Can I multiply an 18" folded horn cab by 0.8 for a 15"?

[Optical]

Or could i just put a 15" speaker into the 18" design assuming it just wont go as loud?

Is that the done thing? Is it possible to get dimentions for an 18" speaker by multiplying a 15" design by 1.2 etc etc??

[BillFitzmaurice]

If you change one thing you change everything. Just like all cabinets a folded horn is specifically designed to work with drivers that have specified T/S parameters.

[Swedish Chef]

This is pretty much like asking if you take a Boeing 747 and multiply by 0.7 - do you get an Airbus A340? The answer is as you might guess and like Bill F said, no. There is a little bit more to it than that.

[Optical]

Hmm, i didnt realise it was as critical for horns as it is for other cab designs..

anyway, i have built the fane 15" scoop rear loaded folded horn and swapped a bunch of different subs that i had lying around into it with some pleasing results, the horn was nicer than any other design they had been in..

well maybe i'll try scaling the box up and down anyway and see what happens

[BillFitzmaurice]

Scoop designs are actually among the least efficient of folded horn configurations. You'd save yourself a lot of time and lumber by spending a few weeks reading about horn design and understanding what they are all about rather than blindly charging ahead. Horns are the most complicated of all cabinet designs; there are many well respected people in the business who've been building horns for 20 years who still don't have it right.

[mike.e]

Horns are the most complicated of all cabinet designs; there are many well respected people in the business who've been building horns for 20 years who still don't have it right.

Bassma**?

[paulspencer]

Optical, most things involving intelligent design and an understanding of the relationship between a number of parameters aren't leant by trial and error! The worst thing that can happen is that you get something that sounds good. Better than that is when you get something that sounds wrong. Then you decide to learn how to actually do it right, and instead of something that sounds good, you get something that sounds extremely good

There are some good horn designs you can use with the correct driver. Have a look at Bill's site for a start.

There is also a program called hornresp that you can use to design your own. You would want to study a little as well to get to know how horns work.

Either of those would work better than the "pin the tail on the donkey" approach.

[dangus]

Check out http://www.speakerplans.com/index.html
Rog recommends specific drivers for the horn bins and provides frequency response graphs. Read the FAQs as well; he explains why scoop bins are nasty, and how T/S parameters relate to horns.