Building a rear-loaded PA horn subwoofer

Can anyone here assist me or refer me to materials that would help me design a rear-loaded PA horn subwoofer? I intend to use two JBL 2226 15" woofers which will be rear-loaded into a folded horn, and I just want to know how long and big I should make the horn and how long to make it, flare rate, etc.

If you could provide me with a site that has equations, I would appreciate it. Horn-modeling software would be even better.
Dinsdale's Classic Horn Articles

Somewhere i have plans for some horns i designed for Celestion 15s (meant to be used 2/side thou ie 4x15")


navin said:
i used to doubt it, Dave but now I am sure you guys are nuts. 4 x 15" what on earth do you need that for?

each side

4x15 - Bryston 4B -- a channel for each pr (4x400W)
A pr of Audax PR17 in front loaded horns - Bryston 4B each driver (4x200W)
Celestion 800Hz horn - Bryston 3B (2x100W)
A quad of Celestion HF50 - Bryston 3B (2x200W)

This was a rock & roll band PA System. It was not bad. And it did play loud. I always wanted to try 4/side but never got as far as going the Mk IIIs.

BTW the bass bins were designed for 50 Hz when used in pairs -- each cabinet front is 33" x 48" and designed so that even the area where the drivers sit is part of the horn, so a 66"x48" mouth. If we could push the open end up against a wall (ie when on a stage) they acted as wings and gave a little more impact and extension.

navin said:
Bryston for PA use? Why not use PA amps?

Bryston are PA amps. About 1/2 their sales go into the pro market. They are very reliable. And if they do break, they will get you a module really quick and they are easy to fix (been there, done that). The fact that they sound damn gound is the reason why they are all i would consider (althou i did on occasion use Quad 303 for the top). Most PA amps suck. Brystons don't.



2002-01-07 6:02 pm
<b>Most PA amps suck</b>

That's up for understatement of the week. I've heard a couple of home-built PA rigs running older Perreaux amps that sounded excellent, and when replaces with standard PA dreck, went all to hell. Quite a dramatic difference.



2002-01-07 6:02 pm

I just read your first post in this thread, and saw your request for modelling software.

Do a search in google for Hornresp by David McBean a really excellent and powerful free program. I wouldn't even think about anything as unweildy as Mathcad until you want something really odd or specific, apart from the standard exp/hypex, trax and conics.

AJHorn is also available but I think it's about 100Euro. Sorry, can't provide URLs as hy HDD died recently and I'm on a borrowed lappie.

Equations and other sundry horn info available at . Go to Single Driver site, and click on horns. There are also some basic calculators online, as well as a number of projects to look at. Ketil Parow's Big Fun and AllFun Lowther horn articles linked from the site also contain a ton of useful info for budding horn designers.

I also have access to a spreadsheet to do some of the calcs for the actual dimensions of the flares, but I can't send it at the moment. Ping me with a PM at the end of the week and remind me.

Optimum throat size (from Keele) is
St = 0.8 x Fs x Qes x Vas
Fs= driver resonance
Vas = cu ft
St = sq in

Then set the flare type to hypex, m between 0.4 and 0.8, although subbing in a short conic section in the throat can yeild big dividends in distortion performance, with little LF loss compared to a straight hypex. Don't use a trax or conic for bass esp for PA. I deally the Fs of your drivers should be near the flare rate of the horn, and you should be looking for around 40Hz to cover the bottom of an electric bass' range.