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About iso

  • Rank
    Advanced Member
  • Birthday 06/12/1958

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    Tampere, Finland
  • Interests
    Classic Hifi, old cars, vintage wrist watches, collecting and drinking good wines, music

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  1. Thank you for your kind words... Autotrafo was only practical way to adjust HF to same level than mid and LF. With 6dB slope crossover this was too much for single AR tweeter but Tom may know if steeper 12dB or 18dB slope had been enough to make single AR tweeter to survive with spectral balance transformer. BTW Crabbe mentioned sometimes "as I happen to be blind". I do not know how blind he was or when he was blinded but this makes the following remark noteworthy "it is true that ear is tolerant of inaccuracies in presentation of a stereophonic aural picture that would seem absurd to the eye if applied to a stereophonic visual picture". Kimmo
  2. I have referred earlier to John Crabbes AR-LST review in Aug 1973 issue of Hi-fi News. It is now reprinted in Aug 2017 issue of the Hi-Fi News. There is also some interesting reading about experimental AR-3F ("F" stood from flat) using similar 6-way spectral balance adjustment that is used in LST. This review was supposed to made by Frank Jones, but as he was recruited by AR editor of the mag stepped in... Kimmo
  3. Has Erse gone belly up as I tried to ask some questions about parts I need for my various projects but never got reply to my e-mail... or is this how they do business all the time? Kimmo
  4. This issue is not strictly AR-related... but may interest you too. My former employee who used to import AR- and BA-speakers did also import Carlsson speakers made in mid 80`s. I bought this pair few times ago. One cab has suffered from water damage and particleboard is like in the second picture. Loudspeaker base is sound and not swelled but looks a bit ugly...any ideas how to improve looks without using paint to hide watermarks? Direct vs. reflected sound issue has been discussed AR-forum quite often. Stig Carlsson published ideas behind his "Ortho-Acoustic"-series speakers. This is quite long summary about design principles, but it may interest some of you. Kimmo
  5. Tapio M Köykkä patented ortoperspekta stereo system that was very useful when listening recordings made using Blumlein principle in 1962. This concept used monophonic center channel for M signal and two smaller speakers to create S (difference) signal. Köykkä patented also vastavaihevahvistimen-principle in 1952, that was later called as circlotron in the USA. Kimmoöykkä
  6. Wide dispersion does have some advantages in listening, but more recent trend of constant but narrow dispersion does offer as better imagining capability in room acoustics. This way reflections in the room do not smear signal as much as when using wider dispersion. Listening dummy head "binaural" recordings with headphones is farthest we can go this way. This way room acoustics do not smear imagining like when using narrow dispersion speakers in the room and even less than when using wide dispersion speakers in the room. Standard recordings are meant to be listened with speakers... ie not usually with headphones. I suppose that this is one reason for cross feed techniques... Kimmo
  7. There are some good mid range domes made even today. ATC and probably Volt unit too can produce something like continuous system SPL @1m: 117dB SPL when crossed at 380 Hz/12dB. They use usually short horn to control dispersion. ATC SM75-150S has been in production since mid 70`s. Volt unit is conventional long coil in short gap design but ATC-dome does use more efficient short coil in long gap and both are of double suspension design to improve linearity. Kimmo
  8. Kent... did you note that MC502 is direct coupled model ie. no tapped choke (which is also called auto transformer) in the output... if this matters to you. Kimmo
  9. I hope that you will find good one and let us know something about your Mac journey... KImmo
  10. Nice to hear that you are not AR7 fan... Kimmo
  11. They can pass AC and hold DC-charge... Kimmo
  12. This calculator and other Pronine online calculators are handy... you will see that reactance of 5000uF cap at 20 Hz is 1,6 ohms.... when you compare effect of series cap at 42 Hz, reactance of 5000 uF cap is similar to 2,85 mH AR3a woofer series coil ie 0,75 ohms... this has been discussed earlier here Kimmo
  13. First I should state that I do hear difference between some loudspeaker cables and absolute phase... But... I think it is a bit silly to pay premium for film cap and downgrade ESR of better and more expensive cap to level of NP electrolytic by adding series resistor. When using series cap in crossover like AR3a, there is far more shift in operating point due tolerance and position of 15 ohm pot than ESR of the cap including proposed series resistor. Which both are in series to signal and tweeter, unless pot is in wide open position. Sound may be better when using film cap for several reasons, but if this ESR issue bothers you why not use NPE:s as they are quite easily available an correct for this period of speakers. There is nothing wrong with wire wound-resistors in audio band... even ARC used 300K ohm special order Dale ww-resistor as anode load in SP6C phono section. Kimmo
  14. I got pissed off on Friday, when I had to relocate one rectifier mounting hole in Scott 299D... battery of my 15-20 year old Elu 18V professional drill was flat and would not take new charge anymore. I had to use old fashioned hand drill. However, I have preferred had tools for screws anyway as you can feel what´s happening on the opposite end of tool. If you mount screwdriver bit on had drill, working time is not too different compared to electric or pneumatic tools unless you have to tighten over 50 screws. Kimmo
  15. Black/red caps look similar to Callins-branded electrolytic´s... are these from similar origin than ones that have been sold as Elcap´s in the Europe? Kimmo