Ever think of building a Cornu Spiral horn? Now you can!

[Chaz H]

Okie dokie, speakers are finally up and running. I will reserve judgement until the drivers have had some time to run in. I only have one viable placement option, which is on the long side of the room facing my sofa, but that seems fairly ideal. I can play with raising or lowering them; they're presently two feet above the floor. The horns are definitely producing a LOT of bass. Compared to my W5s they sound brighter and a bit thinner right now, although I have to say the sound is much more balanced than I was expecting. Even now the sound is VERY big. More to come...

 

[Cal Weldon]

Nice looking units there Chaz.

 

[badman]

Yes, but notice how much people try to add porous dampening materials like felt wool, carpet padding, etc to the inside of cabinets. I think the dampening can be tailored by painting with a nonporous paint over the sections that you don't want as much dampening. This stuff is very dense, not like felt or foam but closer to fiberboard. It has the benefit of reducing reflections from the front, and the Cornu is a speaker with a very large baffle area relative to other speaker designs, exceeded maybe by OB's. In fact, one of the complaints about open baffle designs is that they have such a large surface area of reflection in the room. For the Cornu especially, people seem to getting too much peaky bass behavior and this may be beneficial because there is too much bass.

The concern is that it's a lossy front panel- there will be LF losses throughout the horn's path. It's entirely possible that would make a smoother response at the cost of some bass efficiency.

 

[prezden]

Hello All
I am just about to start running some wires in my Cornu spirals. What has worked for you who have completed yours?

cheers

 

[Cal Weldon]

Wires can be straight through the back behind the driver or if you use your soldering iron, you can melt or poke little holes in the horn and feed the wire up from the bottom, through the channels. I did mine on the back.

 

[prezden]

Cal- did you use a small cup on the back or just feed the wires through

 

[prezden]

While waiting for the drivers for my 18" Cornu I decided to make some babies. They are 8" square with channels a bit over 1". Right now I have only done 1 to see how it would work out. The driver is a crappy one I pulled out of an old portable iPod box I had lying around. I hope to replace them with some Aura NSW1-205-8A's. For these ones I used Cal's rounded curves as they were much easier to fold.

 

[Cal Weldon]

Cal- did you use a small cup on the back or just feed the wires through

Small binding posts in a cup.

For these ones I used Cal's rounded curves as they were much easier to fold.

I am thinking the same thing. I have some LG drivers and some Jordan 6T's that I might have to throw into the ring.

BTW, those curves aren't mine, I just adjusted them slightly. I've blown them up for my BIL but I have an extra for me.

 

[xrk971]

While waiting for the drivers for my 18" Cornu I decided to make some babies. They are 8" square with channels a bit over 1". Right now I have only done 1 to see how it would work out. The driver is a crappy one I pulled out of an old portable iPod box I had lying around. I hope to replace them with some Aura NSW1-205-8A's. For these ones I used Cal's rounded curves as they were much easier to fold.

Cool! New record for smallest Cornu. How do they sound?
Congratulations!

 

[xrk971]

Okie dokie, speakers are finally up and running. I will reserve judgement until the drivers have had some time to run in. I only have one viable placement option, which is on the long side of the room facing my sofa, but that seems fairly ideal. I can play with raising or lowering them; they're presently two feet above the floor. The horns are definitely producing a LOT of bass. Compared to my W5s they sound brighter and a bit thinner right now, although I have to say the sound is much more balanced than I was expecting. Even now the sound is VERY big. More to come...

Very nice work Chaz! The drivers look a little overwhelmed by the big baffle but I bet they have a lot of bass.

 

[xrk971]

There are a couple of other nagging issues with this design which could/should be addressed, if possible. One thing on my mind is the problem of putting the driving smack in the middle of a large square. Baffle diffraction, anyone? Anyway, enough talk; time to mount some drivers.

Now that you are listening to them, are you still as concerned about baffle diffraction? The main reason I want to move it off center is to allow different length horns designed and modeled to precisely fill in each other's dips in the freq response. It would help things to offset the driver location and make box follow golden ratio.

 

[prezden]

I've built the second little 8"er and got them up on the wall. They are held together with elastic bands right now while I test them. The best word to describe the sound is shrill. Listening to some string quartet music the soprano really screams at you while the cello is kind of lost in the mix. This could well be the cheap little drivers that I put in there. I'm sure they would sound better sealed up properly with some better speakers in them.

 

[Cal Weldon]

My idea of using the table saw fence and mitre slot for cutting the foam is more bust than boom. Took me a clamp and 10 minutes to set up and then ruined two pieces before I gave up. Back to the straight edge method. Nothing I could do to make that work. I'm not an idiot but I sure felt like one.

Heading for the Captain Morgan now. Better luck tomorrow.

Cheers.

 

[xrk971]

I've built the second little 8"er and got them up on the wall. They are held together with elastic bands right now while I test them. The best word to describe the sound is shrill. Listening to some string quartet music the soprano really screams at you while the cello is kind of lost in the mix. This could well be the cheap little drivers that I put in there. I'm sure they would sound better sealed up properly with some better speakers in them.

I bet it is because it is not sealed. The leaks will kill any bass from the horn. Glue them and try again, the drivers should work fine.

 

[prezden]

Would it help to take some of the dampening out? Right now the centre chamber is stuffed and the inner channels up to where the second channels begin.

 

[prezden]

On a different note: I tried scoring the foam board by making shallow cuts with a t-square about an 1/8" apart across all of the channel pieces at once then cutting them to width after. This way the curves were pretty much the same on all the baffle pieces. Seemed to work pretty well

 

[xrk971]

Would it help to take some of the dampening out? Right now the centre chamber is stuffed and the inner channels up to where the second channels begin.

A little driver like that only needs some stuffing in chamber. Take it all out of channels.

 

[Xerxes75]

i finally glued my speakers (with visaton frs8)...after drying 1 came apart due to tension in the wood...argh.
But noting even more glue could not fix! So now there are playing there songs..

They play good, there is more bass dann before but they sound a bit hollow. Can be due to damping? i stuffed just the chamber with underfloor carpet. Or must i play a bit longer with my vistatons... these are my first new drivers normally i buy second hand or vintage..

But the project was great fun....accept from the blisters from the glue gun..

 

[xrk971]

Xerxes,
Congratulations! Photos?
Try fiber stuffing, also if it came apart did you reseal all internal channels? Leaks can sound hollow.

 

[Xerxes75]

Photo's will follow but in the dark with a mobile is a no go. I think that I sealed it well altought that is what difficult to see.. But the they sounds the same an the second must be sealed... I will try some different stuffing. ( I am thinking about the build procedure and if this can be done different with a 100% guarantee that it is sealed).

I will keep you posted