DIY Radial Horn

I've decided to do something with my holiday.

I'm going to do a tutorial on a diy radial horn, starting with designing, and ending with a finished product. I got the idea from one of CLsystem's posts on the other side.

I don't have any use for a diy radial (distortion blah blah) so I'll be mailing this one to the UK for you lot to pass-the-parcel with. Details later.

I'd like to see some specifications for it first, though. It will be tractrix, but I want to know what you lot would like in terms of dispersion and mount. example: 1", 90 degree dispersion, 3-bolt, 1200hz cutoff.

It should take a while (don't expect it very very quickly) but I've earned myself a long holiday, I think [img]smileys/smiley2.gif[/img].

There's lots for hi-fi on the internet, but this one is geared towards PA usage in that I'll be making it suit a box.

Edited by: Deadbeat

This will be interesting. The first A.S.S. horn was Radial and was made to the Tractrix calculations. They can still be seen today being used by people who don't know that they are A.S.S. horns.
The radial horn can be good for studios and hi fi systems where wide accurate dispersion is not required. I ended up with a horn that perfectly followed the plane wave tube response of any given 1" compression driver on axis, but unfortunately, the radials do fall off as you go wide. At 1K the TRF 570 at 180 degrees only went off the line by 1 db, but at 8k it got pretty narrow. Todays CD horns do not follow the on axis line of the component, but the deviation is constant, so it can be manipulated. This is why you get a cd button on some x\o's, purely to bring up the hf which gets naturally attenuated by a CD horn.
I await this horn with genuine interest.

That's quite the explanation Tony! My newer ventures are all very CD, which is an integral part of my design philosophy. Older horns like these were aimed at coupling the comp to the air, newer comps don't need this function too much - hence the concentration on CD.

I'm doing this blast to the past to please those who like their radials anyway, despite their flaws. They are very nice for near field usage. I also hear they're quite popular for their looks.

Come one people, is no one interested in trying out a pair of wooden radials on their comps? Post your specifications and I'll try to meet them... on-axis. [img]smileys/smiley36.gif[/img]

The design process:

1. Calculate Tractrix profile using calculator on here (mirror of Melhuish's)
www.rocketsciencecanada.com/rocketscienc...ractrixCalc_Mesh.asp
You could also use graph paper, pen, and calculator, but this is essentially the same, just a few button clicks less.

2. Use values from calculations in bi-radial spreadsheet:
www.audioheritage.org/vbulletin/attachme...d=24799&d=1178186569

3. Draw out values on graph paper for cross section of the radial horn

I'm on stage 2, having designed and saved some popular options. 60 or 90 degree dispersion, in all 3 compression driver sizes. Come on, what cutoff do you want? Decisions please.

Edited by: Deadbeat

1.4" 800Hz[img]smileys/smiley4.gif[/img] ill find a bit of ply and give it ago, new comps should be here soon i hope so we shall see how they get on.

Anyone can make it happen, even with nothing but some ingenuity in making a jig for an electric drill (though a router is infinitely preferable and if you can lathe/mill, that's a nice skill to have)!

sks01, if you are interested in CD, I suggest you also look at other options, such as round horns (OS waveguide, conical, etc). Maybe even a Unity. But if you wish to 'walk the path radial', I've just re-found the link where I got the radial spreadsheet from:
www.audioheritage.org/vbulletin/attachme...d=24799&d=1178186569

im just thinking about having the option to try something for nearfield if and when i need a wide dispersion horn

Okay, I'm on it. Will post some diagrams when I finish working out the cross section.

I have the diagrams and all, but can't find my camera. Have been working on restoring an old Lenco TT actually, multitasking[img]smileys/smiley15.gif[/img].

Anyway, I'll post up the drawings when the old digicam appears and then I'll see whether I have time before I'm off to route it.

after a long delay due to workload...

this project isn't dead yet

I've just calculated plans, and am sticking with the tractrix due to slightly better LF loading than the expo, even though the radial horn makes the spherical wavefront characteristics of the tractrix pointless.

I have revised the making of it - my power drill is probably not up to scratch, so I've kindly been offered usage of a milling machine (not CNC) and a radial table (rotates) which ought to do the trick. It's limited in size (the machine), so the horn won't go as low as originally intended.

I'll get some wood on monday, and be making sometime soon-ish (don't rely on that too much).