down-firing horn sub

[vasyachkin]

with the following horn as a starting point:

http://www.eaw.com/products/KF940.html

step 1: split off the top part (from 2x12" turns to 1x12")

step 2: change dimensions from 16"x36"x52" to 28"x28"x72"

step 3: change 12" driver to 15"

step 4: rotate face down and raise about 1.5 feet above floor on legs.

would it work ?

the reason i want 28"W x 28"D x 72"H dimensions is because thats roughly the biggest box i would be able to roll through the doors and corridors on a dolly.

if i increased the depth to something greater i would run the risk of not being able to turn it around if it had to go through a corridor and then through a door on the side. with a square footprint i will not need to turn it, it would just go sideways without turning.

also considering the doors are 80" high i want to leave some room for the dolly to go under the box. however the legs would be in addition to the 72" height, so assembled it would be about 90" tall.

also i would like to build a pair and not place them in corners but only against the wall close to the speakers for improved integration with speakers and better stereo imaging.

i would like them to operate down to about 18hz using something like 15" TC Sounds LMS woofer ...

i should be able to pack about 15 feet of horn into this thing (folded twice) so i should be able to get 1/4 wave down to 20hz but the mouth would only be 28" square ...

do you see any obvious problem with such a design ?

 

[jnb]

Horns are meant to operate into the room, so pointing them down may at first seem like a bad idea, but here's a suggestion.

If you put it against a wall and point it down, raise it so there's as much area around the base (or a little more) than the mouth. i.e. (width + (2 x depth)) x (height off the ground) = mouth area

 

[vasyachkin]

Horns are meant to operate into the room, so pointing them down may at first seem like a bad idea, but here's a suggestion.

If you put it against a wall and point it down, raise it so there's as much area around the base (or a little more) than the mouth. i.e. (width + (2 x depth)) x (height off the ground) = mouth area

yes thats what i had in mind.

also i could put a little "pyramid" on the floor under the mouth to act as a soft of a phase plug / diffuser.

the point is to make a large horn have a small footprint and be easily transportable.

?

 

[OzMikeH]

I like the sound of this huge sub on wheels. I'll watch this thread closely.
Have you considered Tapped horns? Look in the Subwoofer thread.
Tricky design but huge efficiency.

 

[Magnetar]

With that woofer you will have to use a non conventional horn. It is not suited for a normal horn. Used the Danley 'Tapped Horn" - email him for ideas, he posts here as Tom Danley. There is a thread in subwoofers here. The tapped horn lowers the excursion at low frequencies (mostly) that lowers distortion. I don't think there will be a huge gain in efficiency with that driver.

http://www.diyaudio.com/forums/showthread.php?s=&postid=1389490#post1389490

 

[Brett]

Have you considered Tapped horns? Look in the Subwoofer thread.
Tricky design but huge efficiency.

Sounds like the solution, and there are already some good designs in there.