It seems odd that Audioholics has never come around to review anything from the subwoofer manufacturer REL Acoustics. They have been a big name in subwoofers for at least as long as Audioholics has existed. Today, that will thankfully change since we finally have a REL subwoofer in-house for our evaluation. The model in question is the HT/1510 Predator II, a larger sealed sub with a 15” driver and a 1,000-watt amplifier. By REL standards it is a fairly large sub since REL is mostly known for smaller subs intended for 2-channel systems. This one is a part of their “Serie HT” line which is geared more for home theater than their other lines, so the larger size here is necessary since home theater applications tend to take advantage of deeper bass than most music, and deep bass is hard to squeeze out of a small enclosure. The HT/1510 Predator II is, as the name denotes, a ‘sequel’ to their previous 15” entry in this line, the HT/1508 Predator, which was launched in early 2017. I have to admit that REL is off to a good start with me in the naming of these subs since I love the movies Predator and Predator II, but I will try to keep my bias in check here despite the product sharing the name of one of my favorite movies from my adolescence.
The HT/1510 adds a bit more flair than the usual black boxes that subwoofers tend to be. The most attention-drawing aspect of its appearance, aside from the driver, is the top. The subwoofer is capped with a gloss black plastic piece that has REL’s logo printed in the center. The rest of the sub has a grained black vinyl that we have seen on some speakers before, most notably the Monoprice Monolith THX speakers. It’s a nicer vinyl finish than the usual textured vinyl and has a grained sheen that is also resistant to fingerprints. The vertical edges are rounded which helps to soften the appearance of the sub as a whole. With the grille on, the sub has only the gloss top to distinguish itself stylistically, but with the grille off, the driver cone takes over as the dominant aesthetic feature. The cone has a slick glass fiber weave that looks pretty cool, and it is surrounded by a beefy half-roll surround that looks like it means business. I think the HT/1510 looks better with the grille off, but there are those who seem to loathe the appearance of drivers, although the sub will certainly be more noticeable without the grille. One small but nice touch that REL could do to give the font baffle a slightly cleaner look might have been to use a magnetic grille so it wouldn't have needed visible grille guides.
The HT/1510 is a deliberately simple subwoofer in some respects owing to REL’s philosophy of using as few and as least intrusive filters as possible to modify performance. That being the case, much of the sub’s performance will be determined by the mechanics of the sub, i.e., the driver, the amplifier power, and the enclosure. Let us then start our design analysis with the driver, and here we have a 15” cone with the aforementioned glass-fiber weave. The central structure of the cone, the center cap, is made from carbon fiber for its lightness and rigidity. The glass fiber of the cone body is also light yet tough, and one nice thing about this cone is that it is not very fragile like a paper or polypropylene cone, so if something sharp accidentally hits it, there is a good chance that it will be ok (I am not suggesting that anyone test it out in this manner). The cone is connected to the frame by a 1 1/2” thick half-roll surround and a Nomex-type spider. The frame is a stamped steel construction and has very large spokes that have raised ribs for increased rigidity. While not a cast aluminum frame, it should have more than enough strength to keep a firm grip on the suspension and motor even at higher excursions.
The motor’s magnet is comprised of a 1 ⅝” stack of dual magnet rings that have a 7” diameter. Of course, without knowing the actual flux density in the voice coil gap, these parameters aren’t a guarantee of incredible magnetic force, but it is a healthy mass of magnet that should be enough to throw the voice coil around with a high degree of control. The coil diameter is 3”, which is larger than average for a 15” driver and should be capable of higher power handling and good cone control. Venting is done through the pole piece rather than in the basket above the top plate. Overall, the motor looks pretty beefy and should be capable of exerting a lot of force if given enough power.
Speaking of power, REL has supplied this driver with a healthy 1kW RMS amplifier. This amp has a linear power supply with an enormous transformer and uses four 400-watt MOSFETs, so clearly, no shortcuts were taken in providing the driver with power. The controls for the amp are pretty much the bare essentials with just a volume knob, a crossover frequency knob, a 0-180 degree phase switch, and an auto-on switch. There is no low-pass filter on/off switch, so those who are going to use the sub with external bass management, likely the vast majority of buyers of this sub, will want to set the low-pass filter knob to 200Hz, its maximum value. Connectivity is a set of left/right RCA inputs and outputs (with the right input serving as the LFE input), and a balanced XLR input and output. The signal is filtered by what REL has trademarked the “Perfectfilter” which are very simple filters that do not incur a lot of phase distortion. REL has long touted the transient performance of their subwoofers, and minimal filters would be a way to achieve low-lag signal reproduction with no timing issues on a traditional sound system. The filters employed in the HT/1510 provide around 3dB of lift between 20 to 30Hz and also helps to roll off the high-end above 350Hz.
The enclosure is a stout one with a 1 ¼” thick front baffle as well as the top panel. The side panels are ¾” thick and there is a ¾” thick brace that reinforces the midsection of the sub as well as supporting the driver motor. The HT/1510 doesn’t use feet but rather some thick rails with a soft rubber pad on the bottom. The rails should do double duty as not only a resting surface for the cabinet but also added rigidity to the cabinet in the form of external bracing. The side panels are lined with plenty of polyfill-type stuffing. The enclosure is fairly large for a sealed subwoofer, and that should help to lower the resonant frequency of the system and allow a bit more deep bass output than would be possible with a smaller enclosure. The HT/1510 comes with a pair of brackets that can be used to secure additional HT/1510 subs on the top or bottom of the unit to form a stack. The HT/1510 has screw holes on the back that are spaced to screw in the bracket. The possibility of stacking the subs is one of the reasons for the soft rubber padding on the bottom of the rails, so they wouldn’t scuff the gloss black top of the sub. An example and explanation of this feature can be found in this REL Youtube video.
As we stated at the start of this section, component-wide, the HT/1510 is a formidable but simple subwoofer, and there aren’t a lot of sophisticated DSP features or unusual design traits of the sub. But a brawny 15” driver mounted in a stout enclosure with a 1,000-watt amp can be a recipe for some great bass, so let’s see how it sounds in practice…
The best placement for a single sub in my room gives me a relatively flat response for an un-EQ’d single subwoofer, with a window of +/- 4 dB from 25 Hz to 100 Hz with no broad dips in important ranges. This location trades low-end room gain for a relatively flat response, a worthwhile trade for my tastes. The receiver used was a Marantz AV7705 and the crossover was used mostly at 80 Hz. As always, I will note here that since room acoustics have a huge effect on low frequencies, the way these subwoofers sound in my room at my listening position is not necessarily going to be the way they sound anywhere else for anyone else, so readers would do well to keep that in mind, and not just for this subwoofer in this review but for any subwoofer in any review.
A brand-new release from the German Spektral label has Roman Emilius playing a variety of compositions from famous German composers on an organ recently installed at the Church of the Holy Trinity at Regensburg. This release, titled “Die Neue Ahrend-Orgel - Dreieinigkeitskirche Regensburg,“ is a celebration of this new organ, a type which is called a Bach organ, named for the type that the great Johann Sebastian Bach composed, which is based on the Thuringian - Central German model. The city of Regensburg is famous for its many organs but didn’t have a Bach organ until it was installed in the Church of the Holy Trinity in late 2020. This album isn’t exactly a deep bass bonanza but it has its moments of big pipe organ bass, mainly in Bach’s Toccata and Fugue in D minor and Passacaglia and a few other passages. This nicely recorded album can be found streaming on Qobuz in a 24-bit/88.2kHz resolution.
Much of the bass in this album is present but subdued (excepting Toccata and Fugue, of course) although at times it could be quite powerful, and I found the HT/1510 to excel in both the soft as well as powerful bass in this music. It could bring in some serious muscle when needed such as in Bach’s contributions, but in the middle section, Mozart’s Zauberfloten Suites, it could exercise a delicate touch in shoring up the lower pitches without overdoing it and becoming overbearing. The HT/1510 could realize the scale of the organ and its effect within the acoustic environment of the enormous Church of the Holy Trinity. The reverberant decay of the bass notes could be heard as an acoustic product of the church; it was not an extended ringing that washed out other notation but rather a gentle waning, and the HT/1510 did not seem to miss any of this low-frequency detail. Possibly the best demonstration of this deft alternation that the HT/1510 takes between heavy bass and light bass occurs on the last track, Bach’s “Passacaglia in C Minor,” where soft bass underlines a set of phrases but is then periodically punctuated by a powerful low note as though it were a series of similar thoughts to always end in the same disappointing realization. It sounded terrific, and pipe organ aficionados should check it out with a subwoofer as capable as the HT/1510.
Bassist virtuoso Victor Wootan is always a reliable choice for some low-frequency fireworks for his inventive masterful musicianship in the lower octaves of music, and one double-disc album that serves as a great showcase for this is “Yin-Yang,” a 1999 release in the genre of fusion jazz. This is a cleanly recorded studio album, so the sound mixing is getting at the instrumentation sound itself rather than trying to recreate the acoustic environment of a jazz bar or concert venue. The music in this album will keep any subwoofer busy whether through the mid-bass of a bass guitar or the deeper bass from the double bass or some of the lower tuned percussion. While Wootan is undeniably the star of this show, he is backed by a large ensemble of other talented performers, and a whole host of different instruments get their chance to shine. This album is a masterclass in melodic and improvisational bass rhythms, and if it doesn’t make you feel like tapping your feet, you would have to be in a coma.
From the first track onward, this album was an exhibition for low-frequency articulation and a good opportunity for the HT/1510 to prove its chops. Wootan’s dynamic and dexterous playing keeps the rhythms fresh yet anchored, and he is always ready to break out of a steady rhythm to a new phase when the current stretch has reached a natural conclusion. The HT/1510 had no problem keeping up with Wootan’s rapid playstyle, from the quick pitch-shifting of his slides to the sudden starts and stops of his plucking and muting of the strings. As I have said before, the true test of a subwoofer’s transient performance is not in the attacks of string plucks as many others will say because much of that sound is rich in harmonics that come from the higher frequencies of the main speakers. Rather, it’s the mutes that demonstrate the audible time-domain performance of a subwoofer, and on this count, the HT/1510 does not disappoint. I didn’t hear any bass sound overstaying its welcome at all, and everything sounded natural. Percussion sounded sharp, and the brisk playing of the various bass instruments started and stopped on a dime despite the weighty sound that the HT/1510 could impart. Notable tracks for a serious subwoofer workout include “Hip Bop” and the vocal mix of “Yinin’ & Yangin’” both of which were nicely executed by the HT/1510. I have no doubt that Jazz lovers are going to love this sub.
For a very different kind of bass music, I found a low-frequency heavy album entitled “Whispers of the Approaching Wastefulness” by New Risen Throne. This 2007 release on the Cyclic Law label is very much on the darker end of dark ambient music and sounds like the soundtrack for a tour of one of H.P. Lovecraft’s nightmare worlds. This music utilizes a lot of different bass sounds from distant drones to earth-shaking rumbles to resounding thumps, and it can range from subtle to forceful. Some of these sounds can dig very deep in frequency at a high amplitude, and that is a surefire way to stress a middle-of-the-road subwoofer. On paper, the HT/1510 is no middle-of-the-road subwoofer, but how would it handle some of the more taxing tracks from this album?
The first track, “Signs of the Approaching Wastefulness I,” started things off with some slow-paced and low-pitched percussion and strings, as if to acclimate the listener for the horrors to come, and the HT/1510 rendered the strings with an ominous vigor. The next track, “Blowing Funeral Chant” was where sound frequencies dipped into infrasonic realms, and, aside from the cavernous rumbling from the sub itself, I could hear parts of my ceiling shake from the pressure waves produced by the subwoofer. While the cone of the sub was moving with a visibly wide oscillation, I didn’t hear anything distorted or stressed from the sub itself. This track was a bruiser, but the HT/1510 could handle the tremendous excursion demanded by the music. Much of the remaining tracks had an infrasonic rumble to some degree, among other bass sounds, and I think the reason is that noise in this band has been thought to cause anxiety in some people, so perhaps it was a deliberate ploy by the artists to induce unease. Personally, I would say the atmosphere of the music was enough in that respect, but regardless, the HT/1510 managed to charge my room with a subtle ultra-low frequency rumble that was a persistent undercurrent throughout the album. The subwoofer managed to keep this sound distinct from the other bass sounds, and much of the bass sounds retained their own textures integral in the recording.
For music of a more traditional type that could potentially put a strain on a sub, I turned to some heavy-duty dubstep. There are many different flavors within the dubstep genre, and few of them would go easy on subwoofer band frequencies, but Chee’s “Paralysis Analysis” is a particularly heavy load. Normal people might hear this album and think, “Is there some mistake? Music isn’t supposed to have this much bass” but there is no mistake, and yes, music is not supposed to have this much bass - except this music. This early 2021 release comes from the Deadbeats label and will put any sub through the wringer at a high enough drive level. While this music is very bass-heavy, it isn’t the kind of music that exists solely for pumping out bass, and these compositions can be intricate, inventive, and playful.
Are 1,000 watts and a 15” cone enough to handle this much low-frequency ferocity? I cranked the volume but not without some trepidation about what vibrations of this music through this sub might do to the plumbing in my house. For “Paralysis Analysis,” the HT/1510 held its own against the Arendal 1723 S Towers I was using at the time, and these THX-certified Ultra towers, fed with 160-watts RMS each, are a force to be reckoned with in themselves. This sub could pound my room like a punching bag, and the bass was very much on the chest-thumping level. Low frequencies were given a physical presence to the point where I noticed I was inadvertently bracing myself. Again, while I could see the cone being driven to considerable excursion, I didn’t notice any distortion or unintended noise. The HT/1510 held its composure throughout these extremes. I could feel the basslines throbbing my seat, and the kick drums hit with a tactile impact. My personal favorite track from this album, the aptly named “Operator Bludgeoning,” very effectively demonstrated how much more power heavy bass could have when there is spacing between its use rather than having it constantly active like some dubstep tunes have a tendency for. The HT/1510 was powerful enough to drive this point home with a hammer. Anyone looking for a subwoofer for electronic music has a great choice with this sub.
I hadn’t yet seen the 2016 science-fiction comedy “Colossal,” and I figured that it would be a good time to watch this giant monster movie since I had such a powerful subwoofer in my possession. This movie stars Anne Hathaway as an unemployed alcoholic writer that hits a low point in her life, and in her nadir, she manifests a Kaiju-type monster that ravages cities in Asia. She soon discovers that she has telepathic control over the monster. This movie was critically acclaimed but was a commercial failure and doesn’t seem to get much attention. Any modern movie with giant city-destroying monsters is bound to have some serious bass, so I decided to give “Colossal” a whirl to see what the HT/1510 could do for such a fantastical premise.
“Colossal” wasn’t what I was expecting, but I was not disappointed. I thought it might be a typical Anne Hathaway rom-com with a Kaiju twist, but instead, it was a dark comedy about alcoholism with a Kaiju twist. While “Colossal” didn’t have as much big city destruction as any of the “Godzilla” movies, in the sequences like that it did have, the HT/1510 delivered the goods. Seoul was the city of choice for the monster’s rampages (maybe the producers thought Tokyo was too on-the-nose as far as clichés go?) The footsteps of the monsters were relayed with a subterranean grunt by the HT/1510. The usual ineffective artillery and missile attacks against the giant monsters also carried a resounding boom. One scene that had some real bang didn’t feature monsters at all but rather a drunk man lighting a huge firework piece off in a bar. “Colossal” turned out to be a fun movie and an unjustly overlooked comedy. I can recommend it, and I would also recommend it be watched with a competent bass system like I had with the HT/1510.
One movie that I watched with the HT/1510 that I hadn’t seen since its theatrical release in 2000 was “A Perfect Storm.” For those who missed it, this movie is about the captain and crew of a commercial sword-fishing boat in desperate need of a good catch and decide to go out to sea in a storm that they think is manageable. Little do they know there are two other storm fronts converging on their area in what would become one of the fiercest storms in history. This big-budget box-office hit has lots of work in store for subwoofers owing to the many scenes of raging seas and a severe thunderstorm.
Much like the calm before the storm, there isn’t much bass in the first half of the movie, but once the fishing vessel gets caught in the storm, any subwoofers on duty are rarely given a break. The HT/1510 did not seem to be bothered by the abundance of bass in the movie. It gave an alarming reality to the hurricane-force winds and crashing waves. The waves roared to life as they collided with the various ships that were caught in the storm. The whirring drone of Coast guard rescue choppers also added to the low-frequency chaos. On top of all of the effects sounds is James Horner’s orchestral score which can contribute its own bass instruments to the subwoofer’s load, but the HT/1510 was able to keep track of the many sources of bass and not entangle them into a muddy booming sound. “A Perfect Storm” ended up being quite a bit more shmaltzy than I remembered from seeing it more than twenty years ago, but it still managed to be tense and engaging as the viewer is thrown into the crew of a boat that mistakenly sails into one of the worst storms in maritime history. It definitely requires a good sub like the HT/1510 for the most immersive experience.
James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.
Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!
Copyright © 1998–2022 Audioholics, LLC. All Rights Reserved.