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WMcD

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About WMcD

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  1. Use the forum search function for "polycyliner" for articles. WMcD
  2. I searched and did not find this review having been posted here before. https://www.tonepublications.com/old-school/the-klipsch-lascala/ Enjoy. WMcD
  3. Is there a failure to back up a trash 80 involved? Also an estimate that there were 20 x Heresy? and X x CW and Y x LaScala and Z x Belle?
  4. I should have added: The issue in general also came up when computers had CRT monitors and manufacturers hung speakers off the sides of them. I took apart some Compaq speakers and the magnet did have the shielding cup. Also a mini passive radiator. Some or all CRTs have a degausing coil around the face of the tube. At turn-on it makes a pulse of some sort of signal to degause (demagnitize) the system though maybe it is mostly the mask of color sets. One Saturday afternoon I took a magnet to the face of an office computer and it distorted the image pretty well. I was afraid it might be permanent but turning the CRT off and on cured the situation. No one was the wiser. FWIW the shilding cup is make of out something called mu-metal which is a type of iron which is very conductive of magnetic fields and thus shorts out the field or confines it. FWIW I was reading that trans-Atlantic cable and other long telegraph wires had phase issues which caused the pulse of the dots (and simimlar dashes) to smear out over time and thus run together making them unitelegable. (This reminds me of Chris A's work on DSP phase delay.) In the case of the telegraph systems, the patron saint of mad scientists, Oliver Heaviside, found a solution of adding effective inductance and this was done by wrapping the center conductor in mu metal. We now return you to the normally scheduled program.
  5. Maybe someone should try this on the inside and outside of the horn. Pick a color.
  6. If you have a modern flat-screen TV you don't need shielding. That is to say an LED, OLED, or Plasma. It was only the old CRT type which was bothered by magnetic fields. The cathode rays were actually a stream of electrons and they would be deflected by coils causing magnetic fields but also the stray fields of the driver magnet. Actually I don't know how the K--55 and brothers do as far as sheilding. I recall that just about all similar ferrite speakers did need it. Maybe an alnico driver needs it less. Back in the early days of TV (like when The Honeymooners were in first run) the CRT units used alnico based speakers without shielding. It was only later with ferrite based speakers that mu-metal shilds were added to prevent distortion of the picture. I don't quite know why but it may be that the field of the alnico mmagnet was weaker before being concentrated by the pole piece and magnetic circuit and there were not magnetic fringes coming from the structure. WMcD
  7. Let me suggest that people interested in the field read D.B. Don Keele's paper on his constant directivity horn (which he says resembles the K-5). "What's So Sacred About Exponential Horns" on his website. At page 19 he says he electrically equalized the output of the driver to be flat from 200 Hz to 15 kHz and then the acoustic output of his horn was flat. Crossovers can do this if one doesn't have more sophisticated electronics. You will also find that the acoustic output of most mid drivers begins to run out of steam at 3 kHz, including the Atlas driver. This shows the actual function of controlled directivity horns like the K-400. It narrows the beamwidth above 3000 Hz in the vertical to increase the relative on axis at the expense of off-axis response particularly in the vertical. A type of acoustic equalization. We see this in PWK's article on the K-400 and comparison to the K-5. The bottom line is that it is not the constant directivity horn which needs equalization: it is potentially flat. It is actually the driver which needs electrical equalization when we don't have a controlled directivity horn providing acoustic equalization. Maybe this is a difference without a distinction but I think is worth understanding for the sake of accuracy. WMcD
  8. I read the Greenfield article. I'm also a follower of Nelson Pass and particularly his description of effects of adjusting the strength and phase of the second harmonic. My observation is that Greenfield et al.'s subjective test is done with stereo sound as is Pass's. I don't know about just mono. Perhaps that is in other research. Soundstage is a major issue. The descriptions of subjective effect in Greenfield and in Pass (and maybe in Chris A's) seem a bit similar. I think PWK's favor for first order crossovers came from the days of mono. FWIW. WMcD
  9. You should search the forum for Speakerlab. There has been plenty of discussion. There are Speakerlab catalogs on line too. Google is your friend. As mentioned above, Speakerlab in Seattle made kits and an assembled version of their SK. Apparently PWK sued or threatened to sue over trademark issues related to the "SK" use. His patents on the model had expired. They stopped making them and IIRC they had another bass horn offered for a short time. Speakerlab offered plans, drivers, horns, crossevers, and wooden parts. What they offered in vereer was distinctly different in shape from what you photo shows. It appears the constructor was mimicking the K-Horn model B. Their crossovers varied with one version having variable L pad and another having switches. What is shown is neither from what I can tell. Addition by edit: I have some recall of picture showing the Lpads moved to the face of the tophat where the mid and tweeter are located. Therefore it can't really be determined just how much of the crossover shown is from Speakerlab. Further, SL had some instructions where crossover components were stuck to a board using RTV. All this can look very primitive but I think there is no adverse effect on actual electrical performance. The comments about donuts and toilet bowl seals are just the guys being funny. They are very likely wax dipped inductors. It really isn't possible to say that they don't work properly in the SL design, such as it is. WMcD
  10. You'll like the design patent which is just a drawing, but a nice one. Belle Design Patent 229566.pdf
  11. There are timelines for most Heritage speakers on the Klipsch.com site. These were made up based on information provided by the factory. Please see them for details. I don't see a timeline /history for the Belle (The Prettier Sister; her older sister being the LaScala) --- or I'm doing something wrong. There is a description of Ms. Eva Belle Klipsch, plus some nice historic photos, spec sheet, and an ad. (Search for Belle on that site). Nonetheless, a timeline for the Belle was put up on another site long ago. It is attached. Please note credits there, etc. Others here can give better info on the creation of these timelines. Maybe someone can move the information to the Klipsch site if the appropriate version is not available. It is interesting if brief history. OTOH, it seems to me there were not very many changes to the model which would allow anyone to pinpoint a year of manufacture. It is, though, interesting that you've got the K-55-M midrange driver which is generally considered to be the best of the 55 series. Others can also give details on the import, if any, of the stampings you have found. You should search this site for comments on the Belle. It was reportedly difficult and expensive to manufacturer and never sold well. Congrats on your acquistion. You're a lucky duck. WMcD Belle Klipsch Timeline cached.pdf
  12. Re just the woofer crossover. Every woofer crossover I've seen has a d.c. path to ground through the woofer. I.e. the path from the hot (red) input lead goes though a resistor or two and then to the hot lead (red) input of the woofer, and then the other side of the woofer goes back to the input terminal ground (black) as ground. There may be one or more capacitors across the woofer and these will cause a momentary lower ohms reading on the meter when the probes are first hooked up. This means that the checking ohms across the input to the box will give you the series (adding) resistance of the crossover inductors (usually less than 1 ohm) and the woofer voice coil. If this shows an open (usually infinite resistance) then you very likely have an open voice coil(s) in the woofer(s). Both woofers would have to be burned out for the unit to make no bass noise. OTOH, the midrange and tweeter crossovers do not have a dc path to ground. Their inputs are arranged in parallel with the input terminals and bass crossover input. But because we are measuring DC resistance they do not affect the reading. The ohm meter puts a small amount of current through the circuit which comes from a battery in the meter. I think of this as a zero Hertz signal. The woofer crossover will pass a zero Hertz signal.
  13. Let me suggest that you measure the resistance at the input terminals of the woofer(s). You should disconnect at least one wire feeding the woofer(s). Of course a good woofer will measure about 3.5 to 4 ohms. A bad one will be "infinite" or whatever your meter shows when the probes are not touched together (on the ohms scale). It is unlikely you will get any reading in between. Yeah, pictures! Let us know. WMcD
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