Would it be any good to make a speaker out of concrete? Since it can be poured into a moulding, you could make complicated horn designs more easily. Its certainly very dense which is a good property I believe? Of course problems would occure trying to make anything other than small bookshelf type speakers due to weight, but for those smaller speakers it might be worth a try.
My idea for moulding one isn't fully formed, but could go a little like this. Mould the open horn space out of plaster of paris (sp?) using hands and hand tools (probably a better way). Once set, fix to a wooden framework. Pour in concrete around it. Hopefully the plaster comes away from the set concrete easily (vaseline the plaster?), leaving the horn passage/mouth etc. Turn over to pour the other side panel. The front and back would just be wood, fixed with wall plugs and screws.
I see potential difficulty in removing the plaster mould since if it isn't symmetrical it will become wedged. It is possible to do 3D type moulds I would think by casting half at a time. Any thoughts?
My idea for moulding one isn't fully formed, but could go a little like this. Mould the open horn space out of plaster of paris (sp?) using hands and hand tools (probably a better way). Once set, fix to a wooden framework. Pour in concrete around it. Hopefully the plaster comes away from the set concrete easily (vaseline the plaster?), leaving the horn passage/mouth etc. Turn over to pour the other side panel. The front and back would just be wood, fixed with wall plugs and screws.
I see potential difficulty in removing the plaster mould since if it isn't symmetrical it will become wedged. It is possible to do 3D type moulds I would think by casting half at a time. Any thoughts?
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Hi
I have previously built concrete speakers. My current speakers use a midrange enclosure made of concrete/corian.
My experience has shown that the rigidity that concrete offers is only necessary for the mid range unit. I found that a rigid wood cabinet sounded as good as a concrete cabinet for the base enclosure. I have read similar comments from others.
My last speakers were made from Corian as I found it easier to work and did not need a finish added as the Corian could be polished.
I hope this helps
on
I have previously built concrete speakers. My current speakers use a midrange enclosure made of concrete/corian.
My experience has shown that the rigidity that concrete offers is only necessary for the mid range unit. I found that a rigid wood cabinet sounded as good as a concrete cabinet for the base enclosure. I have read similar comments from others.
My last speakers were made from Corian as I found it easier to work and did not need a finish added as the Corian could be polished.
I hope this helps
on
Thanks. I actually thought it might be easier to use was my main reasoning with it, me not being experienced with wood shaping or having the tools.
It would probably be a full range, but I'm not sure as it'll need to be big to get a good bass and then it'll likely be too heavy.
Is your midrange a spherical shape, like on B&W 800?
I assume concrete is quite cheap too? Not sure about corian, looks better but harder to get and more expensive?
It would probably be a full range, but I'm not sure as it'll need to be big to get a good bass and then it'll likely be too heavy.
Is your midrange a spherical shape, like on B&W 800?
I assume concrete is quite cheap too? Not sure about corian, looks better but harder to get and more expensive?
Sorry to double post, I don't see edit feature. Anyhow, i'm lloking at these:
http://www.spnet.ne.jp/~hasehiro/product/backroadhorn.html
(babelfish will give some degree of translation). They are complicated horns, but could be moulded from concrete relatively easily (possibly...).
Some things I find interesting are that the smaller models (like I want to attempt) use the Fostex FE87E; a driver that I thought had too high a Qts for rear horn loading
. I thought between 0.2-0.3 were the only suitable values? The FE87E is 0.92 . Presumably it works though, they arn't cheap on that site (£115 for the smallest one).
Also it suggests similar replacement drivers. Does this mean it is a fairly non-critical design since it will readily accept drivers with differing parameters? I'm hoping so since I may be able to do one if thats the case . I'm not sure about dimensions. It appears, and the translated text suggests, that the initial folded section is straight and does not expand at all, but that doesn't seem right. Is it an exponential horn of sorts?
http://www.spnet.ne.jp/~hasehiro/product/backroadhorn.html
(babelfish will give some degree of translation). They are complicated horns, but could be moulded from concrete relatively easily (possibly...).
Some things I find interesting are that the smaller models (like I want to attempt) use the Fostex FE87E; a driver that I thought had too high a Qts for rear horn loading
. I thought between 0.2-0.3 were the only suitable values? The FE87E is 0.92 . Presumably it works though, they arn't cheap on that site (£115 for the smallest one). Also it suggests similar replacement drivers. Does this mean it is a fairly non-critical design since it will readily accept drivers with differing parameters? I'm hoping so since I may be able to do one if thats the case
. I'm not sure about dimensions. It appears, and the translated text suggests, that the initial folded section is straight and does not expand at all, but that doesn't seem right. Is it an exponential horn of sorts?
A friend of mine was building concrete enclosures in the 70's. They were full sized floor standing units, and sold commercially.
The problems he had to overcome:
Weight: Mix in some polystyrene beads. The mix is still inert.
Failure rate: The mould must be placed on a vibrator to allow the mix to reach into the corners.
Finish: Gluing veneer to the mix, the glue must bond well, without dissolving the polystyrene. I forget what was used. He did consult with BASF and 3 M.
Is it worth it. You bet. Soncally better. Cheaper to produce, once the buggs are sorted out.
Have fun,
Geoff
The problems he had to overcome:
Weight: Mix in some polystyrene beads. The mix is still inert.
Failure rate: The mould must be placed on a vibrator to allow the mix to reach into the corners.
Finish: Gluing veneer to the mix, the glue must bond well, without dissolving the polystyrene. I forget what was used. He did consult with BASF and 3 M.
Is it worth it. You bet. Soncally better. Cheaper to produce, once the buggs are sorted out.
Have fun,
Geoff
Cool, thanks for that . I expect i'll be making small enough speakers to not require polystyrene beads, but thats a neat trick. Well, I might need some, depends on the design I end up with.
Didn't even consider about the vibrating mould. To implement it I can use some motors I have around fixed with off centre weights, should do the trick. Presumably just sit the mould with the wet concrete on that for a few minutes to get it into all the corners? Possibly more will need to be added whilst this happens as the level would be expected to drop.
Hadn't thought as far ahead as finish, i'm mostly persuing a project for my own interest, but i'll be sure to be careful if I do veneer it.
For designs, i'm looking at the fostex reccomended enclosures. In particular the FE87E and FE103E (they are cheaper drivers ). They are clearly designed for simple construction. My plan would be to hopefully improve it when making them from concrete by smoothing everything. I mean rounding the corners and making continuous changes (thier designs suddenly change from say 25mm diameter to 35mm, I could have it changing continuously which I believe is better ).
If it is made to change continuously, how do I calculate it? It isn't linear is it, it's exponential? IE, if it changed from 25mm to 35mm over a 20cm course, it wouldn't ideally be 30mm at 10cm right?
I've also had more thinking on the moulding. I hope to be able to make it from thick cardboard stacked up the edged with thinner bendable card. It would certainly be easy to work with. A really nice plan would be to make a straight horn out of a material which can then be folded and drawn around as a template since that would make things easier/more ideal. Don't know of any such material unfortunately so it'll be compasses and pencils
. I expect i'll be making small enough speakers to not require polystyrene beads, but thats a neat trick. Well, I might need some, depends on the design I end up with. Didn't even consider about the vibrating mould. To implement it I can use some motors I have around fixed with off centre weights, should do the trick. Presumably just sit the mould with the wet concrete on that for a few minutes to get it into all the corners? Possibly more will need to be added whilst this happens as the level would be expected to drop.
Hadn't thought as far ahead as finish, i'm mostly persuing a project for my own interest, but i'll be sure to be careful if I do veneer it.
For designs, i'm looking at the fostex reccomended enclosures. In particular the FE87E and FE103E (they are cheaper drivers
). They are clearly designed for simple construction. My plan would be to hopefully improve it when making them from concrete by smoothing everything. I mean rounding the corners and making continuous changes (thier designs suddenly change from say 25mm diameter to 35mm, I could have it changing continuously which I believe is better ). If it is made to change continuously, how do I calculate it? It isn't linear is it, it's exponential? IE, if it changed from 25mm to 35mm over a 20cm course, it wouldn't ideally be 30mm at 10cm right?
I've also had more thinking on the moulding. I hope to be able to make it from thick cardboard stacked up the edged with thinner bendable card. It would certainly be easy to work with. A really nice plan would be to make a straight horn out of a material which can then be folded and drawn around as a template since that would make things easier/more ideal. Don't know of any such material unfortunately so it'll be compasses and pencils
I once read an article where a guy described a few versions he went trough when building his concrete boxes. He settle for concrete mixed with foam strips cut from those long sponge floaty things you get in swimmingpools...
I thought about trying to make a cube, and put a ball in the centre, then fill the cube, with neccesary precaution, like wide tube stuck to top of ball to keep speaker opening..., when the conrete sets you just need to pop a hole in the ball and remove it....
I thought about trying to make a cube, and put a ball in the centre, then fill the cube, with neccesary precaution, like wide tube stuck to top of ball to keep speaker opening..., when the conrete sets you just need to pop a hole in the ball and remove it....
Hi again. I'm thinking about this more now but need some more guidance. Basically I want to make the Fostex FE87E design rear loaded horn but as a real smooth horn rather than a more crude, easily constructed, type.
I'm wondering firstly if that will have much impact and also how is best to approach it. Would I simply find the lengths of all the passages and curve each one or would it be better to say the throat starts at X mm wide and ends at X size mouth, with a length of X, then apply a function to define the best curvature.
http://www.fostexinternational.com/docs/speaker_comp/pdf/recom_enclose/87e_encl.pdf
Think I know how to go about the casting now, I've thought that all through pretty much. I will probably make an enclosure/cast first before buying drivers anyhow just to see if it does work properly.
I'm wondering firstly if that will have much impact
and also how is best to approach it. Would I simply find the lengths of all the passages and curve each one or would it be better to say the throat starts at X mm wide and ends at X size mouth, with a length of X, then apply a function to define the best curvature. http://www.fostexinternational.com/docs/speaker_comp/pdf/recom_enclose/87e_encl.pdf
Think I know how to go about the casting now, I've thought that all through pretty much. I will probably make an enclosure/cast first before buying drivers anyhow just to see if it does work properly.
Geoff H said:
Very interesting indeed!
I'm working on concrete speakers myself, and appreciate the help.
One trick that I've had good luck with (using jewler's investment, which is essentially super-quick-setting brittle, crumbly concrete) is putting the mould in a vaccum chamber. The action of the pump both vibrates it (it was on the same table) and pulls out the air bubbles.
I
I have built concrete horns in the past....well only the bends were moulded, and still quite heavy
Actually I dont think it was concrete.... it was I think a mix of plaster and cement only without any sand....very strong mix
Where have I seen a horn where the inside was moulded like fingers inside each other...I think it was a Japanese
Today I guess I would use something foamy stuff
Actually I dont think it was concrete.... it was I think a mix of plaster and cement only without any sand....very strong mix
Where have I seen a horn where the inside was moulded like fingers inside each other...I think it was a Japanese
Today I guess I would use something foamy stuff
concrete speakers
Hi All,
I built concrete speakers while ago. They where MTM satelite and woofer combination (two boxes for each speaker). I made molds for the panels and used steel mesh for reinfrcement (I guess it is called chicken fence in US). So what I've got was very real enforced concrete panels. Than I joined panels and pouted concrete in joints. I believe panels were around 1cm thick.
My major reasoning for building concrete speakers was exactly the same as mentioned in other posts: lack of woodworking tools and cheapness.
Result: MTM enclosure was great. As far as woofer enclosure is concerned, panels were vibrating at moderate levels of playback (although I added kind of bracing inside the box). I could not increase the thickness of the walls because speaker was already very heavy. Construction process itself is messy.
I made the current pair of my speakers from MDF and Plywood, Not having any previous woodworking experience. But I invested in tools and took it slow. Now there is no doubt in my mind that wood and its derivatives is the best material for constructing the enclosures. There is no gain financially and technologically to use concrete for enclosures. Been thee, seen that
Hi All,
I built concrete speakers while ago. They where MTM satelite and woofer combination (two boxes for each speaker). I made molds for the panels and used steel mesh for reinfrcement (I guess it is called chicken fence in US). So what I've got was very real enforced concrete panels. Than I joined panels and pouted concrete in joints. I believe panels were around 1cm thick.
My major reasoning for building concrete speakers was exactly the same as mentioned in other posts: lack of woodworking tools and cheapness.
Result: MTM enclosure was great. As far as woofer enclosure is concerned, panels were vibrating at moderate levels of playback (although I added kind of bracing inside the box). I could not increase the thickness of the walls because speaker was already very heavy. Construction process itself is messy.
I made the current pair of my speakers from MDF and Plywood, Not having any previous woodworking experience. But I invested in tools and took it slow. Now there is no doubt in my mind that wood and its derivatives is the best material for constructing the enclosures. There is no gain financially and technologically to use concrete for enclosures. Been thee, seen that
I make concrete yard furniture and decorations. To make intricate sections of molds I use sheets of styrofoam insualtion glued together. You can use a hot knife or hotwire to cut it. I also have a dremel power toll that I use for carving and shaping.
I use foam to create molds for sinks that I cast into the concrete countertops. The foam molds get hacked apart to get them out.
There are some good books out on concrete countertops (Fu Cheng and Buddy Rhodes) and I would be inclined to use the same type of mixes for speakers. You can also get low density aggregates to reduce the weight as well.
Why cover up concrete with a veneer? You could seed the mix with some nice aggregates (coloured fish tank stones) plus you can colour concrete just about any colour you can think of. Plus with some diamond grinding pads and water, you can make the thing shine like polished marble.
I use foam to create molds for sinks that I cast into the concrete countertops. The foam molds get hacked apart to get them out.
There are some good books out on concrete countertops (Fu Cheng and Buddy Rhodes) and I would be inclined to use the same type of mixes for speakers. You can also get low density aggregates to reduce the weight as well.
Why cover up concrete with a veneer? You could seed the mix with some nice aggregates (coloured fish tank stones) plus you can colour concrete just about any colour you can think of. Plus with some diamond grinding pads and water, you can make the thing shine like polished marble.
From what I've read in books, concrete is better then any kind of wood, because is has better damping, probably due to hi density (2,7 tones/cubic m compared to 0,8 for wood) and the fact that it resists very well to compression and it doesn't tolerate elongation - in the sens that it will crack. Besides these "natural" advantages concrete can take any shape - which is very important because not all the shapes have the same resistances. A curved (rounded) one is better then a flat one, and if it has a second bending is has the best resistance as a structure - for example an egg, a sphere, a mouse (with computers).. so not just a bended surface. Another big advantage is that you only have one piece, not 6 like in a normal box, or 10-20 for a horn design; this is also very helpful for the overall resistance of the structure.
Another very important thing to understand is that there is no standard concrete, you can play with the recipe. For instance, I would recommend a 50% powder mixed with 50% 3-5 mm pieces of stone. Don't forget about curring!
However, I can't say that I'm an expert, but I am listening music in the last 6 month on speakers built from a similar material, and I'm telling you that from now on I'm betting on concrete.
However, concrete isn't light and in case you want something bigger you might end up with something for the real estate market. But don't give up... I thought (because I'm at the drawing board now for my greatest project so far) at something else, something that would still have that stone like substance - glass - why not! But don't think about it like putting your drivers in an aquarium, that's not a good idea. You would have to cover both sides with something, on the interior something thin, less important, and on the exterior you could stick the whole piece to another piece off glass with the same size or a one made off wood. The multi-layer solution is pretty good to. You can make even more complicated sandwiches .. again, there is no standard solution.
Thew glass, however, is not going to give you complicated shapes... unless you know how and have where to build a horn shaped piece off glass.
Another very important thing to understand is that there is no standard concrete, you can play with the recipe. For instance, I would recommend a 50% powder mixed with 50% 3-5 mm pieces of stone. Don't forget about curring!
However, I can't say that I'm an expert, but I am listening music in the last 6 month on speakers built from a similar material, and I'm telling you that from now on I'm betting on concrete.
However, concrete isn't light and in case you want something bigger you might end up with something for the real estate market. But don't give up... I thought (because I'm at the drawing board now for my greatest project so far) at something else, something that would still have that stone like substance - glass - why not! But don't think about it like putting your drivers in an aquarium, that's not a good idea. You would have to cover both sides with something, on the interior something thin, less important, and on the exterior you could stick the whole piece to another piece off glass with the same size or a one made off wood. The multi-layer solution is pretty good to. You can make even more complicated sandwiches .. again, there is no standard solution.
Thew glass, however, is not going to give you complicated shapes... unless you know how and have where to build a horn shaped piece off glass.
Hi
The reason that I built seperate mid/treble and base enclosures is that concrete can not tension - although it is very strong in compression.
To overcome the inability of concrete to take tension that part of the concrete that will be in tension is reinforced by steel bars or mesh. The treble / mid enclosure that I built was a forward leaning pyramid with all flat faces that could be reinforced by steel mesh. The base unit was a rectangle that was deeper from front to back at the base. Again all flat faces that could be reinforced. In both cabinets tha mesh was wrapped around the corners and into the adjacent side.
You can build any shape out of concrete. However it does need to be reinforced to aviod eventual cracking. Steel mesh is easy to buy and can be bent around curves. Adding polystyrene to concrete seems to make it accept tension but it is an illusion as it actually makes the concrete weaker.
When pouring concrete into a mould I normally grease the mould with car grease.
Don
The reason that I built seperate mid/treble and base enclosures is that concrete can not tension - although it is very strong in compression.
To overcome the inability of concrete to take tension that part of the concrete that will be in tension is reinforced by steel bars or mesh. The treble / mid enclosure that I built was a forward leaning pyramid with all flat faces that could be reinforced by steel mesh. The base unit was a rectangle that was deeper from front to back at the base. Again all flat faces that could be reinforced. In both cabinets tha mesh was wrapped around the corners and into the adjacent side.
You can build any shape out of concrete. However it does need to be reinforced to aviod eventual cracking. Steel mesh is easy to buy and can be bent around curves. Adding polystyrene to concrete seems to make it accept tension but it is an illusion as it actually makes the concrete weaker.
When pouring concrete into a mould I normally grease the mould with car grease.
Don
Concrete loudspeaker enclosure
Ah, memories!
I remember, back in the 60's, having a little grey and black booklet of loudspeaker enclosure designs (sorry the title and publisher escape me!). It contained details for a concrete horn enclosure, driven by Lowther PM6 unit. Designed to be constructed in the recesses each side of a standard chimney breast, basically it was and "unwrapped" version of Lowther's folder corner horn cabinet. The design used a cardboard template fixed to wall batterns to give the horn shape, to which nails and a wire mesh were applied as a key for the cement. The throat was approximately 5 feet from the ground. The rear horn gradually expanded to the first of two bends near the ceiling, before the horn returned to ground level and a triangular mouth in the corner - all 8 feet of it. I built these, but used common house bricks, plastered to key in with the chimney breast. Sound emenating from the front of the PM2 unit was deflected into the room using a piece of corrugated plastic roofing material.
How did they sound? Very Good! But to be honest, not worth all of the effort! Maybe they sounded better in the neighbours lounge - I did build them on the shared party wall!
Subsequently I built the traditional wooden Lowther corner units (much easier build) which were enjoyed for several years!
cambshiregordon
Ah, memories!
I remember, back in the 60's, having a little grey and black booklet of loudspeaker enclosure designs (sorry the title and publisher escape me!). It contained details for a concrete horn enclosure, driven by Lowther PM6 unit. Designed to be constructed in the recesses each side of a standard chimney breast, basically it was and "unwrapped" version of Lowther's folder corner horn cabinet. The design used a cardboard template fixed to wall batterns to give the horn shape, to which nails and a wire mesh were applied as a key for the cement. The throat was approximately 5 feet from the ground. The rear horn gradually expanded to the first of two bends near the ceiling, before the horn returned to ground level and a triangular mouth in the corner - all 8 feet of it. I built these, but used common house bricks, plastered to key in with the chimney breast. Sound emenating from the front of the PM2 unit was deflected into the room using a piece of corrugated plastic roofing material.
How did they sound? Very Good! But to be honest, not worth all of the effort! Maybe they sounded better in the neighbours lounge - I did build them on the shared party wall!
Subsequently I built the traditional wooden Lowther corner units (much easier build) which were enjoyed for several years!
cambshiregordon
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