Though I should probably leave well-enough alone... I've been listening to a pair of JBL 4320's and 300B Paramounts, and I hear a slight, kind of "klangy" sound around the 800hz crossover (schematic of #3110 JBL network attached), well below the 1W output level, according to my multimeter. First idea was to replace all but the autoformer in the #3110 networks with really nice parts, but that would run over $1000. Then I thought, just the caps, with some nice Solens, which would run more like $100. But either option would still leave me with a 2nd/2nd order filter with the polarity of the tweeters reversed. Maybe part of the "klangyness" is from unfortunate overlap of the drivers? Maybe a 4th/4th order, in phase filter would sound nicer, to me? Maybe I could even... make it an active filter? Before I continue, I think the nicely re-coned 2215 woofers and 2420 tweeters are just fine, since the stereo image is really consistent and the "klangy" sound, I'm guessing, is more from aging caps than anything else. Of course I could be totally wrong about all this. And maybe its all just an excuse to get a second pair of Paramounts. Okay, so if all goes well, the generic active XO circuit should appear below. For a 750hz XO, and according to Pete Millet's site, I would use .001uF and .002uF caps and 150K and 300K resistors, and 300K grid leak resistors. Cathode resistors would be 50K and the 12AU7's would draw 2-2.5mA. The 5K PSU dropping resistors could be reduced so as to raise the V+ and V- and 12AU7 current draw. At first I was hoping to use a 3-triode compactron (6C10, 6D10, etc.), but it seems important to bias the first triode at at least -4Vg, and I couldn't find a compactron that was a triple 12AU7 or similar. Also, aside from the cool factor of getting a complete 4th order high- or low-pass out of a single tube, a row of 3 12AU7's for a high- and low-pass pair-o-filters or "parafilter" will probably offer better spacing for the R's and C's. Of course the circuit is planned so that I could add in C4S current draws, choke-input PSU, and maybe a little voltage regulation, but first I'd like to see if I can get away with AC heaters on the 12AU7's, since the PGP8.1 can accommodate 1.8A of AC but not 1.8A of DC @ 6.3V (heaters). My initial idea was to leave these 4320's stock while I worked on my other, multi-amping project, but now I'd really like to hear this 2-way speaker with a 4th/4th order filter and a Paramount direct coupled to each of these drivers. From the specs, I think the 2215's are 96dB efficient and the 2420's (WAG) 106dB. Also, I realize that for the HP, I could also use a 2nd order filter and re-size the interstage and parafeed caps in the Paramount, but I really don't want to touch the latter's circuit... yet. Any comments or suggestions on all this rambling would be very welcome. Thanks!