I've used a Helix Floor for years and love it. Still do. But I recently got an FM9 just to see how green the grass is on the other side.
Both units have their pros and cons, and honestly I think the Helix is at least as good overall. But the longstanding opinions of Fractal's Marshall models, and the ability to tweak them to really get what you want, has rung true in my first week.
I'm sure you all know the song Under the Bridge by RHCP. We've heard it a million times. But have you ever listened to the isolated guitar and really tried to match it? I have... for years. It's a JCM800, room mic'd, and somehow it sounds clean yet crunchy, tight and punchy, with a bright compressed edge-of-breakup chime on top, and a distinct bassy growl riding underneath. The attack hits hard, like the amp was thumping off the walls of the LA mansion where it was recorded.
I'd be embarrassed to admit the number of hours I've spent trying to get this sound in modelers/plugins. A tonematching IR doesn't cut it, because the dynamics are key. It's become my "how capable is this?" stress test. The FM9 has gotten closer to it than I've ever been able to get. In the cab block, I used a combo of room mic IRs included in the stock cabs (panned L/R), the proximity adjustment, the room reverb sim, and fine-tuned the alignment of the IRs (boy is this nice with the visual graph that overlays both waveforms!). In the amp block, I made heavy use of the speaker impedance/interaction settings, which was key to getting it to sound right: I tweaked the impedance curve, cab resonance, low frequency peak, low frequency resonance, speaker drive, speaker compression, speaker compliance, and speaker thump. Doing this, I was able to match that bassy resonant growl, the breakup in the highs, and the way it sounds like the cab is vibrating with every attack. It's also very touch sensitive and feels great -- highly reactive to playing dynamics.
Anyway, here's a clip. <edit: sorry for the sloppy playing! Recorded it quickly on lunch and now listening back, it could use some cleanup!>
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