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Positive Feedback ISSUE 57
september/october 2011

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hsu research

HS-1 MkII Loudspeakers and the STF-1 Subwoofer

as reviewed by Steve Lefkowicz


hsu speakers







Direct Acoustics Silent Speaker, Sound Dynamics 300ti, Linn Kan, and Loth-X Ion1.

PS Audio 4H preamplifier, B&K ST140 amplifier, and a Antique Sound Labs MG-15DT-S.

Marantz SA8001 SACD player, IBM T42 Notebook (Win XP Pro, iTunes) 200 GB USB Drive, DAC (tba), NAD 4155 AM/FM tuner, Linn LP12 (Valhalla), Ittok, Dynavector 19a (currently not hooked up).

Nordost Solar Wind interconnects and Nordost Flatine or Solar Wind speaker cables.

Sound Organization stand, Monster HTS2000powerline conditioner, Bright Star IsoNodes (under SACD player), lots of hockey pucks (under pretty much everything else).


As I promised in my reintroduction (It's Good to be Back, PFO Issue 55) my aim is to search out gear that produces real music at affordable prices. One of the most important aspects of that is understanding and accepting what characteristics of sound are more important to you, and which areas you are willing to compromise on. I admit that I have my biases and preferences, and have been consistent with them for close to thirty years. First and foremost for me, a system has to be able to play all the notes. That might sound simplistic, but playing "all the notes" does imply that a system be relatively full range, and that can be very difficult to achieve in budget priced equipment, especially loudspeakers. Getting a low priced speaker system that can play down into the bass range deep enough to play all sorts of music (into the mid/upper 30 Hz range preferably) is neither easy nor cheap.

I don't want my system determining what music I can listen to.

Of course it takes a lot more than bass response to make a system acceptable. Getting the musical aspects of reproduction right means that tone, dynamics, transient response, clarity, resolution and scale all are critical to sense of recorded music. After that (and only after) other aspects of sound reproduction take on significance, such as the ability to produce a large and accurate sound stage, placing instruments believably within that soundstage.

Then of course, an affordably priced speaker system has to be fairly easy to drive. A $500 speaker that takes $10,000 of electronics to sound good isn't really much of a bargain. I believe in setting up systems that are well balanced and sensible, and expect speakers in the under $1000 range to work well with moderately priced integrated amps or budget minded separates. That's not to say they shouldn't be capable of showing the differences in gear, or reproducing improvements wrought by upgraded gear.

I have found a handful of speaker systems over the past many years that fulfilled my requirements. For years I used Sound Dynamics 300ti speakers, which were remarkable in their ability to reproduce real music of all genres, while giving a clear picture into the subtle differences in all the various pieces of equipment I placed upstream of them. They worked well with 15-watt tube amps and 100-watt solid-state amps, and always gave me enough information to use as a primary reference when reviewing. I paid $499 for them back in 1998.

For the last several years, I have also greatly appreciated the Direct Acoustics Silent Speaker (original version, see review in PFO issue 26). Though very different in their presentation, given enough quality power, they have provided endless hours of musical enjoyment. They were $511 in 2006. They have been replaced with an upgraded Mk2 version for $748, which I have not heard, but which were very positively reviewed in Stereophile by the always astute John Marks.

These two speakers set the standard for me in what I want from an under $1000 speaker system. Little monitors that cut off the bass or constrict dynamics just don't cut it for me.

However, I'll also admit that there are many stand mounted small speakers that produce beautiful midrange tone, extended delicate high frequencies and even pure detailed upper mid bass. If one of these speakers can be successfully mated up to a quality subwoofer, with seamless blending of the two systems, then a proper full range system can still be built. The first system like this I heard was the Great White Whale Point 3 back in the late 1970s. Nice sounding system. The old JR-149 system (early 1980s) did a fine job of blending satellites with a matching subwoofer.

The big problems with systems like this are twofold. For one thing, low cost small subwoofers tend not to be terribly musical, being better suited to sound effects in inexpensive home theater systems. Then, it is not easy matching up the main speakers to the sub, where tonality, dynamic output, and overall voicing are not likely to match up too well.

hsu sub speakers

All that brings us to the focus of this review, the Hsu Research HB-1 Mk2 speakers and STF-1 subwoofer. I have been somewhat fascinated by Hsu's subwoofers dating back to the early 1990s, when I saw their large cylindrical offerings. There were three things about them that just struck a positive chord with me.

  • Their products were original in design, and seemed technically sound.

  • Their pricing structure seemed reasonable, affordable and honest.

  • Every time I heard them demonstrated at CES, using extremely low cost mid-fi equipment, they consistently produced remarkably good sounding rooms even when using silly cheap, little speakers.

I never did try one of their subwoofers, though a few times I discussed getting a review sample with them.

A few years ago Hsu Research finally put their own speaker on the market to go along with their subwoofers. I heard the original HB-1 matched up to one of their subs at their head office showroom in California. Though the system was again a low priced home theater setup with a basic HT receiver (either a Sony or Onkyo, I don't remember), the bit of two-channel music we played through it sounded thoroughly delightful and entertaining.

hsu sub speakers

Well now we have the HB-1 Mk2, the new version of Hsu's small two-way speaker. Dressed nicely in a black satin finish, the HB-1 Mk2 looks quite well finished for a $149 speaker. I like that they use magnets to hold the grill cover in place, so the front surface looks clean when exposed for listening sessions. At 15" X 8" X 8", the rear ported HB-1 Mk2 is a little bigger than an LS3/5a or my trusty old Linn Kans. This not only gives a little more internal volume, but also allows for a 6½ -inch mid/woofer driver. Sometimes size is a good thing. According to Hsu's specs, the woofer is treated paper cone woofer with treated cloth surround, flat polycotton spider and high temperature aluminum voice coil. Their focus with this driver to ensure proper handling of upper bass frequencies, allowing for easier blending with their subwoofers. More on that later.

The tweeter on this speaker is described as a "very high efficiency controlled directivity horn with neodymium magnet and ferro-fluid cooled voice coil." I didn't take it out of the cabinet to get any more information about it, but it does seem like a decent little driver for a speaker like this.

There is a single set of standard, angled binding posts on the rear. Though they worked fine with the different speaker cables I used during my evaluation, you should note that they are recessed, and that may pose an issue if you use substantially large cables. Hsu does not recommend "expensive" cables with their speakers, and uses what looks like standard zip chord at trade shows. I basically agree with them, and don't think your speaker cables should cost more than your speakers!

hsu speakers

Hsu offers a wide range of subwoofers, and the HB-1 is designed to mate up properly with every one of them. In keeping with my stance of looking for low cost alternatives, I chose to go with their smallest, lowest cost model STF-1, which sells for just $299. One thing I liked about this sub as my choice, it is only specified down to 32 Hz, rather than 20 Hz or even 16Hz like their more expensive subs. I just felt that this would mate up with my listening room better.

The STF-1 is powered by a built in 150 watt amplifier, that includes bypassable, variable 24 dB/Octave low-pass crossover (30 to 90 Hz), switchable phase (0 or 180º) and auto signal detect to save power. Though the STF-1 amplifier has fewer connection options as compared to their more expensive subs, the choices offered should make for easy setup on almost any system. The amplifier drives a single, down-facing 8-inch driver, vented by a large rear facing port. It uses four large plastic cones to keep it secure on a carpet. They screw into standard ¼ x 20 threads, so you can easily replace them with spiked feet of your choice if feel that is necessary. I did not.

hsu speakers

I only tested this speaker/sub combo in the context of a basic two-channel stereo music system. No home theater, no "multi-channel", no HDMI, no surround, etc. I tried two of the available connections methods, and used a small selection of low priced, or older model gear.

Setting the system up was surprisingly quick and easy. For the HB-1 speakers, Hsu recommends using the ratio 1:1.26:1.60 for distances from the sidewall, rear wall and floor. Using a pair of 24-inch Sound Organization speaker stands, it put the center of the woofer 28 inches from the floor, so I placed the speakers 17.5 inches from the sidewall and 22 inches from the rear wall. I angled straight at my prime listening position. Subwoofer placement was quite easy too. I did try the sub in a variety of places; in a corner (overpowering), near the wall behind the speakers, in front of the coach I sit on to listen (made for a nice place to rest my feet!). In the end, I opted for placing the sub about 10 inches from the wall, between the speakers, a few feet from the equipment rack. This worked well and made for easier connections.

To hook everything up, I basically had two choices. One was running speaker cable from my power amp to the high level inputs of the subwoofer amp, then running a second set of speaker cables from the sub to the main speakers. The other option, which I could only use with one particular integrated amp, was to run a single interconnect from the LFE Out of the amp to the single LFE in on the sub. Then run a set of speaker cables from the integrated amp to the main speakers. For most of my listening I used the former method, and had the best results that way.

Staying with setup, I really was impressed with how easy the subwoofer was to set up. After getting the positioning set, I listened to a variety of tracks from several CDs while adjusting both the crossover frequency and subwoofer level until it sounded well balanced with the main speakers. I settled on a crossover at 80Hz. Below that the mid bass thinned out a little, and higher than that it sounded a little muddied up. After setting everything by ear I checked the setup with a Radio Shack digital SPL meter and Stereophile Test CD 2 and correction factors supplied by someone from audio asylum years ago that I've always trusted. Levels at 400Hz, 250Hz and 40Hz were within a dB of each other. The 31.5Hz track sounded clear and powerful.

Most of the time, the system used was the same that I have used as a steady reference point for many years. CD and SACD were played on a Marantz SA8001 2-channel player. I have used the same PS Audio 4H preamp (always in passive mode) for close to 27 years. It is still a viable, high quality unit, and I suppose I will continue to use it for years to come. I used three power amps, swapping out as my mood changed—a B&K ST-140 amp, an Adcom GFA 535 on loan from Dave Clark, and a low powered (8 to 10 watt) pair of Antique Sound Labs AV-8 Wave amps. I also tried the cute little Virtue Audio Virtue TWO.2 Class-T Integrated Amplifier that bob Levi reviewed in Issue 50 (the same unit, actually). All interconnects were Nordost Solar Wind, and speaker cables were mostly Radio Shack 14-Gauge Flat Megacable® Wire, terminated in banana plugs. I also tried Nordost Flatline speaker cable a few times. More on that later, too.

After a week's worth of break in, I decided it was time to start listening in earnest, starting with the B&K amp in the system, but mostly using the Adcom after the B&K developed a noise issue. Actually, the first thing I did was to determine if there was any negative impact caused by running the signal from the amp through the subwoofer connections and then on to the main speakers. Since the crossover is for the sub only, the HB-1s are still driven full range. I switched the sub off, and alternated running the cables from the amp straight to the speakers, and from the amp to the sub, with additional cables from the sub to the speakers. Try as I might, I heard no difference in the sound. The pass through was totally transparent. However, most of my listening otherwise was with the subwoofer on and part of the system. I took this to be a complete, three-piece system and wasn't really interested in using just the speakers by themselves.

One thing I feel like noting, even if just from a personal standpoint, is that this is the first review I've ever done using just digital sources. Unfortunately, my LP collection is in storage, so the Linn sits unused. About 95% of my listening was to either CD or SACD discs played on the Marantz SA8001 player. The other 5% was playing either my iPod (320 kbps files) or using an IBM T42 notebook playing Apple Lossless files. I only have a small number of CDs loaded on that at this time, and I have not yet acquired a proper USB DAC for this purpose. I used the USB input of my Headroom Total Bithead headphone amplifier to feed the digital signal (16/44.1 only) to the system. This did not sound anywhere up to the level of the Marantz playing CDs, so it was not a major part of the review process.

The first thing I noticed listening to the HB-1/STF-1 system was how well integrated the sound was, top to bottom. With a little bit of adjustment, set by ear, the continuity between the HB-1s and the STF-1 was remarkably seamless. I think the fact that the HB-1 speakers were designed and voiced specifically to mate up to the Hsu subs just shows that the systems approach to audio should always be at least a consideration. I have heard many speakers over the years, even some costing substantially more money, that couldn't integrate the bass with the rest of the music as well. This was especially true in the upper bass region, and around the 80 to 90 Hz range of the crossover.

Another thing that really stood out for me was the image placement of bass instruments. Although low bass is not really directional, and localization of low bass notes is nearly impossible, the image location of bass instruments is set by the higher frequency transients of the start of each note, such as the plucking or striking of the instrument (something I learned from Linn literature years ago). Due again to the excellent blending of sounds from the HB-1 and STF-1, the localization of bass instruments was very precise.

Tonally, the overall balance of the system was certainly in the realm of neutrality, and could be described as neither warm nor bright. There were no serious anomalies in frequency that would detract from the overall tone of instruments or vocals. For those that are new to my reviews, I take small deviations from neutrality as part and parcel of the audio experience, as room interactions and recording variances make any discussion of "neutrality" pretty much a moot point.

At first, the higher frequencies sounded a little tizzy or papery, but an additional week or so of break-in smoothed that out substantially, leaving a pleasant, airy and delicate overall sound, but still with some necessary bite. This was exhibited by the fine job of reproducing cymbals, such as on the nicely done concert recording of Alan Holdsworth, Alan, Pasqua, Jimmy Haslip, and Chad Wackerman, Blues for Tony (Moonjune Records MJR029). As with the integration of the bass, the integration of the tweeter with the rest of the system was very well executed, and never drew undue attention to itself.

I listening to Time Waits for No One by Ambrosia (Ambrosia Anthology, Warner Bros 9 45163-2) I was really struck by how precisely the overall pace of the song was maintained throughout, and how all the little details came though so well. This song (engineered and mixed by Alan Parson, and originally mastered for LP by Doug Sax!) is extremely well recorded and has been a long time test for me for these characteristics. Systems that don't integrate their drivers properly often leave this song sounding confused or relentless, rather than vibrant, rhythmic and expressive, as it should be.

Moving to a few SACD favorites, I listened to the soundtrack of O Brother, Where Art Thou (Lost Highway 088 170 358-2), where all the wonderful traditional sounds, acoustic instruments and phenomenal vocalizing should make for a good time. Whether it was the angelic voice of Allsion Krause on Down to the River to Pray, the incredible harmonizing of Krause, Emmylou Harris and Gillian Welsh on Didn't Leave Nobody but the Baby, or the traditional, somewhat nasal singing of Tim Blake Nelson on In The Jailhouse Now, this system showed that this was a speaker system that could handle vocals with a naturalness that I just didn't expect from a speaker in this price range. Natural and vibrant seem to be the terms that come to mind in describing it.

Moving the SACD reissue of Blood Sweat and Tears eponymous second album (Columbia/Legacy CS 63986, wish I had the MFSL SACD release of this!) I continued to be impressed with how natural Davis Clayton Thomas' voice sounded, with no added chestiness or other impact from blending in with the sub. Listening to the instrumental section on God Bless the Child, again showed great attention to coherency, to acceptable full range reproduction, and better than anticipated dynamics.

Switching them to Peter Gabriel's Security (Geffen 069 493 623-2) really tested the dynamic and bass capabilities of the system. Here was an interesting comparison with one of my other speakers. Compared to the Silent Speakers, the overall dynamics of the Hsu system seemed a little constricted. Not too much, and I'll point out that I think the Silent Speakers do musical scale, forcefulness and dynamics (within their range) better than almost any other under $1000 speaker I've heard, but still, it was noticeable. However, the dynamics in the lower frequencies of the Hsu seemed to correspond to the music a little better, with the Silent Speakers at times verging on overloading the room. Bass depth was surprisingly similar between these two speakers.

Looking more towards an overall picture of how the Hsu system plays music, I listened to a wide variety of tracks from equally wide variety of artists on different genres. I wanted to make sure that I wasn't favoring music that favored the speakers. Large scale complex progressive rock of Genesis' early release Nursery Cryme (Atlantic 82673-2), the live recording Mambo Birdland of jazz legend Tito Puente (RMM 0282840472), and the retro stylings of Bryan Ferry on As Time Goes By (Virgin 7243 8 48270 2) all were well served, musically, rhythmically, tonally, and dynamically. A tried a few large scale orchestral works (most of my classical collection is on LP, so unavailable at this time) and fond them all similarly satisfying.

In fact, over the three months that I had the Hsu HB-1/STF-1 system set up, I never found myself thinking that anything I wanted to listen to would be beyond the capabilities of the system. At times I found myself searching for more challenging pieces to see if I could trip them up.

I could say that at times they sounded a little thin or lightweight through the midrange, but only slightly, and only in direct comparison to the Silent Speakers, which are remarkably rich and full throughout their midrange. I found that my Sound dynamics 300ti speakers also sound a little thin compared to the Silent Speakers. Some might suggest that the Silent Speakers might be a little thick or too full in that range.

The Hsu's are also pretty transparent for a low cost speaker. No speaker under $1000 that I've heard has the level of transparency you get from the expensive models out there. That might have been one of the things that set the Sound Dynamics 300ti ahead of the crowd back in their heyday. They could compete with much more expensive models in this regard. However, the Hsu is more transparent than the Silent Speakers, and that goes a long way.

The imaging characteristics are what you'd expect from small stand mounted speaker. Good, fairly precise image placement, with reasonable depth. They certainly get out of the way and let the music fill the room. Of course image size and placement can be adjusted by careful speaker placement. I positioned for best overall tonality and coherency, rather than ultimate imaging quality.

I should mention that the system is also very easy to drive. I briefly swapped out the 65 watt Adcom amp for the 8-watt Antique Sound Labs Wave 8 tube amplifiers, and was delighted at how nice the system sounded. I certainly couldn't play them loudly, but I could play then loud enough. The cool thing was that the bass characteristics from the sub were totally unaffected, while the rest of the range picked up some nice richness smoothness, though possible at the expense of some fine detail. These amps were only $98 a piece when they were available. However, ultimately, I felt the higher powered Adcom was a better overall match.

I briefly switched out my primary electronics to try the Virtue Audio Virtue TWO.2 Class-T Integrated Amplifier. This amplifier has an LFE output, so I used that to connect the sub, and fed the HB-1 speakers directly from the amplifier. At first I thought it was a fun setup, but pretty quickly I realized that listening to this setup was not all too satisfactory. The integration that was so smooth and unnoticeable otherwise, was replaced with distinctly different characterizes. The main speakers sounded thin and brittle while the bass was disconnected and poorly controlled. I take that as the amp just not being a good match for the Hsu system. I tried the Virtue Audio amp with my Linn Kans just to check it out, and wasn't that impressed there either.

I realize that what I've written doesn't sound as overly enthusiastic as I actually feel about these speakers. In three months of daily listening I thoroughly enjoyed every minute of my time with the HB-1/STF-1 combination. For just under $600, you can actually get real high end sound, reasonably (and acceptably) full range musical reproduction, and a nice level of system flexibility. Match these up to any one of a number of reasonably priced integrated amps, and feed them a decent signal from a CD player or a PC/USB DAC, and you can be assured of hours, days, or even years of musical enjoyment. Overall highly recommended. Steve Lefkowicz

HB-1 Mk 2
Price: MSRP direct from manufacturer - $149 each satin finish, $179 each wood veneer

Price: MSRP direct from manufacturer - $299 black vinyl finish

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