Design help and advise for radial woodhorn

[Flemming Skov]

Hi forum,

I'm have build a corner horn equipped with JBL units (K145, 2445, 2404) and jbl 2397 for midrange.

You can see the pictures here : http://www.hifi4all.dk/forum/forum_posts.asp?TID=33192&PN=3 but, sorry, it's on danish. There is 7 folders, with some pictures. But anyway, my questions are:

Has somebody played with the wood radial horn ala TAD and Fostex (see the link for what I'm considering, http://www.fostexinternational.com/docs/speaker_comp/Wood-Radial-Horn.shtml) , the H200 horn (fn 240 Hz).

The advise I need is the exponential curvature to construct after. Or the math. to do the curve. Anybody here who has some experiance in that?

I have used the jbl2397 mid horn but find that, for the cornerhorn it is nescessary to go even below 500 Hz. First I have done some new "finns" to build a biggere 2397 a like horn but the radial horn came accross.

Another question. Is it possible to drive the jbl2445 below 500 Hz (my point is 250 Hz). I use 24 dB/oct. filters. Is it possible to get an output or is it to low compared with the spl above 500 Hz?

Looking forward to here any comments :)

Regards
Flemming

[Mr. Widget]

Why not buy the Fostex horn? They are surprisingly affordable. They will not do what you want though. A horn with a 240Hz cut off should be used with a crossover no lower than 480Hz.

You will also need a different driver like one of the phenolic diaphragmed JBLs and a radial that can get that low is huge. The JBL 2356 in these links is a radial design that is rated for use down to 300Hz. It is a real monster.

http://www.lansingheritage.org/images/jbl/catalogs/1976-pro/page18.jpg

http://www.lansingheritage.org/images/jbl/catalogs/1976-pro/page19.jpg


Widget

[Flemming Skov]

They are not affordable! 1100$ for maybe 2 but I think it's for one!!

Yes, I do agree that they are really big. But that is if the "stuff" should go for the open field stadium. In my living room I think that placement close to a corner will extend the response.

Here is a picture of the horn Art Of Sound uses for there cornerhorn. The physical measurements are 76 cm wide, 18 cm high and 39,8 cm deep.
http://eckhorn.bonifa.net/Hornlautsprecher/Eckhorn_Standard.php

Here the price is 900€ for 2 pieces. They uses Selenium drivers.

Reg.
Flemming

[Mr. Widget]

They are not affordable!I guess affordable is a sliding scale....:) also, I believe they are less expensive over here.

Anything smaller than that huge JBL will be a compromise that I wouldn't make... but as we've said before, in loudspeaker design it is all about juggling the compromises.


Widget

[yggdrasil]

Last year I did some work on radial wood horns. Designed this tractrix with a Fc of ~400Hz. Used from 750. Made a spreadsheet for transforming from round tractrix to radial.

If you like, I can send you the spreadsheet, basic drawings and how-to.

[rs237]

hello,

owing to the assistance of some forum members I was to be built in a the position a pair A300 horns. If interest exists can I still further pictures show if the horns is completely finished. Apology for my bad English, is from on-line translater.

regards juergen

[pocketchange]

Where can I locate a set of drawing for this horn?

pc

[Jim DiFalco]

I would also be very interested in a copy....

Thank you

Jim

[scorpio]

I have a copy of the drawings for these, pm me your email if interested. I originally received it from another member of this site, but I unfortunately cannot remember who did me the original favor...

[macaroonie]

a plywood extravaganza....:applaud:

[Steve Schell]

John Volkmann of RCA invented the radial horn in the late 1930s, and radial horns began appearing in the RCA product line in the late 1940s after years of development. Though a radial horn could be designed using several types of flare expansions, all the RCA radial horns were exponential as far as I know.

A radial horn is designed to optimize pattern control vs. frequency in one axis (usually horizontal) while sacrificing it in the other axis. Since the side walls of a pure radial horn are straight, it could be considered as "half conical". Conical horns have excellent uniformity of pattern vs. frequency, though they offer less low frequency loading than an equivalent sized exponential horn due to the rapid throat expansion. By placing all the curvature in the top and bottom sides, an exponential radial horn will offer the pattern uniformity of a conical horn in the horizontal axis, while retaining the superior loading of an exponential horn. The downside is that the horn will beam progressively with increasing frequency in the vertical axis, probably twice as badly as an exponential that shares the curvature among all four sides. This is considered to be a worthwhile sacrifice to obtain the superb horizontal coverage.

One peculiarity of most radials is that, since the side walls are straight and expand rapidly from the throat, the top and bottom sides actually have to "neck down" at first to maintain the exponential expansion. This looks a bit strange but actually works fine. Some of the RCA horns were designed for 120 degree horizontal pattern, and they sound almost exactly the same 50 or 60 degrees off axis as they do on axis- amazing.

Some radials like the Altec 511 and 811 begin with an initial straight throat section of a slower flare expansion. This was probably done to increase low frequency loading, and possibly to encourage some on axis beaming of high frequencies. Radials that do not have this arrangement will have better horizontal dispersion and probably sound better as well.

Flemming, I like your bass horn design and can imagine how good they sound. I would encourage you to build some large midrange horns that would permit a 300Hz. crossover point, as most folded bass horns do not work that well running to 400 or 500Hz. even if they measure decently. Some large radials of perhaps 200Hz. flare driven by large format phenolic drivers like Altec 290 or JBL 2482 would really do the job from 300Hz. to 5kHz., providing what I call "big goose bumps" reproduction of vocals.

The early Klipschorns used a decent sized radial midrange horn. There are some pictures of one on Kerry Brown's site:

http://homepage.mac.com/ikecarumba/PhotoAlbum127.html

[rs237]

hello Steve,

thanks for the technical explanations. Do you have designs for a good horn starting from 500Hz ?

@macaroonie

thanks, i used Plywood because it is not as expensive as walnut. I had to test only my abilities relating to crafts.

regards
juergen

[Earl K]

Last year I did some work on radial wood horns. Designed this tractrix with a Fc of ~400Hz. Used from 750. Made a spreadsheet for transforming from round tractrix to radial.

If you like, I can send you the spreadsheet, basic drawings and how-to.

Nice work Johnny . I like the "Two-Tone" color scheme that you chose . ( I thought I had seen in an older post something about this horn . )

How about posting ( into this thread ) your ( Excel ? ) conversion spreadsheet as a zipped file ( for download ) . Also, the "How To" plans would be nice to see .


:)

[Earl K]

owing to the assistance of some forum members I was to be built in a the position a pair A300 horns. If interest exists can I still further pictures show if the horns is completely finished. Apology for my bad English, is from on-line translater.

Very Nice !

I agree, one can always build the nice Walnut version a little later down the line .

:)