I like that TB W3-926SD, good specs and the reviews advise that it has very good high freq. performance, which you need in this design. And the W5-704D is a very nice woofer with great specs that can go up to 9K Hz, which gives you a lot of leeway. Very similar to the HiVi M5N in the freq. range. Both drivers have a very similar SPL 88dB for the woofer, and 87dB for the full range, which depending on your room and amplification you might not need an L-Pad; we can get close to know via simulations. It is an 8 Ohms design, and should be an easy drive for any receiver/amp.
It is my opinion that going with a larger vented enclosure (see enclosed dwg) than the one recommended by PE will yield an f3 of 60Hz without putting much stress on the woofer. As for the baffle, depends on how big you want to go, personally I have found that 16" high is as large as a bookshelf speaker I like, but that is me. Don't know if you are planning on making the cabinets, but Dayton's 0.38 cu.ft. enclosures are ideal for this project. Line them with 3/8" thk. upholstery wool to dampen and use some polyfill (or similar) and you should get great sound; others might chime in on better solutions. The enclosure is 14" tall, so, I would build a taller baffle, as to leave an OB area for the FR driver. Overall outside dia. for the FR driver is 3.19", so no less of 4" tall OB area is needed. Width would be the same as the enclosure, which is 8" wide. Remember, these measurements are using a pre-made enclosure. If you are building your own enclosure you might play with measurements as to get an enclosure that fits your space.
So, our front baffle will be 20" tall x 8" wide; I recommend 3/4" thk. wood to add rigidity and be able to countersink the drivers.
Ran some sims, and your XO point seems to be around 600 Hz. You can go further down, but you would have to check at which point you should go with a Baffle Step Comp Circuit. I didn't use BSC on mine, don't need it at the point I'm crossing. In my case, I did need to L-Pad the FR drivers about -4dB.
SPL response for both drivers is about the same, well inside the 3dB range, so no problems there. There are some bumps that get close to 4dB, personally, I wouldn't worry much, but if you want to control them to below 3dB you will have to do a circuit to do so. I highly recommend a bi-amp terminal(s) as to in the future play with MiniDSP or active XO. Simulations are based on the recommended enclosure/baffle, and the drivers TS Parameters, it doesn't take in consideration room acoustics; independent measurements at your listening room with drivers running full range might be needed to further enhance/fine tune the XO circuit. Actually, I ran mine full range for quite awhile while deciding if going passive or active. I decided active as to fine tune with it, then build passive based on my active set parameters, which at this time is 520Hz/Inverted Phase on one driver/-4dB gain on FR driver. Active is 24dB Behringer, next time I will just get a MiniDSP.
If you want to go active, a MiniDSP will run you around $110.00, and building a 4-Channel Class D 50WPC (TPA3116d2) will run you about $75.00.
