Here's the W90C brochure. Different-shaped cab, but they used several different cabs for these...
Yours look like they have different grillcloth than mine (The cloth on mine is the same stuff they used on the original W60 model when it was first introduced... More-textured). Mine have smooth back panels on both sides of the enclosure, plus the ports are directly-above the woofer as opposed to being closer to the middle like they are on yours (and possibly kfa888's). Also, they have the same grillcloth as the 1960-introduced W60 model, so I figured mine must be the first-generation version. But I haven't opened the back panels yet (I'm afraid to... Don't want to jinx it). Sixcats had told me that they just had two regular alnico W12's, so I didn't bother checking. I need to find an old magazine ad for the first-generation W90's and see what it says. The W90C and W90D both have the 4-way setup with the split bass, but I think mine is just a kind of dual 3-way setup. I still don't quite-understand the venting thing on the later ones. I'm not exactly well-versed in sub-enclosure design. I'm still not even sure what a bandpass enclosure is. The dual-mid/tweeter array really puts out some sound. Very-detailed. Up front when it needs to be, but also laid-back.
Dammit, these sound good (Listening as I type). They can be perfect for so-many things... like mid '70's disco at 2:30AM, or Jethro Tull on a Saturday morning, Beatles on a Sunday morning, or the Dead when you're stoned outta' your gourd at 4:21PM on a Monday afternoon, or some Hendrix while you're catching the first rays of the new rising sun. It doesn't matter. They're good anytime.
Speaking of Hendrix, I guess I haven't listened to "Band Of Gypsys" in a long time (not since well-before I got the W90's, and before I bought the HRT dac). Wow, does this sound different. Boy, if you ever wanted to "get" Hendrix, these are the speakers for it. God, I wish I had them back in the early '90's when I was all over this album. Oh well, I can always get all over it all over again. This really brings me back...
*EDIT* - According to the brochure above, the styrofoam-cone woofer (polystyrene, to be exact) handles the low-bass while the regular W12 handles the upper-bass frequencies. That sub-cabinet is great. I had heard there's a sand-filled panel in between the two woofers (although I haven't cut these apart to find out), plus the back panels are definitely sand-filled as well. I've been reading/re-reading that Briggs biography this month, and cabinet-construction was definitely a high priority, as was driver-design and integration. For how much they charged for their speakers, they definitely gave customers their money's worth. The truly-amazing part is that Gilbert Briggs started the company with no formal relevant training (Back during the depression, he was laid off after working in the textile industry for 20 years, so he completely-reinvented himself as one of the true pioneers of loudspeaker-design... Pretty-incredible when you think about it... The guy was a super-genius).
I just took a good look at the mid/tweeter array on mine. Very-interesting to say the least. The front of the mid/hi enclosure is OPEN. No baffle. And the drivers are set back a bit from the woofer-baffle below them, and each driver mounted to metal rods on both sides, which I assume are connected to some sort of rear-baffle for the upper-compartment. Not sure if they gave it a sand-filled panel or not, but it would make sense (to cancel out any reflections). I wish I had an original factory diagram of the entire design of that first W90 version, inside and out. It would sure clear up a lot. Also, I think mine might also have two different woofers (My cabs are both ported though... Two ports on the front and no slots on either back-panel). It's hard to shine a light through the thick grillcloth to see, but I can only spot a dustcap on the left woofer. The right one just looks black and vague across the whole thing, just like the friggin' monolith from "2001". **EDIT**
