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In Reply to: RE: EV Horns posted by ACMINC on September 30, 2014 at 17:06:09
Ken
Take a look at the pic attached here, it's from Elements of Acoustical Engineering by Harry Ferdinand Olson (recently reprinted in paperback, in the public domain, and very highly recommended). Note that the slower expanding exponential horn has the best bass extension of the group, as it's more "pipe like" than the conical or parabolic. Conical horns quickly become unpractical for bass horns, but in the midrange where spacial considerations are less of problem they have now become contenders along with some oversizing/EQ "dirty tricks" (to paraphrase P.W. Klipsch).
It would be nice to have a rule of thumb for designing a conical mid horn (which is not really my dept.), and perhaps one of the conical guys will be attracted by the subject line here and step forward. In the mean time, an exponential horn (for example) is most efficient when the length of the horn is equal to 1/2 of a wavelength at the lowest target frequency, and the area of the circumference of the mouth is equal to 1 wavelength, where 13500/(Freq. in Hz.)= wavelength in inches. As should be obvious from the graph, you will have to oversize the conical horn considerably to get it to load the bass as well as the exponential horn, and/or use some EQ. You don't mention what you are intending using below the conical mid horn for the bass. If it's a direct radiator box woofer, then EQ may work as you will have to pad the 1823 down relatively to match the level of the woofer anyway. An exponential horn is a rather specific thing, going from the 1 inch or so mouth of the 1832 to the horn length and mouth area dictated by the sound waves, and following an exponential curve. However a conical horn just has to be cone shaped, and this could mean quite different things in practice. At any rate, some "cut and try/cowboy engineering/see what happens" is ahead for you.
Paul
Follow Ups:
Paul, dude! You have "Elements of"?! Wow!
I have "Acoustical Engineering", the 1957 'update' to "Elements of".
Both of these books are quite rare, and I'm glad to see that "Elements of" has been reprinted!
I also have "Music, Physics and Engineering", which is more approachable for the layman and covers some other topics.
Olson was quite the engineer AND writer!
:)
I.
The large hardback 1957 version of Acoustical Engineering was reprinted in the late 90's by Ed Dell's Old Colony/Speaker Builder group. Prior to this, many is the story of people lending the original book out, and never seeing it again. One of the greatest audio discoveries of the 70's was the existence of this book, and you're a brave man for admitting that you actually own it. Until the paperback reprint of Elements of Acoustical Engineering came out, I would have said "maybe I have it, and maybe I don't". Most of the important horn stuff is in the Elements version from 1937, and there's no excuse for anyone not owning the paperback version now. The reprint of Acoustical Engineering cost $80, but that's undoubtedly the best audio book value ever. I've had the Dover paperback reprint of Music, Physics and Engineering since the late 70's and it's also incredible. For the ultimate Olson opus read Dynamical Analogies, now available as a download from Pete Millet's site. It's an utterly staggering Rosetta Stone of analogies between the electrical, mechanical and hydraulic disciplines.
Harry Olson was the Nicola Tesla of audio!
Paul
10-4 on all of that!Yeah, my "Acoustical Engineering" is the brown hardcover. My "Music, Physics and Engineering" is the Dover paperback edition, with the blue and green cover - and, being a musician, I've darn near worn it out. :)
I don't know what your audio emphasis is, but mine is sound, acoustics, psychoacoustics, recording, and loudspeakers. I suck at electronics and couldn't find my way through an amp circuit if I had to, but I know a thing or two about rooms. ;) So, a couple of the other vintage texts I have are "Music, Acoustics & Architecture" by Leo Beranek, and "Acoustical Designing in Architecture" by Knudson and Harris, and a few others.
I think it's so cool to have these landmark works! What an awesome body of knowledge they contain!!
Sorry, OP, didn't mean to hijack your thread, but when Paul posted that pic, I couldn't resist blabbering.
:)
Edits: 10/03/14
It sometimes seems like more things have been forgotten in audio than have been discovered in the last 40 years or so. BTW thanks for the heads up on the Beranek Music, Ac. & Arc., I just ordered a used copy from amazon. You should definitely check out Dynamic Analogies where many electrical concepts are explained with mechanical analogies like gears, levers and springs.
Paul
"It sometimes seems like more things have been forgotten in audio than have been discovered in the last 40 years or so."
That's a very insightful point.
Pretty much everything we need to know was all known by 1965.
Btw, I look at Olson's electrical analogies to various things like musical instruments, voice, etc., and think: He really GOT this stuff!
I'm reminded of having lunch with John Hilliard. He, Olson and others had all of this figured out, and paved the way!
:)
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