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Howard Ferstler

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About Howard Ferstler

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  1. I first suggest that you absolutely make sure that you located each speaker in the same place and fed it the same signals from the same channel. That way, you eliminate any boundary-related issues and any issues with your amp, preamp, or source generator. Assuming you measured correctly, this situation is most likely a problem with driver aging, but the crossover might be having problems, too. A multiple malfunction, so to speak. The pink and white noise broad-spectrum level differences would probably not be related to capacitor deterioration. I suggest you swap the tweeters and see if the d
  2. The Model Four crossover was the most complex one Roy designed for a two-way speaker, excepting perhaps the still later Model Four that he configured for the Kentucky outfit that brought the speaker back to life. Most of those he used with other two-way models simply installed ballast resistors in series with the tweeter. With the Model Four, not only did he use those attenuating ballast resistors, but he also installed a tapped connection to the choke, which allowed it to better dovetail when the tweeters were adjusted in level. Because of this, the level control is more complex than usual.
  3. Some CD-6 models retained the first-order tweeter filtering of the earlier Model 6 version. Many later CD-6 models had the same crossover network as the CD-7. The earlier version of the CD-7, namely the Model 7, had that same simpler network. Howard Ferstler
  4. I need to footnote my own commentary. One other mod I did recently was to insert an 8.2 mdf capacitor in parallel with each of the tweeter ballast resistors in all four networks (4 ohms in the inner panels and 6 ohm in the outer panels), as well as tweeter 4-ohm ballast resistor in the network within the center system I built. Thpse ballast resistors basically pad down the output of the tweeters (similarly to what we get with the tweeters in the Model One), but if one inserts a proper capacitor in parallel with that tweeter, as the frequency climbs the resistor begins to become bypassed and so
  5. The IC feature malfunctioned right out of the box. One or the other speaker would suddenly switch a panel on or off, and nothing I did (or what Roy suggested I do) fixed things. I even taped over the sensors on the fronts of the cabinets. I checked the schematic and there was one 1500 pfd capacitor in there that had me suspicious. (Its sole function, being hooked between the two G terminals in the IC-switching network, was to keep the 12-volt feed to that network from negatively interacting with, I believe, the tweeters.) If one looks at the schematic it can be seen that its insertion was an a
  6. Yes, in the focus mode the attenuated panels are playing so low in level that it is impossible to accurately measure their contributions. The wrap-around sound from the louder panels, cabinet shading notwithstanding, simply overwhelms them. Their output is basically inconsequential as best I can tell. With my new, dual-crossover arrangement the outer panels can be (1) turned completely off, (2) attenuated by one to two dB, or (3) attenuated by perhaps 6 dB. The second assumption is based upon what Roy got with his Model One attenuations. The third is basically a guestimate on my part, since, a
  7. Hey, I am back. Here is some poop on those IC-20s of mine. The IC circuit switching acted up almost from the beginning and I finally decided to hard-wire the things into the omni mode and leave it at that. I gutted the IC network, and removed the sensors and lights on the front, covering the holes with a small brass plaque that says "Allison." This was my first mod and I could pull it off, because I had the crossover and IC schematics, courtesy of Roy. The second mod, done some years later, was a complete rebuild of the crossover network, following the factory specs. This involved replacing th
  8. This is my last visit and last post. I leave the field to Zilch, speakerdave, Ken, genek, and so forth. I move on to enjoying my throwback audio systems and my recording and book collections. Incidentally, I have removed all of the attachments that I previously installed in posts (pictures, graphs, PDF article reprints, etc.), because if I leave this place my stuff leaves, too. I only wish I could eliminate all of my posted messages. Those still itching to view graphs of any kind need only scope those supplied by Zilch, but don't expect to see any photos of his listening room. PS: at least, w
  9. If one cares to, they can go to the "kitchen" section and check on one of my posts dealing with the "Roy Allison interview in 1992 issue of The Audio Critic, David Ranada was the interviewer." Some here may be interested, because that particular post by me (which shows up on page 3 of the series) has an attached review of the AR-303 loudspeaker done by Julian Hirsch back in 1995 (Stereo Review magazine). What may interest some people here even more is that Hirsch does A/B listening and measuring comparisons between the 303 and the AR-3a. I would post the attachement here, but I have only a lim
  10. Attached is a copy of Julian Hirsch's review of the AR-303 in the June, 1995 issue of Stereo Review. I have to assume you were happy with his assessment, too. In it, he does a direct measuring and listening-session comparison between that newer speaker and the AR-3a. Note that he got the crossover specs wrong with the comments on the AR-3a, saying they were 550 and 6.5 kHz, when they were actually 575 and 5 kHz. Well, nobody's perfect. Interesting that the 303 woofer is run up to a somewhat higher (and more directional) frequency than that of the 3a. The important thing will be his listening/c
  11. Two points. First, it is interesting that Allison's article on imaging and directivity that I posted on the "Library Additions and Corrections" page has managed to get a total of 80 hits, while the Kitchen thread that "debated" the issue managed to get over 2500. How in blazes does anybody debate (or read debates even if they are not posting any comments of their own) about what Allison said about dispersion and NOT go and read Roy's paper? OK, OK, I know that some here went into and out of the kitchen debate numerous times and probably only accessed Roy's paper once, but did each of those 80
  12. I recently posted an additional article about Roy Allison in the Library additions and corrections section. This one is an interview Roy gave to Ranada as part of a series in the Spring/Summer, 1992 edition of The Audio Critic. In the article Roy not only discusses the Allison boundary effect (something he discovered as part of his research on the AR-3a in typical home-listening rooms), but also offered comments upon the series of live vs recorded concerts Edgar Villchur presented when both were at Acoustic Research. Virtually all AR fans should be interested in what Roy had to say about thos
  13. In the "Library additions and corrections" section I just posted a PDF copy of a draft that Roy Allison presented at the 99th AES convention in October of 1995 . It deals with loudspeaker directivity. Howard Ferstler
  14. I just posted a PDF copy of a draft that Roy Allison presented at the 99th AES convention in October of 1995 in the "Library additions and corrections" section. It deals with loudspeaker directivity. Howard Ferstler
  15. Obviously, any components other than wire will have some kind of impact on the sound of a crossover network. After all, it is the job of such components to do just that. Assuming equal resistance values, no resistor will sound different from any other. There is no esoteric characteristic that would make one sound different from another. What might matter is power-dissipation ability, however. I suggest using at least ten-watt rated versions for AR speakers of this vintage. Howard Ferstler
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