This is topic Horns vs Direct Radiator Bass Cabinets in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Gordon McLeod (Member # 33) on 06-07-2001, 05:49 PM:
I remember reading once about the mouth size and horn length vs flow frequency response and that was the reason that most horns don't go to as low of response as a direct radiator cabinet
Does any one have the formula
Posted by Stefan Scholz (Member # 147) on 06-10-2001, 12:14 PM:
I found in Tremaines "Audio Cyclopedia" a good description of the formulas. In my book it is pg. 1098 Chapter 20.51. Not really possible to include the formulas in ASCII text.
Posted by Kent Elliott (Member # 487) on 06-14-2001, 10:11 PM:
Most horn-loaded cabinets also have ports. The gain in efficiency from the horn section is low-frequency-limited by both the depth of the horn, and the mouth size of the horn. It takes a really long horn, coulped with a decent mouth size, to get into serious bass frequencies. But, the ports on a modern, well-designed ported-horn cabinet can equal the low-frequency output of a direct radiating horn-- it just won't seem like it, because the effiency in the mid-bass will be even higher as a result of the horn.
If you're looking for a horn-loaded sub-woofer, you might look at the EAW LA400 cabinet. About 36" x 21" x 36" deep, -3db @ 45hz, and very efficient-- and from a single 12" speaker!
Kent Elliott
Posted by Greg Mueller (Member # 17) on 06-15-2001, 12:04 AM:
About 30 years ago I saw some wooden horns that had been built as an experiment at a rock festival in Satsop, Washington. I don't remember the exact dimensions but they were huge. The mouth might have been on the order of 15' square and the throat 30' long, if memory serves me correctly (what memory). They turned them on and played the 2001 music. And you could hear everyone say "big deal" collectively. If it had been indoors it might have been better. They were supposed to be the bottom end for the PA system. Hmmm, I wonder whatever happened to them?......------------------
Greg Mueller
Amateur Astronomer, Machinist, Filmnut http://www.muellersatomics.com/
Posted by Jerry Chase (Member # 660) on 06-15-2001, 09:12 AM:
The flare constant formula in the Tremiane book is:Flare Constant = 4 * pi * cutoff frequency / velocity in inches per second
An example is given that the rate of flare for a cutoff of 64hz doubles every 12 inches. A key statement would seem to be "The use of an exponential flare rate will provide a sharp rise in throat resistance at the lower frequencies for a given horn length.
My father once built a sound truck for a customer. The pictures of the long horns on top of the truck date it. From what I understand, horn design is more suited to musical instruments (Sousaphone, tuba, french horn, trumpet, etc.) where a changable length of resonant piping can reinforce a particular tone before it gets to the bell. I hadn't thought of it before, but the horn family of instruments could be considered similar to lasers in operation, which is why a little buzz of the lips can turn into such a loud tone.
Posted by Robert Throop (Member # 61) on 06-15-2001, 10:24 AM:
When the "New York Experience" first opened in NYC, it used a straight horn for a subwoofer. I think it was 26ft. long and 11 ft. square at the mouth. I remember seeing it and was awestruck. They had problems with blowing drivers though and after a few years had switched to SenSurround horns for subs. ------------------
Bob Throop