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Discussion Starter · #1 ·
While researching THT designed subwoofers, I ran across this

http://www.newton.dep.anl.gov/askasc...9/eng99594.htm


"Folded Horn Subwoofer


Name: Carlos

Status: student

Grade: 9-12

Location: MI

Country: USA


Question: What are the advantages of having a

folded-horn subwoofer?

---------------------------------------

Hi Carlos,


In order to have true horn loading in a subwoofer, the horn must be

monstrously long, opening up to at least 5 feet square at its large

end. Folding the horn reduces its size. But whether folded or not, a

horn loaded subwoofer that has good response down to 30 to 50 Hz, must

be massive in size. A folded horn that can accurately reproduce bass

this low (and after all, that is what a subwoofer is supposed to do),

will be at least 4-5 feet wide, by 5 feet high and 4 to 5 feet deep.

This size is needed because the wavelength of sound at low frequencies

is very large.


If the speaker system in question claims to have folded horn loading,

and is a lot smaller than the above dimensions, then it is just a

useless sales gimmick. Basic physics dictates that for horn loading

(folded or not) to have any effect at all at the low frequencies a

subwoofer is intended to reproduce, the horn must be very large.


As an example, the famous Klipschhorn folded horn speaker sold for

decades was about the size listed above, and even then it had to be

placed in the corner of the room so that the walls of the room acted

as an extended horn, Even so, its bass response was only barely

equivalent to a modern (and far smaller) ported system.


But to directly answer your question, the advantage of a folded horn

(over a non-folded horn) is reduced size. There is no other advantage.

Compared to a non-horn loaded subwoofer, a folded horn woofer will be

massively larger, and have some minor sonic problems as a result of

the sound waves having to navigate the folds in the horn. A true horn

speaker (folded or not) does have the advantage of higher efficiency.

This has nothing to do with sound, but only means a lower power is

needed to produce the same volume as compared to (say) a more standard

ported enclosure.


Having said all that, rest assured that a true folded horn subwoofer

will have a hard time fitting on your parent's living room! Anything

smaller, means the folded horn is just a useless gimmick. Basic

physics dictates that, in order to work, low frequency horns are huge!


Regards,


Bob Wilson"




Doesn't sound like he's ever heard the THT subs built by the DIY's here.
 

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From the site:

Quote:
I'm in my early 60s, and have had a dual career in mechanical engineering and electrical

engineering. I have 9 patents (US, German and EU) in both domains. Most recently I was

employed as a mechanical engineer, designing electronic packaging systems. Previously

I have been involved in microwave system design (mainly the mechanical packaging), and

also some years ago designed the first practical ultrasonic burner atomization system

for a German company. Since April 2008 I took early retirement.

I live in Vancouver Canada.
http://www.newton.dep.anl.gov/scicorps/wilson9.htm
 

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Obviously knows theoretical physics as opposed to applied acoustics.
 

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He is obviously discussing it from the point of view of a full size horn, not the truncated, reduced mouth units that I have seen made.


 

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Quote:
Originally Posted by WiSounds /forum/post/18149602


Obviously knows theoretical physics as opposed to applied acoustics.

Or he's read a book or two but never actually designed or built or even heard a folded horn sub. Therefore the word 'armchair' belongs in his official title.
 
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