One thought that comes to mind is this peelable caulk. Some physical plant guys used some to seal a window air conditioner in my office window so that they could easily remove it in the fall. I was struck by the potential for speaker building applications and bought some at a Home Depot (I think that's where I got it...). I haven't yet used it to hold a driver in place but based on my experience with it I think it would work well. If it does you could get a resilient gasket, a reversible mounting system, and an air-tight seal, all at the same time. It dries clear, by the way.
Alternatively, maybe you could build oversized holes into the "baffle" to match the hole pattern of the driver. You could then epoxy threaded inserts into the holes. To hold the threaded inserts in the correct locations while the epoxy hardens you could put matching bolts through the bolt circle on the driver's flange, thread the inserts onto the bolts, and rest the driver in place on the enclosure. A little mold release on the bolts would keep the bolts from getting permanently epoxied into the inserts.
These are two untested and potentially hairbrained ideas, but maybe they'll trigger an idea you like.
Few
Anyone who has worked with ceramic knows that the material has very high compression strength but has very little strength in shear. Pressing equally on both sides is allowed, pressing on only one side, even a little, is not. Bolting directly to ceramic or through holes molded in ceramic is a bad idea. Any force generated on the bolts will put the cermic into shear, and it will inevitably, eventually, break.
Make your baffle from an inert, stable material such as plywood or MDF, shaped to form the curve you need to provide a smooth radius from the front of the speaker to the walls of the enclosure. Plastic would be even more stable, and you could consider machining stock material or molding something yourself. Permanently attach the baffle to the ceramic with epoxy. Yes, it will be complicated, but it will be strong and functional. If you wanted something simple and easy, a ceramic enclosure was not the way to go about it. I don't mean it's not a good idea; I mean it won't be easy.
Peace,
Tom E
Make your baffle from an inert, stable material such as plywood or MDF, shaped to form the curve you need to provide a smooth radius from the front of the speaker to the walls of the enclosure. Plastic would be even more stable, and you could consider machining stock material or molding something yourself. Permanently attach the baffle to the ceramic with epoxy. Yes, it will be complicated, but it will be strong and functional. If you wanted something simple and easy, a ceramic enclosure was not the way to go about it. I don't mean it's not a good idea; I mean it won't be easy.
Peace,
Tom E
Thanks for all the great ideas and suggestions, much appreciated.
Few- I can't say I've ever seen the "seal n peel" caulk before looks like interesting stuff, thanks for the link. "madisonears" is right about the bolting directly to the ceramic enclosure even via epoxied inserts. I imagine if you were very careful you could probably bolt a driver to a ceramic enclosure, but it would break eventually. If you were careful it might take several years.
I think I will probably glue on some kind of 'plastic' baffle. I feel most comfortable with plastic due to the fact it wouldn't expand or shrink no matter the conditions. Using the removable caulk would certainly be a simple way to attach the driver. I just worry that I'll have trouble getting the curve perfect all the way to the edge of the driver. With a added baffle you can account for slight variation in angles on the ceramic section with different thicknesses of baffles and machining down to meet the baffle.
Simon- I googled Tufnol and found the Tufnol company but they have quite a few products which in paticular are you refering to? I also found a couple posts by you on this forum "15mm paper grade Tufnol" glued with "epoxy/ microsphere mix". Any more information you have on this would be appreciated, as I couldn't find "paper grade" on their web page. Also it's not clear if this is sold in the US. It appears to be manufactured in Scotland.
Corian seems to be reasonably easy to come by around these parts. Anybody here worked with it before? Any guesses as to what would be the best way to adhere it to a ceramic enclosure? Also does it hold a screw well, or am I better off with some kind of threaded insert?
thanks everyone
Joe
Few- I can't say I've ever seen the "seal n peel" caulk before looks like interesting stuff, thanks for the link. "madisonears" is right about the bolting directly to the ceramic enclosure even via epoxied inserts. I imagine if you were very careful you could probably bolt a driver to a ceramic enclosure, but it would break eventually. If you were careful it might take several years.
I think I will probably glue on some kind of 'plastic' baffle. I feel most comfortable with plastic due to the fact it wouldn't expand or shrink no matter the conditions. Using the removable caulk would certainly be a simple way to attach the driver. I just worry that I'll have trouble getting the curve perfect all the way to the edge of the driver. With a added baffle you can account for slight variation in angles on the ceramic section with different thicknesses of baffles and machining down to meet the baffle.
Simon- I googled Tufnol and found the Tufnol company but they have quite a few products which in paticular are you refering to? I also found a couple posts by you on this forum "15mm paper grade Tufnol" glued with "epoxy/ microsphere mix". Any more information you have on this would be appreciated, as I couldn't find "paper grade" on their web page. Also it's not clear if this is sold in the US. It appears to be manufactured in Scotland.
Corian seems to be reasonably easy to come by around these parts. Anybody here worked with it before? Any guesses as to what would be the best way to adhere it to a ceramic enclosure? Also does it hold a screw well, or am I better off with some kind of threaded insert?
thanks everyone
Joe
Hi Joe, Tufnol is a composite used mostly for its good electrical insulation properties, but is very good mechanically too. Wilson used it a lot before they moved to making their own composites.
The paper/phenolic resin grades are Kite and IP1/13, which by happy coincidence have the best mechanical properties and the lowest cost. The other grades use woven cotton or fibreglass are more costly and have better electrical properties. Any grade will do the job. The phenolic resin used is "self lubricating" and so it machines like a dream if you keep the cutter speed and feed rate low on your router.
Any grade is miles better than wood for baffles IMO.
The paper/phenolic resin grades are Kite and IP1/13, which by happy coincidence have the best mechanical properties and the lowest cost. The other grades use woven cotton or fibreglass are more costly and have better electrical properties. Any grade will do the job. The phenolic resin used is "self lubricating" and so it machines like a dream if you keep the cutter speed and feed rate low on your router.
Any grade is miles better than wood for baffles IMO.
Hmm sounds like good stuff... however this is the only place I could find it for sale in the US: tufnol $60 plus shipping for a 2'x1' sheet. A little steep for me. This is for the 'kite' composite, I couldn't find any p1/13 in the US which is the cheaper of the two composites. Unfortunate since it seems like it would be great for baffles. Hard to justify though when corian is practically free in the small pieces that I need (12"x12" at most). From reading your posts Simon, it sounds like corian might have similar characteristics for use in a baffle, but the Tufnol is much easier to machine?
Tufnol in my experience is easy to machine with standard woodworking tools, i've not used corian but it looks a heap better than wood. Tufnol is a brand thats common in the UK, loads of companies make similar stuff. Try looking for phenolic resin/paper composite.
PAPER PHENOLIC - GRADE X - PAPER PHENOLIC - ORDER ONLINE
Was the first thing I came across, good luck Joe!
PAPER PHENOLIC - GRADE X - PAPER PHENOLIC - ORDER ONLINE
Was the first thing I came across, good luck Joe!
I've bought paper-based phenolic in the US from McMaster-Carr. They call it Garolite. You'll want sharp tools to work with it--fresh carbide blades or bits help quite a bit. I'm using it to build the frames for the stators in my electrostatic speakers.
Epoxy seems to bond well to it. I've been using West Systems 105/205 epoxy with either talc or microspheres as a filler. You can even add pigment to the mix if you want to match the color of the phenolic or ceramic.
Few
Epoxy seems to bond well to it. I've been using West Systems 105/205 epoxy with either talc or microspheres as a filler. You can even add pigment to the mix if you want to match the color of the phenolic or ceramic.
Few
If you are really dedicated to using plastic for a baffle, which I think will make a good combination with your cool ceramic enclosures, let me recommend molding something yourself with polyurethane. I recently completed my own baffles using this method, and they are strong, stable, inert, non-resonant, and easy to machine, including threaded holes.
What I did was make a "master" part (an exact model of the final shape) to the proper size and geometry required out of common paraffin wax: easy to work and inexpensive. Make a mistake? Melt it and start over! I then sunk the finished wax part into a bath of plaster to make the mold. After finishing the plaster mold and painting it, I then poured polyurthane. Result: a plastic casting with the exact geometry required (I did NOT mold the speaker opening or mounting holes--those need to be machined), including a very large, smooth radius that joins the four walls of the enclosure to the fronts of the drivers without any edges or corners. Polyurethane is not cheap, but you need only a gallon to make your smallish baffles. Mine are quite large and an inch thick, and I needed only 2/3 gallon each. I got my poly casting materials from Smooth-On. They have a large selection of poly and epoxy grades. I used "Smooth-Cast 385" mineral-filled polyurethane.
Peace,
Tom E
What I did was make a "master" part (an exact model of the final shape) to the proper size and geometry required out of common paraffin wax: easy to work and inexpensive. Make a mistake? Melt it and start over! I then sunk the finished wax part into a bath of plaster to make the mold. After finishing the plaster mold and painting it, I then poured polyurthane. Result: a plastic casting with the exact geometry required (I did NOT mold the speaker opening or mounting holes--those need to be machined), including a very large, smooth radius that joins the four walls of the enclosure to the fronts of the drivers without any edges or corners. Polyurethane is not cheap, but you need only a gallon to make your smallish baffles. Mine are quite large and an inch thick, and I needed only 2/3 gallon each. I got my poly casting materials from Smooth-On. They have a large selection of poly and epoxy grades. I used "Smooth-Cast 385" mineral-filled polyurethane.
Peace,
Tom E
hmmm. that does sound perfect, I'm almost embarrassed I didn't think of it myself. I think we might even have some plaster around here, from making other molds. Do you need to coat the plaster with oil or anything to keep the polyurethane from sticking to the mold? I was trying to figure out exactly how I could machine the baffle to match the curve from the ceramic enclosure... I was just figuring on a lot of elbow grease... It would be quite simple to make the positive mold out of clay on the wheel. How hard is it to sand the "Smooth-Cast 385"? It still seems like a good idea to make the baffle 1/8" or so too big and then sand it to fit. How was it to cut out the driver hole? You mentioned you used 2/3 of a gallon per baffle. How large was your baffle? I imagine I could get away with a single gallon. Lastly how did you glue these to the rest of the enclosure? Sorry, lots of questions...
thanks
Joe
Hi Joe,
Sorry if I've contributed to you being led around to lots of different options, but after I posted the polyurethane option (post #16) back in February, and the discussion continued in other directions, I didn't get the sense that it was what you were looking for. Perhaps the sand-filled option confused matters.
Few
Any polyurethane mold requires a mold release. Smooth-On sells a compound which is very effective and does not affect the final casting, other than that it should be washed off thoroughly (or sanded off) before painting.
The poly sands very easily--like a soft wood or any other plastic. The poly can be tinted to achieve color through the material. It's costly, but it works very well.
Making the model on the wheel is a good idea. I think making the mold on the wheel might prove difficult, but since you're skilled at throwing you could give it a try. Plaster works well because it's easily modified by sanding or adding more plaster or even joint compound. Make a wooden box or use a small container, fill it with plaster, and set the model into it. I coated my wax model with cooking shortening so it would release cleanly. I had just a couple spots and some minor porosity to repair
The poly will not shrink at all during cure, so you can cast very close to net shape. I used a jigsaw with a standard wood cutting blade to cut the driver openings. I used a router with a standard carbide bit to countersink the drivers. Cuts like butter, but makes a mess.
My baffle is big enough to hold two four-inch mids and a tweeter with a four inch flange. It is 14 inches tall by 10 inches wide, one inch thick. It weighs about five pounds.
I attached the baffle to the rest of the enclosure by bolting through a wooden flange into holes threaded into the poly. Rather complicated to descibe, fairly simple to execute. Since bolting to ceramic is a no-no, you could try gluing with epoxy if you rough up the poly to give the epoxy a "hook" to grab onto. The joint would probably be as strong as the ceramic.
Next question....
Peace,
Tom E
The poly sands very easily--like a soft wood or any other plastic. The poly can be tinted to achieve color through the material. It's costly, but it works very well.
Making the model on the wheel is a good idea. I think making the mold on the wheel might prove difficult, but since you're skilled at throwing you could give it a try. Plaster works well because it's easily modified by sanding or adding more plaster or even joint compound. Make a wooden box or use a small container, fill it with plaster, and set the model into it. I coated my wax model with cooking shortening so it would release cleanly. I had just a couple spots and some minor porosity to repair
The poly will not shrink at all during cure, so you can cast very close to net shape. I used a jigsaw with a standard wood cutting blade to cut the driver openings. I used a router with a standard carbide bit to countersink the drivers. Cuts like butter, but makes a mess.
My baffle is big enough to hold two four-inch mids and a tweeter with a four inch flange. It is 14 inches tall by 10 inches wide, one inch thick. It weighs about five pounds.
I attached the baffle to the rest of the enclosure by bolting through a wooden flange into holes threaded into the poly. Rather complicated to descibe, fairly simple to execute. Since bolting to ceramic is a no-no, you could try gluing with epoxy if you rough up the poly to give the epoxy a "hook" to grab onto. The joint would probably be as strong as the ceramic.
Next question....
Peace,
Tom E
On second though about attempting to machine ceramic for direct-mounting of drivers -
Madisonears: "Anyone who has worked with ceramic knows that the material has very high compression strength but has very little strength in shear. Pressing equally on both sides is allowed, pressing on only one side, even a little, is not. Bolting directly to ceramic or through holes molded in ceramic is a bad idea. Any force generated on the bolts will put the cermic into shear, and it will inevitably, eventually, break."
This is probably why ceramic automotive engines haven't been mass produced. They can't be conventionally machined and they are prone to catastrophic failure, ie., breaking to bits. I withdraw my machine-direct-mount brainstorm! Driver, then a transition baffle machined from one of the materials proposed here, then fastened in a manner that applies clamping force but avoids shear forces like bolts.
Madisonears: "Anyone who has worked with ceramic knows that the material has very high compression strength but has very little strength in shear. Pressing equally on both sides is allowed, pressing on only one side, even a little, is not. Bolting directly to ceramic or through holes molded in ceramic is a bad idea. Any force generated on the bolts will put the cermic into shear, and it will inevitably, eventually, break."
This is probably why ceramic automotive engines haven't been mass produced. They can't be conventionally machined and they are prone to catastrophic failure, ie., breaking to bits. I withdraw my machine-direct-mount brainstorm! Driver, then a transition baffle machined from one of the materials proposed here, then fastened in a manner that applies clamping force but avoids shear forces like bolts.
Lower Q in Thrown Enclosures
Planet10 Dave,
Gotta quote for context -
Originally Posted by paulfx
"knuckle-knocking sounds changed from a single note to a more pink, wider frequency sound"
Planet10 asked
"It goes from the single note, to the wider with the addition of the lead? (ie hi Q to low Q)... what happens to the frequency?
dave"
It stayed the same! This was counter-intuitive for me. I did one enclosure first to compare. Each staggered-area panel was about the same f from lead to no-lead. At the time I was trying for a Dynamat from Hell. While Dynamat works great on metal panels and thinner MDF, on thicker HDF it didn't seem to make a difference, maybe because its mass is too small to act on massive enclosure walls. Back to direct topic, both dynamat and lead tiles should stick much better to the inside of a ceramic enclosure than a wood fiber one. I had to use Gorilla glue over a wetted HDF surface as a sealer in order to make the damping material stick. Silicone based ashesive likes the lead, and it's made for ceramic tile, it would like this enclosure as well.
Planet10 Dave,
Gotta quote for context -
Originally Posted by paulfx
"knuckle-knocking sounds changed from a single note to a more pink, wider frequency sound"
Planet10 asked
"It goes from the single note, to the wider with the addition of the lead? (ie hi Q to low Q)... what happens to the frequency?
dave"
It stayed the same! This was counter-intuitive for me. I did one enclosure first to compare. Each staggered-area panel was about the same f from lead to no-lead. At the time I was trying for a Dynamat from Hell. While Dynamat works great on metal panels and thinner MDF, on thicker HDF it didn't seem to make a difference, maybe because its mass is too small to act on massive enclosure walls. Back to direct topic, both dynamat and lead tiles should stick much better to the inside of a ceramic enclosure than a wood fiber one. I had to use Gorilla glue over a wetted HDF surface as a sealer in order to make the damping material stick. Silicone based ashesive likes the lead, and it's made for ceramic tile, it would like this enclosure as well.
Few, you certainly don't have anything to apologize for. I've really appreciated your contributions. It's just taken me a while to wrap my head around all the posiblities. I think I also misread your post and thought that you were suggesting the polyurethane as an option for coating the inside of the enclosure to reduce the resonance of the enclosure. Either way I didn't have my head in the right place... no worries.
The sand polyurethane mix sounds interesting. I would think you could really destroy some router bits and saw blades trying to cut it after words though?
I'll probably attach a circular piece of wood to my wheel so I can remove it after throwing (I do the same thing throwing plates since you can't pick up a plate with out deforming it after it's thrown). Usually then we build up a wall around the positive using metal flashing and clay. Then mix the plaster in a bucket and pour it over the positive mold. I imagine that's what we'll do here. The bottom of the plaster mold is never flat but that's not really the side that matters any way.
Thanks for all the info. I'll look into epoxies, not something I really know anything about. Shouldn't be too hard to find a good epoxy for plastic/ceramic joints.
We just had our friends over to discuss the up coming firing. Sounds like we'll start loading the kiln April 5th. Time for round 2! Thanks everyone for all the great suggestions.
Joe
That the frequency did go down is not what i'd expect.
From your description of the sound, you have moved from a hiQ resonance to a lower, more audible resonance.
dave
You sure got that right! I wouldn't try to machine the polyurethane if it has sand in it. I was envisioning an approach that wouldn't require any machining.
The idea I had in mind was to pour the polyurethane directly into the ceramic enclosure rather than make a mold. You'd be guaranteed a perfect baffle-to-enclosure fit, and the polyurethane sticks very well to many surfaces so there would be no need for epoxy. Conveniently, the polyurethane doesn't stick at all to some materials, so it would be easy to fabricate a speaker-shaped plug that would reserve a built-in pocket for your driver when everything hardens up. That would eliminate the need for machining the baffle. I'm envisioning pouring the polyurethane into the enclosure with the enclosure sitting baffle-down on a smooth surface. This approach would require an opening at the non-baffle-end of the enclosure so you have a way to pour in the polyurethane. You'd also need to seal the baffle end to the supporting surface so the polyurethane won't leak out before it hardens, but that wouldn't be too tough.
The polyurethane matches the shape of whatever you pour it into down to the finest detail, and since I've had no trouble molding it in cheap plastic cups, I'm confident it wouldn't introduce too much stress into your ceramic enclosure while it hardens.
Few
Hagia Sophia and the Ceramic Speaker
I was watching a show on TLC, I think, and they were looking at the earthquake resistance and survival of this ancient church in Instanbul. The mortar contains elongated particles of brick dust which helps damp resonant movement during an earthquake. One could experiment with simple test boxes made of clay mixed with ground brick and other fired ceramic bits to see which one is deadest after the kiln.
Is particulate mixing done in the pottery world?
Are there any sands or fragments that are known to be differently dense than clay and can be fired after shaping along with the clay?
I was watching a show on TLC, I think, and they were looking at the earthquake resistance and survival of this ancient church in Instanbul. The mortar contains elongated particles of brick dust which helps damp resonant movement during an earthquake. One could experiment with simple test boxes made of clay mixed with ground brick and other fired ceramic bits to see which one is deadest after the kiln.
Is particulate mixing done in the pottery world?
Are there any sands or fragments that are known to be differently dense than clay and can be fired after shaping along with the clay?
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I have to say I never would have thought of that. That would certainly save you from having to make a mold for the casting. Unfortunately the way I'm making them with the baffle on the wheel head it would be difficult to get the last of the round over with out adding a baffle. Certainly possible though.... It will take me a while to wrap my head around how to make that idea work. Maybe for a future version. I've already started the second round which will require a added baffle(I would post a picture, but they look almost exactly like the last round).
Our clay contains 8% ground brick particles. I mentioned in the beginning of the thread that our clay does not ring like commercial porcelain, this is certainly one of the reasons why.
Joe
So For a Cole-Madisonears Enclosure
I could have my niece throw and fire an enclosure with a resonably flat 1" internal lip around inside of the baffle opening. Then I'd carve a baffle out of parafin wax that fits snug maybe a quarter inch back into that baffle opening, and is maybe 3" deep with a nice anti-diffractive curve in the front. I'd be too afraid of casting voids to do the driver cutouts. But it would start as the baffle of my dreams, in wax, if I'm correct.
Then I'd dip this thing in coats of plaster and let it dry. Drill holes in the top and bottom, melt and drain away the wax without setting fire to the house, and let it cool. This is the lost-wax process, right?
Spray in some Pam, pour in the mineralized polyurethane. Oh wait, plug the hole in the bottom. Could I just break the plaster after it cures?
Drill holes in the beautiful molded-and-sanded baffle for the drivers and also for the recessed screws that will go 4" or so into nuts on the plywood flange ring I put inside the internal ceramic lip. Apply the temporary sealer, tighten evenly and we are clamping, not shearing!
Before she throws the enclosures I give her a template baffle wax piece maybe 15% bigger to offset clay shrinkage and help her size the opening lip. Then I cast the baffle.
It sure would be different, and would solve a bunch of problems at once.
I could have my niece throw and fire an enclosure with a resonably flat 1" internal lip around inside of the baffle opening. Then I'd carve a baffle out of parafin wax that fits snug maybe a quarter inch back into that baffle opening, and is maybe 3" deep with a nice anti-diffractive curve in the front. I'd be too afraid of casting voids to do the driver cutouts. But it would start as the baffle of my dreams, in wax, if I'm correct.
Then I'd dip this thing in coats of plaster and let it dry. Drill holes in the top and bottom, melt and drain away the wax without setting fire to the house, and let it cool. This is the lost-wax process, right?
Spray in some Pam, pour in the mineralized polyurethane. Oh wait, plug the hole in the bottom. Could I just break the plaster after it cures?
Drill holes in the beautiful molded-and-sanded baffle for the drivers and also for the recessed screws that will go 4" or so into nuts on the plywood flange ring I put inside the internal ceramic lip. Apply the temporary sealer, tighten evenly and we are clamping, not shearing!
Before she throws the enclosures I give her a template baffle wax piece maybe 15% bigger to offset clay shrinkage and help her size the opening lip. Then I cast the baffle.
It sure would be different, and would solve a bunch of problems at once.
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