Guest esmachers Posted January 11, 2006 Report Share Posted January 11, 2006 This thread was originally started in #377, "Advent experiment - mod - much better sound IMO" and was taking it off track. This is really more about problems I'm having with my large Advents after replacing my electrolytic caps with Polys.Below is where this picks up from over there. I hope others find this useful. Hi Pete,Thanks for the great suggestions and offer to check out my network. I live in Maryland near Annapolis so doing this in person won’t be possible. Let me try your suggestions and see where it gets me. If I get lost perhaps I can mail some parts to you. I don’t have a good supply of resistors so it’ll take me a little while to come up to speed. I’ll draw out a schematic and post it to make sure I’ve got things right before starting. I REALLY appreciate your help with this. I really am having fun.Steve>Hi Steve,>>The 2.2 ohm reading is just fine, mine measured 2.35 and>Advent says approximately 2 ohms. If your curious it is good>to also measure each of the drivers to see if they match and>far off readings can indicate a problem. One thing to note is>that the tweeter connections, on those old tweeters go through>screws that you might want to make sure are clean and making>good connections. You might have also noticed my comments>about the switch:> >http://www.classicspeakerpages.net/dc/dcbo...g_id=&page=#707>>Remember that cleaning all these connections will bring the>tweeter level up if there was corrosion and high resistance.>>The most likely issue is that the ESR of the electrolytics has>gone up with age and it is likely that the polys make the>system sound more like it did when new.>>First I suggest that with the speakers as currently wired you>put your system in mono, put the speakers side by side, and>use your balance control to switch between the two.>Do they sound the same?>>If they do we can leave one as is and wire the poly back up>but with a 1 ohm resistor in series to simulate the ESR that>you prefer. It would be best to bring out the connections so>that you can try different resistor values in order to match>the reference speaker. Use music that your familiar with,>interstation FM noise, or test CDs. Try the poly alone but>this time compare against the other speaker with the>electrolytic still in place - do you still hear a large>difference?>>New electrolytics typically have about .2 to .3 ohms of ESR>and this is just about 10% of the 3 ohm decrease resistor, so>it is not that significant but probably is barely audible.>>I'd be willing to measure the electrical frequency response of>the network with the electrolytic, and the poly in order to>determine the best way to address your question, are you in CT>or nearby by any chance?>>Let me comment that you now have a hybrid of Rev1 and Rev2, to>complete the Rev2 upgrade you need a low DCR, .45 mH inductor>in place of the old 2.2 ohm red dot type. It is true that the>difference is only in the extended position and even the>hybrid is better than the original.>>Pete B.>>>>Hi Pete,>>>>I replaced the capacitors in my large Advents with Bennic>>polys from Madisound: 16uF for the C1 capacitor and 8uF for>>the C2 “increase” capacitor that was previously 16uF. While>I>>was in there I disconnected the tweeter and measured the DCR>>of the L2 shunt inductor. It read 2.2 ohms in each speaker.>>Note: I don’t have the most accurate DMM so that could be>off,>>but L2 is definitely not shorted.>>>>I replaced the caps in one speaker first and thought I liked>>the sound so I did the other speaker. After that is when my>>ears started to hurt. The speakers were incredibly harsh in>>all 3 switch positions. This setup truly sounded like a>>transistor radio with a subwoofer. And, if I was listening>to>>a weak FM station, i.e., one with a little background>static,>>it was unbearable. >>>>Undaunted, I left the caps in place over the weekend to see>if>>it was just me being overly sensitive. By last night my>>soldering iron couldn’t heat up fast enough. I put my>original>>16uF electrolytics back in. I left the 8uF caps in place for>>now since I usually listen to these speakers in the “normal”>>position. >>>>Anyway, I’m at a loss. I don’t have a capacitance tester so>I>>can’t verify the Bennics but they are marked as 16uF and>>physically they are about twice the size of the 8uFs.>Further,>>after heating up the electrolytics twice now to>>desolder/solder them I’m really concerned about their>>reliability.>>>>Ideas and comments are appreciated. >>>>Thanks,>>Steve>> Link to comment Share on other sites More sharing options...
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