HSU Research VTF-TN1 Subwoofer Review

HSU Research VTF-TN1

☆☆☆☆☆ 4.5/5

The HSU Research VTF-TN1 is a high-performing subwoofer known for its flexibility, allowing users to adjust tuning to fit their preferences and space. It delivers impressive sound quality for both music and movies, supported by durable construction and versatile inputs. While its large size and manual setup may be drawbacks, it remains an excellent value in its price range.

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HSU Research: Reading this article on Home Theater Forum means it’s all but guaranteed you already know about this company. Founded in 1991, they are one of the original pioneers in the ID (Internet Direct) market. These folks have been a stalwart of the industry for over 30 years. Known for their value-based products and exceptional customer support, HSU has garnered a stellar reputation.

Today we’ll be looking at their recently released VTF-TN1 subwoofer. For those of you familiar with HSU’s nomenclature the VTF part of the name should be recognizable. If you aren’t, it stands for Variable Tuning Frequency. Essentially it means you can adjust the output and frequency response by blocking one or more ports and flipping a switch on the amp, thereby making it suit your particular situation. Want really deep bass? VTF can accommodate that by plugging one of the two ports and switching to EQ1. Prefer a lot of output? VTF has you covered there as well, don’t plug either port and use EQ2. You can also block both ports, effectively creating a sealed subwoofer. If you prefer that alignment it’s probably better to get HSU’s highly regarded ULS-15 MK2 instead.

Now we know what VTF means, but what about the TN part of the name? That’s a tribute. TN are the initials of the late Tom Nousaine, the highly esteemed writer, reviewer and measurement guru whose influence still resonates in the industry to this day. Dr. Poh Hsu must hold a special place for Tom as this is not the first time he has paid homage to him. Over 20 years ago he released two subwoofers with TN in their name, the TN1220HO and TN1225HO. That name breaks down as follows…

TN – Tom Nousaine
12 – Driver size
20/25 – Tuning frequency in Hz (this was before VTF)
HO – High Output

A lot of improvements in electronics and materials have occurred in the 2+ decades since the original TN models were released. Today, a single VTF-TN1 can essentially do what a pair of TN1220HOs once could. That’s pretty impressive considering what the VTF-TN1 costs. That’s perhaps a good segue to list out the specifications of this new model…

Driver: Front Firing 15″
Ports: Two, Down-firing
Alignment: Sealed or ported (2x 4″ diameter, 25″ long)
Amplifier: 600 Watts RMS, 2000 Watts Peak
Extension: 15 Hz (1 port open), 20 Hz (2 ports open)
Q Control: 0.3 – 0.7, variable
Crossover: 30 – 120 Hz, variable
Crossover Slope: 24 dB/Oct
Phase: 0°/180°
Inputs: Balanced XLR (2), Line Level (2), Speaker Level (2)
Dimensions: 30″ H x 18.5″ W x 18.5″ D
Weight: 85 lbs
Warranty: 7-years on driver, 5-years on electronics

The driver is a fiberglass impregnated paper cone with a pretty substantial foam surround. It’s backed by a pair of 2″ magnets, all housed in a solid cast aluminum basket. Motivation is provided by a 600 watt BASH amplifier. Perhaps unique to HSU, the amp has no DSP tuning. It’s actually class AB, which is analog. In a world increasingly dominated by app-controlled subwoofers, HSU has decided to take the path less traveled. Other than the obvious advantage – less fancy does lead to less cost after all – it means there’s no delay to account for when adjusting for distance as there isn’t any signal shaping going on.

HSU is known as the value leader in the segment so their choice of amps makes sense; the company isn’t inclined to use exotic materials with unpronounceable names, nor have they chosen to incorporate bleeding edge technologies. Instead, they prefer proven methods and materials, a tried-and-true approach is what HSU favors.

Don’t think modest means they’ve skimped anywhere though, HSU includes plenty of features for the price. We’ve already touched on VTF, but there are other notables as well…

Inputs – Low level, high level and XLR. There’s probably no system you can’t hook the VTF-TN1 up to.
Q Control – Adjustment for headroom and in-room response. 0.3 provides the highest mid-bass in any sized room, flattest deep bass in smallish rooms; 0.5 flattest deep bass in medium rooms; 0.7 flattest deep bass in large rooms
EQ Setting – Used in conjunction with the tuning of the ports. By setting the EQ switch to 1 or 2, and plugging or unplugging 1 or more ports, you can adjust the capabilities to perfectly match your environment and preferences.

Because they’re physical switches it’s simple and straightforward to configure the Q Control and EQ settings. The owner’s manual clearly spells out all the combinations, speaking of which…

Like always, HSU includes a comprehensive one. It explains in detail things like placement, hookup, tuning and troubleshooting. For those who don’t like reading manuals there’s also a quick start guide that covers all those areas (except for troubleshooting) in a brief, concise manner. And in keeping with tradition, HSU throws in their ubiquitous test disc. It contains several challenging orchestral passages, pink noise and test tones. It can be used to evaluate your new HSU sub, along with being a tool to help tune it.

Impressions

You can’t help but notice the cabinet, it’s about the size of a little refrigerator you might find in a downstairs bar.

Realistically the dimensions are pretty much the same as any ported 15″ subwoofer, only this one is perched up on its hind legs. Rather than the enclosure being deep, it’s tall. The layout seems unconventional at first, but in reality it makes a lot of sense.

Most in-room placement difficulties don’t result from the width or height of a subwoofer, it’s typically depth that causes a problem. After all, you don’t want the thing sticking out in your room so far that people end up tripping over it. For a subwoofer to provide deep bass and substantial output you need a big enclosure. While advancements in drivers and amplifiers have allowed engineers to shrink cabinets to some extent, at the end of the day you can’t really cheat physics. The bottom line is, the bottom end of the frequency spectrum needs a sizable enclosure. By going vertical rather than horizontal you kill 2 birds with 1 stone; you can achieve sufficient cabinet volume to provide deep bass and high output, while simultaneously ensuring the sub doesn’t protrude egregiously into your room.

Like most of the HSU Research product line, the VTF-TN1 comes covered in satin black paint. This is perhaps my favorite type of finish; I’m not a big fan of gloss paint, vinyl wraps or veneers. I did notice the review unit had some artifacts in the paint, a few slightly sandpaper-like rough spots that suggest it might have been applied in an area with errant dust particles. The coverage was very good however, no blotches or thin spots were found.

Like most subwoofers today, the cabinet is made from MDF. It’s .75″ all around except for the front baffle, which is 1.25″. There are braces at the top and bottom, along with a pair in the middle. The walls are lined with damping material. Because of the down-firing ports the rubber feet are pretty tall, even if you have thick carpet they should lift the enclosure up enough to give them room to breathe.

Listening

When I’ve spoken to Dr. Hsu in the past, he’s indicated that his philosophy is to create subwoofers and speakers which aren’t intrusive, those that don’t draw attention to themselves. Instead, he prefers they blend in, become part of the tapestry of your audio system. I’m paraphrasing slightly as I don’t recall the exact words he used, but it was clear to me he didn’t want to be known for any “in your face” products. Just speaking with Dr. Hsu makes you realize they mirror his own personality. Well, sort of anyway. The one area where his creations likely differ from the man himself is that they will most definitively get your attention when the time is right.

I don’t evaluate products like most other reviewers, for me anything that spends less than a month in my HT simply won’t do. I want to live with a piece of equipment in a similar manner to what an actual owner would, day in and day out. I don’t feel you can truly understand the essence of a product unless you experience it for a period of time, in my opinion that’s the only way to fully know what something can or can’t do. In the case of the VTF-TN1, it was in full time rotation for about 6 weeks. That gave me more than ample time to get familiar with this subwoofer.

This is actually my 4th HSU product – 3rd sub – and it turned out to be more of the same. Right about now some of you are probably thinking “that’s not really complementary”, but nothing could be further from the truth. By now I’ve come to expect certain things from this company, and the VTF-TN1 did not disappoint in that regard. You will soon come to understand why.

Movies

A ported subwoofer with a 15″ driver screams out for some fierce movie action, or should I say action movies? Ironically a ported subwoofer can be tripped up by that same material, once frequencies drop below the port tuning the driver is running in “free air”. If you haven’t properly engineered the system, damage to the driver can occur. For a subwoofer that runs mostly in the analog realm it’s even more important, there are no digital protection mechanisms to rely upon. So naturally, what did I do? Opted for some pretty punishing material, even using something from HSU’s own test disc against it.

Edge of Tomorrow

I choose this movie for one reason, one 10 second reason. I doubt I even need to tell you what that is, I suspect you already know. That reason happens to be at the beginning of the movie where a subsonic torture test comes out of nowhere. It’s a plateau-type of effect, encompassing 5 different levels that decrease in frequency. The first 3 were really intense, instantly grabbing my attention. The 4th was a bit less pronounced, but still formidable. By the time it got to the 5th, and deepest of them, you could tell the VTF-TN1 had started to roll off. The driver was gyrating wildly, but the output wasn’t quite as prominent. At no point did I hear any unpleasant sounds from the driver or ports, quite a feat given how difficult this part is and how loud I had the volume.

U571

During World War II, German U-Boats, which we call submarines, were a fearsome weapon for the enemy. At the time they were more effective and advanced than their counterparts that the allies had in our arsenal. As this movie opens, the Americans happen upon one of those U-Boats and launch a vicious depth charge assault, crippling the ship with their relentless bombardment. Explosions from the 55-gallon, drum-sized weapon were potent, each packing a noticeable wallop upon being detonated. The foreground blasts were sharp and hit hard, those in the background rumbled menacingly. Low frequencies groaned, sending deep pulses through my floor with each blast.

Later in the movie the roles are reversed, this time an American submarine is attacked by the Germans. I have always wondered if the engineers who mixed this soundtrack deliberately kicked it up a little for this battle scene, everything seems to be a bit more ferocious. The VTF-TN1 was ready, willing and able to take on the challenge. Despite the increased demand placed on it, there was enough headroom left that you still got the full effect.

How to Train your Dragon

Did you ever notice that animated movies often have the best soundtracks? How to Train your Dragon is no exception.

The movie is about Vikings who inhabit the island village of Berk, they’re constantly harassed by dragons who steal their provisions. Disgusted, the Vikings decide to end the reign of terror and take the fight to them at their lair. The Vikings assemble and sail to the dragon’s haunt where they find them buried deep in a mountain. To get at the beasts, the Vikings use catapults to hurl boulders and blast through the rock face. Instantly I knew the VTF-TN1 was up for the challenge, the thump of the catapult launch and the impact from the boulders hitting the mountainside were both resounding.

After a couple of well-placed hits, they break through and expose their foe, a massive dragon known as Red Death. In a rage he vaults out of the mountain, as it crumbles down around him the rumbling sounds it produced were commanding. Even more noteworthy was the thud each time one of his enormous feet hit the ground.

The ensuing battle takes to the sky, each flap of Red Deaths wings caused the driver to pulsate. Ultimately Red Death’s fury makes him miscalculate his rate of descent and he plummets headlong into the earth. The soundtrack during the impact is purported to have content in the single digits. While the VTF-TN1 can’t effectively do much below 10Hz, it most certainly has solid output in the mid-teens. Because of that it sent a nice shock wave at me, lending a sense of reality to the dragon’s demise.

Underworld: Awakening

Vampires fighting someone or something has been a popular topic in movies and TV shows for a number of years now. When it comes to the former, the Underworld franchise has proven quite popular. In the Awakening installment of the series, our heroine – a vampire named Selene – is set to do battle with her archenemy, Lycans. These creatures are akin to bipedal werewolves, truly the stuff of nightmares.

The battle takes place in an underground hideout where the vampires have been holed up. As they attempt to repel the beasts, the vampires unleash all manner of small firearms, from pistols to machine guns each produced a satisfying pop that had just enough percussive kick to differentiate between them. Selene’s automatic pistols were particularly strong, despite their rapid-fire ability the VTF-TN1 was able to separate each round while maintaining an authoritative sound.

The Lycans are ultimately vanquished, save for one that is about 3x the size of the others. The soundtrack shifts to overdrive here in order to create a palpable representation of its sheer size. That can cause lesser subwoofers to start making offensive noises, so what does that compel me to do? Turn up the volume, of course. As the creature comes at Selene his footsteps were thunderous, pounding the ground with each step. Even his growl was powerful, enough so that I could feel it in my chest.

Perhaps the thing I admired most was the dynamic range of the VTF-TN1; from the subsonic frequencies made by the beast’s footsteps to the potent sounds from gunfire, each element was distinct and maintained its own unique characteristics. The very deep frequencies did not overshadow sounds 2 octaves above, it all blended seamlessly.

In spite of some difficult soundtracks that were played at an elevated level, I never heard the driver make bad sounds, I didn’t even hear any port noise. The latter is partially due to the fact they’re firing down into my carpet, but also because the system was designed properly. I should have known Dr. Hsu wouldn’t release anything that didn’t fully adhere to his company’s long-established ethos.

Music

There are those who don’t believe a subwoofer belongs in a 2-channel system. If your speakers are large enough it is possible for them to play the full frequency range required to effectively play music. However, that leaves you exposed to the potential pitfall of having everything – bass, midrange and treble – all originating from the same location in your room. Usually, the best place for the enclosure responsible for lower frequencies (subwoofer) is not the same spot where mid and upper frequencies should be originating from. My preference is to have a sub, I like what it adds. There’s really no right or wrong answer, circumstances and preferences dictate what works best in your situation.

But therein lies a problem, a subwoofer that sounds good for home theater does not intrinsically sound good for music. Often, you’ll see the term “musical” thrown around if a sub has exceptional detail and transient response. That description is generally reserved for sealed subwoofers, and it’s not uncommon for them to also have smaller drivers. With that in mind, how does a tall ported 15″ subwoofer fare in this area? As it turns out, rather well.

Big Log, Robert Plant

There are times in one’s life where a song harkens back to another time, be it good or bad. Robert Plant’s Big Log recalls good times for me.

I’m in my early 20’s when this one is released, and it’s unfamiliar territory for me. For some reason I’m ahead of the curve, doing better than any of my similarly-aged friends. Part of that is the result of having a good job that comes with several perks, one of which is a company car. A BMW no less. I loved cruising in that thing; windows down, sunroof open, tunes cranked. It was a period of my life I remember fondly. Big Log was all over the radio that summer, it seemed to come on whenever both the sun and I were out. It wasn’t just simple nostalgia that made me choose this tune however.

Despite being recorded 40 years ago this track has a solid mix with a strong bottom end. Big Log has a simple, hypnotic rhythm that just poured out of the HSU. The bass and drums have a laconic flow, yet together they dominated. The sound was rich and lavish, instantly transporting me back to a time long gone. This one got played more than once.

The Way, Fastball

This song isn’t from a band most would consider mainstream, but popularity is not part of my decision criteria when I’m choosing material. Fit for purpose is, and when testing a subwoofer this one qualifies. Like Big Log it has a lazy rhythm, with perhaps not as good a recording quality. No matter as it does have what I’m looking for, emphasized bass.

As the track unfurls it becomes clear they intended it to have a heavy feel, and the VTF-TN1 complied. Not heavy in the metal sense, but heavy as in a certain prominence. The kick drum and bass guitar were hitting in time, creating a satisfyingly dense feel that supported the guitar and vocals. No matter how high I cranked it this subwoofer would not stumble. The Way sounded great.

Down, 311

Since the previous two choices were on the slower side it was time to kick out the jams. To escalate things a bit I reached for Down from 311. This song did very well for the band, ending up in heavy rotation on the radio. Bet you can’t figure out the lyrics without looking them up, I never could at least. I’m not testing speakers though so that part doesn’t matter right now, what does is the type of workout they give the VTF-TN1.

This tune has a funky, infectious beat. Anything described like that had better have some well-defined bass and drums – Down certainly does. Both instruments are accentuated, the HSU VTF-TN1 seemed to sense that and played each with vigor. This subwoofer was in its element, adding the right amount of weight to make the groove come alive. Notes stopped and started on a dime, changes were fluid and seamless.

Saint-Saëns Organ Symphony

How about a 4th song? For those of you who know my review MO it’s pretty much always been 3 songs per article, but this time it’s different. I figured if HSU is going to supply a test/demo disc with the VTF-TN1 then I should include a selection from it. After scanning through the tracks, I went with Saint-Saëns Organ Symphony. Why? Primarily because of what it says I shouldn’t do. Yea, I’m that guy.

The CD comes with an insert that describes what each track is, for the Saint-Saëns Organ Symphony the description starts with “WARNING: When playing this track for the first time lower the volume as your woofers may be at risk. The bottom octave of this recording may damage vented loudspeakers”. It goes on to say “this recording has the strongest and cleanest 16Hz of any recording I have come across”. You include this type of content with your subwoofer and then say I should keep the volume down? Um, no.

To be honest, I did hesitate for a brief second. Dr. Hsu has a PhD in engineering from MIT, the man clearly knows what he’s talking about. But the counter argument is that means he can design something to protect itself when pushed hard, so that’s exactly what I did. Multiple times during this song there is a staccato pulsing of the aforementioned 16Hz tone. It happens so rapidly that the driver pumps like a piston in an engine, yet the VTF-TN1 never lost its composure. It was surely working hard, a fact evident by the rattling of my blinds, yet it remained poised. I was so impressed by the equanimity of this subwoofer that I decided to resurrect the ‘ol bag test. What is that you say? Allow me to explain.

At various times while reviewing subwoofers in the past I’d check cabinet integrity by using the plastic bag the owner’s manual came in. I would lay it on top of the enclosure then place the manual on that. It takes very little vibration from the cabinet for the manual to start sliding on the slippery bag. That’s especially true when the finish is painted like on the VTF-TN1.

Combine a subwoofer sitting high up on rubber feet with a soundtrack that causes the driver to pump in a pistonic manner, and I’m expecting the manual and bag will do the electric slide right onto the floor. That didn’t happen though, it was resolute and stayed put. I actually played this song a total of 3 times, increasing the volume on each pass, yet it didn’t budge.

Why is that a big deal? The less an enclosure vibrates, the less it reverberates and colors the sound. The walls of a subwoofer cabinet can create sympathetic vibrations that adversely affect what you hear, think harmonic distortion. Resonance is drastically reduced if the structure is rigid and properly dampened, something HSU nailed with the VTF-TN1.

Conclusion

HSU Research is almost like a silent partner in the Internet Direct market, despite being one of the pioneers in the ID space they somehow fly under the radar. These folks design superior products for the masses, price them reasonably and support their customers like few others. For sure they deserve more visibility. I have yet to review a single thing from HSU that wasn’t both inexpensive and impressive, and the VTF-TN1 is certainly no exception. Not sure how this company continually does that, but I’m glad they do.

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