I played an OLP passive once that had a nicer MM pickup swapped in, it still didn't sound like a real MM. Wood may have played a part, but I think the preamp plays a big part. The Ibanez ATK is the same way, at least the 2008-ish ones--take the preamp out, it doesn't sound nearly as good. Someone mentioned the magnets, those do make a difference too...Some are ceramic, and some are alnico.. Also, not all MM pickups even in the EBMM model family are equal--There's a tri-coil (humbucker with a dummy coil for single coil operation), a dual coil, and I think a quad coil in some models. I think the newer MM's sound a little thinner than older ones do. I thought a lot of the models were Basswood, not Ash. At looking at their site, looks like the Classic series is made of Ash, but they call the Ray5, Sterling, and Sterling 5 body wood as "Select hardwood" (kinda scared of what that means at that price range). I don't like how you have to have this color to have this fingerboard. They do that with the new Sterling brand too, can't get maple fingerboard unless you buy the black bass...If it weren't for that, I'd be all over a Cherry Red Sterling 5-string Ray35 with maple fingerboard.
That aside, the MM pickups sound good even when passive, just won't be the Stingray sound.
That aside, the MM pickups sound good even when passive, just won't be the Stingray sound.