Lars

Hi all, Just wanted to show you the result of 1200 km of driving, about 20 hours of workshop time and 800 USD in total spending incl gas, hotel, caps, woofer surrounds…... I am now evaluating which position (of 6) that I like the most for different material. They sound extremely precise, almost analytic but at the same time very open and ”airy” One example of this is that I have had trouble before listening to a ”full” opera in my other systems. I get tired. (Probably, my brain gets tired of correcting all the time) In the LSTs, I can listen to opera for hours on end. And, of course, any other material. Best regards, Lars Stockholm, Sweden

Hi and thanks for the couraging answer, Pete. I really enjoy the system very much and more for each passing day. Being an engineer, I always think in terms of improvement. I have abanoned the idea to stabilize the backplate for now but there is a 2500 uF cap in series with the whole XO. I have bypassed it with a small 1.5 uF as can be seen in the pic. in the post above but perhaps the big cap should be replaced with something better (and younger). Is there a known brand of caps that large suitable for loudspeaker XOs, do you think? (By the way, it is a personally frightening thought, to replace old but good capacity with new ones, just younger....) Regards//lasse

Hi Pete, And thanks for your input. Yes, judging from comparason with the factory curves, the tweeters seem to be 4 ohms indeed, which is good. The curves are from the complete ”arrays” (two pairs of parallell tweeters in series, interconnected as in the factory XO-drawing)of four tweeters in both speakers. All eight tweeters work OK. I have cauciously tested them with low-level testtones and the all respond upp to 20 Khz (I only hear up to abt 8 Khz nowadays….) When I rebuilt the XO with new caps and resistors, I worked from the assumption that they were 8 ohms so I replaced the 6 uF cap with a 4.7 one. Perhaps I should try adding 1-1.5 uF? I attach a picture of the ”upgraded ” XO showing all the new caps and resistors Sound-wize, I am very glad. After a period of something one could burn-in, they sound very nice. I have learnt to appreciate the switch with six positions very much. Regards//lasse Stockholm, Sweden

Hi all, Three questions. The speakers are now in service and have been so for a few weeks. I think that they are ”opening up” graduakky. Remember that they come out from a >10 year long storage period soo… Now to my questions: 1. Is it my imagination or do you think that there is some truth in speakers ”opening up” sonically when getting ”exercise” after a long period of non-use? 2. See post above this one. Does anyone of you have measurements of the ”tweeter-clusters” in your AR-LST to share and to compare with mine? 3. I have realized that the LST have a back-plate that is completely un-braced. When loading the units into the trunk of my car, when transporting them from the seller, I notised that the backplate was flexing. Has anyone considered bracing the back plates, perhaps externally?? Regards//lasse

Hi, Attached are pictures of impedance-sweeps for the two "Tweeter-clusters" What do you think? 4 or 8 ohms?

You get them anyway

By the way, the woofers are back from the company in Stockholm that mount new surrounds. Would you be interested in the DATS-measurements after repair?

Hi, I will try with 4.7 uF but why electrolytic capacitor? Do you think that all the caps in this system woluld be electrolytic ones? Best regards//Lars

Ah, now I get it. The 1-5 uF is // with 2500uF and //10 ohms. This morning, I have replaced the old 10 ohms resistors with MOX and also modified a thing that perhaps not all of you agree on: I have replaced the fuseholders on the back with ordinary "banana-plug-terminals". I plan to use ordinary 2A fuses hanging on the back of the speakers. Now I wait for the woofers to be ready with new surrounds and at the same time, I will buy (22+18)uF caps and 0.5 ohm MOX´s. 55 USD, but it will be worth it! Regards//Lars Stockholm, Sweden

Hi and thanks for your input. Yes, I suppose that it´s a good way to go to replace all the caps and resistors to better ones. (and younger ones, too) That is: 6uF, 40uF, 150uF (Bipolar), 0.5ohms (Mid) and 10ohms (//2500uF) But where are you suggesting to put the 1-5uF-cap? On the woofer-shunt? Regards//Lars

Hi and thanks for the reply. Other posters have adviced against replacing the capacitors. I haven´t tested them but the impedance plots seem to indicate that the XOs are OK. What is your opinion on that? (My reaction to abt 50 years old caps is to replace them...) It turned up that my tweeters are 8 ohms. I will listen and measure SPL and see how well they blend in, in spite of the wrong impedance. It could work or one could modify the 6 uF-cap to something a bit different. Best regards//Lars Stockholm, Sweden

Hi all, If you have f****d up and made a fool of yourself, the best way to deal with it is to admit, take the blame and move on……… I have shown to myself (and to all of you) that even a schematic as simple as the one on AR-LST present difficulties beyond my capacity to deal with! I have now made the correct impedance sweeps and it is obvious that the XO is intact and that I have 8 ohm tweeters.. I attach pictures from one of the six positions with/without the 2500uF/10 ohm series components and yes, the effect is below 20 Hz. My amp, H/K 870 can deal with loads down to 2 ohms so I think that I could remove the combo. Next thing, after reading your comments (that is if you think that I am worthy of that) will be to refoam the woofers and then measure the SPLs Best regards//Lars Stockholm, Sweden

I read somwhere on this board that 200013-1 are 4 ohms tweeters and 200013-2 are 8 ohm ones. I plan, among other things tomorrow, measure the combined impedance behaviour of the respective tweeter and mid "clusters" Is the added cap/resistor-combo meant to be a correction to 4 ohms operation? (They are not connected on the tweeters today, as far as I can see) Will be back! (I never give up!) Regards//Lars

Hi again, Sorry, my fault! I forgot to mention that My units weren´t delivered with fuses. And my measurements are made without the 2500uF cap I try to attach the six screenshots from measurements of the six positions för the knob. And I realize that this line of questioning is a bit much to throw at you from a rookie on the board but hopefully, there is someone who realize what is going on.... Best regards//Lars Stockholm, Sweden

Hi, Yes I was hoping that my measurements would be like the published ones from AR, but obviously, something is wrong. If you "scroll" through the six positions in the PP-presentation, you see that the impedance peak "evolves " towards higher frequencies. I wonder if anyone has experienced something like this before??