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A site visitor pointed me out the I never made an intended write up about the David Haigner horns. I just forgot about them… OK, let analyze David’s claims and his Alphahorn design. I would say right the way that I do not like the Alphahorn’s ideas.
 David Haigner wrote: | | I started to develop hifi horn systems as someone coming from the prosound camp. Constant directivity (cd) characteristics are not optional but necessary for pa-applications, but obviously hifi fans had learned to live with horn systems that have acceptable dispersion at low to middle frequenciy, but dramatically increasing directivity from 5 kHz up (so called "tractrix" horns). Just like sitting in front of electrostatic loudspeakers, you are limited to sitting in a very narrow "sweet-spot" if you want to hear "hifi" quality. But how about listening together with your family and visitors? |
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Oh, boy, where to start. If you about listening together with your family and visitors then sit a few feet further but it is not the point. I think what David does in here is misleading himself and others by identifying a false causality and then addressing the “virtual problem” of the false causality. A horn is a relatively narrow dispersion devise but only if not used properly. People love to take any “stupid” horn, load into it any 20-20.000 driver and then scream – look, it has narrow dispersion at HT. Do not blame narrow radiation of a horn just because you decided to use a horn within an inappropriately-wide bandwidth.
| David Haigner wrote: | | Well, many pa-horns with good cd-characteristics at that time suffered in terms of frequency- and time-domain-response. But well done designs from altec, electro voice and others have shown that you can have your cake and eat it, too. |
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YES, but the CD horns are not a solution but the addressing of the contrived “virtual problem”.
| David Haigner wrote: | |
Point source and constant directivity characteristics over the widest possible frequency band (wide sweet-spot)
LF and HF sections are time-aligned, working with the same polarity
High sensitivity and high electrical impedance, as constant as possible (easy amplifier load)
Smooth amplitude response, without detectable coloration
Shallow acoustical crossover slopes (even better imaging and naturalness)
Moving mass as low as possible |
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Ok, let leave the damn “point source” phrase also – people love to use it but they have no idea what they are taking about. David claims that widest possible frequency band and the “constant directivity” assures wider sweet-spot. I personally see absolutely not connection. The LF and HF sections are time-aligned? Good, the mouth of your LF section and your HF end up at virtually same location and they are time-aligned? This is ONLY an indication that your LF section does not act as horn- loaded at LF. Where is 6dB of this upperbass horn’s equal stops? I bet it is above the 100Hz. The high impedance, good amplitude, shallow acoustical crossovers and low moving mass are good however…
| David Haigner wrote: | | Even outside of the nominal +- 45 degrees radiation window the response is very well controlled over a wide frequency range (the horn is designed to work from about 1.5 kHz up). |
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This is a typical CD horn argument but I disagree with it I think I need to address the whole CD misleading.
| David Haigner wrote: | | The nearly perfect constant directivity characteristic is one reason why our loudspeakers are easy to integrate into your room acoustics, presenting the music over a comfortably wide listening zone. |
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Actually it is very much not true. The CD horns do have wider HF directivity and this make them more toss HF to the side walls. So, the wider directivity horns “see” the rooms more. I do not say that it makes them harder to integrate but it is NOT make them “easier” to integrate. So I find what David said is misleading.
OK, I think I need to address the major subject of Mr. Haigner’s design – the CD or the constant directivity.
I have to admit that what I first saw he David’s horn I was taken by the elegance of the elliptical horn idea. Then looking deeper I understood that it was not a cool elliptical horn but David’s way to deal with the facts that CD horn can demonstrate constant directivity ONLY within one surface. The CD horn does the constant directivity trick in horizontal plane by killing directivity in vertical plane, so it is not “getting richer” but rather the redistribution of the wealth. There is however in this “redistribution of the wealth” some ugly moments that the “constant directivity” devotees fail to realize. Pay attention that I took the “constant directivity” in quote and it was not an accident. The constant directivity is just a marketing BS phrase, the very misleading one as there is not such a thing as constant directivity. There is a “slightly better directivity” and it is what it is. Let look in past.
The notion of constant directivity was injected into use by Electro-Voice in mid seventies. Whoever are interested find the Broadus Keele’s AES paper where he will-defined the rules of the game of CD concept.
http://www.xlrtechs.com/dbkeele.com/
The CD horn has is by nature a triple-bent horn where flare move from hyperbolic to exponential and then to conical profile. The whole idea is based upon the navigation of the edge diffraction around the bends. Sounds elegant, doesn’t it? Well, only on a paper and if the directivity was the ONLY concern that a loudspeaker has. The CD horn have very-very bad on axis equalization characteristic – try to get + 6db from CD horn and you will see. So, to get some equalization of juts the “horn gain” the CD horns shrink vertical dissipation and make itself narrow-rectangular. Sure, the narrowing the radiation angle helps to find a few dBs of horn gain but it makes the wavefront non-spherical – here is where the imaging goes… The pro audio folks hardly care about imaging as they never have it. Imaging is not a commodity of pro audio and they juts case to pass FCC (or whoever regulated them) limits by less expense. The CD horn was perfect for them and it allows spreading sound across wide area - with minimum efforts.
But the edge diffraction around bends of the CD horn are very tricky as they behave different at different db levels. Try to make 90 degree turn in your car driving 30 miles and 130 miles per hour. Feels different? Take a camera-obscura and observe the diffraction. Diffraction is a deviation of light in the region of geometrical shadows. The deviation of light in the region of geometrical shadows will have chromatic aberrations. It is because color of light raven with different speed and different speed had different diffraction power. The example with you, taking 90 degree turn in your car become very intuitive… Ironically the very same happened with CD horn – the diffractions around the profile’s bends are subject of pressure change and it makes the directivity horns to sound different at low and high sound levels. At low levels they lose the “more constant directivity” effect and at high levels they sound like overdriven direct radiator. A properly designed and used Tractrix driven with a proper SET in class A1 has very clean ability to raise dymick – it happens gracefully and very effortless. The horn juts does not care how much pressures it handles – if the horns driver and the amp can do it then the horns has no attitude about it. With CD horn, that has the broken up profile, the raise dymick is always accompanied with unproportionally-high elevation of distortions.
There is another thing that the CD horn enthusiasts do not mention. In horns there are no fantasizes - you have pressure and your have dissipation angle - you have one converted into other. Wider angle – less pressure and here is nothing you can do with it. In CD horn HF are tossed wider out of the horn and therefore the CD hoe loose HF much fasters then it shall. To combine the CD horn with a supplementary tweeter is not a good idea and the whole idea of CD horn is to put one ass on all chair and to have so called wide-bandwidth horns. If we have multiple channels then they would not suffer from any directivity “problems” and the CD horn would not be needed to begin with. So, how the CD horn enthusiasts deal with the problem of high frequency lost in CD horns? Well, they use one of two methods. The first method is to use VERY horribly hard-sounding drivers for the horns that have LOT of HF energy in them. The second method is to electronically equalize the CD horns driver with first order, almost writing the RIAA curve into the driver. ALL , with no exception, so-called constant directivity horns are driven by super-bright drivers (mostly in very cheap models) of equalized electronically….
Well, didn’t not you think that it all abs it too much price to pay for the opportunity to “listening together with your family and visitors” at the distance of one-two feet closer than you would do otherwise? Do not forget that the “constant directivity” idea was invented ONLY to get rigid of the multi-channel configuration and to make the horn installation cheaper. Cost - it was the ONLY a key as a properly made multi-channel has no narrow directivity disadvantage. So, I think in high-end audio, where we do surface cost and comfort for some result the we believe are worthy I think the CD Horns is not too much useful concept. I would be interested if David Haigner convert his CD Horns in elliptical horn of CONTINUES profile, get rid of his QE, use better drivers and add a few more channels. Well, he might end up with Macondo configurations then but does not know about it yet….
Rgs, Romy the Cat
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