The TABAD (Tang Band Dual) ~ A DCBR For Tang Band W4-1337SDF Driver... With the success of the Peregrine TABAQs as mains in the Nest GR8 room, and enough 12mm Baltic birch left over from their build, I decided to design a somewhat unique cabinet for the center channel in that room. I alluded to a dual chamber bass reflex (DCBR) during the choice to build QWTLs using the Tang Band W4-1337SDF drivers. I have now done one, using another 1337SDF driver, for the center channel, alongside the QWTLs. Yeah, that's Molly Tuttle and her band covering Thriller in costume for Halloween. The TABAQs are raised 10" onto the fireplace hearth, getting the drivers nicely to ear level at listening position.

The TABAD design... is not like those I've seen before for a DCBR, I am using 2 major chambers inside the box; they are about 2/3 and 1/3 the volume of the entire cabinet and coupled by a port; that's all largely known. I am also using rectangular slot ports to the front, tuned for bass from the back throw of the driver; slot ports are somewhat unique in a DCBR. Tuning performance is not a lot different than a normal single port - single chamber bass reflex, but it is less stressful on the driver and should deliver a smoother bass response. My driver does not have a lot of xMax throw. I won't get the low end from my 1337s as with my transmission line designs, but I don't need that from the center channel. Too, I know the slot ports are less efficient than more normal round ports but again I'm sacrificing that (knowing I have an efficient driver and usually don't play loudly in this room), for hopefully tighter bass above 60Hz. Modeling came out fine: the combined (red) response from the driver (blue) and the cabinet/ports (gold) delivers solid bass at 65Hz and is pretty smooth to 1KHz. I was a bit concerned for air speed in the ports given they are less efficient and will have more friction (23cm rectangular circumference vs 8cm round circumference), but it's fine.





Building The TABAD... Cutting the parts from the leftover sheet of birch plywood was easy; given all the straight cuts it was all done on the table saw in <1hr. That is except for the 101mm hole in the 110mm wide baffle and the drill saw holes in the chamber section pieces. I epoxied in the internal port and then dry fit the pieces to assure dimensions. I put the back, sides and chamber reinforcements together on the bottom during the 1st clamping. Then I added the front/baffle and the port boards; I used a .5cm "measuring jig" to assure the positioning of the port boards was correct and they were straight. I then used spray adhesive to put 1/2" carpet underlayment throughout the cabinet to limit resonances, leaving the last pieces till I was ready to put the top on the cabinet. I received the W4-1337SDF driver and the binding posts and finished off the speaker.





I finished the speaker with inexpensive binding posts and installed the driver with gasket tape as usual. I soldered the speaker and posts ~ I won't be changing drivers on this one.
Measuring & Listening... I installed the TABAD center channel in its location directly below the TV monitor in the Nest GR8 room. I placed a measurement mic at the prime listening position and measured it's performance using REW (mono signal to just the new TABAD; all other speakers were off). It measures and sounds smooth & awesome... pretty flat but as expected, not much bass below 75Hz...NP. I cranked it up and it remains coherent and smooth.
I could smooth the curve somewhat with DSP but I don't really need to do that externally IMO ~ I'll allow Denon's own Audessy measurement and correction do that. I next listened and measured a 3.0, and then a 3.1 configuration. Sounds excellent and the TABAQ bolster the lows to 45Hz and even smooth the highs, being at ear level. Adding the Velo servo sub gets the whole thing down to 20Hz. Finally I did the whole 5.1 thing and listened again... back surrounds are fine here for movie effects but don't add a ton to music listening.
Sanding & Finishing... I decided not to wait for spring to finish the TABAQs & TABAD. Getting the Nest GR8 room looking better heading in to winter is warranted... and the garage is heated so not too bad. Sanding in 120 then 240 grit papers via finishing sander is the start... I "plug" the ports and the driver hole in the baffle to stop ingress of dust or liquids.
I finished all 3 speakers as usual with true black stain and several coats of clear polyurethane. I yet need to tack down the new wire runs but the look and sound are right on.
I do need to figure out what to do in the 'holes' that'd be left when I remove the decommissioned NHT 1 L&R mains on the mantle. Too, I'd consider continuing to build TABAs ~ maybe some TABAOs, Tang Band Onkens, for the surround spots.