One way my thoughts on the ULS-15 mk2 can be summed up is that I am sad to have to send my review sample back. If I didn’t already have so much subwoofage, I might have purchased my review unit. There is so little to complain about, and so much to praise with the ULS-15 mk2. Nonetheless, I will get the criticisms out of the way before moving onto the compliments.

The chief criticism I have of the ULS-15 mk2 is the potential for misuse of the EQ1 mode. The reader will recall that the EQ1 mode makes the frequency response flat down to 20 Hz with a steep drop-off below that. That can be a benefit in situations where room gain does not shore up the low end, but the problem is that in large rooms or open areas, and the subwoofer is more likely to be played very loud. This can end up being very taxing on the driver in the boosted frequency ranges in the EQ1 mode, and the sub can quickly reach its limits if played too loudly in this frequency band. We can see the consequence of that in the distortion sweeps in the 15 to 25 Hz band. While the sub can survive that kind of use in short bursts, you definitely do not want to push it that hard very frequently. I would only recommend the EQ1 mode in either near-field use or in large open areas with the stipulation that the subwoofer isn’t going to be played loudly below 30 Hz or so. The EQ2 mode has a lot more headroom, so if you want to blast content that has deep bass, use EQ2 mode. Those who want big-time headroom at 20 Hz would do better by looking at the ULS-15 mk2’s ported siblings, the VTF3 mk5 and VTF15h mk2.

A minor criticism I have of the ULS-15 mk2 is that the slope in EQ1 mode becomes a bit steep at the bottom due to a subsonic filter, and a shallower slope would be able to take greater advantage of room gain. However, this criticism also leads to some praise; the steeper nature of the rolloff helps protect the driver. In all of our testing, we were never able to get the driver to bottom out. We were able to push it past its linear excursion, but we never heard any noises that indicated the sub was in danger in either EQ mode, and our testing procedures pushes the driver very hard, much more so than most ordinary users ever would. I am not saying it’s impossible to bottom out the ULS-15 mk2, but that if it is possible, it is very difficult to do so; you would really have to make a point of doing it. One factor in this might be that since our review sample is new, the suspension might be a bit tighter than a unit that has been in heavy use for a long time, but even so, the ULS-15 mk2 looks to be very well protected against damage from the driver reaching its mechanical limit.

Now let’s briefly go over some of the highlights of the ULS-15 mk2. Its sound quality is superb, and the high fidelity that was heard in the listening sessions were confirmed by the measurements. The ULS-15 mk2 is a very accurate subwoofer and demonstrated highly linear behavior across a slew of different measurements. The output is tremendous for a sealed subwoofer at this price point, and this sub qualifies for Audioholics’ Bassaholic ‘large’ room size rating (in other words it should be able to meet the target 115 dB peak in seating positions in a 3000 ft^3 to 5000 ft^3 room). The tremendous output can be gleaned from the burst tests and compression sweep measurements, but nothing is as convincing as sitting cross-legged on the floor with the ULS right behind you only a couple inches away, and then cranking a hard dubstep tune to reference level on the AVR. Do that and you will know what a punching bag feels like.

Another admirable trait is the appearance, a slick satin black or Rosewood veneer with a gleaming concave cone- no way am I hiding that cone behind a grille. The manageable size and weight certainly deserve mention as well; this is a sub that does not take two people to move around. One person of average build can carry the 65 lbs ULS-15 mk2 around without too much of a strain. Since the enclosure is just an 18” cube, it does not eat up a lot of room. Some people might not consider that a small sub, but for the firepower it packs, it is remarkably small. Another point for the ULS-15 mk2 is that its amplifier has a lot of flexibility for different setups, so this is a subwoofer that can be integrated into a variety of systems, and with its adjustable response, its sound can be tailored to suit a variety of tastes.

Outside of the subwoofer itself is Hsu’s reputation for great customer service, a reputation established over many years. Packaging is, as was discussed before, exemplary, so if you ever had to ship it somewhere, you are covered if you hold on to the packaging. The warranty is not bad, but not great; 2 years on the amplifier and 7 years on the driver. An extended 5-year warranty on the amp can be purchased for an additional $90. And that brings us to one of the major high points of the Hsu ULS-15 mk2, the cost: $779 with a $69 shipping fee for shipping within the continental USA. $848 is not inexpensive (to most of us anyway), but if it is compared to many other subs in the Audioholics Bassaholic data compilation, it can be seen to punch way above its price point. When you consider all of the other assets it brings to the table such as its tasteful finish, manageable size and weight, and great customer service from Hsu, it has to be considered one of the top bargains in subwoofers to date.