The easiest way is to model it with Akabak. My model using Akabak (1-dim lumped element model) compares well to a full 3d FEA Comsol Multiphysics model done by Onni here:
http://www.diyaudio.com/forums/full-range/225622-ever-think-building-cornu-spiral-horn-now-you-can-149.html#post3871894
Compare the frequency response to:
http://www.diyaudio.com/forums/full-range/225622-ever-think-building-cornu-spiral-horn-now-you-can-150.html#post3872084
There is a Cornu Akabak script that Don Hills posted somewhere in this thread you can use.
Say my name 3 times and I appear... 
A good source for drivers for Cornu experimentation is the small satellite speakers used in cheap HTIB setups. Look for a "name" brand rather than the super cheap ones from the Warehouse etc. They show up often at thrift shops and recycling centres. Computer speaker sets are also worth a look at. Logitech made some with high quality drivers with phase plugs.
A good source for drivers for Cornu experimentation is the small satellite speakers used in cheap HTIB setups. Look for a "name" brand rather than the super cheap ones from the Warehouse etc. They show up often at thrift shops and recycling centres. Computer speaker sets are also worth a look at. Logitech made some with high quality drivers with phase plugs.
TC9FD Dimensions
This is my first speaker build. I have obtained a pair of TC9FD drivers. It is a very long thread, but based upon palmiepaul's excellent summary post, I reckon the dimensions should be scaled to 650mm x 650mm x 75mm (26" x 26" x 3") and going for a 25mm throat width. Are these figures OK?
This is my first speaker build. I have obtained a pair of TC9FD drivers. It is a very long thread, but based upon palmiepaul's excellent summary post, I reckon the dimensions should be scaled to 650mm x 650mm x 75mm (26" x 26" x 3") and going for a 25mm throat width. Are these figures OK?
Hi Guys
I plan to build up a Monster Cornu spiral Horn with 2 fostex Fe206en (with additional Magnets) one driver on each side of the Panels.
The Horn will be mounted under the Ceiling with distance.
The dimensions can be scaled up to 5ft up to 6 ft and 2 ft thick.
My Goal is the Subwoofer Horn Response down to 32 Hz (-3dB) or slightly lower and up to ~100Hz.
Will it work at 6ft x 6 ft ?
Greetings
I plan to build up a Monster Cornu spiral Horn with 2 fostex Fe206en (with additional Magnets) one driver on each side of the Panels.
The Horn will be mounted under the Ceiling with distance.
The dimensions can be scaled up to 5ft up to 6 ft and 2 ft thick.
My Goal is the Subwoofer Horn Response down to 32 Hz (-3dB) or slightly lower and up to ~100Hz.
Will it work at 6ft x 6 ft ?
Greetings
Wow that is huge! Probably does not need to be 2ft thick, 12in to 16in should be enough. You will easily have 30Hz. I am away from my akabak computer so cannot sim it for you. Bravo! Good luck and hope you build it.
So I've made some progress, have machined the front and back faces, but I think I'm going to have some trouble assembling them. I've ironed the 3mm mdf to get it near the curves required and have it sitting in one face to get used to the shape, meanwhile I've got the speakers mounted in the front face.
Mounted on the 76x76cm front baffle in "open baffle" format they do sound rather nice already! Need to do some frequency measurements, but am wondering how different they sound open Vs cornu...
Also am curious how the final sound is compared to the sims from akabak as they seem very peaky.
Ps, the horn is another experiment, good fun and seems quite good. A "through the window" fun-fi listening session while cooking dinner.
Sent from my iPhone using Tapatalk
Mounted on the 76x76cm front baffle in "open baffle" format they do sound rather nice already! Need to do some frequency measurements, but am wondering how different they sound open Vs cornu...
Also am curious how the final sound is compared to the sims from akabak as they seem very peaky.
Ps, the horn is another experiment, good fun and seems quite good. A "through the window" fun-fi listening session while cooking dinner.
Sent from my iPhone using Tapatalk
Hi
@xrk971
Not really - my Room has a Ceiling height of 3.8m (~13ft) - so i can use the Space from ~8 ft up to 13 ft for "Horn relevant Space..."
About the thickness: the modified Fostex's with the additional Magnet (146mm x 20 mm - as large as the original Magnet) needs more Space in the Chamber Volume. Now i'm a litte bit unsure about the Chamber Volume the Drivers need now.
Btw: the additional Magnets cannot be removed and they push the Drivers in new Sound Dimensions.
I want to use two of them for Movement compensation (and Power, of coarse).
The Horn will be mounted with adjustable elastic Spacers under the Ceiling for best Bass Adjustment.
I will begin to build up this in Spring/Summer 2016 - so i have enough Time to look out for Materials (e.g. bendable MDF, the Springs for the Spacers and so on).
Theoretically i can scale up to a real Monster of 10ft x 10 ft... There is enough Space for it.
Thank you
Greetings
@xrk971
Not really - my Room has a Ceiling height of 3.8m (~13ft) - so i can use the Space from ~8 ft up to 13 ft for "Horn relevant Space..."
About the thickness: the modified Fostex's with the additional Magnet (146mm x 20 mm - as large as the original Magnet) needs more Space in the Chamber Volume. Now i'm a litte bit unsure about the Chamber Volume the Drivers need now.
Btw: the additional Magnets cannot be removed and they push the Drivers in new Sound Dimensions.
I want to use two of them for Movement compensation (and Power, of coarse).
The Horn will be mounted with adjustable elastic Spacers under the Ceiling for best Bass Adjustment.
I will begin to build up this in Spring/Summer 2016 - so i have enough Time to look out for Materials (e.g. bendable MDF, the Springs for the Spacers and so on).
Theoretically i can scale up to a real Monster of 10ft x 10 ft... There is enough Space for it.
Thank you
Greetings
I finally got around to building a pair of cornu speakers. 650mm x 650mm x 75mm. Vifa TC9FD drivers. On first test, without any stuffing, I have to say they were a bit disappointing. However, after stuffing the chamber with rock wool, they sounded much better - particularly the bass. I then added some square horns that expand from 84mm to 180mm over 100mm. These are made from some leftover foamcore and push fit onto the driver bezels. The horns definitely improve the midrange - vocals and drums are a bit flat without them. Next plan it to add a chamber at the front to see if it will flatten out the bass.
My friends cannot believe how good the sound is from a 3.5 inch driver.
My friends cannot believe how good the sound is from a 3.5 inch driver.
An externally hosted image should be here but it was not working when we last tested it.
Great job! Nice to see a front horn on this - yes, the mids will get a nice boost. Do you find the highs still sufficient now with the enhanced mids? I like the look of it with the the thin plywood - that is definitely the way to go to make it look good, keep it light and inexpensive. Glad you were able to find foam core where you are. Not alwys easy outside of USA.
Best I have found is to not use the front horn and add stuffing to even out the bass. The TC9 by design is very flat from mids on up naturally. You just need to manipulate the bass below 250Hz to be reasonably flat.
You can add a piezo super tweeter with a simple high pass capacitor. I think Cal did that once with a driver he had that had limited highs.
You can add a piezo super tweeter with a simple high pass capacitor. I think Cal did that once with a driver he had that had limited highs.
OK, I will try adjusting the stuffing and also try with smaller horns. I like the look of the cornu speakers but am tempted to have a go at the 0.53x Karlsonators for my next project.
And yes, you can get foam core quite easily here. It is sold as foamboard from one of the hobby/craft chains. I used a snap-off blade for cutting as it is easy to maintain sharpness that way.
And yes, you can get foam core quite easily here. It is sold as foamboard from one of the hobby/craft chains. I used a snap-off blade for cutting as it is easy to maintain sharpness that way.
Hey X, Cal doesn't do piezo tweets. They have a funny effect on his ears. IOW they hurt.
The only time I added a tweet was with the CSS WR126 mid bass in the Penthorn, not the Cornucopya and it was a little dynamic metal dome.
I just want to thank everyone who has spent the time to create, document and share the ideas behind these speakers.
I've spent the last couple days reading through all 214 pages of this post and I've learned quite a bit. But I still need to learn more.
I have the oppurtunity to get a pratically free pair of Visaton FR13-4 5" and I'm interested in putting these into a cornu spiral. I know these will be pretty large and I'm fine with that. I have a well stocked workshop so building on a larger scale would be fine, actually I would prefer making a larger set. I know Cal built one using a 5? speaker, so it must be possible.
Would the Visatons work? I'm not apposed to buying another 5" If someone thinks the Visatons will sound like crap.
Thanks guys!
I've spent the last couple days reading through all 214 pages of this post and I've learned quite a bit. But I still need to learn more.
I have the oppurtunity to get a pratically free pair of Visaton FR13-4 5" and I'm interested in putting these into a cornu spiral. I know these will be pretty large and I'm fine with that. I have a well stocked workshop so building on a larger scale would be fine, actually I would prefer making a larger set. I know Cal built one using a 5? speaker, so it must be possible.
Would the Visatons work? I'm not apposed to buying another 5" If someone thinks the Visatons will sound like crap.
Thanks guys!
So I'm in the process of building a 40 inch Cornu. I'm using a little bit different construction technique that I will post about when I finish them.
I'm still a little unsure on what driver to buy. What size should it be 5.25 or 6? I'm looking to stay around 50 each. I'm also making the box 6 inches deep. Anyone have any recommendations?
I'm still a little unsure on what driver to buy. What size should it be 5.25 or 6? I'm looking to stay around 50 each. I'm also making the box 6 inches deep. Anyone have any recommendations?