I am guessing that is a labour of belief rather than a labour of fruition.
I am also known to have been worng. 😉
I am also known to have been worng. 😉
No air leaks on mine there friend. As mentioned a few posts ago, The pressure on either side of each spiral wall is not very different. I fix the foam core by spot adhering with hot glue and then caulk as I go along. That's for the front.
For the rear, the two step process of adding glue to the spiral, then a layer of paper strips before adding a second layer of glue ensures there is no leakage at the back panel.
I think you might be the only one to use the PVA and plaster route. It does seem a bit extravagant for what the result might be. You realize the larger horn of mine has 44 ft of spiral IIRC.
On top of that, when would you apply it? If you do it ahead of time, I think it might be damaged when bending the spirals, and very difficult to apply if done after.
Unless you are referring to only the driver chamber and it that case, I would just glue two pieces of foam board together.
By golly you're right. I don't see it in the catalogue before 1989. I honestly thought it was older than that.
Seems that 1993 was the last year. For such a well regarded driver, I find that surprising.
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There’s a guy who took a different approach, using a router guide and a former. It does seem more labor-intensive than the foam method, in my opinion.
https://muzzargh.blogspot.com/?view=classic&m=1
https://muzzargh.blogspot.com/?view=classic&m=1
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great idea to insure a good seal. I have not built a cornucopya yet as I am away from home in Nova Scotia with my daughter and two grandchildren and I won't get home to Calgary till the end of October. the amount of additional panel stiffness could be established by a deflection test on a small section and comparing to untreated foam core. As I said I am unsure if it would help with the sound or not but it is a way to increase the panel stiffness.
Remember, some who've built foam core speakers report disappointment when duplicating in wood. Just because stiffness = better is intuitive, may not work out that way in practice. Or it could be due to some "ear training" phenomena acquired when listening to the foam core models first and for some time. Just a heads up about that ;')
The only time I listened to the real thing was many moons ago in a sofa laden jazz bar kinda place with canned music. I asked the guy behind the bar where the woofer was. He smiled and said there wasn't one. I asked again. He basically said you are free to ask again but if you don't believe me, just over your left shoulder is the door.
I began my research and quit when I saw what it would take even if I didn't router and use bendy ply.
XRK is our saviour. I admit to having doubts. Then I thought about it and said, I am a fool not to try.
My name is Cal and I am a speakerholic.
I began my research and quit when I saw what it would take even if I didn't router and use bendy ply.
XRK is our saviour. I admit to having doubts. Then I thought about it and said, I am a fool not to try.
My name is Cal and I am a speakerholic.
I agree but for the curious there is one way to find out for sure.
So... I found some foam that might work @ Michaels... Only in Canada...24 in X 60 in X 4mm !!? They have 6mm as well...
Also foam board for the enclosure. Does this look like the right stuff?
I have yet to go to Dollarama, at least if this is ok I will know what to look for 🤓
Were you thinking of EVA foam for the curved inner wall? Best to use paper face foam core because it has structural stiffness. Score lines to make it bend.
The premium foam core uses thick smooth paper stock almost like cardboard. Elmer’s brand is $5/sheet but worth it. The speakers are more durable and look nicer. Also comes in multiple colors.
The dollar store stuff is very thin by contrast and may delaminate from humidity in a few years.
The premium foam core uses thick smooth paper stock almost like cardboard. Elmer’s brand is $5/sheet but worth it. The speakers are more durable and look nicer. Also comes in multiple colors.
The dollar store stuff is very thin by contrast and may delaminate from humidity in a few years.
in another life I built concept models for buildings out of fome-core. great stuff. hard on Xacto blades. dangerous on fingers when you combine the two.
i used the 1/4" stuff since the models tended to be larger scale and rough. my brother built fancier "show" models that sometimes used thinner 1/8" material that was more plastic than paper.
one thing about scoring for the curves that might need to be said (because we're all laughing at "stiffness" jokes)... score the inside (smaller) curve and throw some glue into the scores whilst holding the curve to shape to achieve useful structural strength. the curved walls will still be solid.
you could be "calculating" about the frequency of the cuts such that the correct differences in circumference were created. but since most of the curves are internal less than perfect smoothness of the curves is likely acceptable.
i used the 1/4" stuff since the models tended to be larger scale and rough. my brother built fancier "show" models that sometimes used thinner 1/8" material that was more plastic than paper.
one thing about scoring for the curves that might need to be said (because we're all laughing at "stiffness" jokes)... score the inside (smaller) curve and throw some glue into the scores whilst holding the curve to shape to achieve useful structural strength. the curved walls will still be solid.
you could be "calculating" about the frequency of the cuts such that the correct differences in circumference were created. but since most of the curves are internal less than perfect smoothness of the curves is likely acceptable.
The Cornu spiral is one of my on hold projects, I will start one as soon as possible. I have searched the thread and also the forum, but did not find an STL file for 3Dprinting, so I have started working on a 3D sketch to make the Cornu printable:
It's not tested yet. I will try to test it and make 2 parts design that can be divided in many parts so it can be printed on a regular 22 x 22cm FDM bed printer.
It's not tested yet. I will try to test it and make 2 parts design that can be divided in many parts so it can be printed on a regular 22 x 22cm FDM bed printer.
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I like your ambition but I have to ask what you feel the advantage in 3D printing is?
Also, you seem to show a gap between the edge of the baffle and the spiral. Again, can you help explain what that is for?
That extra bit on the template was there to make layout easy, there is no real gap there, Just a foam core thickness inset to make gluing less cumbersome.
Also, you seem to show a gap between the edge of the baffle and the spiral. Again, can you help explain what that is for?
That extra bit on the template was there to make layout easy, there is no real gap there, Just a foam core thickness inset to make gluing less cumbersome.
What I like about 3D printing is the possibility of reproduction for many DIYers around the globe that may not have the skills (or space) needed to do woodwork, or even foam work. I know that foamboard make this project very accessible to everyone, but even though it does require some manual skills to put it together.
The gap is not there effectively, I have just put a square under the guts of the cornu to make it visible. I have some 1.5" drivers that can be a good test for a "nano cornu", really desktop sized.
But my plans are also expandable for the W5-2143 drivers that I have laying around here in the future.
Basically, my target is fun, and once finalized, share the STL with the community so anyone can use it in any possible way.
The gap is not there effectively, I have just put a square under the guts of the cornu to make it visible. I have some 1.5" drivers that can be a good test for a "nano cornu", really desktop sized.
But my plans are also expandable for the W5-2143 drivers that I have laying around here in the future.
Basically, my target is fun, and once finalized, share the STL with the community so anyone can use it in any possible way.
I have been doing a little experimentation with Cornucopia materials, foam core to be specific. I went to some dollar stores and found three different types of foam core though I am sure there are more. My interest in this experiment stems from a few comments about Conucopia stiffness and also because I also want to build some DML loudspeakers and would like to use a thin foam and the art foam core foam looks to be a possible choice. My preference would be an EPS foam (expanded polystyrene foam) and foam core art board is an XPS (extruded polystyrene foam) but it is the general thickness I was looking for and I wanted to establish its density and structural stiffness. Local availability is a big bonus too.
I purchased some typical thickness foam core board in both white and in black and a thinner white board which is the thinnest core I have found which is sold as a "dry eraser" board. This last foam core board has a pair of thin paper laminate layers probably a third the thickness of the paper thickness found on standard foam core art board. In addition to this it has two different plastic top/outer surface skins on the back and front side of the board. The back plastic skin is a thin semi-gloss film and the front is a thicker high gloss Mylar (polyester) type film.
I cut some samples of each type and soaked them in water over night. I was able to peel off the plastic skins after about four hours of soak and put them back in the water to finish soaking the remaining paper skins. The next day I was able to use my fingers and some running water to roll off the paper layers. All three different foam core boards came clean as a whistle so the adhesive used is water based. All three types of foam core I looked at have a mild surface texture on both sides of the extruded core. The last characteristic while not unexpected did turn out to be a surprise, and that was the degree of difference in the core material stiffness specifically the difference in stiffness between the direction of the extrusion (length) and the width, The black and the white foam core boards of the same thickness seemed identical so far as stiffness went but this change once the paper layers were removed. While the two cores had similar stiffness in the length of the extrusion they had very different stiffness in the opposite direction. The white board was the stiffer overall of the two colours found a Dollarama.
Interestingly the thin core of the "Dry Eraser board" was the stiffest over all and was the sample with the closest stiffness in both directions. Also of interest was the fact that you cannot count on or assume without testing which direction is which on any given board in other words the extruded length in any of the types I tested might be found in the long direction of the board or it might be in the width of the board. This suggests that large cores are extruded and they are then cut into rectangles or squares or rounds etc. so you will need to west a board to know which direction is which.
I hope this may be of interest to some here. I can say that if you want to have the most core strength in a cornucopia you will want to have the extruded direction of the core running in the front to back direction, this will also insure that the most flexibility for bending of the spiral will be in the opposite direction.
I purchased some typical thickness foam core board in both white and in black and a thinner white board which is the thinnest core I have found which is sold as a "dry eraser" board. This last foam core board has a pair of thin paper laminate layers probably a third the thickness of the paper thickness found on standard foam core art board. In addition to this it has two different plastic top/outer surface skins on the back and front side of the board. The back plastic skin is a thin semi-gloss film and the front is a thicker high gloss Mylar (polyester) type film.
I cut some samples of each type and soaked them in water over night. I was able to peel off the plastic skins after about four hours of soak and put them back in the water to finish soaking the remaining paper skins. The next day I was able to use my fingers and some running water to roll off the paper layers. All three different foam core boards came clean as a whistle so the adhesive used is water based. All three types of foam core I looked at have a mild surface texture on both sides of the extruded core. The last characteristic while not unexpected did turn out to be a surprise, and that was the degree of difference in the core material stiffness specifically the difference in stiffness between the direction of the extrusion (length) and the width, The black and the white foam core boards of the same thickness seemed identical so far as stiffness went but this change once the paper layers were removed. While the two cores had similar stiffness in the length of the extrusion they had very different stiffness in the opposite direction. The white board was the stiffer overall of the two colours found a Dollarama.
Interestingly the thin core of the "Dry Eraser board" was the stiffest over all and was the sample with the closest stiffness in both directions. Also of interest was the fact that you cannot count on or assume without testing which direction is which on any given board in other words the extruded length in any of the types I tested might be found in the long direction of the board or it might be in the width of the board. This suggests that large cores are extruded and they are then cut into rectangles or squares or rounds etc. so you will need to west a board to know which direction is which.
I hope this may be of interest to some here. I can say that if you want to have the most core strength in a cornucopia you will want to have the extruded direction of the core running in the front to back direction, this will also insure that the most flexibility for bending of the spiral will be in the opposite direction.