REL Acoustics S/510 Subwoofer is the latest in their current line up and interestingly is stackable. Dan Worth dials the S/510 into his system to hear what this £1799 subwoofer can do.

REL’s new S series of active subwoofers came as somewhat of a surprise to me and other industry professionals, it seems like REL wanted to make a statement and surprise the world with rumours of the new S range gently gathering momentum shortly before its release. They have quite firmly stated that the new S Series is the largest upgrade and leap forward in technology for the company’s mid-sized units. Many upgrades have taken place, from amplification, driver, radiators, chassis and bottom rail support system allowing for system stacking of multiple units.

The S/510 has had a huge power upgrade and in order to cope with the 500 watts of amplification, the ContinuousCast alloy driver has too required a further upgrade. The previous S ranges driver is incredibly fast and has a long stroke, however, to stabilise it under greater torque and brake horsepower whilst still remaining as light and agile as before, the design team created a carbon fibre film, which when added only to the rear of the driver and in very strategical positions gave the driver the strength, speed and agility that required, along with cancelling out reversion to a far greater degree, where the rear dispersion of bass notes doesn’t affect the front-firing note, retaining better phase control and increased levels of dB in the lowest octaves for a more dramatic and accurate tuneful bass.

As with the previous design, the new S series still retains a passive bass radiator. However, like all other aspects of the build, it too has been updated. A newer, stronger and more flexible system dubbed “SuperProgressive” has been employed giving an extra 8mm of linear excursion, delivering bass notes reminiscent of a subwoofer far greater than the confines of the 510’s modest dimensions and 10” driver.

The Nextgen3 monoblock amplifier is actually the highly regarded amp cell from the previous flagship REL subwoofer that is tuned to deliver 500 watts of continuous power with incredible current delivery so it gives 20% more power than the previous S3 subwoofer, which, coincidentally, has been my daily driver for a good year or so now. With that extra power comes claimed benefits of more drama and spaciousness – especially for music lovers, which REL always regard as high priority. However, for home theatre enthusiasts, using a S/510 should be nothing short of explosive! With its inclusion of XLR balanced LFE input, movie lovers will be able to attach their latest spec receivers and enjoy what REL says is some of the most dramatic, engaging, detailed and accurate bass possible.

Because of the increase in power REL have added PerfectFilter which they say this about; “This increase in power is necessitated by our development on the musical front of an all-new circuit termed PerfectFilter™ that balance both frequency extremes. PerfectFilter performs two seemingly disparate qualities; extending the strong, even response of the extreme low end of bass frequencies while simultaneously opening up air and delicacy in the middle and high frequencies of one’s system. Additionally, we applied customised PureTheatre™ filters to allow S/510 to keep up with modern theatre effects without breaking a sweat.”

In addition to RELs signature floating design which allows the sub to look as if it’s floating above the floor, much like the design of some modern televisions, the S/510 along with the S/812 are stackable, just like the higher-end models from the previous range.

Stacking has some benefits say REL “In the real world, bass occurs with width, depth and height. By stacking up to three units per side (stereo or theatre main L-R speakers) the proper perspective and height of sonic events are illuminated. This elevates reproduction from conventional stereo or theatre to a floor to ceiling panoramic, full-scale perspective of each sonic event. Reviewers are lining up to marvel at the transformation of music and film into the full-scale representation that REL Line Arrays uniquely deliver.”


The finish on the S/510 is absolutely superb – it looks great! The lustre of the lacquered finish is deep. Style-wise I love how the sub just seems to float over my wooden floor. It’s a little bigger than the S3 but not so much so that it’s noticeable.

Rear panel layout is as comprehensive as ever, with a new inclusion of an XLR based LFE input and a place to bolt on the Airships transmitter – see below.


Unlike the Longbow, which was REL’s previous flagship wireless module the Airship comes in two parts; the Airship Transmitter and the Airship Receiver. Previously the receiver was housed inside the S3 but here they are two separate units, allowing Airship to be purchased separately for use with any subwoofer on the market if one chooses to go down that route.

The previous model had a 2.4ghz radio but Airship has a more stable higher bandwidth 5.8ghz radio. The Longbow was in itself solid in its transmission of an audio signal and I never had a single dropout, distortion or compromise with it in use, but Airship is claimed to be a better solution by the companies engineering team and not confined to use with only Rel subwoofers.

Installation was as simple as expected, bolt the receiver to the rear of the sub and connect an RCA cable from either the Hi/Low terminal into the rear of one of the S/510’s Low-Level inputs or an RCA from the LFE output on the receiver to the LFE input on the rear of the sub. Then simply add the included wallwart style DC adapter.

For the transmitter side of things, either XLR or RCA LFE cables can be used – which is then reflected in the output of the receiving unit. Likewise a high-level input from an amplifiers speaker binding posts or low level from a set of variable RCA outputs will equally work, again reflected in the choice of output when connecting the receiver to the S/510. Another DC wallwart is provided to power the receiver and when both are active they pair almost instantly. If you do suffer any connection anomalies, simply tap the pairing button on each unit and they will begin to talk to each other.

Now my initial thoughts when connecting dreaded switch mode power supplies into my system is the injection of noise they can bring. In my setup, in particular, the transmitters power supply is sat on a different ring to my systems radial, purely not to inject any noise into the systems line rather than the audio signal path itself. The transmission of wireless audio will not be affected by the switching supply. However, my concerns lay purely with the receiver as it’s output is electrical. I initially used the receiver with its own power supply and then changed it for an SBooster linear power supply, there were small differences but it was more for my own peace of mind really, knowing that the receiver is hardwired electrically to the sub but other than that most people really wouldn’t notice a difference. I’d suggest that if you are quite OCD about ensuring routers, switches and other ancillaries with your entire system chain are all on linear power supplies then grab a non-expensive 5v 1 amp power supply online for around £60, as for the transmitter, if you can plug its supply off grid so to speak, do so, if not a linear then doing this will ensure no dirt is fed back into the system, but again I’m coming from the perspective of an OCD power supply tweaker and cannot report any misgivings by using what REL include in the package. If I didn’t mention this you guys would have probably thought I had a bang on the head recently, as you all know what I’m like when it comes to good clean power in a high-end setup!


In the previous T9i review I conducted, I detailed my own setup process I use when marrying a subwoofer to a 2-Channel system, it can be found here. REL provides a comprehensive guide on their website with regards setup, which is great and will give you some real insight into how to get the best out of their subwoofers, or any other subwoofers for that matter. I always have and always will use this same process and once you get used to how your room behaves, subsequent installs are a lot quicker and go a lot smoother.

In comparison to installing the T9i, I am not using quite as much volume on the dial from the S/510 due to its greater power reserves, crossover is the same and something that often gets a click either side now and again (just one of those things dependant on taste and genre really) and the low-frequency cut-off point again may get the odd click up or down if I’m having an acoustic session or a more beat driven session – these clicks really are negligible and if I didn’t adjust the subwoofer whatsoever I’d be completely satisfied with my music, but it’s just that constant urge that I personally get at times and is something I’ve always done, but honestly, once dialled in the S/510 can rest untampered and just do what it does so well.


Give the unit a while to run in, a good 50 hours will loosen things up a lot and in order to not cause undue stress on the driver, don’t pump it to its limits straight away (as with any drive unit) and allow the diaphragm to become a little more elastic. After 150 hours you will notice the bass becoming much freer and more open, so I suggest you do those final and very fine adjustments after this period of run-in. For me, I dropped the crossover point a notch or two and increased the level by a notch.

In comparison to the S3 I have used previously the S/510 has a little more bottom-end detail and weight around the mid 20hz region and this was evident on double bass and bass guitar with more rolling of the note and a fraction longer decay resonance. It’s terribly difficult to intently listen and report on the more specific attributes of bass note performance when listening to two very accomplished subwoofers, but over time it became evident that the S/510 was indeed the better performer.

The S/510’s cabinet construction and drive units really and truly express bass so well that this review wasn’t quite as difficult as I first believed it would be and as the new amplifier came into its own with the grip, drive and tactile nature of the sub proving again that REL’s topology and design approach was a step above many other home subwoofers. Ordinary non-ported designs don’t have the depth and weight of a REL and, although inherently fast, a REL will still be faster – ported designs, although able to express bloom and rollout well, generally cannot deliver the detail and grip of a REL – they cannot stop and start as well and have muddier dynamic bursts in my experience.

Listening to electronic music or even pop is a great way of appreciating the flexibility of a subwoofer. These genres can get busy in the layers of bass the engineer overlays and it takes a great implementation to pick this all apart, not smear the treble and midrange, not localise the sound and to collaborate with the main speakers so well that the delivery is coming from the main soundstage, integrated with the bottom-end of the main speakers and also staying in line with the depth and breadth of the main speakers.

Throughout all the tracks I played the music was nothing short of exhilarating. Many times I had to turn the wick back down as it gradually crept up further and further over the course of my listening sessions. The underpinning solidity that the S/510 offers is seamless once dialled in correctly, giving better pace and rhythm and with a more tuneful bass.

I’m sure anybody who uses a good subwoofer with a 2-channel system will agree, once integrated the effects are frequency wide. Midrange becomes richer, embodying male and female vocalists alike. Male vocals sound deeper and more chesty, with female vocals tending to shine more in the upper midrange as their range is fuller in the lower registers allowing for higher notes to impress further. Midrange depth when listening to a well-recorded band is deeper and broader, allowing instruments to find a more realistic position within the performance, whilst acoustic reverbs and tonal colours appear in a more natural and reflective manner in the recording.

Treble too benefits greatly from a high-performance sub such as the S/510, underpinning treble notes and giving more body and in turn allowing for more perceived delicacy in the higher frequency and more so here than with the S3, which is an attribute I personally have worked hard to achieve over the past few years. We all work hard to pursue more detail out of our systems, but it is often detrimental to tonality.

Trying to reintroduce that tonality is something that often people give up on and resolve with comments such as “I’m not a detail freak” or “I find I like things warmer”, which is fine, but often it isn’t out of choice. In my experience and in my humble opinion I believe that being able to balance detail with tone is just such a hard feat that often people revert to one or the other, where in reality the will is to pursue both. Surely anybody spending thousands or tens of thousands of pounds on Hifi is doing so to bring them closer to the realism of a performance, to extract as much from the music as possible?

The problem lies with the difficulty in balancing this extra detail with tone; additional warmth will mask detail and additional detail can leave the sound feeling cold. This is where a great subwoofer like the REL can really help. As well as bringing in the lower registers which the main speakers may not be able to reach down to, a good subwoofer will reinforce the entire frequency response.

Building a detail-rich system isn’t a bad start, so don’t feel dejected by an initial lack of tonal warmth – extract all the detail you can, without going clinical, we still want this to be Hifi rather than a pro monitoring rig. Find some good synergy in electronics and speaker choice and then add the additional timbre, body and warmth separately with a subwoofer.

This method to building a system works, it isn’t about thunderous bass (although there’s enough power in the S/510 to dislodge fillings) it’s simply about giving the sound some real backbone – I only ever use subwoofers around 1/4 of their own gain level. In my system, with the S/510 I can hear even more inner detail in the top end and dynamically the entire frequency range along with the treble is far more tactile and energetic, more playful and bouncy. Overall balance is better and the sound is far more natural and effortless.

Soundstaging as a whole gets noticeably better with a good subwoofer too. I mentioned the increased depth above, but the overall reference to the acoustic space and realism in each recording depicts the best explanation of the soundstage – focus was strong with the S3 in place and although richer sounding than the ceramic Ayon’s on their own there was never any muddying of the air and space around instruments, quite the contrary in fact, these darker areas stand out more as the full tonal balance and decay of instruments are presented more naturally. With the S/510 I found a few more quieter spaces in the music as if it was truer to the acoustic space and more refined in how it allowed the synergy of itself and the main speakers to behave in a more three-dimensional manner, dealing with layers more intelligently.

There is a stronger reflection of the recording for sure. Bad recordings are also treated a little better with the S/510. It’s no cure, of course, but the additional body definitely helps take the edge off the nasties reported through the speakers. If you have a great album you love but are disappointed with the recording a little trick is to raise the crossover point of the sub by a couple of notches for the duration of the album, introducing a little hump a fraction above the lower end of the main speakers will thicken and flatter the sound a little better and make those rougher recordings a little more bearable.


Employing a subwoofer into a system can be a little time consuming and fiddly at first but REL do offer an easy to follow setup overview on their website and my review of the T9i as mentioned earlier is how I generally initiate the process (they really don’t differ much). Time and listening will encourage and allow you to make those final finer adjustments to bring true synergy between the subwoofer and the main speakers and by then a true appreciation of what a REL subwoofer such as the S/510 can bring to the party.

Would I say that the S/510 is a dramatic difference over the S3 in a Hifi system played at reasonable volumes? maybe not. Is there a clear discernible difference that would leave me wanting to go back to the S3? Yes for sure! The new cabinet design and isolation, improved amplifier and more rigid and tactile driver and radiator takes president over the previous design in every way, it’s just that REL do such a sterling job at producing subwoofers that even the older model still impress so much and it’s difficult to say a bad word about them, even when discontinued and replaced with a better model. I still have incredibly fond memories of my old Strata and Stadium even though they are a good decade or two old now.

Whether you opt for a single S/510 or a pair in stereo, for the money, and in my opinion and experience, there isn’t anything else out there that will perform as admirably and REL’s reputation proceeds them.


Build Quality: Exceptionally finished, with a deep lustre automotive quality lacquer and great styling to boot

Sound Quality: The new range takes a big step forward over previous models which in my experience were industry-leading
Value For Money:  For a product of this pedigree any potential customer will feel absolutely satisfied by the outlay

Pros: Vast array of controls for great integration. Detailed rich and expressive sound. Dynamic fast and rhythmic. Handles subtleties with ease. Airship wireless system is superb. Attractive, well built and surprisingly compact.

Cons: Hard to be negative about the product,  but I advise some patience in setting up.

Price: £1,799






Dan Worth

REVIEW SYSTEM: Xodos xo|one streamer, Audiobyte Hydra Z Clock w/Paul Hynes SR7 LPSU, Lindemann 825, Audio Music Reference T1 preamp, David Berning ZH270 power amplifier (modified), Ayon Seagull Ceramic Loudspeakers (modified), Atacama ECO Evoque rack, Studio Connections Black Star Power, Speaker, Digital and Interconnects – Mundorf Power – Gobel High-End Lacorde Statement Ethernet and USB, Custom made Balanced Power Supply, Finite Elements/SSC Isolation


TYPE: Front-firing active woofer, down-firing passive radiator

ACTIVE DRIVER SIZE & MATERIAL: 10 in., 250mm long-throw, die cast aluminium chassis



INPUT CONNECTORS: High Level Neutrik Speakon, Low Level stereo RCA, LFE RCA, LFE XLR


POWER OUTPUT: 500 watts (RMS)


WIRELESS CAPABILITY: Yes- REL AirShip system [required]. Sold separately.

Protection System




MAINS INPUT VOLTAGE: 220-240 volts, 110-120 volts for certain markets

FUSES: 5 Amp semi delay 220 volts operation 9 Amp semi delay 120 volts operation

DIMENSIONS: W X H X D 15.7 x 16 x 18.25 in., (400 x 410 x 464 mm) Add 1.75in (44.5mm) in depth when using Hi Level connector

NET WEIGHT: 70 lbs. (31.7 kg)

FINISH: Piano Black Lacquer, White Lacquer, 10 coats

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