Guest Posted January 17, 2003 Report Share Posted January 17, 2003 I have a pair of LSTII's that are original except that the previous owner replaced two tweeters out of the three in each system with "other brand" tweeters--one Yamaha and one KEF dome. I have owned these now for 16 years and have never been happy with imaging. They also cause listening fatigue at fairly normal listening levels. My AR3a's are much easier to listen to.Recently, Edward Arnold of this site was kind enough to ship six AR tweeters which, I believe came from a LST, not LSTII. Four of them work, so I now have a chance to restore the LSTII's to original drivers--or do I? Here is the problem. Are the LST, AR3a, etc. tweeters all 4 ohm and the LSTII, AR5, AR2ax, etc. tweeters all 8 ohms. If so, how do you determine which is which. As most of you know, DC resistance of these is nearly zero, so an ohm meter reading is meaningless. Is there another way to determine whether a speaker is 4 or 8 ohms? These six tweeters have dates of January and March of 1973 on them. Only one has other numbers on it that appear to be 591 T3 ?8. The ? looks like a 1, 2, or 3. If they are the wrong impedance, what about using series and parallel combinations to put an equivalent load on the crossover? To do this, a schematic would be required, which I have not seen.Your help would be appreciated.Richard Boneske Link to comment Share on other sites More sharing options...
Guest Posted January 21, 2003 Report Share Posted January 21, 2003 I posted a message asking about AR LSTII tweeter impedance last week. Does anybody have an answer? It appears that nobody read the posting. Please respond fellow AR enthuiasts. The topic is certainly more pertinent to AR speakers than a discussion of speaker cables. Link to comment Share on other sites More sharing options...
tysontom Posted January 21, 2003 Report Share Posted January 21, 2003 >Recently, Edward Arnold of this site was kind enough to ship >six AR tweeters which, I believe came from a LST, not LSTII. > Four of them work, so I now have a chance to restore the >LSTII's to original drivers--or do I? >You should be able to measure around 2-3 ohms resistance on a 4-ohm tweeter, and 5-6 ohms resistance on 8-ohm tweeters, but to be sure you might want to use a Fluke or similar volt-ohmmeter to get a good reading. I wouldn't trust an analog meter-type, unless it is a Simpson 260 or an HP or something. If you still can't get a reading, you might have a open coil.>Here is the problem. Are the LST, AR3a, etc. tweeters all 4 >ohm and the LSTII, AR5, AR2ax, etc. tweeters all 8 ohms. If >so, how do you determine which is which. As most of you >know, DC resistance of these is nearly zero, so an ohm meter >reading is meaningless. Is there another way to determine >whether a speaker is 4 or 8 ohms? These six tweeters have >dates of January and March of 1973 on them. Only one has >other numbers on it that appear to be 591 T3 ?8. The ? >looks like a 1, 2, or 3. >Those numbers probably do have revelance, but I don't know what they are unless they are lot numbers, mfg. numbers and the like. Without the AR part number (these were not printed on the production-line drivers until the middle 1970s), it's difficult to know the impedance if they are out of the enclosure. The 4-ohm, 3/4-inch dome tweeter usually had a hand-written red grease-pencil "a" on it, signifying AR-3a I think, but that's probably not reliable.>If they are the wrong impedance, what about using series and >parallel combinations to put an equivalent load on the >crossover? To do this, a schematic would be required, which >I have not seen. >Can of worms. Even though the LST and LST/2 used a series-parallel wiring arrangement for the midrange drivers and tweeters, I don't think you would never get it matched up properly with a combination of 4- and 8-ohm drivers, no matter what you did. You could pad-down an 8-ohm driver to four ohms while reducing sensitivity; going the other way would require adding resistance. There would be no good way to do it.Sorry I could not be more help to you. The resistance measurement would still be the best way, if done carefully.--Tom Tyson Link to comment Share on other sites More sharing options...
Guest Posted January 21, 2003 Report Share Posted January 21, 2003 Tom,Thank you for the response. I will try a better ohm meter. The analog one I have now reads very close to zero on the RX1 scale. These do have the black grease pencil markings on most of them, which, I agree, was commonly seen on the AR 3a tweeters. If they are 4 ohms and do not match the only original tweeter left in my LSTII's, I'll use them in my other AR 3's##### Boneske Link to comment Share on other sites More sharing options...
Guest Posted February 6, 2003 Report Share Posted February 6, 2003 HEYI see you are in the process of getting things in order. I'm pretty sure the one that was pushed in is from a 3a and four were from the others are from an lst. I do knew they are all 4 ohm units. I really donot know which model they were from. If I was you and trying to match resistence, I would grab some non-inductive 4 ohm resistor and put it in the signal path before the tweeter in series(they look like a like ceramic block). You could get them at radio shack. Look at this attachment. The side with the two resistor you could also use 3,5,6 ect. you would just have to adjust the resistor value to match you final need.If you have any ???'s let me know. Link to comment Share on other sites More sharing options...
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