It’s similar to ST10/GT12,
ST10:
Sub-woofer: Sonion 38 AcuPass (2BA)
Bass-Mid: Sonion 37 (2BA)
Mid-Treble: Sonion 2389D (2BA)
Super Tweeter: Knowles SWFK (4BA)
GT12:
Sub-woofer: Sonion 38 AcuPass | 2BA
Lower Mid: Sonion 33 | 2BA
Upper Mid: 2 x GS Custom TWFK | 4BA
Super Tweeters: 2 x GS custom TWFK | 4BA
So my understanding for SD9 is
Bass:1DD (sound like DD, for tonal coherence)
Bass-Mid: Sonion 37 (2BA)
Mid-Treble: Sonion 2389D (2BA)
Super Tweeter: Knowles SWFK (4BA)
So SD9 is basically identical to ST10 except what sub-woofer they use, SD9 uses DD, and ST10 uses Sonion 38 AcuPass
I’m sure you will like SD9
Top notch technicalities if there is no bass bleeding.