VTF-3 MK3 Build Quality

Build Quality

Remove the VTF-3 Mk3’s amplifier and - after the size of the driver’s motor structure - probably the most interesting if not downright fascinating feature are the ducts (as seen below). They’re lonnnnng and bent: at a 90° angle, which really is the only way you could fit a pair of ducts, each 4” in diameter, of the length necessary to tune the particular driver/cabinet combination that makes up the VTF-3 Mk3. Having worked out some of the engineering challenges getting the air flowing correctly through that 90° bend is the subject of a Hsu Research patent, now pending.

The cabinet itself comprises panels of various thicknesses, glued together, secured with glue blocks throughout, cross-braced (said bracing doubling as a mechanical support for the ducts) and lightly lined with fiberglass cladding on some of its interior surfaces. The driver (and power amp) both bolt directly to the cabinet. Hsu Research have taken steps to keep mechanical noise down, such as employing the vibration-resistant banding used in clamping the interior end of the ducts securely to the cabinet. That’s a nice, basic feature when you consider how easy it is for mechanical vibrations to set up in a sub, resulting in one of the most instantly annoying sounds ever heard! Fit and finish were very good. I found no flaws worthy of mention anywhere.

The VTF-3 Mk3 features a 350W Class-AB output stage with tracking power supply. The unit is bolted into the back of the sub and sits just below and to the right of the system’s ports. It features a 3-way power switch (On/Auto/Off), continuously low pass filter (30 Hz – 90 Hz, with 4^th order/24dB octave crossover slope), crossover bypass switch, 2-way phase (0° - 180°) switch, two line-level inputs, a pair of speaker-level inputs & outputs, and a switch used for selecting either max. extension or output modes. There’s also the polarized, two-conductor power jack, user-replaceable fuse and protected input-voltage switch. This is, by the way, a new, updated version of the amp that was originally released with earlier versions of the VTF-3 Mk3. (See Figure 1b below for a comparison of the old & new amp’s transfer function).

For my money, the real star of this show is the VTF-3 Mk3’s driver. It’s a nominal 12” unit, with a half-roll surround, and sporting a massive vented motor assembly. Hsu Research has, from its inception, focused on 12” driver as its driver of choice and they have over the years refined their design approach to where their products perform out to the limits of what a12” driver can do. In the world of subwoofers it’s easy to overlook 12” drivers, seemingly overshadowed by their 15” and 18” brethren. Underestimate the VTF-3 Mk3 at your own risk – this is one potent sub! For the specification-inclined I’ve included a table with some of the driver’s T/S parameters.