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TubeCraft

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  1. Al, was there a reason you mounted the mid-horn and the woofer to the back of the motorboard? Since on the Heresy II they're mounted to the front, I always thought that, if I was "reboxing" my Heresys, I'd do the same. Any thoughts on this?
  2. It sounds great, John! Suddenly, I can hear the Woofer. I eventually removed the resistor and changed the first cap to a 1uf "NYT" (New York Telephone?) paper in oil cap. It had mounting ears just like the original. Easy peasy. I would recomend this mod to anyone who has their Heresy's up on stands away from the walls, like I do. Perhaps I'll fool around with changing the speaker taps to 16 ohms since the mid impedance is so high... but it does sound great just the way it is! In case anyone is wondering my system includes: Dual 505 Turntable w/Ortofon OM5e Phillips CD Burner/Player Dyna FM3 Modified Dyna PAS-3 Preamp (tone controls removed, boards recapped, and generally tweaked) Homebrew Amps: 6B4G PP (approx. 8 watts) 6B4G SE (approx 3.5 watts) (One or the other is always on my workbench) Two homebrew sub cabs (15") driven by an Adcom GFA-1 through an old Heathkit(!) sub crossover
  3. I've tried lots of plastic caps in tube audio circuits, Solen, Auricaps, Musicaps, etc. and I always seem to come back to paper in oils, wherever they fit and whenever I can find the appropriate value. And when I use plastics, I can't really tell the difference between Solens and anything fancier... If the price is really right try the ebay PIO's.... even if they're vintage, as long as they're still sealed, they'll probably work great... that goes for the ones that came in your Klipsches, as well....
  4. Sorry to be a pest, John. Of course you are right. After doing the math a bunch of times, I finally figured it out. Anyway, I tried this mod, and it works quite well, especialy if your Heresys are up on stands, away from the wall (like mine are). Anyone who's thinking of trying something drastic (like swapping woofers) should try this first. Now I'm going to pull the resistor, and try a 1uf NYT/Westrex PIO cap in place of the 2uf... I'll post results over in Odds and Mods....
  5. I still think the squawker and tweeter are basically in parallel. I mean, you wanted to put 8 ohms across the tweeter as well, originally right? I don't think tweeters impedance at 700hz is very relevant, as that first cap also sees the tweeters impedance at every frequency above 700hz as well, probably dipping down to 8 ohms or lower at some points, hopefully for an 8 ohm average at the tweeters normal operating range.... I know actual impedance is complex, but we use nominal impedances to calculate starting points for crossovers, don't we? No, I still think the tweeters impedance in its normal operating range matters a good bit at that first cap.... I'll happily change my mind if you can set it out for me..... I'm also beginning to think that a resistor isn't the way to go, for me. I calculated 180mw loss across the resistor at 1000mw input for my method, and my favorite amps only do 3500mw and 8000mw respectively. Now I'm trying to recalculate the first cap... I have some nifty vintage NYT/Westrex 1uf paper in oil caps lying around that would probably sound pretty good..... All this is important, even from an experimenters standpoint, because you could fry a horn midrange by sending it too much bass, and raising the effective impedance seen by that first cap will lower the effective crossover point, yes? It would be a bummer to fry a K-55-V.... Once again, I'll happily change my mind about anything if you can lay it out for me... I have no formal EE training, I do have experince in professional sound reinforcement (theatre and music) and building tube amps....
  6. John, thanks for the schematic, BTW! Notice the multipliers for the taps? I think that's the key where PWK is telling us how to use that autoformer to change the spectral balance of the Heresy to suit the installation. "One step reduces the output 3 dB and doubles the impedance seen by the amp." Yes I agree that one step reduces output by 3db but I don't think that it doubles what the amp sees. The amp sees the impedance of the entire system, woofer, tweeter and crossover. What matters is that we've changed the impedance seen by the first 2uf cap that feeds the autoformer. By moving the taps, we've doubled the impedance, as you said. That's the balance that needs to be restored. So we need to calculate the original impedance seen by that cap, then add the appropriate resistor across the autoformer. The impedance seen by that first 2 uf cap is the impedance of the tweeter (8 ohms multiplied by the "tap factor" 8x4=32ohms) in parallel with that of the squawker (16 ohms multiplied by the "tap factor" 16x8=128 ohms). A 32 ohm impedance in parallel with 128 ohm impedance = 25.6 ohms Double the 25.6 = 51.2 ohms seen by the cap. Parallel that with 51.2 ohms to bring the total seen by the cap back to 25.6. I think this is roughly what AL K. was talking about...
  7. John, your revised schematic still shows a 16 ohm resistor across the squawker. (Was at terminals 0-2 you changed to 0-1 -- where the numbers are the autoformer terminals.) I think Al K. was suggesting a single resistor across the autoformer (0-5). Al, what would be value of that resistor? Any help would be appreciated as I intend on trying this out this weekend. Thanks! TC
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