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

[petervr]

Perspex / clear Cornu's

Decided to make some (more) Cornus as per the original XRK71 model, this time out of clear perspex for the front and black MDF for the back, so the spirals stand out really well.. Very happy with the end result.

I would have preferred to hang them a bit lower on the wall, but this is the only wall space I have available, so I have tilted them downwards a little bit.

I've had a pair of Cornus like this (made from all MDF) for a few years now and I still really like the sound.

I have a little Sure Electronics TPA3116 amp driving them (stock except for Panasonic Oscon caps upgrade) and I really think its a great combo. All thats left to do now, is to make a perspex case for the amp..

 

[xrk971]

Petervr,
Cool - those look great! What a neat idea to use Perspex. You can run strings of LEDs in them for Xmas

Good amp to go with it.

 

[Scott the shepherd]

I just found this thread, so I haven't had a chance to read all the way through it. I was wondering if anyone has tried Bendy MDF? I found it at Rocklers. It comes 1/4" thick, in pieces 24" x 48", and, I think it can be cut on a table saw. It has grooves cut into one side to allow it to be curved, so I don't know if this would adversely effect the sound. It may be abother way to accomplish the spirals.

~Scott

 

[xrk971]

Bendy mdf or ply is a great idea. The ridges are actually beneficial at filtering out high frequencies. Give it a try.

 

[kodomo]

Maybe using clear 12mm acyrlic and using cnc to have the pattern with 6mm deep and 6mm wide on both front and back plates. Then cut the 5mm bendy plywood by 30cm's and fix it in both sides. It can be very neat and stiff. I have some alpair 7.3's in my hand. Would they work on it?

If so, and if I can find a good plan, I have access to cnc facilities! Any help out there with plans and experience with these drivers?

ps. I already built frugal horns with my other pair of alpair 7.3's

 

[xrk971]

The A7.3 is a 50cm2 4in class driver. I would make a 28in x 4in deep Cornu per the PDF plan.

 

[kodomo]

You mean 4" total or two 4" on top of each other.

 

[xrk971]

4in depth total.

 

[kodomo]

this template ok?

Ok, I decided to do the first one out of wood. So you say make it one layer, 4" deep and 28" by 28"...

I will do that next weekend most probably! Etch the pattern 5mm deep on front and back plate, and try and bend the bendy plywood (towards the center, it will seem hard to accomplish)

I will try this template, is this one ok?

 

[Cal Weldon]

There must have been a reason the original was a rounded square rather than a spiral so you might want to use the template at the beginning of this thread.

 

[xrk971]

Kodomo,
The square edges help somewhat to act as a low pass filter to reduce the mids from leaking out. Round can work and probably just requires more stuffing - but may have advantage of easier build if using one long channel piece spiral wound onto a slot.

For a more guaranteed speaker to work, the original plan has been modeled and demonstrated to work. If you make a new one - you are on your own sort of - but if you are curious if your design can work and don't mind potential for it not working - try it. That's how progress is made sometimes.

 

[kodomo]

Thanks for all the suggestions. The last back loaded horn I did, the high frequencies coming out from the horn was not really to my liking and too much stuffing kind a killed its sound, so I will try the original plan!

 

[kodomo]

parts cut

I got the parts cut and I tried them, everything fits

I have a week of leave and will be travelling off country, when I come back I will finish these can't wait

The front plates are 18mm mdf and the back plates are 12mm mdf. The flexible plywood are 5mm thick.

When I am putting it altogether, I will have better photos and with all parts together...

 

[xrk971]

Nice work there Kodomo - great to see someone make it with CNC channels and flex plywood. Should sound very nice.

 

[zman01]

Kodomo,

Nice work indeed. Let us know how they sound.

 

[nerg]

Has anyone done simulations on a non-quadratic cornu with the driver non-centered, like glowglass did?

 

[xrk971]

No, but it would be a simple mod to existing Akabak script for Cornu. Similar sims for non-equal length horns have been done for example:

http://www.diyaudio.com/forums/full-range/236779-panpipe-pentahorn-blh-speaker-2.html

 

[nerg]

No, but it would be a simple mod to existing Akabak script for Cornu. Similar sims for non-equal length horns have been done for example:

http://www.diyaudio.com/forums/full-range/236779-panpipe-pentahorn-blh-speaker-2.html

Thank you. Anyone knows the easiest way to run Abakak in Win10 64 bit?
Could you send me the 5 horn script, xrk?

 

[xrk971]

You need to install Windows XP Virtual Machine on your box. PM me and I can send you script.

 

[Ricren]

Hi X, can I ask for the scrip, please?
Thanks!