# How would you create a cone/horn shape?



## scottyeyre (Oct 14, 2012)

I saw these speakers online and was instantly blown away by the design and instantly curious how to create a similar shape. for the smaller tweeter receded into a cove.










I can see that the timber has been ripped down the center and joined back together, So perhaps creating the cove shape in 2 parts possibly. If its CNC then it would be simple, Otherwise perhaps its done with a spindle moulder? On the extreme side of things it could be possible to have a custom shape forstner style bit to cut the shape out??? Probably not though.

For now I'm just curious in expanding my knowledge of techniques, as I am a cabinetmaker apprentice in my second year. Im working for a small company that does 90% custom commissioned work using recycled rimu.

The company has a spindle moulder however, can you make custom cutters for them?

Regards
Scott Eyre


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## scottyeyre (Oct 14, 2012)

Perhaps a 2 stage router process using something like this?


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## bbasiaga (Dec 8, 2012)

Given that the grain is no longer straight, could it be that the wood was steam bent over a mold?

-Brian


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## scottyeyre (Oct 14, 2012)

Ahh. good spotting. Could be onto something with that


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## scottyeyre (Oct 14, 2012)

Also if I made a panto-router, a copy carver you could turn the shape on a smaller board, then copy carve it into the speaker tower


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## bondogaposis (Dec 18, 2011)

It could be done on a lathe easily, if you had enough swing clearance.


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## scottyeyre (Oct 14, 2012)

Mount the whole entire board?


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## scottyeyre (Oct 14, 2012)

I guess you could cut it into two parts then align the grain and glue it back together


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## JoeinGa (Nov 26, 2012)

I think the grain is still straight. It's an "optical delusion" because of the cone shape being cut out.
.
Edit ** I also think it looks like it could have been a 4X4 or maybe even a 6X6 that was split in half, then hollowed out. The cone and the recess for the lower speaker was cut into both halves, and reassembled.


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## knotscott (Feb 27, 2009)

Dunno about how to cut the cone, but I can't help wonder what it does to the sound of the tweeter….most dome tweeters like that weren't designed with a cone in mind, so it'd likely effect many aspects of the output of the tweeter.


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## scottyeyre (Oct 14, 2012)

Aesthetically it looks amazing, sound wise I'm not sure. They are supposed to sound amazing. Ive researched speaker design a while ago, It was interesting and still want to make my own speaker cabinets sometime too.


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## B4B (Sep 6, 2014)

Are these mass produced or were these a one off pair? If they are a one off they could have been hand carved.


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## bbasiaga (Dec 8, 2012)

There is long grain running vertically to the start of the cone on both halves. In the middle of the cone the same grain now meets the other side end grain. Could be an optical illusion I suppose ,but I don't think so.

BTW, the dress was blue and black. 

-Brian


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## Ghidrah (Jan 20, 2015)

Looks like reclaimed Fir to me, I'm having a hard time seeing how it would be steamed and pressed into a mold to take that shape without some major distortion. Some woods avail themselves to steaming, I've seen trick toys where only steaming allowed the trick to work. The object looks solid from the sides, if so then I don't think it would perform as a resonating box and Fir may not be the most appropriate materials for a resonator.


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## scottyeyre (Oct 14, 2012)

They look like they could be a limited small batch, not certain though. I think they have access to a cnc carver.

the wood is Heart Pine apparently

https://www.fernandroby.com/products/details/the-beam-tower-speakers


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## Kazooman (Jan 20, 2013)

Still thinking about how they made the cone (other than CNC) but the additional pictures help. The one in the lower right hand corner shows the cabinet looking down from about a 45 degree angle relative to the front. You can see how the pieces were glued up. It explains the grain pattern in the cone. Not an optical illusion, just the result of the unusual cone shape and the concentric rings wrapping around the pieces of stock.


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## SCOTSMAN (Aug 1, 2008)

You could easily with a little practise make this hollow , with an angle grinder four and a half inch type and a few flap sanding discs.This set up can work wonders if you adapt yourself to it's use .Just take your time and work methodically finishing with a two or three inch normal small disc sander,often used on bowls being turned try it it does work. Alistair


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## timbertailor (Jul 2, 2014)

From an acoustical standpoint, is the cone physically amplifying the sound much like a horn loaded speaker?

If so, then the shape of the cone is important to its acoustic qualities and may not be easily duplicated.

Just food for thought.


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## dhazelton (Feb 11, 2012)

They probably have a custom bits to cut that, and a machine like a BIG drill press. I'd talk to a place that makes moulding knives to see what they say is possible with home equipment.


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## Daruc (Apr 20, 2015)

I'm sure there are many ways to do it. Steam bent into a mold?? Probably not.

I can think of one easy way right off the top of my head. 
Turn the radial arm saw side ways, 
Hold one half of the pc at an angle (in a jig). Simply pull the saw out lowering it a little at a time.

Might have to use a smaller blade to get that tight of a radius. Actually the radius could be controlled by the angle of the pc to the blade.
Sort of the same process as making cove molding on the table saw.


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## ElChe (Sep 28, 2014)

Circle cutter on drill press with progressively deeper cuts of smaller diameters and then scrape or sand? I'm thinking CNC is a good bet.


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## RichardHillius (Oct 19, 2013)

It looks to me like two half's where glued together down the center. A bull nose bit in a shaper could make the two haves than they could be glued together to form the whole. I have never seen a bull nose bit that large so if they don't exist my next guess would be a CNC machine cut it out.


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## Ripthorn (Mar 24, 2010)

If they are a speaker manufacturer worth their salt, they have precisely designed and machined those horns to modify the tweeters response curves so that the entire system is well tuned. You will only do that with CNC. If you try doing something freehand, any small imperfection, like a ripple or something, can drastically modify the wave propagation of certain frequencies. You could try to do it, but I wouldn't. I have done a lot of acoustic design stuff both professionally and as a hobby, and I wouldn't dare try to reproduce that with anything short of a CNC if I wanted it to do anything more than to look cool (which it does).


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## longgone (May 5, 2009)

A very large countersink.


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## wormil (Nov 19, 2011)

I imagine it was cut while the boards were flat. CNC cuts half the cone shape in each board plus hogs out for the other speaker then the boards are folded up and glued together. Wasteful and inelegant but plausible considering the price, $4500.


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## runswithscissors (Nov 8, 2012)

Since the wood is in two halves, it shouldn't be hard to tilt the bandsaw table and cut an arc into each half. You'd have to practice to get the angle right and the arc right, and then of course smooth it up before gluing back together.


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## JeffP (Aug 4, 2014)

Being a recovering audiophile, I can say that this is an excellent example of something that runs rampant in the high end audio world. It is the acoustical equivalent of "The Emperors New Clothes". If you build something like this and price it high enough, people with more money than brains will buy them and convince themselves they sound awesome.

99.999999% of all speaker cabinets are made primarily of composites (like MDF). This is not primarily for "IKEA reasons". It is because composites have a natural tendency to minimize resonance. They have much less of a tendency to have a natural sound of their own.

This is why even the cheapest of string instruments are still made from solid hard woods. You simply cannot get a piece of MDF or particle board to resonate.

Speakers are supposed to sound like the recording being played through them…not like a hollow log.


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## scottyeyre (Oct 14, 2012)

True about the MDF. Is it difficult to create the cove in MDF then veneer it smoothly?

Considering all the unique and informative advice I might consider using some plans for a floor standing speaker from online, and instead of the tweeter recessed like that I would make the port look something like this










This wont affect the sound waves of a speaker or tweeter but still has that wow factor.

Veneering something like this would be difficult though… my designs usually end up impossible to achieve sometimes though… haha


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## dhazelton (Feb 11, 2012)

You could always turn a bowl to that shape and insert it into the flat speaker box.


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## timbertailor (Jul 2, 2014)

> Being a recovering audiophile, I can say that this is an excellent example of something that runs rampant in the high end audio world. It is the acoustical equivalent of "The Emperors New Clothes". If you build something like this and price it high enough, people with more money than brains will buy them and convince themselves they sound awesome…......................................................
> 
> - JeffP


The design is not a gimmic. As a self proclaimed audiophile, you should know that. Horn loaded speakers do have a purpose. So, using the Emperors New Clothes analogy is way off base. I have not heard these speakers or know if the cone design has any acoustical research behind it, but if it is a speaker mfg worth their salt, no one is going to easily copy its design. Horn loaded speakers are designed to physically amplify the sound, control phase timing, control dispersion, and minimize secondary audio reflections.

So, unless you have an anechoic chamber in your garage, best leave this kind of build to the professionals.


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## Ripthorn (Mar 24, 2010)

> The design is not a gimmic. As a self proclaimed audiophile, you should know that. Horn loaded speakers do have a purpose. So, using the Emperors New Clothes analogy is way off base. I have not heard these speakers or know if the cone design has any acoustical research behind it, but if it is a speaker mfg worth their salt, no one is going to easily copy its design. Horn loaded speakers are designed to physically amplify the sound, control phase timing, control dispersion, and minimize secondary audio reflections.
> 
> So, unless you have an anechoic chamber in your garage, best leave this kind of build to the professionals.
> 
> - timbertailor


Not in my garage, but I do have three anechoic chambers at work that I use every day .


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## a1Jim (Aug 9, 2008)

I believe this may be possible by using a series of progressively larger holes as patterns perhaps using a forestner bit to start the center hole and a router starting with the inner circle out and adjusting the depth as you go(this might need a router bit extender). It would be very important to keep the patterns centered. Then use an aggressive grit flap sander on a drill press to remove the steps made by the routing.
As an alternative, I can imagine developing a jig that would hold a router at an angle and have it follow the inside of a hole pattern or maybe even use a large lazy susan hardware to achieve the circular motion ,this too would need a router bit extender.
I'm sure both of these ideas are as clear as mud, LOL


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## Ghidrah (Jan 20, 2015)

Timbertailor,
I'm certainly no audiophile, I still have and use the same Optimus speakers I bought from Radio shack in 1980 and the newer receiver and equalizer I bought in 84. I may have it all wrong but everything about the speakers seems gimmick. Tonal woods are used because of the resonating qualities they add to an instrument, speakers are instruments too. Whether the species is Fir or not, debatable, (I think it is) it's reclaimed lumber, all the holes and splits in it would wreak havoc with sound reproduction and or dampening. MDF or not some systems are tuned and ported for passive sound channeling, speakers, acoustic, guitars, cellos, etc..

The electrical components, regardless of the quality of the units they can be wrecked or enhanced by the materials they're attached to. Can you imagine the cost of a set of speakers if they were made of acoustic quality rosewood or maple? Spruce and maple can take up to a decade to cure let alone the milling to tune it.


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## altendky (May 7, 2012)

You can generate or find cones in any number of forms. If you happen to go with a positive you can mold clay, plaster, etc to make it a negative. Then you can use a 3-d pantograph router like from woodgears.ca. Not the quickest way since you have to build an entire tool but a very general technique to keep in mind. If you want a paraboloid, you can make one by spinning a liquid. I didn't find any reference quickly but I seem to remember people doing this with plaster and letting it set while spinning to end up with a hard paraboloid. I'm not saying it's want you want but I know a tractrix is a term commonly used when talking about speaker horns.

As to the acoustics. My understanding is that until you get to a truly horn loaded tweeter (I don't think that's anywhere close, much too wide and too large of a tweeter cone to get any real impedance matching through that 'horn') the shape around the tweeter generally affects the diffraction. Looking closely at the close up of the tweeter you'll notice that the seam is not straight so it does appear to be something a bit more complicated than just a simple cone.

On guitars vs. speakers, their acoustic purposes are very different. The guitar is intended to not only take the vibrations from the string and help transfer them out into the room efficiently but also to provide extra coloration along the way. The goal with speakers is often to avoid any additional coloration at all and as perfectly as possible reproduce the original signal. Now, certainly some people want distortions introduced in their music playback (cheap records with their clicks, etc) but it is my impression that the majority of the technical effort has been focused on the avoidance of distortions of the recorded signal.


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## scottyeyre (Oct 14, 2012)

I like the idea of a veneered MDF cabinet with a turned port inserted into it.

Thanks for all your ideas!


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