twinbugles Posted January 20, 2013 Report Share Posted January 20, 2013 Greetings all:Newbie here to this site, and to AR speakers, but an old hand at collecting, enjoying, and restoring vintage hi fi.Recently, I purchased a pair of LST 2's from the original owner. They appeared flawless, not a mark or scratch anywhere, grills still nice and clean, etc..in the original boxes! I removed the grills and found rotted foam surrounds on the woofers, no prob, easy fix. Hooking up the speakes revealed sound coming from all of the mids, but no sound at all from ANY of the 6 tweeters. Large fuses on the backs of the cabinets are intact.What are the chances of all 6 tweeters being bad? I pulled them to check wiring, and all are connected. Checkingwith VOM and I get no response, so it appears they may be all open, unless I am doing something wrong here.Any suggestions? If they are all bad, what will be the best replacement tweeter to use?Thanks in advance here, I am enjoying reading the many posts and threads you all share here.Cheers!Bill H. Link to comment Share on other sites More sharing options...
RoyC Posted January 20, 2013 Report Share Posted January 20, 2013 Welcome to CSP, Bill...I have worked with another forum member who replaced all of his LST-2 tweeters with HiVi Q1R tweeters. We made a couple of easy crossover adjustments, and he seemed quite happy with the result. We added a small parallel coil to the tweeeter circuit, and reduced the tweeter cap from 12uf to 5uf.Roy Link to comment Share on other sites More sharing options...
twinbugles Posted January 20, 2013 Author Report Share Posted January 20, 2013 Thanks for the greeting, and your reply, Roy. It is appreciated. Would you happen to have a diagram showing the location and values of the necessary crossover changes, or tell me where I may find a schematic of the crossover?Best regards, and thanks again,Bill Link to comment Share on other sites More sharing options...
rjr513 Posted January 20, 2013 Report Share Posted January 20, 2013 Bill I ran into similar situation on my purchase of a second pair of AR-LST2 i did basically same thing replaced all my tweeters with the HIVI Q1Ri decided to reduce my tweeter capacitance down to 4 uf and added the .05 coil very pleased with the results so far attached is edited version of the LST2 schematic to show my modifications. Link to comment Share on other sites More sharing options...
twinbugles Posted January 20, 2013 Author Report Share Posted January 20, 2013 Hi, RJRThat is exactly what I need to know! Thank you for sharing! Now I have the information I need to pull myself out of the "I cant believe I bought these" doldrums.Cheers,BH Link to comment Share on other sites More sharing options...
RoyC Posted January 20, 2013 Report Share Posted January 20, 2013 BH,You may have noticed that Ron installed a 6uf cap in series with the original 12uf cap to produce the desired cap value. You may want to take the opportunity to remove the old 12uf cap and simply use one new cap of the appropriate value (which seems to be in the 4uf to 5uf range).Roy Link to comment Share on other sites More sharing options...
twinbugles Posted January 21, 2013 Author Report Share Posted January 21, 2013 Thank you, Roy:I do like the idea of the cap upgrade you suggested.Bill H. Link to comment Share on other sites More sharing options...
fast_eddie_72 Posted January 21, 2013 Report Share Posted January 21, 2013 Just a couple of thoughts. I own a pair of LST2s and was very lucky to find all the tweeters working. Only had to replace one mid. I can tell you they're worth the trouble. They sound absolutely amazing. Mine benefited greatly from a complete recap, so as Roy suggested, you could correct the value if you use the HiVi tweeters. Don't neglect the 1000 uF cap in the woofer circuit. I used a Bennic electrolytic there. It made a significant difference in the bass extension. Good luck and enjoy! Link to comment Share on other sites More sharing options...
RoyC Posted January 21, 2013 Report Share Posted January 21, 2013 Don't neglect the 1000 uF cap in the woofer circuit. I used a Bennic electrolytic there. It made a significant difference in the bass extension. If the big cap is a Sprague Compulytic, it is more than likely to be OK. The old Spragues often test better than modern non-polar electrolytics, which are pretty cheaply made.Roy Link to comment Share on other sites More sharing options...
fast_eddie_72 Posted January 21, 2013 Report Share Posted January 21, 2013 If the big cap is a Sprague Compulytic, it is more than likely to be OK. The old Spragues often test better than modern non-polar electrolytics, which are pretty cheaply made.RoyThey were all Srague Compulytics. They all tested in spec for capacitance, but I think the ESR must have been out. I was told by many people that they shouldn't need to be replaced, but just listening to the speakers it was clear to my ears that they needed caps. The difference wasn't subtle. I did one speaker so I could A/B them. It was dramatically improved. Mine may be outliers, but the caps were definitely past it. I didn't do the 1000 uF cap thinking that it shouldn't be as critical. Then I did a pair of AR5s for a friend. I did all the caps in those, and when I hooked them up I was shocked that they had much deeper bass than my LST2s. So I thought it might be worth a shot. I ordered the Bennic caps and again did only one speaker. Again, it was a clear improvement. Dunno. But my speakers sound fantastic now. Link to comment Share on other sites More sharing options...
RoyC Posted January 21, 2013 Report Share Posted January 21, 2013 They were all Srague Compulytics. They all tested in spec for capacitance, but I think the ESR must have been out. I was told by many people that they shouldn't need to be replaced, but just listening to the speakers it was clear to my ears that they needed caps. The difference wasn't subtle. I did one speaker so I could A/B them. It was dramatically improved. Mine may be outliers, but the caps were definitely past it. I didn't do the 1000 uF cap thinking that it shouldn't be as critical. Then I did a pair of AR5s for a friend. I did all the caps in those, and when I hooked them up I was shocked that they had much deeper bass than my LST2s. So I thought it might be worth a shot. I ordered the Bennic caps and again did only one speaker. Again, it was a clear improvement. Dunno. But my speakers sound fantastic now. Forum member John O'Hanlon conducted extensive measurements with very sophisticated equipment some years ago, and found some original Spragues to have less ESR than new npe's. These old Spragues can sometimes be an exception to the rule, but new npe's will work better than the vast majority of old electrolytic crossover caps.An LCR meter is a great investment for a speaker hobbyist.Roy Link to comment Share on other sites More sharing options...
twinbugles Posted January 22, 2013 Author Report Share Posted January 22, 2013 Thank you all for your thoughtful input. I will be putting together an order with Madisound (best price on the tweets) and include your suggestions.Bill h. Link to comment Share on other sites More sharing options...
RoyC Posted January 22, 2013 Report Share Posted January 22, 2013 Thank you all for your thoughtful input. I will be putting together an order with Madisound (best price on the tweets) and include your suggestions.Bill h.Bill,If you do replace caps, I would use film caps for the tweeter and mid circuits. Madisound has a good selection at reasonable cost, with Carli mylars being the best value.Roy Link to comment Share on other sites More sharing options...
fast_eddie_72 Posted January 22, 2013 Report Share Posted January 22, 2013 Completely agree on using film, and those Carli caps are what I just put in my 3s. Very happy with them. But listen to Roy. If he says your Compulytics are likely to be okay, give them a good listen before you make any decision. My LST2s lived a hard life. They may have just baked in a storage locker too long. Link to comment Share on other sites More sharing options...
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