My Final Hsu VTF-2 Subwoofer Settings Thanks to REW

Hsu VTF-2 Frequency ResponseLast weekend, I got the Room Equalizer Wizard (REW) fully working under the latest Parallels beta. With the latest beta I was able to calibrate my soundcard and output test signals without pops and clicks causing impulse errors and data corruption.

At the click of my mouse, REW shows me exactly what my Hsu VTF-2 subwoofer's output looks like. After hours of tweaking I decided on a 3 o'clock low pass crossover (between 80 and 85 Hz) and a level a large hump from 20–38 Hz and a relatively flat response from 40–100 Hz (see chart, this measurement is with both the sub and main speakers active). I figured action movies would benefit from the deep bass boost and music would benefit from the flatter response in the mid-bass (I'm pretty sure the indie-rock I like doesn't have much information below 40 Hz, electronica, though…). At the end I adjusted the sub to get 63 Hz (a bass kick drum's fundamental frequency) as close to the reference line as possible.

Arriving at this optimized setting was not easy, I had to set every knob on the sub wrong before I knew I was right. REW showed me that at any other crossover setting I had a sharp null at around 50 Hz. If I switched phase to 0 degrees on the Hsu VTF-2 subwoofer I could see a definite dip at 80 Hz (telling me the 180 degrees was the best setting, my mains are wired in reverse polarity because my Rogue Audio 99 pre-amp inverts absolute phase). I first thought the level increase in the deep bass was bad so I moved my sub out of the corner closer to me along the left side wall. Interestingly, moving the sub had no effect on the lowest octave but I lost significant volume in the mid bass. So the sub is back in the corner, I even moved it as close to the wall as I could to further improve the mid-bass response.

Movie viewing is much more exciting now. We watched Finding Nemo on Sunday after an early dinner (my bad idea, it kept up our daughter way past her bedtime, I just wanted to hear some Pixar bass). Where bass had been constricted before by my improper settings, it was now full and authoritative. The mine explosions at the end of the submarine chase had a satisfying ka-boom that made my daughter jump (and me grin with a tweaker's satisfaction).

In music acoustic and electric bass lines are no longer recessed and ill-defined. Depending on the recording I can hear the full note defined by the bassist's fingers hammering and plucking. The bass player has earned a place in the soundstage. Bass kick drums are tighter while remaining full and balanced. It's easier to visualize the mallet striking the drum's skin and the damping. pillow inside hopping.

So, integrating your subwoofer into the rest of your system is not as easy as playing some pink noise and watching your SPL meter's needle fluctuating wildly above and below your reference level. The flaw with the wide band pink noise method is the averaging. If I took the average level of my subwoofer, the bandwidth I care about (40–100 Hz) would still be set too low, and I would still be plagued with lean bass.

It really takes the power of REW and its limited sine sweeps to show you what is really happening. If you have a PC you can drag into your listening room cabled to your system and an affordable SPL meter, then there's no reason you can't have optimized, deep, balanced and natural bass from your subwoofer (unless your sub sucks, then you should buy a Hsu).

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