Horn Fanatic

I would be very interested in purchasing a pair of those D.A.S. acoustical lens', should anyone know where an old dusty, neglected pair may be.

I never suggest the mod was a bad idea, just stating some facts about horn design. I see the mod as compensating for the shortcomings of the La Scala, which by horn design parameters is not so much a horn, but a discontinuity. I've heard plenty of La Scalas, and I think the stock design would benefit more by being mounted in a wall to reduce the solid angle. I also think the La Scala would benifit more by including angled panels in the rear corners. Doing so can inhibit back reflections off the side panels, and perhaps get rid of that 250-500 Hz dip in the responce. The 22.5" internal width of the La Scala translates to the wavelenght at approximately 602 Hz. Half that wavelenght translated to approximately 300 Hz, where that frequency bouncing from sidewall to side wall can cause resonance. Then again, the mouth area may be the culprit.

I have seen this mod being implemented for quite some time. What I find odd, and it's only a guess, is the chap who first came up with the mod obviously has not read any papers written by Paul Klipsch on horn design. By turning the La Scala into a vented system, the reactance annulling provide by the chamber Klipsch wrote about is essentially null and void. There is a formula Klipsch cited that he borrowed from Kellogg that specifies the chamber volume based off the cut-off frequency, ergo, the length of the horn where the area from the throat approximately doubles. I use this formula as a redundent back up along with volume calculations based off the work of Keele and Beranek which are integral to a horn design program I wrote. The chamber volume and throat area are inter-related. Changing one or the other throws the horn design parameters out the window. A larger chamber volume translates to an increase in throat area. If Klipsch saw fit to turn his folded horns into vented system, it would stand to rerason he would have done so. Just sayin'... H.F.

I have been designing and building speaker enclosures for over 40 years for various purposes, and I have never heard anyone refer to a compression driver as a CD. The letters CD are also used as an abriviation for Compact Disk. Due to my sound reinforcement background, when I hear someone say CD I automatically think, Constant Directivity. I deal with professionals, I don't follow DIY groups, nor do I give much attention to their pet names for transducers and such. The bottom line is, a horn by any other name, is a horn. By definition, all horns are waveguides. Some do a better job than others, but at the end of the day they are just all horns, no matter how particular some people may be. If some manufacturers wish to elevate themselves by calling their horns, waveguides, more power to them. "what do you get if you screw a CD into a horn?" Uh, a compression driver / horn assembly? - Superior directivity control <<< "Constant Directivity" - Linear horizontal coverage for great off axis response - Reduced vertical coverage for less ceiling and floor bounce <<< Not a very technical description. Ceiling and floor bounce could have been referred to as room reflections in the vertical plain. - Extremely wide listening area giving you a huge sweet spot <<< An "extremely wide listening area" can promote room reflections in the horizontal plain. - Improved imaging and clarity for both music and home theater use - Reduced High Order Modes to do away with the dreaded 'horn honk' <<< I haven't heard "honk" since the middle 70's, when ALTEC A7's were the popular choice for band P.A. systems. With a judicious choice of a properly designed crossover and crossover frequency, and exponential horn will perform every task on that list, admirably.

I noticed some time ago folks began calling horns, waveguides, about the same time folks began to call a horn, a lens. As I was formally employed at a company that manufactured microwave antennas, the term waveguide was the technical description for what is basically a rectangle tube with an internal crossection that looks like an 'H', except with a small gap between the horizontal line. The semi-rigid cable used between microwave components and antennas could be considered waveguides as well, as the electro-magnetic energy is guided to it's destinations. In that case, the E-M energy is transmitted through the center conductor, along with what ever electrical power is required to operate microwave components. Calling a horn a waveguide makes a bit of sense, but I think whom ever it was that began calling a horn a waveguide was attempting to describe it's function. It actually does 'guide' the pressure wave, but I'd rather call a horn, a horn, and be done with it. I'm unclear by what you call a, "horn/CD combo". If you mean Constant Directivity, then a "CD" as you call it, is a horn. As for using the larger horn, it was discovered after the advent of sound systems that were designed for talking movies that large horns image better, although the acousticians back then didn't call it imaging, they called it separation. Yes, stereo sound existed even back then. All that would happen if you leave the horn mounted in the enclosure as it was originally intended, rather than blocking the woofers, is that you will experience less dispersion on the horizontal plain, and more on the vertical plain. If you use, for example, a horn throat for an ALTEC Mantaray, or JBL Bi-Radial horn, in essence you would have a horn slot that would behave in the same manner as the JBL 2405 tweeter. A vertical slot by it's very nature provides better dispersion on the horizontal plane than the vertical. It's why column speakers work so well. It's kind of an acoustical phenomena. All I can suggest, is that you try the combinations you're interested in. If one works better than the other for you, then go with what works best. It's easy to armchair quarterback, but it's your ears that will make the final decision.

FYI - The device you're calling a horn lens, is not a lens. It's plainly called, a horn, or, waveguide. An acoustical lens is an entirely different device, as it alters the pressure wave by literally bending it by either converging, or diverging it depending on the geometry of the lens elements in the same manner light passes through an optical lens. Whereas a horn, or waveguide has only a single pattern of dispersion. I don't know who originated the misnomer of calling a horn a lens, but I have seen that term used in after market audio component catalogs all too often. However, if it were a choice between the small horn or larger horn in your photograph, I recommend using the larger horn.