tysontom

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  1. Difference in sound between AR3 and AR3a

    Roger, The large AR live-versus-recorded concerts were with the AR-3/Fine Arts Quartet. 75+ concerts in 5-6 cities across the US: New York, Boston, Chicago, LA, Philadelphia and Washington, DC. Probably 10-15K people attended the Fine Arts Quartet concerts alone. Next were concerts done with classical guitarist Gustavo López and finally a demonstration with a 1910 Nickelodeon. No one has ever attempted a facsimile live-versus-recorded demonstration with a full orchestra; Wharfedale attempted it around 1955, but the comparison was flawed. Looking back in history, only AR has successfully attempted live-versus-recorded demonstrations where the audience was unable to consistently detect the switch-overs from live to recorded. Important: neither Ed Villchur nor Roy Allison ever "voiced" AR speakers for a particular sound. Both were interested in power response; i.e., the maximum amount of energy propagated into the reverberant field. Both were interested in maximum smoothness and maximum dispersion; both were interested in the lowest harmonic distortion, but there was never any "voicing" of the speakers. "Voicing" is a purely subjective way of designing a speaker, and a lot depends on the whims or tastes of the designer or engineer. AR was more into the objective results of quantitative testing and measurement. These end results were done primarily in the anechoic chamber and reverberant chamber with final listening tests to verify results. What measured well nearly always sounded good, anyway. Speaker designers such as Henry Kloss of KLH and Advent, and Andy Kotsatos of Advent and Boston Acoustics did "voice" their speakers almost exclusively, and they got good results, but AR did not. --Tom Tyson AR-3s and Fine Arts Quartet Concert Carnegie Hall AR-3 guitar LvR, Dave Jones with Ampex 351 in background.
  2. AR-3a improved need "warm up" ?

    Hello Luigi, There are many very fine amplifiers capable of driving these three AR speakers, but they all share in common relatively high power, great stability into capacitive-reactive loads and stability into very low impedances. These are common to all of the amps capable of driving these speakers, and I doubt that anyone could ever detect differences between them with a proper double-blind listening test. That said, I can tell you the amplifiers I have used over the years with my AR-LSTs, AR-3as, AR-10s and AR9 speakers (and other speakers). I have used a McIntosh MC2500, Threshold s/500, Crown Studio Reference I, and more recently a QSC PLX-3602 (still in use). Each of these amps performed well with these speakers without any issues whatsoever, and I don't think I could ever have detected any differences between them. So, to answer your question, there is probably no "best" amplifier for driving these speakers; only those amps that are stable and powerful should be used, and there is no real sonic differences among them. 1. McIntosh MC2500 amplifier (500/500). The McIntosh amplifier is built very much like a Hewlett-Packard instrument, lots of cast-aluminum, stainless-steel hardward, military-grade gold-plated printed circuit boards and so forth. Built to last. It will produce full output power into 1, 2, 4, 8, 16 ohms without any problems. 2. This shows the power output of the MC2500 (720 watts/channel continuous until the 20A circuit breaker tripped at the McIntosh Clinic). 3. Heavy construction and auto-transformers used in the MC2500. There was no transformer-output phase shift or other issues sometimes reported in the audio press, as these were special "bifilar-wound" (very closely spaced windings) transformers patented by McIntosh years ago. These transformers were 100% linear within all audio frequencies, but the transformers added hugely to the cost and weight (130 lbs). 4. Threshold Stasis S/500 Stereo Amplifier (250/250). This amplifier is unconditionally stable into any load of any impedance. It also has gold-plated, military-grade epoxy circuit boards and very high-quality components. Threshold is gone now, but it was one of Nelson Pass' better efforts over time. This particular S/500 picture was courtesy of the internet. 5. Crown Studio Reference I, a powerhouse amplifier drawing a lot of line current. 6. Crown Studio Reference I 30-Amp TT30 NEMA power cord, requiring a special 30-amp receptacle or 220 wiring. 7. QSC PLX-3602 Class-H 3600 watt pro amplifier currently in use. --Tom Tyson
  3. AR-3a improved need "warm up" ?

    I also use QSC and Crown pro amps now simply because of their excellent stability, low distortion and reliability. You just don't need to worry about problems with these amps, and they can easily drive any loudspeaker load without issues. --Tom Tyson
  4. Measuring the AR-3

    Adriano, I have seen it, but I can't find a copy of it. I think I have it somewhere, but for the life of me I can't locate it in the AR files. I do remember that the response was very similar, but the dispersion advantage of the AR-3a seemed to be a slight advantage, as expected, in the acoustic-power response. There was a bit more energy at the very high end, but not by much. Differences between these two speakers becomes less noticeable once you are back in the reverberant field, but I still prefer the clarity and smoothness of the AR-3 a bit over the AR-3a, though either speaker could sound better than the other in A-B comparisons (as AR used to point out to listeners in the AR Music Rooms). --Tom
  5. Measuring the AR-3

    I worked for Hewlett-Packard for 28 years, and I can tell you that HP equipment (test equipment and otherwise) was built to a higher standard than just about any competitive equipment in the field, anywhere. All HP products for many years were heavily strife-tested, drop-tested, salt-spray tested and accelerated MTBF tested. To have this level of reliability, these products were built with gold-plated circuit boards with conformal coating (tropicalization) and 100% incoming tested components. All machine screws were stainless-steel Pozidriv units, and most chassis components were based on the corporate chassis (various versions) with cast-aluminum side rails and anodized-aluminum side pieces, etc. Few other companies made equipment like this to meet this level of reliability. Of course, HP equipment cost more, too, but if it was a better product, justification could be made by the buyer to purchase more reliable, long-lasting equipment that would result in lower "life-cycle" costs over time! --Tom Tyson Construction of a Hewlett-Packard 3312A Function Generator. Note the aluminum frame, gold-plated boards, etc. Top view of 3312A showing the gold-plated board, aluminum rails and premium components. All parts were 100% incoming-tested for conformity. HP later pioneered in the use of surface-mount component technology, which followed this generation of products a few years later.
  6. Measuring the AR-3

    One little minor suggestion: don't attempt to measure the AR-3's "frequency response" as a system. It will tell you exactly nothing, even if you have an anechoic chamber. The interference effects, phase issues, diffraction and so forth are extremely difficult to separate from true performance, especially with a speaker with wide dispersion. Those measured anomalies will cancel themselves out once the sound is reflected energy back into the reverberant listening field. You should remove each driver (mid and tweeter) and measure them on a flat baffle in anechoic space (you could do it outside if you don't have an anechoic chamber or gaited measurement instruments) and measure them separately -- with the crossover in place -- to determine if they are performing correctly. You could compare them to the calibrated measurements AR did through the years to determine if the drivers are working okay. You could also measure the woofer in a near-field environment with the microphone very close to the woofer cone's dust cap, and you could get an idea of how it is doing compared with the original. It would be better, of course, to measure the woofer at one meter, facing into 180-degree solid angle, to get a proper idea of its performance now, compared with the original measurements. Finally, the best way to determine the performance of the AR-3 is to measure it in a reverberant test chamber. This, of course, is not easy to do without the chamber itself, but this testing shows a composite picture of the total energy -- acoustic power -- that the speaker puts into a room and what is actually heard. The acoustic-power response is a sum of all of the energy radiated from the speaker and reflected back into the room. 1. This is one of AR's early reverberant test chambers to measure the total radiated energy from the speaker. Over 1000 speakers of all types were tested in this chamber and other AR chambers. 2. This is the reverberate-chamber response of one of the AR 3-way systems, measured above 1 kHz. Note the uniform overall energy being radiated into the chamber. The speaker is placed inside the door of the chamber, and the microphone (B&K condenser measurement microphone) is placed behind the speaker. 3. Measurements of AR-3 drivers in one of AR's anechoic chambers and woofer in open field, facing into 180-degree solid angle. 4. AR-3 laboratory and free-field response measurements, showing the extremely fine, linear performance, on- and off-axis of the drivers measured individually in an anechoic chamber. —Tom Tyson
  7. Nice LST's on the auction site

    Thanks for the compliment! The AR-4 pair below the AR-4x look fantastic! Really beautiful speakers!
  8. Nice LST's on the auction site

    Had the seller worked the level controls back and forth about a thousand times, the tweeters would "reappear." It's rare that the tweeters would be non-functional on a pair of AR-4s, especially in this condition. These speakers should have sold for $600-700. This pair is in good condition, and the speaker is increasingly rare these days, having been made for only one year. --Tom Tyson Had the seller worked the level controls back and forth about a thousand times, the tweeters would "reappear." It's rare that the tweeters would be non-functional on a pair of AR-4s, especially in this condition. These speakers should have sold for $600-700. This pair is in good condition, and the speaker is increasingly rare these days, having been made for only one year. A pair of AR-4s I recently sold for $800. This pair worked perfectly, but I had to rotate the level controls back and forth to get the tweeters to reappear. --Tom Tyson
  9. Nice LST's on the auction site

    Had the seller worked the level controls back and forth about a thousand times, the tweeters would "reappear." It's rare that the tweeters would be non-functional on a pair of AR-4s, especially in this condition. These speakers should have sold for $600-700. This pair is in good condition, and the speaker is increasingly rare these days, having been made for only one year. --Tom Tyson
  10. The Beautiful AR-3

    It is possible that this was special-ordered; however, with the absence of the standard grill molding frame line (it was veneered-over), I suspect that a cabinet-maker added veneer to the original AR-3 cabinet. I'd love to see more pictures of this speaker from the sides, front and rear (e.g., does it have a plywood cabinet, or is it an MDF-type cabinet?). It's really hard to tell, but since the veneer is over the molding, I really doubt this was a factory special order. --Tom
  11. The Beautiful AR-3

    This pair of AR-3 speakers, C 17533 and C 17534, were special-ordered cabinets for a professor at MIT. The cabinets were, if I remember correctly, stained birch, but the cabinet molding was done in stained red or white oak. I'm not altogether positive about this, and I only have a few pictures of these speakers. I suspect this was a one-off special order. The speakers had an oil finish, too, which was unusual. --Tom Tyson
  12. The Beautiful AR-3

    One of the things I've always admired about the AR-3 was that you could see the very faint image of the "fried-egg" midrange and super-tweeter through the grill. Note that the term "fried egg" belongs to the AR-3, but it has been used for other speakers, even the Advent tweeter! This pair of AR-3s was ordered by an MIT professor back around 1963 or 1964. I bought them out of an estate sale years ago, and I sold them around 1995 or so. Care to guess which finish? --Tom Tyson
  13. Dave, The auto-transformer is part of the "Woofer Environmental Control" portion of the 10π's crossover, and it is a precision impedance-matching device, in conjunction with other crossover elements (the 10 has a full half-section, 12 dB/octave π crossover on all drivers) to alter the level of bass energy as appropriate for π, 2π or 4π room placement. The transformer also alters the slope of the woofer's response to maintain flat output in the crossover region. Some have asked why not just use an equalizer to do the same thing? An EQ setup would certainly work, but it would not be more accurate, and it would be needlessly complicated and more expensive. The auto-transformer also does not have any effect on transient response or phase shift, and most amplifiers could accommodate the impedance shifts. However, a high-quality, stable and sufficiently powerful amplifier should always be used with the AR-10π. When you place a speaker in a corner, along a wall or out in the open, the balance of midrange and treble stays relatively constant; however, the level of bass energy is affected—due to the very long wave lengths—by the position of the speaker in relation to the room. The optimum position for these speakers would be 2π, or 180˚ solid angle (in a bookshelf or back against the wall but up off the floor), but it was felt that a lot of rooms would not accommodate this mounting position, and some speakers would have to be placed out from the wall or even directly in a corner, etc. The 10π's auto-transformer "Woofer Environmental Control" compensated for the woofer's output to keep the optimum balance between bass and midrange/treble, regardless of speaker location in a room. It worked, but it came at a $100 higher price than the otherwise equal AR-11. —Tom Tyson
  14. AR3a Unfinished Pine Plywood Cabinets

    KLH used some marine plywood for their early cabinets, but it was expensive, heavier and served no real purpose, and the company soon moved to MDF-type panels for veneered cabinets. It was part of the "trial-and-error" period at KLH in the late 1950s. Marine plywood is typically 9-13 ply and is stronger than cabinet plywood, but it's not necessary for speaker cabinets. --Tom Tyson
  15. AR-3a improved need "warm up" ?

    I've use the Bose 1801 power amp with a pair of AR-3as (and also AR-LSTs), and this is an outstanding amplifier. Probably hard to find one in proper-working condition now, but it is a superb amplifier. It is a low-distortion, "brute-force" design that is largely bullet-proof driving low-efficiency, low-Z loudspeakers such as the AR-3a. --Tom Tyson