the centre of the exciter works as a piston and a lot of the hf above 10k comes from here

...not quite correct, just look at pics taken from the plate theory:

mode1


mode2


with a plate stiff enough the material within the driving ring bends in mode1 way;
when a plate is not stiff enough/lossy the material within the driving ring bends in mode2 way (or even more weird)...
...and at a high frequency a bending magnitude to drop rapidly with distance from the driving ring, so the highs are like a flashlight spot around the driving ring.

[zygadr]

I have resurected the 2.7 mm , 4 X 3 foot  plywood panels  -  nothing special...........no exotic woods........just plain old thin plywood with only ONE Dayton exciter ( this has never been tried in my neck of the woods!! )


The highs are electrostatic sounding ( you can throw as much crap at me at this comment..........I don't give a damn!!!) there is no self panel noise that I can detect.
There is an obvious drop in sound pressure output, but the music is absolutely fantastic!!!!
One tends to forget and get confused with the vast range of possible contenders in the materials department, but I am certain that this is the material or DIY possibility that will end the search for a DML  panel to satisfy our " ultimate" substance "to attach our exciters to.

I have found the best exciter to make thin plywood sing and will place an order shortly.

LONG LIVE "THE MOTHER OF TONE"

[zygadr]

O.k, I have no doubt that by now, you all are probably thinking that " Ziggy " has lost his marbles and is going backwards and forwards with his panel material recommendations?????   

I regret to advise that you are probably right to some extent. However, as I am now retired from a government job, I have had a great deal of time testing all the "favorites" in respect to materials used in our search for audio nirvana !!

 Please guys, trust me on this one ......................of all of the substances I have tested, it seems that a thin as possible plywood laminate  has without doubt a realism that can not be ignored.

As I have already mentioned, there is a new exciter available that should (if marketing hype is correct) easily drive plywood panels without breaking a sweat!

After treating CC with various coatings, it can not match plywood ........period.........a sad fact.

In respect VH EPS..............what a pity.........I could not make this stuff sound natural no matter what I tried............it just sounds wrong.............I don't know why???

In regards to Gatorfoam .............again.............far from "HI-FI". Sounds OK', But lacks high frequency extension which is most important !!
I don't know about the white stuff, but I am not going to blow a heap of dough to find that it sounds like EPS !

It seems that, after all these years that we have gone the full circle and not used any expensive exotic material to achieve a sound that is the envy of many who HAVE spent big bucks on their panel systems, only to discover the DML is equally as good if not better than their expensive "slabs".

Those of you that are thinking of Balsa wood laminates, please wait as I am on the verge of testing something far less expensive and easy to imploy.

Rob.

[oldschoolVlad]

Rob, could you specify the type of magical exciter? Very interesting to look at its specifications.
That's cool that you have new findings. I also started thinking about the 2mm thin plywood after a video of laminated balsa. It seems, there due to the low thickness of the plate the peak of the highs moves strongly in the right of 10 kHz, and the inevitable loss of bending rigidity is compensated by a particularly strong in tension double-sided coating (that's why theese A3s give out up to 150Hz).
Do you plan to solve the problem of insufficient bending rigidity of your thin plywood panel? Or the lows suit you so far? And do you hear the details now as if you were in phones?...

[zygadr]

Hi Vlad, I wouldn't call the exciter ''magical'' just yet, but it does look promising. Check out the product details and compare to the Podium type DAEX25SHF-4.

This new exciter interests me due to the RMS high power handling and the steel spider which will avoid ''voice coil droop''. Also, it is designed to drive unusually large and heavier panels than other exciters, so, we may have some further options and possibilities than we have had so far to date? :

http://www.parts-express.com/dayton-audio-daex32ep-4-thruster-32mm-exciter-40w-4ohm--295-230

I will look at the bending rigidity after the exciter is received. It may well be possible to use a thicker, more rigid plywood.....who knows?

At present, the bass is quite acceptable - even with an unmounted panel.
The current plywood sheets with middle ground exciters provide exceptionally clean and crisp, sweet highs and there is lots of detail evident.........almost as good as headphones.

Rob.

[j gale]

Rob,  Did you notice the new one?  DAEX32U-ULTRA. Looks to be similar but it's uncoupled Fs is 160 Hz vs about 395 for the one you are looking at. Not much info given by Parts Express

[oldschoolVlad]

Rob, I considered that DAEX32EP-4. Look, I'll be glad if I were mistaken, or there is a mistake in the datasheet, but that one called "thruster" can't "easily" drive plywood panels cause the motor strength  parameter BL it has is lower than the motor strength of theese DAEX58 you already use (4.2 against 5.0) ... These marketers will finish us off some day ...    The real "thruster" on the market was DAEX32UT-4 with its BL=16.4, but it is unavailable now... However, it's the theory naked. And maybe it turns out different on practice...

[zygadr]

Hey Jim and Vlad!!!
Thank God I have not placed an order as yet, because the exciter that you have brought my attention, I have totally missed and it could (?) be a better alternative  in the area of fs - lower resonant frequency. Does this make a difference? - I have no idea as we are not talking about your average speaker driver.

The spider on the other version seems to be either black metal or stiff plastic. Either way, this type of suspension will not require rear bracing and hopefully only one driver will be adequate?

My only question is -  what is the difference in BL ?..........if any.......?................this could make a difference possibly?.....or perhaps none at all. This is all guess work at this present point in time.

Anyhow guys, I will hold off until some further information is obtainable. If not I will go for your recommendation gentlemen...............many thanks, and much appreciated 

[zygadr]

Well, I have checked the Dayton website and there is no BL rating listed. Everything else is very similar to the other model I was interested in but the newer version has a low inductance and superior fs.
I guess that this will be the one to go for guys. It should by all sense of reasoning, be a very good exciter.
Could be some interesting times ahead guys?!...............we shall see.

[oldschoolVlad]

What is the difference in BL? Oh c'mon, Rob, that is of huge importance for DML, you can  google all the info:

" BL: Expressed in Tesla meters, this is a measurement of the motor strength of a speaker. Think of this as how good a weightlifter the transducer is. The formula is mass in grams divided by the current in amperes. A high BL figure indicates a very strong transducer that moves the cone with authority.”

“BL is also known as the 'force factor' because the force on the coil imposed by the magnet is multiplied by the current through the coil. The higher the BL value, the larger the force generated by a given current flowing through the voice coil.”

“BxL - The product of magnet field strength in the voice coil gap and the length of wire in the magnetic field.“

As for the DAEX32U-4, have to disappoint you, but… it has similar with DAEX32EP-4 Voice Coil Inductance (Le), thus it has similar length of wire in the magnetic field. And thus - it has similar, ordinary BxL. Sorry…
The Resonant Frequency (Fs), it should not worry us at all (for exciters only). It refers to the free air voice coil. If it is attached to a panel, the resonance now refers to the system voice coil- panel , and Fs disappear as a term.

What I think, guys, all of that braced exciters are obviously made for a not demanding, “mass” consumer (…Aha, you want a singing door – here you are…).  If we need hi-fi speakers in our rooms, hence we need exciters for commercial audio, of higher grade. Even without that “voice coil-panel coupling losses” bla-bla etc. I see now only two of them on the market: DAEX25SHF-4 and HIAX25C10-8/HS. The minimal driving ring/ maximal force factor combination. And, it seems, no more powerful ones available. Not so handy in assembly, but worth it. So, as before, 4+ of them per panel is needed. That’s it. I personally tend to buy a bunch of HIAX25s…
…And yet, Rob, you can try to do a remake of your DAEX58s without those plastic plates and mount them on a Podium-like frame finally. Possibly these will suit to your new panels and will sing better.

[zygadr]

Well Vlad, actually, I am very familiar with"BL" factor. If you have read my posts you will know that I have built three way HORNS and the BL of the drivers I used all had very high ratings of such!!!. Horns require this desperately or they WILL NOT WORK.
I have tried so many different exciters with varying BL factor and none of them stood out as being better than the rest. What does this tell you? .........it tells you that the ultimate exciter needs more than what is common with a shitty cone driver that most on this forum seem to forget!!.......BTW - high BL is well known to equate to lousy bass response in regards to standard drivers..........which we seem to be comparing to exciters at the moment?

As wood seems to me to be far superior to the other materials we have tried, I am reluctant to start the multiple exciter braced at the back B.S..........Again!?..........why?- because I have found that it detracts from the sound of one only exciter mounting.
My very first experiment in this technology was a piezo cone taped to a polypropylene corflute real estate sign that I stole 
The addition of multiple exciters loses a lot of the magic of a single exciter - whether freely mounted or braced.

Try it and see if you feel different?