You may use EC 2. However, Infinity crossover has Servo to control woofers. This servo is Arnold Nudells key design feature. http://www.genesisloudspeakers.com/index.html Read The Servo-Bass advantage article under Technology.
Some people drive woofers without servo, but you are giving up the main feature of RS1b if you do so.
You need real high power/high current amp for bass. I think Krell is a good choice. Mark Levinson or Pass Lab will do the job as well. D-250 has been used for RS1b demo at trade shows.
150Hz is normal cut-off, but you may experiment with other settings and slopes. Its really room dependant.
Never had major problem with the Infinity. In rare occasion, fuses blow on H/M panels but you can easily replace them. There are some people who have EMITs & EMIMs for sale; I saw them at Audiogon site, and other Internet vendors. (I never replaced any driver; they are reliable) http://sphl.audiogon.com/cgi-bin/buy_cl.pl?spkrplan&1145510864
How much power do you need? It depends on various factors; room size, volume level, kind of music you play, etc.
One thing is certain; RS1bs must be played loud. The servo woofers will not generate enough bass unless they are fed with real power. At low volume level they are so slow and lame.
However, that doesnt mean you cannot enjoy harpsichord solo or string quartet at low volume level. If source material doesnt have much information below 150Hz, EMIT/EMIM panels will give you beautiful rendition of the music (sans woofer).
1. You need a large room. Its true to any planer speakers; they need sufficient air volume, especially at the back of speakers.
2. Placements of High/Mid Panels and Woofer Towers are critical. The hardest thing to accomplish is to blend sound of EMIT/EMIM with Servo Woofers. There is no absolute topological formula. It all depends on given room acoustic, you may spend next 12 months moving those heavy cabinets around to obtain optimum result.
3. Crossover point. As you know, the factory crossover has four positions; 100, 150, 200 and 250Hz. 150Hz is recommended. If you set it at higher crossover point, lower mid-range gets muddy and loses definition.
4. Does EMIT has linearity problem? Some audio critics pointed out that Infinity tweeters are incapable of obtaining linear high frequency response when they are pushed to max level (thats why IRS has so many EMITs to minimize the burden on individual unit) I found it is crucial to maintain linear response of EMITs as much as you can, to avoid bright and harsh tonal quality. (Id like to have comments from Albert Porter on this issue)
5. Thats why Audio Research works well with Infinity speakers. ARC has just that; extended high frequency response. After tried many powers amps in 100 - 200W range both tube and solid state, I concluded that D-70 has enough power to drive High/Mid Panels. I didnt hear significant improvements from more powerful amplifiers. When you select power amp for Infinity, the most important thing is to avoid amps with high frequency roll-off. Without enough power to drive EMITs to optimum frequency extension, the result will be thin and screechy sound.
6. Tube Rolling. When D-70 had Sovtek 6550s, the sound was steely and bright. KT-88s transformed overall sound quality; rich and warm with lots of harmonics. Was I lucky? Maybe. I dont know if other KT-88s will bring the same result. The guy installed new tubes said he changed bias settings also. So, bias maybe another factor.
A road to audio Nirvana is long and winding road. But reward is more than satisfying.
Beethovens No.23 Piano Sonata CD was playing when pizza delivery guy came in. At doorway, he said, "Oh, I didn't know you had Grand Piano in your house." That was the best compliment for my RS1b!
