Jubilee Alternate Folding

[Marvel]

Notice the Product Number? The first four digits are the version - the next digits are probably the build number. Dr. Who's is a later build, which probably has included the extra feature.

I suspect that the product number is the date of download.

Probably not since it is the same number today. Product Number 1700-071208 []

[Edgar]

Got it. Looks like he revised the code without revising the revision number.

[DrWho]

He tends to do that, so I just download the program again everytime I sit down to model stuff. I'm hoping to design myself a folded bass horn with an F3 of 25Hz and have been finding any threads concerning horns very interesting. I built myself a tapped horn a few months ago which turned out very close to the predictions in the program (which was rather comforting).

[Edgar]

I'm hoping to design myself a folded bass horn with an F3 of 25Hz and have been finding any threads concerning horns very interesting.

My experience with trying to design a 25 Hz horn has been ... disappointing. I have concluded that one would be better off using the volume that such a horn would require as the rear enclosure in an infinite baffle, along with a multitude of 18" woofers and lots and lots of Watts.

(Dang it; how do I insert a clickable URL?) http://ibsubwoofers.proboards51.com/index.cgi

Greg

[DrWho]

Right now I'm sitting on a tractrix design that "only" takes up 16 cubic feet and has a horn path length of 10 feet. While large, I think it can be folded so that the foot print is acceptable while also maintaining a HF corner above 800Hz (at least that's the goal).

My goal isn't so much achieving insane bass performance as it is being able to go 2-way without requiring a subwoofer to hit all the fundamentals in most of the music I listen to. The polars on a multiple driver "subwoofer" would be awful for reproduction above ~80Hz.

[PrestonTom]

Right now I'm sitting on a tractrix design that "only" takes up 16 cubic feet and has a horn path length of 10 feet. While large, I think it can be folded so that the foot print is acceptable while also maintaining a HF corner above 800Hz (at least that's the goal).

My goal isn't so much achieving insane bass performance as it is being able to go 2-way without requiring a subwoofer to hit all the fundamentals in most of the music I listen to. The polars on a multiple driver "subwoofer" would be awful for reproduction above ~80Hz.

I am coming to the same conclusion about the tractrix. For me it is the size of the mouth that is the killer - it would be huge!

However, these Klipsch engineers seem to be okay with undersizing the mouth and foreshortening exponential horns and not killed with the ripples in the spectrum (see the graphs by Olsen that others have posted). I am wondering if the tractrix would be "robust enough" if we used some of the same shortcuts? Hmm.... does anyone want to start making sawdust?

-Tom

[DrWho]

However, these Klipsch engineers seem to be okay with undersizing the mouth and foreshortening exponential horns and not killed with the ripples in the spectrum (see the graphs by Olsen that others have posted). I am wondering if the tractrix would be "robust enough" if we used some of the same shortcuts? Hmm.... does anyone want to start making sawdust?

That's exactly what I'm thinking []

Also, as long as the frequency response abberations are minimum phase, they can be corrected (perfectly?) with EQ...it just so happens that I'm also building my own active crossover right now (for school credit of course). I guess I'll just have to make sure it has enough of the 'right' features []

[bluesboy]

I'm well known for making tons of sawdust.

[djk]

The cyclical peaks and dips in the bottom two octaves of a too small horn are caused by reflections from the mouth back down to the throat.

Some add, some subtract.

EQ is not of much use on the ones that subtract.

It's not of much use on the ones that add either, as the time delay of the reflected wave imparts an 'echo-ey' sound to the music even though it measures flat.

[DrWho]

The cyclical peaks and dips in the bottom two octaves of a too small horn are caused by reflections from the mouth back down to the throat.

Some add, some subtract.

EQ is not of much use on the ones that subtract.

It's not of much use on the ones that add either, as the time delay of the reflected wave imparts an 'echo-ey' sound to the music even though it measures flat.

Wouldn't it be the same problem for a tapped horn?

[Islander]

However, these Klipsch engineers seem to be okay with undersizing the mouth and foreshortening exponential horns and not killed with the ripples in the spectrum (see the graphs by Olsen that others have posted). I am wondering if the tractrix would be "robust enough" if we used some of the same shortcuts? Hmm.... does anyone want to start making sawdust?

If one were to make up an extension (of plywood or whatever) to restore the "missing" horn length and mouth area, on a La Scala, for instance, how big would it be and how much would it improve the bass response?

[PrestonTom]

"...

If one were to make up an extension (of plywood or whatever) to restore the "missing" horn length and mouth area, on a La Scala, for instance, how big would it be and how much would it improve the bass response?

...."

As I understand things, it is not the case that the low frequency extension would go lower. Rather, it would minimize some of the periodic peaks & dips in the amplitude spectrum in the lower frequency range. I don't have easy access to the Olsen figure right now, but he showed the general nature of the problem.

Regarding the La Scala, usually folks are concerned about their low frequency extension and would want it to go even lower. I don't think this would help that, it would require a basic re-design. A crude way to think about it is by comparing the La Scala to the K-Horn. The drivers are the same but the cabinets are quite different (overall size , flare rate, folding)

-Tom

[Islander]

Actually, I find that the La Scala's bass response is relatively smooth, at least when compared with my previous bass reflex speakers. The sub fills out the bottom octave or two nicely, so the very low bass is missing nothing.

I like what I hear coming out of the system and the more I read, the more I think the designs are in effect optimum or close to it in several ways. Nirvana may be a theoretical concept, but actual contentment can be found without endless headscratching or hair-pulling...

[DrWho]

the La Scala's bass response is relatively smooth, at least when compared with my previous bass reflex speakers.

I don't mean for this to be a "contradiction", but I don't think the smoother sound you hear is strictly because of the frequency response. In fact, the raw numbers will indicate quite the opposite (a good bass reflex will be much flatter). []

The good thing is that the frequency response doesn't tell the whole story. At first I was skeptical of this notion until I had it demonstrated for me in a controlled environment...the experience was very eye opening. It then begs the question, what causes it to sound smoother? [^o)]

My impression of Klipsch designs is that they exhibit a very good understanding of the compromises being made. Nothing is ever over-engineered.

[djk]

"Wouldn't it be the same problem for a tapped horn?"

Yes, any horn actually.

A while back Meyer made a HF horn with a block of foam in the throat to help deal with reflections. Much later (now) Geddes is touting using foam in the throat to reduce HOM (his name for the reflections).

[Islander]

I don't mean for this to be a "contradiction", but I don't think the smoother sound you hear is strictly because of the frequency response. In fact, the raw numbers will indicate quite the opposite (a good bass reflex will be much flatter).

Maybe I didn't have a good bass reflex. The Audio Logic speakers are nice enough, but not in the class of Klipsch, and they measured with more peaks and dips than the Scalas, in the 25-200Hz region at least.

[ZAKO]

I believe too much emphesis is being made in the bass region of 25hz to 30hz...Not much music bass line there.

[Guest " "]

"...

If one were to make up an extension (of plywood or whatever) to restore the "missing" horn length and mouth area, on a La Scala, for instance, how big would it be and how much would it improve the bass response?

...."

As I understand things, it is not the case that the low frequency extension would go lower. Rather, it would minimize some of the periodic peaks & dips in the amplitude spectrum in the lower frequency range. I don't have easy access to the Olsen figure right now, but he showed the general nature of the problem.

Regarding the La Scala, usually folks are concerned about their low frequency extension and would want it to go even lower. I don't think this would help that, it would require a basic re-design. A crude way to think about it is by comparing the La Scala to the K-Horn. The drivers are the same but the cabinets are quite different (overall size , flare rate, folding)

-Tom

On the subject of adding an extension to the LaScala....you can get an indication of this by evaluating the Jubilee. Jubilee is basically a LaScala core with an additional fold (the extension). A smaller woofer with more extension was used that have a reach down to 20hz. The diff in lower reach between the LaScala and the Jubilee is in the area of 15hz. 53hz for the LaScala. Low 40's for the Jubilee.

[DrWho]

Maybe I didn't have a good bass reflex. The Audio Logic speakers are nice enough, but not in the class of Klipsch, and they measured with more peaks and dips than the Scalas, in the 25-200Hz region at least.

I'm not familiar with Audio Logic. How was that measurement conducted?

[Islander]

Audio Logic was a speaker manufacturer located near Toronto, but I think they closed sometime in the '90s. I"ve got a pair of their A-750s, circa 1980, a 2-way bass reflex design with cabinets similar in size to Fortes, each with a pair of 1" dome tweeters and a pair of 10" cone mid/bass drivers, crossed over at 1800Hz.

They were my main speakers, but were shifted to the bedroom when the La Scalas arrived. The A-750s begin their bass roll-off around 70Hz. These measurements were done with a test CD and an RS sound level meter, so it's far from lab standard, but much better than my bare ears.

Interestingly, some of the bass region peaks and dips were similar with both the ALs and the LSes, making me think that the room was as much a factor as the speakers. The test method may seem low-tech and old school to someone with access to all the latest gear, but it did help me with speaker and sub locating, as well as with some rudimentary room treatments.