REL Acoustics HT/1510 Predator II Sealed Subwoofer Review

REL HT/1510 Predator II Subwoofer Introduction

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.  

Appearance

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.

Design Analysis

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…

Listening Sessions

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.

Music Listening

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. 

Movie Watching

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.

REL Acoustics HT/1510 Predator II Subwoofer Conclusion

Testing on the REL Acoustics HT/1510 Predator II was conducted with the microphone facing the woofer at a 1-meter distance with measurements scaled back to a 2-meter distance by subtracting 6dB. The temperature was recorded at 49F degrees with 70% humidity. The subwoofer’s gain was set to maximum and the low pass filters were set to their maximum range.

The above graph shows the measured frequency responses for the REL Acoustics HT/1510 Predator II subwoofer per its low-pass filter settings. Unlike most other subwoofers, it doesn’t have a switch that defeats the low-pass filter, so, as we mentioned before, this setting should be left to 200Hz, the maximum low-pass filter setting, for anyone using external bass management. The responses shown here do not have the typical flat response that we see so often but rather have a greater resemblance to the driver’s natural response in this enclosure. This isn’t all that surprising given REL’s philosophy of minimalist filters, so there isn’t much intervention in the response with filters. The response with the low-pass filter set to 200Hz is relatively flat in that it adheres to a +/-3dB window from about 25Hz to 110Hz. Some people might think that not having a flat response here would lead to an inaccurate sound, but the reality is that the room acoustics will inevitably mangle the response badly, so those manufacturers that give us a ruler flat response pretty much only do so for academic purposes rather than because there is any real-world benefit for that.

The low-end roll-off holds the classic 12dB/octave slope inherent in a natural sealed loudspeaker, even though not many commercial sealed subs actually use that since most manufacturers use a high-pass filter to protect the sub from over-excursion. The benefit of this gradual roll-off is that it will take greater advantage of the acoustic gain that almost all normal home audio spaces have, and this will shore up the low-end of the response more than normal. That means users can expect more deep bass in practice than what is seen on this graph. I would guess a strong response down to 20Hz could be had in a normal room with this sub and even deeper bass in a small room.

The above CEA-2010 measurements are short-term bursts that show the subwoofer’s clean peak SPL before heavy distortion sets in. Our measurements have been referenced to 2-meter RMS, which is 9dB down from the standard requirement for the measurements to be shown at 1-meter peak. However most publicly available CEA-2010 measurements are shown at 2-meter RMS, so we followed that convention. The HT/1510 posts a good showing here with the highlight being major mid-bass output of 115dB at 50Hz and above. Its deep bass is nothing to sneeze at either, with over 101dB at 25Hz. This sub can hit hard. Due to REL’s relaxed limiters, it is distortion-limited at all frequencies except 50Hz which looks to be a system resonance. One unusual feature is that the limiting harmonic for the mid-bass band is the ninth harmonic; normally it is a lower harmonic. The overall measurement set here nets our Bassaholic Room Rating on the higher end of the ‘Large’ Room Size Rating meaning that it should be able to remain powerful in a room of up to 5,000 cubic feet

For information on how the room ratings are determined, please read our article “Bassaholic Subwoofer Room Size Rating Protocol”. 

Testing for long-term output compression was done by first conducting a 20-second sweep tone where 50Hz hit 90 dB with the subwoofer 2 meters from the microphone. We then conduct further 20-second sweeps by raising the gain by 5dB until no more output could be wrung out of the subwoofer. These tests show us the long-term continuous headroom that the subwoofer is capable of. The HT/1510 maintains its response shape until the last 5dB when it starts to run out of gas. It tops out at over a continuous 110dB at 40Hz which is pretty dang loud. From 30Hz to almost 150Hz it can maintain over 105dB continuously. One odd thing we see in the absolute highest drive level is that there more mid-bass in the response from 90Hz and above than at nominal levels, and I would guess that is due to a filter being over-ridden at the high drive level.

The above graphs show the corresponding total harmonic distortion to the long-term output graphs. Essentially, they depict how linear the subwoofer remains for the corresponding drive level seen in the long-term sweeps. The quantity being measured is how much of the subwoofer’s output is distortion and is shown here as a percentage. At the highest drive level, the HT/1510 can be pushed into some heavy-distortion, but I don’t want that to overshadow how extremely low-distortion the performance is at lower levels. At 40Hz and above, this sub maintains less than four percent total distortion unless you blast it as hard as it can possibly go. At nominal levels of 100dB for our reference 2m, it maintains relatively low distortion down to 16Hz. At the 90dB level, much of the distortion that I was measuring wasn’t coming from the sub but rather the background noise of the testing environment, and even that would not break 1% THD above 40Hz. With its relaxed filters and limiters, it can be pushed into heavy distortion at a high enough drive level, so those who push their audio equipment really hard shouldn’t be surprised if they start hearing their HT/1510 complaining especially in deep bass. It didn’t bottom out or make any mechanical rattling noises in my tests so I think it’s well protected against damage from high drive levels, but it obviously is not very happy at full throttle below 30Hz- but then again, few subs would be.   

The above graphs depict measurements of the constituent harmonics from the long-term output sweeps and are what the total harmonic distortion measurements are composed of for the 2nd and 3rd harmonics. These individual harmonics can give us a clue as to what might be the cause of some quirk or non-linearity. We are only showing the 2nd and 3rd here because they more or less reflect the higher even-order and odd-order behaviors, although higher-order harmonics tend to be much further down as a percentage of distortion compared to the second and third.

The HT/1510’s odd-order harmonic distortion is very much what we would expect from a typical sealed sub except perhaps for how extraordinarily low it is above 40Hz. Almost all of the total harmonic distortion that this sub can produce above 40Hz is even-order, but only at the highest drive level. That means at the highest drive level, there is something inhibiting only one way of travel of the moving assembly. It could be the suspension hitting some kind of tension limit for one of the directions of the driver’s stroke or perhaps the magnetic field of the motor isn’t completely symmetric out to that far of an excursion level. The good news is that second-order harmonics are the most difficult to perceive, so even the relatively high levels of harmonic distortion in mid-bass might well be inaudible or very difficult to hear. 

Group delay is the measurement of how much time it takes for individual frequency bands of an input signal to be produced by the speaker. It can indicate that some frequency components are developing slower than others or are taking longer to decay. It is generally thought that 1.5 sound cycles are needed for group delay to be audible at bass frequencies, although there is an argument that group delay should remain under 20ms to be completely unnoticeable, but that is likely meant for mid and upper bass frequencies.

This is an extremely low amount of group delay and a superb showing in the time-domain. Indeed, this is one of the top subwoofers that we have seen for this measurement. This shows what REL’s light use of filtering is all about. On average, group delay stays well below one cycle, and keeps its head low in the low frequencies where most subs blow up in group delay due to high-pass filters. This sub isn’t going to have any overhang or laggy bass. There is a cost in that the HT/1510 can be pushed into some heavy distortion in deep bass with a large signal, but the reward is this near-pristine time-domain performance. 

Conclusion

Before bringing this review to a close, let’s first go over the strengths and weaknesses of the product under evaluation, and, as usual, we will start with the weaknesses, since I am the kind of guy who wants the bad news first. The only aspect I would complain about of the HT/1510 also happens to be responsible for one of its strengths, so this is a trade-off that each prospective buyer will have to decide is worthwhile for themselves. The mild filtering used to shape the response and protect the sub will enable it to get into some heavy distortion when driven very hard. Other manufacturers can use fairly strict limiters to keep the drivers on a tight leash, so they can’t be made to produce much distortion at any drive level except in extremely deep frequencies. Or, some manufacturers allow moderate levels of distortion, but not a whole lot. REL is very relaxed about these limiters. Although the HT/1510 isn’t allowed to beat itself to death, it will strain audibly if pushed very hard.

This probably won’t be a significant issue with most buyers because most people would rarely if ever push their subs that hard- especially a subwoofer with as much headroom as the HT/1510. This might be a deal-breaker for some buyers who demand perfection at all drive levels, but it shouldn’t be a big deal to anyone else. Indeed, it wasn’t an aspect that bothered me in my own listening since I hardly ever pushed it that hard, and I am probably harder on subs than most people.

This leads to one of the HT/1510’s strengths: its time-domain performance. This sub has extremely low group delay across the entire bass frequency range, and that means it doesn’t allow the reproduced sound to last much longer than the input signal at all. Bass notes will not linger longer than they are supposed to with the HT/1510. This has always been an important performance criterion for REL Acoustics, but I don’t regard it as a serious problem so long as it is kept under a certain level, and most competently engineered subs are able to keep it below a level where it could become an audible problem. For this reason, I regard this more as an academic achievement rather than one that brings practical, real-world benefits. I think many instances where the bass is heard to be laggy or boomy are due to room acoustic setup problems rather than the decay times of the subwoofer itself. In my view, it is the frequency response problems that come from room modes that are usually the source of any perceived lack of “quickness” or “tightness” (for more information about this issue, Audioholics has multiple articles that cover this problem in our room acoustics article category). Nonetheless, if you want a subwoofer with excellent group delay, the HT/1510 is a great choice.

Along with its superlative time-domain performance, the HT/1510 also has very good dynamic range performance, as would be expected from a beefy 15” driver mounted in a healthy-sized enclosure and driven by a thousand-watt amplifier. As was said before, that is a recipe for massive bass, and the HT/1510 delivers it. A stack of these things, as we see in REL’s array system, would provide an insane level of output, and that would make me afraid for the structural integrity of my home (but would still be very cool to have). 

Aside from the HT/1510’s performance, it has a very respectable level of build quality. Its near 100 lbs. weight comes largely from the solidly built enclosure. While I have dealt with heavier subwoofers in the past, it was still very much a two-person job to pick up and move around. It looks nice too, and the gloss black top adds a touch of luxury that suits the REL brand. The glass fiber cone looks much slicker than most matte cones. The feature set has all the basic controls, but not much else, and most of the extra control features that other subs have such as equalization is usually done outside of the sub anyways and so can be extraneous.

In the end, I found the HT/1510 to be a very good addition to my audio system that took care of the low frequencies beautifully. At $1.9k, it’s not the cheapest sub out there, but it’s not tremendously expensive either. Given the performance, build quality, and aesthetics, I would say it is very fairly priced. Anyone looking for a solid, well-rounded 15” subwoofer has a great option in the HT/1510. The good news for those who are interested is REL will give buyers a 60-day in-home trial with free shipping both ways for anyone who wants to return it for any reason. That says a lot about the confidence that REL has in making the end-user happy, and after spending time with the HT/1510, I think they are correct in doing so.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Bass Extension
Bass Accuracy
Build Quality
Ergonomics & Usability
Features
Dynamic Range
Fit and Finish
Performance
Value