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Name: Carlos
Status: Student
Grade: 9-12
Location: MI
Country: United States
Date: November 2008


Question:
What are the advantages of having a folded-horn subwoofer?



Replies:
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



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