Joey -
Sorry, didn't see your message asking about Steinberger amid the stream! I'm a big Steinberger fan too (I'm one of the moderators of the Steinbergerworld e-mail group) and have a bunch of Steinbergers of various vintages. I had most of these basses before I got married - I would call them a collection although my wife calls it an affliction.
The construction of Modulus necks is really different than Steinbergers. The Modulus neck is laid up from graphite cloth that's impregnated with epoxy, then it's cooked under heat and pressure in a big autoclave (the size of a small car). The finished neck is hollow which is a strong structure from the physics standpoint. Geoff Gould worked at Ford Aerospace building satellite parts so his techniques and materials carried straight over to guitar necks.
The Steinberger neck is a solid casting of resin that has a backbone that's made of graphite fabric and kevlar. The (small) body of an L2 or XL2 is hollowed out (it looks like a TV dinner tray in there) to keep the instrument from being too heavy (most people are suprised at how heavy a Steinberger is when they first pick one up). The construction technique was developed by a consultant who made power boat hulls. There's no better or worse, just different.
If you played a Steinberger and a Modulus with the same EMG pickups, you'd definitely hear the difference. The Steinberger sounds more like wood, and the Modulus has more high end. Both are much more even across the neck than wood instruments.
The Steinberger is so different than a J-Bass that it can't help but sound different. The Steinberger is much stiffer and denser than maple, it's a through-body, it's headless, and has really massive hardware. Wood neck guitars don't suffer too badly from the wolf-tone problem, but the resonance frequency of a bass neck is in the audio range of the bass' notes, so when you hit one of those notes, the neck just swallows up the energy and you get a weak note. The composite instruments are a lot stiffer, so the resonant frequency is shifted up, you don't get the dead notes, and the instrument sounds much more even across the range. Laminating a wood neck or adding ebony laminates similarly affects the stiffness and resonance and changes the sound.
In theory, the wood necks will vary from neck to neck because each piece of wood is different and composites should all sound the same, but in practice there's so much handwork in a Modulus or Steinberger neck that they all end up having individual voices as well. I've got a bunch of L2 basses (the original model) from different factory locations (Brooklyn, Newburgh), and I can tell them apart by sound, although they feel exactly the same.
FYI, the Status basses from England are similar in construction and materials to Modulus and the unplugged sound is very similar. Their process is more modern then Modulus so they can make more complicated shapes. The Moses Graphite necks are a cast structure more like the original Steinberger.
David Fung