Edgar

Um ... when this "popping noise" starts, is the audio already so astonishingly, unbearably loud that there is blood oozing out of your ears?

I'll second that. You've already tried isolating the turntable from the floor and it really hasn't helped. The problem appears to be that the vibration is being picked up by the turntable base itself. If that's the case, then the neoprene isolation may actually make the problem worse. Try adding some mass to the turntable base. For a test, maybe carefully place a couple of bricks wherever you can on the base (no, not on the platter!) such that they don't interfere with the operation of the turntable. If that helps, then you need to damp the base. Otherwise, as others have already mentioned: - Move the turntable to a different location. It could be located in a bass "hot spot" just by coincidence. - A rumble filter is a good idea, too. Not only will it reduce bass output, it will shift the phase of the bass and possibly destroy the positive feedback loop. - It may actually be a microphonic cartridge. Try a different cartridge. I'm out of ideas at this point. Greg

HI-FI: My most recent equipment purchase. MID-FI: The equipment that is being replaced by my most recent purchase. LO-FI: My neighbor's most recent equipment purchase.

Any engineer who doesn't admit that he's bewildered by at least something is not keeping up with technology.

You are not an engineer, yet you are making pronouncements that require an engineer's understanding. The mathematics contradict your statement. Well, I am one of them. I like the sound of vinyl, and I like the sound of tubes. But I have found that the implementation of digital just keeps getting better, and has reached the point where it preserves the unique sound of vinyl and other analog sources very well. And it will only improve in the future. So why forsake the advantages of digital for superstition about its alleged disadvantages? Greg

Isn't it about time that this superstition was put to rest? A/D and D/A conversion change the sound in ways that may or may not be audible. It is not the fact that the audio is digitized that is at fault; it is the fact that the audio is processed. Processing can be done well, or it can be done poorly. Any and all forms of processing change the sound in ways that may or may not be audible, including amplification, attenuation, and just passing through a wire. There is nothing inherently "evil" about digitization, any more than there is anything inherently evil about any other form of processing. So keep your audio in the digital domain throughout the signal path. Only perform one D/A conversion, at the amplifier. There's nothing wrong with EQing by ear. In fact, learning how to do exactly that taught me how to be a better listener. Greg

At the fundamental level, filtering is filtering, and "analog" or "digital" is merely a detail of implementation. However, it's a LOT easier to make a good digital filter than a good analog filter. Think about it; 24-bit arithmetic is roughly comparable to components having 0.00001% tolerance. Greg

I agree, in this price range used (ahem ... "pre-owned") is the way to go. Price is high enough that used items are almost 100% likely to have been well cared for -- usually a finicky audiophile fell in love with the speaker, lived with it for a while, then fell in love with a newer, younger model. That said, some of the Legacy Audio products on the used market offer a lot of performance for a reasonable price. Greg

In the engineering world, there is no such thing as "best". The value of every engineering decision, every component selection, every aspect of a design is judged in the context of the constraints that are in place, and every conclusion is a compromise. So when you read an advertisement that states that some item is a "no-compromise design", reach for your BS button. And when an engineering design is proclaimed to be "best", what it really means is "best, within the design constraints" -- and you may not be aware of all of those constraints. In the marketplace, the number one constraint is almost always cost (or, at least, some computation involving cost -- think back to that course on microeconomics that you took in college). So, while someone might, for example, offer compelling evidence that replacing the K400 with a Tractrix horn improves sonic performance, the cost of such a substitution might not be justified by the anticipated change in revenue for Klipsch. The end-result of this is the healthy aftermarket that we observe, through which those individuals for whom the sonic improvement justifies the added cost can make the change. But it is unrealistic to assume that, just because a modest number of Klipschorn owners think that the sonic improvement outweighs the added cost, enough others will feel the same way to make the change profitable for Klipsch. And that's really the bottom line, isn't it? Also, even when solid, objective data are available in support of a change, highly qualified people can honestly disagree upon their interpretation. For example, though I hold Al Klappenberger in very high regard, I respectfully but strongly disagree with him that "extreme slope" filters are a good idea. Why? Because my crossover designs emphasize time domain performance (see here), while Al's emphasize frequency domain performance. I am not proposing that we debate the subject; I am only saying that even reasonable people can disagree as to how to satisfy the engineering constraints. Finally, even in the presence of objective measurements, we cannot forget that audio quality is ultimately judged subjectively. And we can still perceive things that we do not yet know how to measure. (I'll offer a concrete example: I was recently involved in a project where my objective was to find an analytical method to detect a certain type of audio signal manipulation. I threw every mathematical technique at it that I knew, and a few more that I had to learn. Ultimately, however, the single best way to detect this particular manipulation was to listen to it with a set of human ears. None of the analytical techniques even came close to the performance of a human who knew what to listen for.) And, once perceived by a human, the subjective assessment of whether it is "better" or "worse" comes in to play. In that case there is no right or wrong, only consensus. Greg

Current version is 16, for $129. Older versions are commonly available from ebay for much less. I'm still using version 7, and find it quite adequate for enclosure design. Greg

When I turned 50 at the beginning of 2009, my father told me not to worry, that his fifties were the best years of his life. Let's just say that, so far, It's not working out that way for me.

Years ago I had an old Knight-Kit tube amp melt-down and burst into flames while I was out of the room -- that almost "ended it all" for me. Seriously, though, give the Atma-Sphere OTL stuff a listen. It tends to be finicky, but when it works, it works really well. Though I've never auditioned Atma-Sphere with Klipsch, I've heard it tame some very nasty loudspeakers and actually make them listenable. Greg

It's an attractive idea, except for one unfortunate problem -- that 200 Hz crossover is squarely in the vocal range. If there are any anomalies in the crossover, they tend to be very obvious. I agree. Remember the rule-of-thumb, though; a horn typically has to be at least a quarter-wavelength long to be effective. A quarter wavelength at 125 Hz is a little over 2½ feet. Add room for the driver, and it's a 3 foot horn. Not huge, but getting there. Greg

This stuff is so much fun that it's easy to get carried away. I apologize, as well. Greg

Okay, now I'm really confused. Greg, originally I thought that you wanted to custom-build an all-new design that fit in the KHorn footprint. Later, I thought that you wanted to modify existing KHorns for better performance. But Wrinkles just commented about building improved KHorn speakers from scratch. I'm not certain which of the above is really what you're trying to do. But Wrinkles makes some really good points, and I have fallen on the side against people cloning Klipsch products in the past. So I must be more cautious when/if I post any further comments on this topic. Greg

I'm sorry, Greg; I misunderstood your objective. If you want to keep the basic KHorn design and just make performance improvements, then I suggest that you make internal modifications to eliminate the discontinuities in the contour shown here. As I mentioned further-on in that thread, if you eliminate the "bumps" at between about 80 cm and 115 cm (that's the part where the path goes from the front of the enclosure to the back), and install a woofer with better high frequency response, Hornresp says that things will smooth out very nicely. See, for example, here.

Understood. It's a valid design criterion. Each designer has to decide for him/herself which criteria to maximize and what compromises to make in the process. Again, it's all in the compromises that one is willing to make. The asymmetry in the design is only about nine inches, i.e., the opening is only displaced about nine inches from the center of the face of the enclosure. That means that it can't possibly have significant effect until the wavelength is about eighteen inches -- about 750 Hz. By that point the audio should be crossed over to the midrange horn anyway. It's a worthwhile goal. Unfortunately it makes the horn very difficult to build. Again, understand that I'm not disagreeing with any of your comments. We just seek to optimize different things. I should also add that I haven't built any prototypes, yet. So there's always the possibility of some unforeseen problem(s) ... Greg On edit: Correction: The asymmetry could have effect at 375 Hz -- half what I originally said. The path length is 9" longer in one direction, but 9" shorter in the other, for a total of 18".

http://forums.klipsch.com/forums/p/98253/992045.aspx#992045 Why do you say that? Because at low frequencies, the walls, floor, and ceiling provide the pattern control. By the time you get high enough in frequency to where you need the horn to provide pattern control, you're usually in the midrange horn anyway. Greg

It's not distortion. It's exactly the kind of "clover-leafing" polar pattern that you mention later in your post. See here. I'm trying to keep the horizontal response as nearly omnidirectional as possible. To do that, the mouth dimension needs to be reasonably small relative to the wavelength. With the bifurcated design, the polar response narrows into a central lobe as the frequency rises. If the distance between the mouths is much larger than half the wavelength, then multiple lobes form. Essentially true. Reflectors become effective when the width of the acoustic path in the region of the bend is a significant fraction of half the wavelength. See here. Also true, which makes it advantageous to minimize the number of folds in the horn. The calculations are straightforward. In the KHorn it starts around 200 Hz; in the Jubilee around 300 Hz. I'm not convinced that pattern control is a big issue when radiating into half-PI space. I can't argue with anything you've presented here. I might fine-tune some of the numbers to my own liking, but basically I think you're on a good path. Frankly, for such a short horn, it doesn't matter very much. Greg

JC, I couldn't agree more. PWK succeeded in creating a loudspeaker that fit fairly unobtrusively into a moderate-sized living room, and looked GOOD. Browse through the designs shown here and you'll see what I mean -- they're universally UGLY, at least to non-audiophiles. Furthermore, he got a LOT of performance out of a relatively small horn volume. I design speaker cabinets for fun. For a long time I have been trying to get more performance out of the same volume as the KHorn, and, frankly, it's darned-near impossible. And I have my CAD program to change designs at will; PWK had pencil, paper, and woodworking tools. The fact that the KHorn still stands up really well 60+ years later is quite a testament. Again, I agree. But I don't understand why PWK limited himself to 12" drivers in the Jubilee. Perhaps it was because 15" drivers typically can't handle the midrange frequencies as well as 12" drivers, due to mass rolloff, but there are 15" drivers that do much better in that region than even the 12" K31! I am referring, in particular, to drivers from Altec, B&C, BD Designs, Ciare, and even EV. If they can design a better driver, PWK and Roy could have, too. I have noticed something about the design of the KHorn and Jubilee that may offer an explanation, though. In both designs, they seem to have tried to extend the LF response by perhaps 1/4 octave by resonating the driver below the horn cutoff. That might explain the use of high-mass, low fs drivers like the K33 and K31, but it comes at the expense of poorer midrange response. Nowadays, with so many high quality subwoofers available, I wonder if the tradeoff can still be justified. Greg

Jubilee comparison.

KHorn comparison.

Greg, You've already seen the following in a private email message, but the other forum members have not. Both the KHorn and the Jubilee have approximately 400° of folding angles. They also have split mouthes, which cause "double-slit" diffraction well within their upper frequency ranges. Reduce the folding to two 90° bends, and eliminate the split mouth. Use two Altec/GPA 515-8GHP woofers in a cabinet approximately the same size and shape as the KHorn. Do that, and you'll have something that looks like the attached rendering. Optimize the design to compete with the standard KHorn, and the first Hornresp plot results (KHorn in gray). Optimize the design to compete with the standard Jubilee, and the second Hornresp plot results (Jubilee in gray). (another) Greg

Vacuum tubes are like tires -- two tires may be designed to fit the same rim, and may have the same overall diameter, tread width, aspect ratio, etc. But they'll perform differently, depending upon how they're made and what they're made of.

Roberts' Acoustical Woodcrafting