Lars Posted December 26, 2022 Author Report Share Posted December 26, 2022 You get them anyway Quote Link to comment Share on other sites More sharing options...
giovanni56 Posted December 26, 2022 Report Share Posted December 26, 2022 8 minutes ago, Lars said: Li prendi comunque You can't see anything Quote Link to comment Share on other sites More sharing options...
Lars Posted December 31, 2022 Author Report Share Posted December 31, 2022 Hi, Attached are pictures of impedance-sweeps for the two "Tweeter-clusters" What do you think? 4 or 8 ohms? Quote Link to comment Share on other sites More sharing options...
Lars Posted January 11, 2023 Author Report Share Posted January 11, 2023 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 Quote Link to comment Share on other sites More sharing options...
Pete B Posted January 18, 2023 Report Share Posted January 18, 2023 Your tweeter impedance certainly looks to be 4 ohms. That is of each series-parallel array? If they all work, I would just use them and listen for distortion in case any of them have problems. Perhaps they were already rebuilt with 4 ohm coils? Both arrays have an impedance peak around 4KHz which is very high and makes them super tweeters. Most of those tweeters that I've measured, perhaps were worn out, did not show much of a peak at all. I don't know what the correct impedance peak frequency is for those tweeters. As far as caps go, I would replace the tweeter and mid caps as soon as possible. I prefer film caps because I don't like to have to change them every 10-20 years. I'd probably replace the cap across the woofer with an NPE. The large input cap I'd check for leakage and it might be okay, otherwise you might want to replace them with new. See how they measure for leakage and how they sound. Quote Link to comment Share on other sites More sharing options...
Lars Posted January 18, 2023 Author Report Share Posted January 18, 2023 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 Quote Link to comment Share on other sites More sharing options...
Pete B Posted January 19, 2023 Report Share Posted January 19, 2023 Great that you already rebuilt them! Yes I'd add the shunt cap but no rush. Hope you enjoy them very much. Quote Link to comment Share on other sites More sharing options...
Lars Posted January 21, 2023 Author Report Share Posted January 21, 2023 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 Quote Link to comment Share on other sites More sharing options...
Lars Posted January 31, 2023 Author Report Share Posted January 31, 2023 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 Quote Link to comment Share on other sites More sharing options...
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