[zygadr]

Not that I could tell, no.  Couldn't hear the panels in the mic at all.  Rather amazing.  The real test will be lavaliere (clip on) and lectern mics, those are the tough ones.

Frank: Exactly.  We will be scrutinizing them further this summer.  I'm setting up a demo in a large hotel ballroom here in town.  It's an acoustic nightmare of a room (200'x200') that we've been fighting for over 20 years - and losing.  If these panels can come close to fixing the problem there, it will be a miracle.

I realize that this is not home use, not DIY, no where near cheap.  But it's very informative to hear just how far this DML technology has come and can go.

I would have thought that a P.A. horn system should easily handle a large room like that?
With modern feedback cancelling equipment available today, there should be very few problems to end up with?

[panomaniac]

If only it were so easy.    There is only so much you can do when the acoustics are fighting you - and you don't have much choice as to speaker and microphone placement.
No one, in over 20 years, has been able to tame this room.  It's much better than it used to be, but it's still a problem.  It will be very very interesting to hear if the DML technology actually makes a significant difference.  If it does, then I'm sold.

I wish that I could dig deeper into what they are doing right.  The panels, I was told, are Kevlar and carbon fiber.  The cut-away looked like a Kevlar honeycomb with a carbon fiber skin.  There were tiny brass weights at various places on the panel to cancel nodes.  Careful panel tuning seems to be important.  I do know that they used laser interferometry to analyze the panels.

[FrankCA]

Having received my "exciters" and playing with them for a couple of days, the absence of directivity is the most appealing thing about this tech.  That's the problem with trying to "heat up" a room that is as wide as it is deep with a conventional system.  The highs start interacting due to phase differences...  I'm no engineer, but I do know that if your high end originates in different places or is pointed in a multitude of directions in order to get coverage, there will be places where it is really hot, and other places where it is nonexistent, at least at some frequencies.  That's why two people can go to a show and one will praise the engineer and the other is throwing rocks.  Short wavelengths are especially prone to phase interaction, both additive and subtractive.  Solving directivity opens a new book. 

With that said, has anyone tried an aluminum strip with an exciter at each end with JUST the highs going to it and a way of balancing it with the main panel?  These tectonic guys are using a ribbon...  can we come up with a DIY "plate" tweeter? 

OR Imagine a full range speaker with a whizzer cone...  Mount some sort of stud on the panel (in the center?) and attach said aluminum plate or strip to it.  Might not be aluminum, of course, and size, shape, and thickness would all come into play.

The question posed is:
Is the lack of highs in the exciter, or the panel?  If it's in the panel, there may be a way to physically compensate through either an attached "sub-panel" (analogous to the whizzer cone) that by it's size and composition would naturally reject the mids, but add dazzle in the higher hz.   If the exciter just can't push those frequencies, then another avenue must be employed, such as the ribbon.  But that wouldn't be any fun, now would it?

Anyhoo...  even though I've just got the exciter taped to a generic (untreated) piece of card board about 11"X20", and I am just running it with a computer sound system that is of minor quality, it sounds quite nice.  The amp has an integrated sub, and the sound from even this small panel really blooms when I dial in some lows.  The folks I've shown this to are amazed that in my 20'X20' garage, there is little or no drop off anywhere you move in the room.  Infinite sweet spot!  This is audio!

[panomaniac]

Great question.   Is it the panel or the exciter motor - or both?  I do know that the Tectonic guys are working toward a high frequency DML for their speakers, but I don't know what the engineering challenges are.

[zygadr]

I would take an educated guess and say that the panel is responsible for lots or no highs from my experience.
It's all about ALL the frequencies transmitted(as we have a full range transducer) which can be greatly affected by the choice of panel material. For example, 3mm plywood produces tons of high, mid and even low frequencies, but the penalty is much lower output.
I have not tried the newest range of P.E. exciters which can really excite large(and heavier) panels with their extra ''shove power'' and power handling.
Perhaps it's time to obtain one of the top of the range units and revisit plywood again?  I have been troubled by the great sound of plywood haunting me since I last tried it 

[FrankCA]

So... I started a gallery.  Probably of most interest is a little thing I have dubbed the "whizzer plate".  Not exactly a plate at all, but it DID enhance the highs, and though I heard a small loss in the mids, I'm not sure whether it was due to an actual  loss, or just hiding it because the highs jumped.  It is probably because I was just holding the whizzer plate against the panel with my hand!  Any way, there was an audible difference both in the note I was testing it on and overtones that appeared.  Test was the last long duration high frequency note on "The Wall" by Kansas.  Once I have got a few more panels to test and destroy, I will report back with more findings.  In the gallery there are some photos of shellacking my panels,  especially the corrugations, using many ideas I have learned from this thread of legend!

zygadr-
It would seem your guess is indeed educated.  Now, go get a piece of aluminum angle and see if you can repeat my experimental results!
Just kidding...  I am going to look into this much more though.  If just gluing a piece of scrap metal to the panel would boost the highs and yet still maintain the omni aspect of the sound, my next project will be a couple of PA panels.  I am sick of hauling around cabinets with a 15" and a horn.  At 57, it's no fun lifting them onto the stands!  Plus, I've got a nice folded horn cab that will serve as a sub, and an active x-over and plenty of amps to tie it all together!

Frank

[FrankCA]

zygadr-   From experience with live sound and instrument amplification, I have noticed many times that a speaker with higher power handling sometimes sacrifices efficiency, and even fidelity.  High power handling speakers end up needing that high power in order to perform well.  This is one reason I opted for what appeared to be a more robust design rather that the one with the highest power limit. 
Of course, my focus for this project dictates that very high SPL will not be needed... Frank

[zygadr]

FrankCA, with the exciters we are using for our panels here on this forum, the introduction of higher powered units was a much needed breakthrough from the el- cheapo exciters that could barely handle 5 watts. The higher power only enabled a small increase in efficiency, but allowed four units to be joined and placed on the panels using the Monacor method and greatly reduced the problem of frying exciters in order to get a realistic sound output for the first time.

I realise that what you are trying to achieve is on a different level, but I would still use the more robust exciters.

[FrankCA]

zygadr - I'm using this one. http://www.parts-express.com/dayton-audio-daex25shf-4-steered-high-flux-25mm-exciter-20w-4-ohm--295-238     It's all metal (the housing, that is) and it has a nice strong mounting method to attach it to the frame/mounting bracket.  Someone in the reviews used the holes to mount it to the panel...  not too bright.  Handling 20 watts, it should do very well.  Today, I got some thin plywood sheets, and also some thin Coroplast.  Based on the info here, I don't have a lot of hope for the Coroplast, but I just happened onto them... might as well light 'em up!  Frank

[zygadr]

FrankCA................................ will be interested to hear your thoughts on the thin plywood....................

[FrankCA]

Back again...  had to build this in the meantime so I took a little time off from my speaker project!


Back on track now, and I have been progressing even during the distraction.  More photos in the gallery.  I opted to actually attach the exciters to a small circle of plexiglass, and then glue this circle to the panel (shellacked cardboard).  Adhesive is called E6000.  I painted the back of the panels white for aesthetics, since this (the back) will be seen from the room.  The front (facing the performers) I will do in a faux woodgrain of shellac.  Oh, and I scraped the spray paint from the contact area prior to gluing.  All in all, I am pleased with the sound, and believe it will serve it's purpose quite well.  I may add a subwoofer though... it sounds a little "thin".  I'll see what the choir director (my sister) thinks.

[emailtooaj]

Hello everyone!

FrankCA nice job on your back porch!! Looks like it's free standing and not attached to the house. Those tend to be the more "Pain in the #@$" jobs 

I was also checking out your other photos on the speaker project. Those are going to look awesome to!!
But please, please, please don't use those plexi glass mount rings!!!
You will not be as happy with the end results! That plexi glass will "soak" up the sound energy from the exciters and won't transfer to the panels as desired.

Just trying to help out a fellow builder 

[FrankCA]

emailtooaj,   Thanks for the compliment.  It is free  standing, and yes, getting it stable was indeed tougher than just nailing it to the wall. 

As for the plexiglass, I thought long and hard about that...  I had originally bought the remnant as a test, to see what the panel would sound like.  VERY DEAD.  But then, I reasoned that it could be because the plexi being so dense, it would have no resonant abilities.  So here is my thought process... the contact point on the exciter is only about an inch in diameter, and the adhesive is one time only.  Since these panels are for a production use, it is reasonable to assume that sooner or later I would need to replace the panels.  The plexi will allow me to tear off the old panel, scrape and sand the contact area and replace with a new panel without disturbing the original bond directly on the exciter.  By making them as small as reasonable, I get a larger (relative to the exciter's factory size) contact with the panel while keeping them small enough to avoid deadening the resonance of the panel.  All indications seem to say it worked.  Now, this is only ear testing, but I believe the increase in durability and ability to maintain would make up for any loss I might have experienced.  That said, I am nearing completion and will start testing in a production environment soon. 
Also - and this might be of interest- I wanted to place some small pieces of foam between the frame and the panel.  I opted to glue the foam to the panel rather than the frame.  This way, any "rubbing" issues will not affect the sound of the panel.  Also, since the panel itself is largely a disposable commodity, when the panel gets changed, it will also be time to change the foam.  This I have not yet sound tested... results soon.   Also, more pictures posted

[FrankCA]

I now have finished both panels, mocked up mounting in my "studio", hooked up the amp I will actually be using to drive them, ran a bunch of different music genera through them, and they are going to be GREAT!!!   They sound really stunning on everything except when there is an overabundance of bass.  Small panels seem to lose their way when the lows go beyond a certain point at high volume.  Not a problem for my application though.  At the levels they will be played, they are far more than adequate.  Epic win!  WOO HOO!  This is premature, and I will repeat it at the end of the project, but THANKS TO ALL WHO CONTRIBUTED TO THIS THREAD!  Your hours of experimentation saved me from a lot of dead ends I might have reached had I never happened on this from a Google search.  The only snags I hit was in the making of the panels.  It took some time to understand shellac, which I have never worked with before.  Check out the gallery!

[FrankCA]

New photos of the mock up installation for testing.  Our choir does not generally convene in the summer (we are a tourist area, and we are all too busy!), so the director rounded up all the singers that were around.  Hooking this up was taxing due to a lack of adapters.  The sound guy brought speaker cords instead of shielded lines, so we had to cob together a single line running from the mains bus rather than the actual monitor bus (I know this won't make sense to everyone...).  The upshot is that we had one output source splitting to drive two inputs instead of two separate lines from two separate outputs.  We should pick up a lot more gain and better impedance matching when we get the proper cabling.  ANYWAY... the sound was a huge improvement over the system that was used in the past (wedge floor monitors).  After we tested the choir, we used it with a solo clarinet and it sounded amazing!  The player (like myself) is an ear player, and could never hear himself well due to the proximity of the piano.  He said it was great sound, and you could tell it during the performance because he played with far more confidence than usual.  SCORE!  I think this will be an awesome solution to our sound problems.  Thank God!



 
The final mounting will be slightly closer to the ceiling, and will mount from above like a pendulum.  Also, no telling how much sound was lost from the way they were mounted for the test... a good, solid mount will transfer a lot more energy to the panels rather than vibrating that whole rickety stand!  Frank

[CZ Eddie]

Hey folks, this thread seems to be the premiere info thread on acoustic transducers.
I just got a pair of Dayton Audio DAEX25's in and I like them.

BUT, I am now in need of some transducers that are 1.5" wide, circular shaped.  And full-range.
I found the Dayton Audio BCT-2 and it's shaped cylindrical, and is only 1/4" larger than my needs are.  I might be able to fit them into my project.

BUT, it seems they are only rated down to 300hz?
Could someone more knowledgeable with these devices let me know if they will play down as far as the DAEX25's go?  The DAEX25's do not have a frequency rating anywhere that I can find.  If the BCT-2 will play the same frequency on the same material as my DAEX25's, then they'll work fine for me.  Does anyone know?

[CZ Eddie]

Actually, this 1.3" diameter cylindrical transducer from Adafruit is even better since it fits inside my 1.5" requirements.

http://www.adafruit.com/products/1785

Again though, not sure if it's capable of bumping the bass a bit.
I don't need audiophile.  But I do need a clear, full range sound with a bit of bump. 

[CZ Eddie]

Ignore the above two posts from me.
I mutilated my DAEX25's shell and wire mount to get them to work in my application. 

NEW question is... how do you guys replace the adhesive? 
I've got some 3M auto adhesive tape. 
It's working, but I have to wonder if I'm missing some sensitivity due to the thickness of the tape?

[Odal3]

First of all - thank you all who have contributed to this thread, and especially zygadr for starting it. I have followed this thread for a few while and it inspired me to order a couple of Hiwave 25mm Soundpax exciters to play around with. Most have already been said on this impressive thread so I just wanted to share my experience.

I went down the same route as probably many of you with the thrill of experimenting with different panel materials. Early on different types of foam boards were my favorites based on the recommendations on the thread, but then I tried 1/4 in  2 x 4 ft birch ply boards. I didn't like it at all at first and shared the opinions of others who didn't like it. Main thing was that they were not as efficient and lost output compared to the lighter boards.

But then I "tuned" the birch boards by ear by putting four exciters on the sweet spots. I ended up with a triangle in the upper half of the board with a forth one close to the upper right corner. The legs of the triangle is about 14 cm each (with the peak pointing upwards), and the sound is improved vs a line array or other set-ups I tried.  The best sounding placement varies slightly between different panels. I hooked them up in parallel and connected it to a Lepai amp and the guitars, and pianos sounds much warmer and more detailed than any other panel material I have tried. I'm not going to try to explain the sound, so I'm just going to say it is one of the better set-up I have heard for acoustic live performances with natural sounding wood type instruments. My Klipsch reference speakers have quickly been downgraded to the back-up system. I haven't tried all the options on this thread, so I'm sure there may be better alternatives, but the birch boards are by far my favorite. I found that birch boards with a lot of heartwood sounds better than cleaner looking panels with only sapwood. Thinner boards resulted in more output and bass, but was too flexible (problem with having them stand up properly without adding something to the panel) and vibrated too much resulting in more bass which unfortunately was "boomy" so the sound lost its magic. So the 1/4 in thickness stayed as the favorite.Rounding the edges and corners seemed to improve the sound as well but I never did an actual a/b listening test. I have now used them for about 6 months.

The stand for the panels have two spikes on the bottom that the panel stands on and it then leans on the stand with only touching the back of one of exciters - it's connected with velcro to allow some movement. I'd be happy to share pictures if anyone is interested.

I'm more than happy with this set-up, so thanks again for all the advice! The panels plays relatively load but not super load. I missed the depth to the low-end when playing rock or electronic type music and decided to "cheat" a bit by adding a Dayton based 10" sub. It was easy to integrate with the cross-over on the plate amp and made drum or bass solos a treat.

Next upgrade is to try it out with a TPA3116 amp, and perhaps get some of the transducers that can handle higher wattage (but they are a bit too expensive vs. the ones I bought for $3.50 each). I'm also thinking of staining the panels but worried it may mess with the sound. The intent was for a stereo set-up but they worked surprisingly well also as mains for HT, so I'm thinking of maybe making two smaller panels to be used as surrounds. Has anyone played around making panel based surrounds, center or matched them up with an open baffle type of subs or one of the Servobased subs?

[j gale]

Hi, Interesting post. I have tried various 1/8" plywood but not 1/4"  Did you try woods other than birch? Many of us have been interested in getting enough output from wood but without much success. Some of the new exciters seem to be designed for heavier substrates and might be worth experimenting with for thicker wood. I would like to see a picture of your panels with exciter location. The fact that you are still satisfied over time makes me want to try a thicker panel. One thing I have learned since I have been experimenting with this is NOT to dismiss ideas based on what I think I know. Seems that perhaps thinnest is not best.