@GM thanks for giving me that understanding-it is a simple relationship. @Nelson Pass, thanks for the insights on your Lii's--I'm a bit gobsmacked that you replied but very appreciative. Have you used them with any of your voltage source designs, and if so what if anything did you use to tidy up the response? As noted above I don't think your network intended for current source amps will fly with my F5 so I was thinking I'd have to come up with something like the filter Decware sells for this. I want to play with DSP and Omnimic to figure out what's needed in my room and with my subs but would like to implement a circuit based fix ultimately. Thanks for any advice!
@Nelson Pass, I understand there's an improved version of the network in the store, but isn't this statement from your article here still true?
https://www.firstwatt.com/pdf/art_cs_amps.pdf
"Remember, you don’t have to own a current-source amplifier to put this information to work. Placing R0 in series with the output of a powerful voltage-source amplifier instead of in parallel with a current source will give similar results. If R0 is 47 ohms or higher, you are going to want a big amp, say 300 watts, but in any case, be certain to use a high power resistor of 50 watts or more."
I don't know where the final R0 value for the Lii Audio Fast-15 might end up but the 17 speakers you tested in that article had a range from 10-47 and were physically much smaller than the Lii, of course. This made me pessimistic about the potential of driving the speakers using my F5 and with your filter. I wondered if I should instead just hack up this circuit suggested by Steve Deckert here https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1658916276/155 that's suitable for the low powered tube amps he sells.
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1658916276/155
You may get tired of hearing this but I have to say thank you for being so incredibly generous with your time and your brilliance! Rather than hoard it like most of the other geniuses of the world you just give it away. It's beautiful and much appreciated by everybody here.
https://www.firstwatt.com/pdf/art_cs_amps.pdf
"Remember, you don’t have to own a current-source amplifier to put this information to work. Placing R0 in series with the output of a powerful voltage-source amplifier instead of in parallel with a current source will give similar results. If R0 is 47 ohms or higher, you are going to want a big amp, say 300 watts, but in any case, be certain to use a high power resistor of 50 watts or more."
I don't know where the final R0 value for the Lii Audio Fast-15 might end up but the 17 speakers you tested in that article had a range from 10-47 and were physically much smaller than the Lii, of course. This made me pessimistic about the potential of driving the speakers using my F5 and with your filter. I wondered if I should instead just hack up this circuit suggested by Steve Deckert here https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1658916276/155 that's suitable for the low powered tube amps he sells.
https://www.decware.com/cgi-bin/yabb22/YaBB.pl?num=1658916276/155
You may get tired of hearing this but I have to say thank you for being so incredibly generous with your time and your brilliance! Rather than hoard it like most of the other geniuses of the world you just give it away. It's beautiful and much appreciated by everybody here.
Attachments
I'm not Nelson, but until he can reply:
With an output impedance of 0.1ohms & a damping factor for the FAST 15 of 81.25 based on its stated Re (Lii must be able to at least get that right), then you've basically got a voltage source there, so I'd just stick with the basic bypassed LP shelving filter Steve suggested, & adjust the values as desired. Size taken purely in itself has no direct relevance to these filters which are designed purely for the relevant impedance & FR. Steve may have specified the values for the higher output impedance of his valve designs, since the FR will to an extent track the impedance curve as it would with one of Nelson's current-source designs, but from a quick eyeball they don't look particularly unusual, so I'd be inclined to keep the L & bypassing cap value as-is initially, and then simply use a pot to dial in your preferred quantity of resistance, measure it off & replace with a fixed value.
With an output impedance of 0.1ohms & a damping factor for the FAST 15 of 81.25 based on its stated Re (Lii must be able to at least get that right), then you've basically got a voltage source there, so I'd just stick with the basic bypassed LP shelving filter Steve suggested, & adjust the values as desired. Size taken purely in itself has no direct relevance to these filters which are designed purely for the relevant impedance & FR. Steve may have specified the values for the higher output impedance of his valve designs, since the FR will to an extent track the impedance curve as it would with one of Nelson's current-source designs, but from a quick eyeball they don't look particularly unusual, so I'd be inclined to keep the L & bypassing cap value as-is initially, and then simply use a pot to dial in your preferred quantity of resistance, measure it off & replace with a fixed value.
Your strategy makes sense, @Scottmoose, thanks for replying. Looking forward to screwing around with all of this once I get my baffles back from the wood shop (cheater!).
Can't comment on inductors since I always 'wound' mine by de-winding factory made rolls of wire, but caps, if it ain't the pioneer's PIO in the signal path you're potentially 'selling yourself short' IME, especially WRT 'FR' drivers and/or any vintage spec system, though I've always found plenty of folks who disagree, so YMMV, etc.. Note too that even when young I've always relied on various young females' hearing to 'voice' components, systems since they have the best hearing and regardless of age if there's any in your life you've got to make their (differing IME) musical choices sound special first and foremost IME.
FWIW, TTBOMK, motor run caps are closest to the pioneers', no clue about $$esoteric$$ offerings.
FWIW, TTBOMK, motor run caps are closest to the pioneers', no clue about $$esoteric$$ offerings.
Inductors are straightforward enough -technically air cores are preferable if you have the space (since they get physically large for low DCR windings). 14ga should be fine; Solen, ERSA, Jantzen etc. all offer that or near-as, or wind your own if you feel so inclined. I'm not a fan of foil types; litz is a bit pointless but doesn't do any harm. Just a quality round or square-section wound copper is fine, preferably in self-amalgamating or dipped in varnish or similar to eliminate any possible mechanical movement. Caps -PIO as GM said are theoretically ideal, but hellishly expensive if you can't get motor-run in or near the desired values, and most have fairly wide tolerances (although that's not hyper critical for this applicaion). Otherwise -polystyrene if you can get in or near the correct value & parallel them up, film & foil or a decent MKP -preferably oil impgregnated if you're not paying a silly amount for the privilage, which you probably would be. I often like to quote this, from Jeff's Place, as it shows just how far things can get. Full marks for the vivid attempt at describing subjective impressions -perhaps a little extreme on the old analogies though. 
Blimey.
Blimey.
Well my goodness, what type of website is this Jeff's Place anyways? Maybe he needs to visit one of those other sites and get it out of his system before writing up blog posts?
Just kidding, I did check that site out years ago when I was looking for blocking caps for a power amplifier. Could not believe how much some of those Duelund, etc. caps cost! I guess all I can say is it would be great to have a system and ears that were so fine tuned. @rdf your advice sounds good-I'm not going to go crazy. @Scottmoose and @GM thanks for the inductor info. I was mostly wondering about the awg.
Just kidding, I did check that site out years ago when I was looking for blocking caps for a power amplifier. Could not believe how much some of those Duelund, etc. caps cost! I guess all I can say is it would be great to have a system and ears that were so fine tuned. @rdf your advice sounds good-I'm not going to go crazy. @Scottmoose and @GM thanks for the inductor info. I was mostly wondering about the awg.
Still waiting on the speaker cabs (stands, really) and am puzzling over capacitors after buying the variable resistors and inductors. I was going to cheap out a bit and go with poly film caps but I'm afraid they'll sound harsh. For PIOs, should I take a chance on some cheap obnoxious green Russian surplus K75s or spring for the AmpOhm copper foil? Only others I've seen with the correct value that aren't outrageous was Jensen copper, listed as discontinued. Hard to find other 0.68uf PIOs around. Vintage seems like a bad idea although people say they last forever (people say a lot of things). And then there's the sound. Reading through several other posts other than Jeff's place with winetastingish descriptions didn't really help. Motor run caps in the metal housings just seem too steampunk to take seriously. Thoughts from anyone?
Re inductors, I used 12 ga. since it was cheapest in bulk.....last time I checked motor run caps were quite inexpensive new, though imagine there's used also from scrapping various appliances, though with limited choices nowadays will probably have to make a mini capacitor bank if wanting a precise value.
I ended up getting these 15ga Jantzens-did not think the small difference in gauge would matter and the other ones on PE were for much more power than needed https://www.parts-express.com/Jantzen-1898-1.0mH-15-AWG-Air-Core-Inductor-255-422
I assembled an amplifier based on a GM70 with direct coupled to a 12GN7A driver and automatic control of the GM70 current, but with a capacitor at the input. I started reading reviews of capacitors and realized that I couldn’t choose a good capacitor for a price less than the cost of the entire amplifier. I had to remake the amplifier without a capacitor to input.