JKent Posted June 12, 2020 Report Share Posted June 12, 2020 sounds like that’s the problem. LSTs are 4 ohm speakers Quote Link to comment Share on other sites More sharing options...
genek Posted June 12, 2020 Report Share Posted June 12, 2020 2 hours ago, JKent said: sounds like that’s the problem. LSTs are 4 ohm speakers And that's nominal impedance. At some frequencies, impedance can be as low as 2 ohms. Quote Link to comment Share on other sites More sharing options...
JKent Posted June 12, 2020 Report Share Posted June 12, 2020 Right. Not 8 or 10. I don't have LSTs or an MC2205 (I wish) but as ar_pro pointed out, Michele is using the wrong tap. Quote connected to 8 ohms ampli tap, lst impedence 10,4 ohms Michele, the speaker impedance is 4 ohms--not 10.4. Attaching them to the 8 ohm output is a mistake. Use the 4 ohm or perhaps the 2 ohm and see if that corrects the problem. Quote Link to comment Share on other sites More sharing options...
ar_pro Posted June 12, 2020 Report Share Posted June 12, 2020 Michele - if you don't already have a manual for your MC2205, you can download a copy from Berner's excellent McIntosh site: http://www.berners.ch/McIntosh/en/MC2205.htm Quote Link to comment Share on other sites More sharing options...
Michele Posted June 22, 2020 Author Report Share Posted June 22, 2020 Many thanks for the manual link... Grazie Quote Link to comment Share on other sites More sharing options...
Michele Posted June 22, 2020 Author Report Share Posted June 22, 2020 On 6/13/2020 at 12:19 AM, JKent said: Right. Not 8 or 10. I don't have LSTs or an MC2205 (I wish) but as ar_pro pointed out, Michele is using the wrong tap. Michele, the speaker impedance is 4 ohms--not 10.4. Attaching them to the 8 ohm output is a mistake. Use the 4 ohm or perhaps the 2 ohm and see if that corrects the problem. JKent good afternoon, just to better understand... i tested with fluke ohmmeter the impedance on the LST terminals and the reading is 10,4 ohm. Looking into cross-over there is one 10 ohm resistor connected in parallel on the 2500 uF capacitor.. it is correct? many thanks Quote Link to comment Share on other sites More sharing options...
JKent Posted June 22, 2020 Report Share Posted June 22, 2020 Michele, You measured the resistance at the terminal. That is not the impedance, even though both are measured in ohms. The speakers are 4 ohm impedance and connecting them to an 8 ohm amp will cause problems. Use the 4 ohm output from the amp. Kent Quote Link to comment Share on other sites More sharing options...
ar_pro Posted June 22, 2020 Report Share Posted June 22, 2020 As we know, the impedance will vary with the setting of the LST Spectral Balance control, but I don't know the minimum load value that the LST could present (where in the heck is Frank?). Anyway, according to the Mac literature, better to have your speaker connected to too low an autotransformer tap, than too high of one. I'd be interested in knowing how they'd sound on the 2 ohm tap. Quote Link to comment Share on other sites More sharing options...
lakecat Posted June 23, 2020 Report Share Posted June 23, 2020 21 hours ago, ar_pro said: As we know, the impedance will vary with the setting of the LST Spectral Balance control, but I don't know the minimum load value that the LST could present (where in the heck is Frank?). Anyway, according to the Mac literature, better to have your speaker connected to too low an autotransformer tap, than too high of one. I'd be interested in knowing how they'd sound on the 2 ohm tap. I use the 4ohm tap on my 2205 when using the LST's and all is good. If I was going to blast it at over 125 watts or so....maybe move it then....but I find it not necessary to be at anything over 70 watts. Quote Link to comment Share on other sites More sharing options...
fedeleluigi Posted June 23, 2020 Report Share Posted June 23, 2020 On 6/10/2020 at 5:28 PM, Michele said: I measured the impedance of my LST and shoved on my Fluke instrument 10,4 Ohms: looking into cross over layout there is one 10 Ohms resistor connected in parallel of capacitor Ciao Michele, If your AR-LST crossover has a 10 Ohm resistor in parallel with the 2500 uF cap you are basically measuring the resistance of that resistor. You can see some AR-LST measurements here AR_LST impedance at two different switch positions (2 and 6) Quote Link to comment Share on other sites More sharing options...
ar_pro Posted June 23, 2020 Report Share Posted June 23, 2020 2 hours ago, lakecat said: I use the 4ohm tap on my 2205 when using the LST's and all is good. If I was going to blast it at over 125 watts or so....maybe move it then....but I find it not necessary to be at anything over 70 watts. That's some useful practical information, lakecat - thanks. Many years ago, I owned a 2205, which drove a pair of early AR-9 speakers; the performance was excellent, and it was a great combination - almost as if the two had been made for each other. I'd imagine that the MC2205 and the LST would also be a perfect pairing. Quote Link to comment Share on other sites More sharing options...
lakecat Posted June 25, 2020 Report Share Posted June 25, 2020 On 6/23/2020 at 2:20 PM, ar_pro said: That's some useful practical information, lakecat - thanks. Many years ago, I owned a 2205, which drove a pair of early AR-9 speakers; the performance was excellent, and it was a great combination - almost as if the two had been made for each other. I'd imagine that the MC2205 and the LST would also be a perfect pairing. I love the 2205 paired with the MX-117. I got these units to play all my AR 4ohm speakers and take turns rotating them. The trick with LST's is to put them up high to sound best. Have then 66" high now. Wish I could get them against the walls but can't because of windows...but they sound really good anyhow. Quote Link to comment Share on other sites More sharing options...
Pete B Posted June 26, 2020 Report Share Posted June 26, 2020 On 4/6/2018 at 7:39 AM, Michele said: Good day, the tweeters are with new dome due to damaged ones from previous owner... Would you please tell us where you got the new domes in case anyone wants to repair an AR tweeter in the same way? Quote Link to comment Share on other sites More sharing options...
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