Edgar

Coincidentally, here's a LaScala model that I worked up last night, from plans here. Edit: see post 1184729.

I doubt it. The devil is in the details. See the "bump" in the curve at around the 96 cm point? Reduce the area there from ~1600 cm^2 to ~1250 cm^2, and Hornresp says that the peaks and valleys in the frequency response will be reduced significantly. An exponential model wouldn't even see that bump in the first place. Um, thanks. In any other context, that could be ... embarrassing. [] Greg

There are plans here http://hornloudspeakermagazine.blogspot.com/2008/11/comprehensive-list-of-klipsch-plans.html. I cannot vouch for them; I found them with a Google search. To get my KHorn model, I entered the Speakerlab K plans into my CAD program, then extracted and unfolded the acoustical path. I took an area measurement at every point where a significant "change" in the path occurred (corners, kinks, etc.), and plotted the results. Then I created a piecewise linear model for Hornresp. I've attached that plot. The red line is the actual area; the blue line is the Hornresp model. Greg

http://forums.klipsch.com/forums/p/76425/753287.aspx#753287

And ElectroVoice DL15X.

Cast-frame Crites.

Same with stamped-frame Crites.

I don't have the LaScala, and I don't have an actual KHorn to measure, but the attached model was adapted from very precise measurements of an old Speakerlab K. I understand that, dimensionally at least, the K is a very good match. Others may want to comment about that. Greg

Yes, as a result of those meetings we'd undoubtedly recognize each other in person now. Alas, that was the beginning of the end for the Burnsville DSP group. At the end of 2000 the group was disbanded and all of its work sent to Straubing. Greg

I used Opera for years, but eventually gave up because it reached the point where too many Websites just wouldn't render at all. Switched to Firefox a couple of months ago. It's okay, but painfully slowwwwwwwwwwwwwwwwww. The basic Firefox browser leaves a few things to be desired, but there are add-ons for just about anything you'd want.

Ian, I recognize your name but it's been too long to associate a face with it. I am Greg Berchin; I was originally the DSP engineer with the digital group in Oklahoma City, also under Dave Merrey. We developed the Merlin ISP-100, then eventually moved to Minneapolis, where we attempted to develop several KT digital products before being disbanded. Welcome to the forum. I hang out here because, in addition to DSP, I like to dabble in horn loudspeaker design. Lots of nice folks here. Greg

Thackmate; your bio doesn't give your real name. I was with EVI 1995 through 2000, first in Oklahoma City with Altec and eventually in Minneapolis with Telex. I wonder if we ever met. Greg

For a SWIM?!!! In JANUARY?!!! Sometimes I hate living 20 miles from the Canadian border. Edit: No offense to the Canadians. It's COLD up there, and it takes a braver man than I to survive it.

Nope. It's intermodulation: "Ultrasound audio technology is based on this non-linear property of air, creating interference patterns between tones in the ultrasonic frequency range (beyond 20 KHz) lower difference tones can be generated in the audio range (between 20 Hz and 20 KHz)." It's an important difference. Beat frequencies do not actually exist. They are perceived by our ears (well, actually, our brains), but if you do a spectral analysis upon the sum of two linearly mixed tones, you find only the original two tones. Intermodulation products DO exist. If you do a spectral analysis upon the sum of two nonlinearly mixed tones, you find the original two tones, plus their sum and difference (and possibly higher order products, depending upon the nature of the nonlinearity). It is all explained by trigonometric identities.

AFAIK, it's not beat frequencies, which is a result of linear mixing, but intermodulation distortion, which is a result of nonlinear mixing. Air is only slightly nonlinear, so the carriers have to be way up around 130+ dB SPL for this technique to work. Nobody knows the effects of 130 dB SPL ultrasonic waves upon humans, but I'm not thrilled about being bombarded by them.

We are in an interesting era; the parents know more about the kids' music than the kids themselves.

I am currently in-transition and therefore without a system of any kind, but when I was set up I had a pair of Legacy Focus actively triamplified. Crossover was a Merlin ISP100 (great-granddaddy to the EV DX38) with both analog and digital inputs (according to type of source); amplifiers were ancient but wonderful-sounding GAS Grandson, Threshold SA100, conrad-johnson MV50. Crossover topology was my own design. Based upon the results, I'll never go back to passive. Greg

I just experienced my 50th the day before yesterday. Birthdays don't usually bother me, but this one hit like a brick to the head. That said, I'd really like to have a Honda Mini Trail 50 like the one in Chicago_Pete's avatar -- I had one when I was a kid, but sold it to buy a "ten-speed" bicycle (back when they really WERE ten speeds).

Not quite sure what "recorded not to sound good" means. I do like your definition that it should be a reproducer, not a producer, of sound. I look at everything as an engineering problem, so "to sound good" to me means creating the most accurate reproduction of sound possible within whatever external constraints apply. Greg

To sound good, of course! []

Again, we are talking about two different things. You are talking about the assumptions made to derive the expressions that describe the acoustical impedance, while I am talking about the actual shape of the wave front as it propagates down the horn. In the real world, neither assumption is exactly correct. Greg

Hmmmm ... I think that an infinitely long tractrix would have a point source, just like an infinitely long exponential, hyperbolic, etc. Exactly. It comes back to those assumptions again. Ah, but amplifier distortion is typically orders of magnitude smaller than speaker distortion. Again, it's about what you want to optimize. There is a whole school of speaker design that says that the sound should be omnidirectional, which would maximize the room reflections that you note. There is yet another school of speaker design that says that the sound should be tightly controlled, which would minimize the room reflections. The fact that superb-sounding speakers are available from both camps tells me that neither assumption is 100% correct (or incorrect). I am not disagreeing with you ... just playing Devil's advocate.

Roy and Edgar are in full agreement that, "how each distributes the area is related to how each thinks the wave is propagating down the horn and how each thinks the loading should be. in all cases, assumptions are made but real world measurments can reveal some errors in our thinking." I'm not familiar with Post's thesis, but then I have to admit that horns are a side interest for me and I'm always learning new stuff about them. All that aside; even in a round tractrix horn the wave front is not perfectly spherical. The only horn that supports a truly spherical wave front is conical with a circular cross section. Earl Geddes published papers on this sort of thing. It really comes down to what you want to optimize. Nowadays, when Watts are super-cheap, do you really care about maximum power transfer? In the pro audio world, pattern control is most important -- they want everybody in the audience to hear essentially the same thing. In your living room you don't care much about pattern control -- you just want the best sound quality possible at a single listening location. People have been moving away from exponential horns and toward tractrix horns because tractrix horns sound better. Since the frequency response and loading characteristics of similarly sized exponential and tractrix horns differ only by small amounts, the differences in their sonic quality must be due to something else. Again, Geddes enters the picture and claims that the sonic differences are due to "higher-order-modes" -- resonances within the horn body due entirely to the shape of the horn itself. Maybe there is something to that. I honestly don't know. Edgar (Greg)

I have argued that the tractrix curve describes a radius expansion that is translated into an area expansion, but it's a minor point that does not affect the current discussion. Exactly. I see now that I misunderstood your statements. We are in complete agreement here. Was that the recent JAES paper (within the past few years) where they analyzed the errors in the plane-wave assumptions behind Webster's equation? Again, we are in better agreement than I originally thought. See my earlier comment, in which I said, "I just apply a small fudge-factor to the horn design ... and otherwise don't worry about it." Thank you and have a safe and prosperous new year. Greg

Respectfully, Roy, I don't see how you can start with the defining differential equation for the tractrix curve (see the PDF in my previous message), and reach your conclusions 1, 2, and 3. Greg