This project began as another "buyout special"using the HiVi A3SII, and the sale on the Tangband W5-1138SG. The current version of the TB is the W5-1138SM - a version that may or may not work the same but it should be close. Several folks liked the idea of my Periscope project, but wanted something a bit more compact. I chose the Dayton ND16FA for the tweeter to keep the MTM spacing as close as possible. I moved the woofers down on the baffle to get as much floor assistance as I could. The safe way would be to run a WMTMW configuration, but I wanted to get the tweeter well up off the floor.
The box is 1/2 " baltic birch with braces between the woofers and beneath the lower MTM driver. The mids are in their own sealed chamber. The mid chamber is 2.5" deep and 10.5" high, and the width of the box (about 2.3 liters).
I tried to keep the crossover fairly simple with a reasonable part count. For modelling I wound up using the a spliced nearfield/farfield measurement for the woofers and reducing the sensitivity to farfield levels. Final tweaking has been done by ear and SWAG modelling. (Those double woofers present some interesting measurement challenges). The TB's actually measured remarkably flat out almost 1000 hz. The HiVi's run out of gas about 350 Hz. [Measurements Here]
As with any 3 way, keeping the impedance up is always a challenge. I'd have to call this a 4 ohm design, (6 ohm if I were commercial) But it should be safe for decent solid state gear. The crossovers are at 350 & 4500. The series notch on the woofers enabled some necessary shaping in mid cross area. The mid circuit is basically 2nd order electrical. (All the resistors are real and have been adjusted for DCR of 20ga coils where appropriate).
As of this writing, I have only one prototype box finished with a cobbled up crossover. To get any significant bass volume, I wound up padding down the mids & tweeter considerably. Overall, the prototype is very "precise". Nice airy presentation, a bit of emphasis on the upper mids, but not really harsh. The HiVi's are a little bit edgier than some mids I've heard, but very listenable and articulate. If you like the B3S, you'll like these too. Very good off axis dispersion. The hand off from the mids to the woofers is basically smooth at 6 feet or more, but there is a little bit of muddiness at closer ranges (different arrival times from the woofers.)
I ran some signals from WinISD to break in the Tangbands. The cones were well controlled at 40 hz, flapping wildly at 30 Hz. Exactly what was predicted. In listening, the low bass is present, and well produced, not overwhelming. (But certainly better than one would expect from any 5" driver) I think near wall placement, and a fully prepared, damped, cabinet will bring up the bottom. For music only, I think this is truly a full range speaker. You will need a few watts to get that potential. Probably 81-83 dB sensitivity as I have designed it.