HORN FOLDING Questions...

[screamersusa]

I'm reading like crazy but still can't figure out one thing that I feel I'm doing wrong.

If you have made a styrofoam mockup of your horn.
If you have cut and folded it to fit in a box shape.
What compenstation to horn length do you need to make it correct using 90 degree bends or 180 degree (roughly).
It seems that mine may be coming out too long. Folding screws stuff up. I could divide the box section by section working from driver to mouth through each section with an rta if that would help. The box I am working on does have some space left to add curved corners in the first three of 4 bends which I'm starting to think may be the easiest solution to get it up to 120hz cleanly.

Would be nice if there was a Horn theory and practice sticky where links to this stuff would be.

[GM]

It's all about preserving its expansion rate, ergo area change over distance and while many folks claim that the center-line is down the middle, it's not, though it's 'close enough' when parallel walls is used in one plane: http://www.users.bigpond.net.au/ggoo.../hornfold.html

GM

[screamersusa]

Thanks GM, I've seen that. I stink at autocad but probably need to change that, especially since none of the walls are parallel in this last box..
There were some other hornfold docs on the net but the links all seem to be dead.

[GM]

Did you 'jump' into the Wayback Machine (net archive) to try and retrieve the dead links?

GM

[hm]

Hallo,

look my HP, a lot of different foldings,
with plans,
to calculate such horns try this:

Calculation of expo horns

If you have AH, AM, l,
k still lacks the flare rate:

ln (AM / AH) / l = k

so you can see the surface
each point out (Al):

INV ln (l * k) * AH = Al

l m, AH + AM + AL in square meters

By Al e.g. m in width and divide
you have the distance in meters

AH = Horn throat
AM = Horn mouth
k = flare rate
l = length


Lengths and flare rate VALUES

K VALUES:
0.37 ~ 10 Hz
0.55 ~ 15 Hz
0.7 ~ 19 Hz
0.9 ~ 25 Hz
1.1 ~ 30 Hz
1.3 ~ 35 Hz
1.48 ~ 40 Hz

About an octave above k plays the horn,
if the length matches. At BL horn lengths
over 3.4 m, you get a suck out
below 100 Hz

4/lamda lengths VALUES
3.4 m ~ 25 Hz
2.8 m ~ 30 Hz
2.4 m ~ 35 Hz
2.1 m ~ 40 Hz
1.7 m ~ 50 Hz
1.4 m ~ 60 Hz