owlsplace Posted May 7, 2015 Report Share Posted May 7, 2015 I know I saw the LST xover diagram recently but can't seem to find it; then I remembered I saved a copy of RoyC low-res version.I would like to experiment with the capacitory (sic) protection circuit. See bottom left of diagram.I'm I correct in assuming these are npe caps?Roger Link to comment Share on other sites More sharing options...
Carlspeak Posted May 7, 2015 Report Share Posted May 7, 2015 Yes, very high value NPE's. Madisound's Bennic's go quite high in uF. IIRC, up to 1000 mfd. Link to comment Share on other sites More sharing options...
Andre Posted May 7, 2015 Report Share Posted May 7, 2015 http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4541 Link to comment Share on other sites More sharing options...
owlsplace Posted May 7, 2015 Author Report Share Posted May 7, 2015 Thanks, Andre. That diagram is a wee-bit different from the first one Have to do a little research on parts unless someone has a photo of the actual crossover. What would be the power rating on the 10 ohm resistor? Link to comment Share on other sites More sharing options...
Andre Posted May 7, 2015 Report Share Posted May 7, 2015 Are the first two pics showing the LST crossover ?http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4541 Link to comment Share on other sites More sharing options...
owlsplace Posted May 7, 2015 Author Report Share Posted May 7, 2015 Well, they are making me work today so I won't have time for this perhaps until later on but it looks like those are polarized electrolytics and the second diagram doesn't block DC in the woofer circuit which was what I was interested in doing....Roger Link to comment Share on other sites More sharing options...
owlsplace Posted May 8, 2015 Author Report Share Posted May 8, 2015 Pricey experiment (8) 5000mfd 75V for about $200 from Mouser ... will have to muse on that one for awhile update: Well, you can get a lot of entertainment out of reading old cap posts -- perhaps even write a comedy routine or script for a Broadway play. Not finding much for specs on these caps which means a higher reluctance to drop that kind of cash...http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=953&p=53815 Link to comment Share on other sites More sharing options...
KlausDK Posted May 25, 2015 Report Share Posted May 25, 2015 This diagram would be from my description of the restauration of my LST's in this post:http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2201&p=63384The evolution of the LST DC block circuit is roughly as this, it started with no caps, and a lot of burned amplifiers, since it would be a short circuit at 0 Hz, then 4 x 5000 PE's where added, then two 5000 NPE's in series, resulting in a capacity of 2500 uF 120 Volt, in the end a 10 Ohm resistor was added and the two big cap's was changed to a single 2500 uF/60Volt capacitor (like it was later used in the rossover for the 10Pi). I have upgraded my LST circuit with a non-inductive resistor (10 Ohm MOX, 10 W), and some smaller filcaps in parallel with the NPE's, to aid the HF signal across the big caps, as shown in my modified crossover above.BRgds Klaus Link to comment Share on other sites More sharing options...
owlsplace Posted May 25, 2015 Author Report Share Posted May 25, 2015 Klauss,Thanks for chiming in. The final LST circuit that you are using looks good for that application.I had an idea to use the four cap design for a protection circuit for "classic era" speakers since the woofers are becoming rarer. A lot of aging amps are still in use and stories of fried voice coils due to failed output stages keep appearing.I haven't ruled out trying this for a project although it is not a priority at the moment. I have located some less expensive caps. The original circuit shown in post #1 apparently caused loading problems with some amps: two sets of 5000mfd parallel PE cap pairs in series, so the total capacitance was reduced to 2500mfd, or so I've read elsewhere.Roger Link to comment Share on other sites More sharing options...
KlausDK Posted May 25, 2015 Report Share Posted May 25, 2015 I had an idea to use the four cap design for a protection circuit for "classic era" speakers since the woofers are becoming rarer.Hi RogerWhy not use fuses for that, as recommended by AR? I have all my 10" and12" AR speakers fused, and at least in 1 case it saved the life of a 12" woofer.BRgds Klaus Link to comment Share on other sites More sharing options...
owlsplace Posted May 26, 2015 Author Report Share Posted May 26, 2015 Yep, mine are all fused also but for some reason I'm stuck on trying this out Link to comment Share on other sites More sharing options...
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