[zygadr]

If Pine or spruce could be thinly cut or sliced with the appropriate carpenter's machinery, to a thickness of 3mm or so and glued together, segment by segment in to a large panel, we may have an interesting start to a wooden panel speaker.

Pine is cheap, easy to work with and can sound good from what I have read. They can be treated with Shellac varnish to harden the cell structure within.

Wood has been used in smaller NXT satellite speakers a while back and were expensive.............can't remember who made them, but they were a laminate of various types of woods and had cuts all around the perimeter. 

I would not use the cheap exciters for this theoretical wood panel............only the more expensive and powerful ''HIGH SHOVE'' version that Parts Express sell.

We MUST remember that the ''MOTHER OF TONE'' is ...........''WOOD''.
Whatever we attach these exciters to, will take on the sound of that material : cardboard sounds like cardboard, glass like glass, metal like metal......etc.

[CLS]

Hi zygadr,

Before we discussing more on wood, let's rewind a little to the thickness, shall we?

You've confirmed that the thicker panel (of the same EPS) is louder. Would you please share more? How is the sound compared to the thinner one? Less HF? Better damping? Or?....

Thanks a lot,
CLS:)

[zygadr]

CLS, the thicker EPS sounds louder and better damped overall. There is a slight diminishing of highs that is noticeble.

In general, I think that the thicker panel is thus more rigid and sounds different to a floppy thinner one. This is expected of course.

The fact that we are unable to crack the obtainability of honeycomb Nomex is why the EPS has been so favourable : very light, very transmissive, very loud/efficient 

HOWEVER!...................it sounds good, but it sounds like EPS because that is what is producing the sound and therefore carries it's own tonal charachteristic.

I still have a soft spot for corrugated cardboard as to me, it sounds the best out of all materials.
It's not as efficient in output and mutes the high frequencies somewhat,................BUT!..................it sounds more NATURAL 

I have no idea what the Podiums sound like. Their panels are made of paper honeycomb (good) that's soaked and hardened with Phenolic resin(bad : synthetic resin!) and covered with mylar (bad!: plastic!).

So, as you can see, even the ultimate panel material deviates far from the ideal ''Mother of Tone'' principle of only using natural organic materials to make speakers from and what to coat them with.

I don't expect everyone to follow or believe the Mother of Tone theory, but it has some valid points that really makes you think why some speakers sound so much more real than others.

I did a small experiment with an equipment base : one made from solid very thick pine, and another made from thick white plastic food cutting boards.
The equipment tested was a CD player. The pine base produced spectacular bass and a wide enveloping soundstage. The plastic was indistinct, the bass was just wrong, and the soundstage all over the place. Wood showed great superiority in this particular test.

http://www.mother-of-tone.com/

[CLS]

Already a product here:

http://www.jmclutherie.com/en/Soundboard

Yet another:

http://www.operesonore.it/en/le-opere-sonore.htm
 

And I've found a simple chart of the tones of different woods:
http://www.taylorguitars.com/guitars/features/woods/Tone/

 

I like ovangkol, but I don't even know what is that! 
And it sounds expensive. 

[zygadr]

Great find CLS!!!!

The first speaker/link is exactly what I was trying to describe as the panel material we should be looking at. It looks like 4 or more exciters (in stereo???) per board.

When you read the FAQ's, there is a LOT of nonsense and ''snake oil'' mentioned about how the wood is chosen, matured under a certain '' moonlight''

This speaker would cost a fortune.....................as expected

[usp1]

Returning to this after some time. I bought some eps board 3/4 inch thick which is used for building insulation. I tried some basic panels 2'x4' with two exciters each. Compared to the old gatorbord and corrugated cardboard the highs are much more extended although there seems to be some ringing. ( I think that is the correct term).

Unfortunately, I have not yet figured out how to stick the exciters to the board. I tried using the 3m tape but it does not stick well to the plastic film on the eps board and the exciters fall off in a few hours. Not sure if superglue will work.

[bobloblob]

So far I haven't been able to find a bare eps foam in my area, but I haven't had time to look much.  I hope that will come in a few more months.  The bare eps should work well with different adhesives.  The problem you are having is undoubtedly with the plastic film, as I'm sure you know.  It can often be nearly impossible to find effective glues for some plastic films.  The best bet, if you are going to try it again, would be to rough up the surface of the film in the area you want to attach an exciter to as much as possible with sandpaper or the like to get the best possible mechanical bond, though it may still not be ideal.  The roughness creates a larger surface area so that a weak bond will have more area to bond to.  If you use the tape again. you might find that warming the tape and the surface of the eps will help strengthen the bond, as it increases the flexibility of the adhesive and lets it "flow" into smaller spaces in the bonding area.

You can find superglues that are slightly flexible that claim to bond with plastic better than the standard superglues (these more flexible ones are also sometimes used to fix tears in driver cones), but a standard superglue may work in this case too.  Worth a shot.

What would concern me more is the possible damping effect of theses extra layers of plastic film over the eps.  Is it possible to remove the film without destroying the eps?  I'm thinking it would be extremely difficult to remove it, if it's like the ones I've seen.

[jackman]

I would look into companies selling guitar kits to see if you can buy the raw soundboard tonewood.  It's got to be inexpensive.  I noticed one of those guys (the Italian artist) used regular guitar braces to support his flat soundboard.  Pretty cool looking stuff and something even I can DIY.  I'm going to give it a shot when I have a chance.  Just need to find some inexpensive tone wood and some glue. 

You can even use laminated wood like some cheap companies use to make sundboards.  It's not as good for a guitar but we aren't making guitars anyway.   Might be better for a tonewood NXT speaker. 

[usp1]

bobloblob - I did find bare eps in Michaels (the hobby store) but they have small pieces only. I will experiment more with what I have when I get some more time.

As for the sounndboards, early on in this thread I experimented with using a guitar. Interesting sound but definitely not outstanding.

[bobloblob]

Using guitars for NXT-type panels does not seem like a good idea.  However, how about making a panel with exciters, then putting a rack on it to hold a guitar?  It would seem to any casual listener that the sound was actually coming from the guitar.  It would take a bit of juggling with the build to implement this, but I think it might be the best way to get reasonably acceptable sound.  The panel need only be large enough to carry the range of a guitar, so no deep bass requiring a large surface area would be necessary.  As a bonus, you could also mount a picture or poster of a guitarist of your choice on the panel too.

[el`Ol]

What about using 0.3mm glassfiber reinforced epoxy? Unfortunately one layer has enough mass, so a sandwich is not possible, but one could laminate it with sofa cloth (suede, microfiber, etc) to achieve both better damping and high WAF.

[bobloblob]

One could use carbon fiber cloth and get both strength and relative lightness, and it is light enough to do more than one layer, but I don't know if there would be any advantage over Zygadr's eps panel.  It would also be a lot of work, and messy, and hard to control the outcome in a one-off diy project.  And it is probably chasing after something beyond Jackman's modest demands for his project.  I like the thinking, though.  For a trial, one could buy a small piece of carbon fiber cloth and a bit of epoxy (and here you have to find a hard epoxy - it comes in several varieties, from very flexible to rigid).  I'm not so sure that damping is a quality you want in a panel beyond what will reduce any tendency to ring.

[usp1]

How about using two sheets of veneer back to back?

[bobloblob]

I think model shops and some larger lumber/hardware stores sell three-ply sheets.  Unfortunately they are usually in small sheets, much smaller than optimal even for a guitar display.  In larger sheets, I suspect they might still be too flexible compared to either eps or Nomex, and I suspect a two-ply sheet would be quite flexible.

I don't think mecessarily that musical instrument soundboards provide good models for what is wanted in a panel.  They do conduct sound, but they are not used with the intention of providing no colorations; in fact, they are often part of what gives an instrument its particular flavor.  Furthermore, soundboards, at least all that I can think of offhand, get their rigidity by being constrained under pressure, and usually are bowed somewhat, on purpose, from this pressure. Otherwise they would flop around a lot.  Guitar soundboards are flat, but have a lot of bracing.  Piano soundboards usually have a lot of crown, and extra bracing too.  Steinway uses a variation, putting the soundboard under pressure, but shaping the soundboard thicker in the center and thinner at the edges, giving it that crown shape, rather than by pressure alone.

Ultimately, there is a lot that goes into making an instrument soundboard, things that may not be relevant to the problem at hand.

For what its worth, spruce is the choice for piano soundboards because it is relatively straight-grained and is one of the harder softwoods, so there is a consistency of response across the expanse of the soundboard.  Also, Douglas fir is one of the hardest softwoods, and most stable of woods, and may be a reasonable choice for experimentation.  I don't think either comes in veneers, though, at least not publicly available.

I think Ovation makes their guitar bodies with a resin impregnated carbon fiber cloth, but not their guitar soundboards, which are wood.

The most expensive guitars use one-ply wood for the soundboard, less expensive ones use two-ply.  Kawai was making its vertical pianos with high-quality plywood and said that in testing, they heard no difference between that and the one-ply (i.e. solid wood) soundboards, but eventually changed back to single-ply soundboards because this was used against them in the marketplace.  They always used single-ply in their grands, where they said it did seem to make a difference.

You can take all this for what it's worth, which may be nothing.

[usp1]

For what its worth, spruce is the choice for piano soundboards because it is relatively straight-grained and is one of the harder softwoods, so there is a consistency of response across the expanse of the soundboard.  Also, Douglas fir is one of the hardest softwoods, and most stable of woods, and may be a reasonable choice for experimentation.  I don't think either comes in veneers, though, at least not publicly available.

I found this.. http://wood-veneer.com/product.php?veneer=Spruce  and http://wood-veneer.com/product.php?veneer=Fir

[bobloblob]

I was surprised to see spruce and Douglas fir in veneers.  One of my major concerns with using veneers in this application, and I probably should not have used the term veneer, is that modern veneers tend to be paper thin.  I don't remember when they started to change, but older veneers were much, much thicker, more like the thickness of the plies in plywood.

Modern veneers are so thin that you would most likely have to stack several to keep the panel even remotely stiff.  Then you would be using quite a bit of glue, so that the glue itself would be creating some of the characteristics of the panel.  Veneers also tend to be expensive.

If you really want to go down this road, a single-ply relatively thin sheet of spruce soundboard material may be the best choice.  There are people out there who make piano soundboards for piano rebuilders.  It is a small industry, so often the soundboard makers are doing one-off jobs  They edge-glue planks to make the soundboards, but through mentorship, practice, and making mistakes, they have become quite skilled.  After talking with some of them, I know it's not something I want to jump into.  However, making a flat rectangular panel should be a no-brainer for any of them.  I think it would also cost a bit.

There is also a lot of voodoo out there about finishes on soundboards.  Some refinishers swear that varnish is the only finish to use.  All modern pianos are finished with nitrocellulose lacquer and, so far as I know, no one who has done anything resembling an a-b comparison (a pure a-b comparison can't really be done in this case) has heard any difference that shows varnish to be superior.  A few manufacturers tried polyester (similar to "boat resin") but that did have negative effects.

My own feeling is that this may not be a very productive road to follow for panels.  I look forward to being wrong on this one, as I just like wood.

[el`Ol]

One could use carbon fiber cloth and get both strength and relative lightness, and it is light enough to do more than one layer, but I don't know if there would be any advantage over Zygadr's eps panel.  It would also be a lot of work, and messy, and hard to control the outcome in a one-off diy project.  And it is probably chasing after something beyond Jackman's modest demands for his project.  I like the thinking, though.  For a trial, one could buy a small piece of carbon fiber cloth and a bit of epoxy (and here you have to find a hard epoxy - it comes in several varieties, from very flexible to rigid).  I'm not so sure that damping is a quality you want in a panel beyond what will reduce any tendency to ring.

0.3 mm glassfiber reinforced epoxy boards are very common and easy to get. And resins behave more linear than thermoplastic substances. Phenolic resin was the usual substance for spiders before the war. There are worlds between the Podium with epoxy/aramide and Rohacell (a thermoplastic foam) in neutrality. The Rohacell cost me quite a lot of money, but I couldn't stand the neutrality problems, so the boards went into my garage very soon.

[CLS]

What do you mean by "neutrality problems"? Is it the coloration (resonance) problem?

Did you try damping or ribs?

[el`Ol]

I mean coloration. Maybe I could have made it with balsa plywood. But the damping I applied to it (two layers of hardwax oil) were too much and made the sound muffled.

[CLS]

Oh, I see.

So, there're still chances to be a good panel, I guess. Originally it's too hot somewhere, later it was turned down too much. So it must be somewhere in between which is just fine

I haven't given up my foam panel yet. At least before I try real wood, I give it another chance. I've been working on them lately by adding ribs... etc. It's not finished, yet. I'll update here once I have something to report.