REL 212/SX Subwoofer Review

Over the years that I have been writing audio reviews, it has been funny to find out just how many audio/music fans like myself are also big-time car nuts as well. I was chatting with a friend of mine who’s also an audio journalist and a true car guy and he asked me if I had ever reviewed REL subwoofers. I told him that I had not, and he said that he would introduce me to John Hunter of REL because he too was really into cars (one of “us”, I think he told me). Once on the phone with John for a while, it was easy to see that we were two of a kind. We chatted cars and stereos for a while, then he asked about my current system so he could recommend the appropriate sub(s) for my setup. A short time later, I received a pallet with 2 of REL’s 212/SX subwoofers for review. Little did I realize this would end up being much more than a subwoofer review. This journey ended up taking me to an entirely new realm of audio reproduction!

REL makes subwoofers. Period. With that, they have a single focus on designing and creating the finest subwoofers on the market as they are not burdened with the development of other types of products. At the time of this writing, they have 13 different subwoofers divided into 5 different Serie, with prices ranging from Tzero MKIII at just $499 up to the No. 25 at $7,500. The subject of this review is their 212/SX at $4,999.

If you ask around the industry about REL, the most common summation of their subwoofers would be “musical”. REL isn’t making subs just to pound out the bass in home theater applications; they are designing subs to blend perfectly in 2-channel stereo systems that also happen to equally excel in home theater applications.

Also, what makes REL stand out is how they use high-level connections (speaker-level) as their primary and most effective setup as opposed to low-level connections predominantly used by most other sub manufacturers. This type of connection, combined with their advanced filter technologies, allows the subwoofer to receive the exact same signal as your speakers are receiving from the amplifier or receiver.

The REL 212/SX subwoofer is a double-stack design with two, 12” active drivers in the front, with a passive 12” driver on the rear, and one 12” down-firing driver at the bottom. The front-firing active drivers are driven by a 1000 watt, NextGen5 Class D amplifier. At 33” high, and weighing in at 128lbs, they are not small, but their good looks and piano-black finish allow them to blend in nicely with any décor.

On the back of the REL 212/SX, you will find a lot more inputs and outputs than you normally find on a subwoofer, but these configuration options provide for a variety of ways to incorporate the subs into even the most complex systems. The most frequently used inputs, and the ones recommended by REL, will be your high-level Neutrik Speakon connectors for blending with your main speakers, and your LFE connections (offered in both RCA and XLR depending on your needs) for use in a home theater. You will also find an L and R RCA low-level connection, although REL recommends the high-level connections for best results whenever possible. In addition to the inputs and outputs, you will find an adjustable phase switch, a high/low-level dial, a separate LFE level dial, and finally a dial for adjusting crossover levels.

As for power, you will find a master on/off switch at the back, along with a toggle to select either “always-on”, or “standby”. For my setup, I switched them both to standby, so they turn on automatically when they detect a signal.

When using the high-level Neutrik Speakon connectors, the REL 212/SX comes with a 32’ cable with the Neutrik Speakon connector on one end, and bare wire for connecting to your amplifier on the other end. Once you have established your setup, you can cut down the cable to suit your needs, or simply tie it up neatly in case you move things around in the future. As always, don’t tie it tightly and do so in a loose circular pattern in order to avoid turning the excess cable into an electrical coil.

As for connecting to your amplifier(s), REL provides in-depth instructions on their website depending on what kind of amplifiers you are using. It is very important to read through their articles and/or watch their videos to ensure you are setting things up properly. A full page of various videos and wiring diagrams are available on the header labeled “Our Pursuit.”

And speaking of setting things up, REL also does a great job of walking you through what they find to be the best process for tuning your sub(s). If you don’t take the time to follow these instructions, chances are that you will not get the opportunity to hear the true potential of their subwoofers. I read through the instructions and watched the informative videos several times before getting started just to make sure I was going in the right direction.

Since my system operates with a pair of McIntosh MC611 Quad Balanced monoblock amplifiers, I had to get my hands on 2 of the REL 212/SX for proper setup. Per the REL website: “We do not recommend the use of a single REL with ANY brand of monoblock amplifier as it is possible to observe slight channel-to-channel dc offset that can result in mild oscillation. For any monoblock, we recommend the use of stereo pairs of the appropriate model of REL sub.”

So, when you’re talking about 2 of the REL 212/SX subs, that equals 256 (unpacked) pounds of equipment to wrestle from the garage, through the house, and down into my media room. Fortunately, REL did a great job of designing the packaging to make moving them and getting them out of the boxes a relatively painless task.

When I first received the subs, I placed each of them in the corners, just outside and behind the Sonus faber Serafino Tradition speakers so that I could see the outer half of the sub’s drivers. Based on REL’s fantastic how-to videos and articles on their website, and my experience with other subs in my room, I thought that would be the perfect starting point. I went through their well-documented tuning procedure and found that to be the best placement.

To blend with the Sonus faber Serafino Tradition speakers, I used the high-level Neutrik Speakon inputs on the REL side and connected that to the 8-ohm taps on the McIntosh MC611 amplifiers. This connection handles all the bass to the Sonus fabers in both 2-channel and in multi-channel theater mode, then an additional connection for LFE via the JBL Synthesis SDP55 was made via XLR on the REL. So, in theater mode, the mains are set to receive the full signal (as set up in the HT processor), providing the REL 212/SX’ with all of the bass associated with those channels. Additionally, the subs are also receiving a separate LFE signal that is encoded within the movie. John Hunter and the design team at REL have obviously thought through all connection types and needs when developing these subs!

I was extremely fortunate that REL’s regional sales representative, Jerrad Perkins, was scheduled to be in my area shortly after receiving them, and he wanted to swing by the house to help with any final tuning. While I was enjoying the sound of the REL 212/SX, I knew that there was some room for improvement and simply waited for his arrival.

Jerrad immediately went into tuning mode using John Hunter of REL’s “M.A.S.T.E.R.S technique” of system tuning that first started off with disconnecting the subs to make sure that the speakers were in the optimal position. To my credit, I had just finished up a 3-month re-build of my media room that included (of many things) new back and side wall treatment from Kinetics Noise and hadn’t spent a lot of time re-configuring everything. But when Jerrad employed John Hunter’s techniques which resulted in very minor adjustments to speaker placement, the soundstage grew in width and height, with a much more defined center focus. Hmmm, I was just outdone in my own house! After my pride was swallowed a bit, I accepted the fact that it now sounded better than before, and this is without the subs in place. Next up was the tuning of the subs, with Jerrad carefully adjusting one sub at a time. Once again, only very slight adjustments were made that netted far superior results than I was previously getting. Whatever John Hunter is teaching out at REL in Berkely, CA, I want to pay a visit so I too can learn!

After a great visit for about 3 hours, Jerrad was pleased with the setup, and so was I.

Associated Equipment:

McIntosh MC611 Monoblock amplifiers
Sonus faber Serafino Tradition loudspeakers
JBL Synthesis SDP55 Surround Processor (theater mode)
PS Audio BHK Signature Preamplifier (2-channel mode)
PS Audio DirectStream DAC
PS Audio PerfectWave SACD Transport
Auralic Aries G2.1 Streamer
AudioQuest Niagara 3000 Power Conditioner
Room treatments by Kinetics Noise Control and Vicoustic

If you’ve never had the opportunity to listen to properly integrated subwoofers into either a 2-channel system or a full-blown home theater setup, you may mistakenly think about them simply in terms of purely bass output. We’ve all heard demos where you have 2 separate sound sources…one of them being the main speakers, and the other being the over-blown subwoofer(s). Yes, you can get some smiles from the unknowing who simply love the slam-factor, but the whole experience can be disjointed.

With the REL 212/SX, you can easily achieve volume outputs that will shake the foundation of the house like most quality subwoofers, but it’s how they integrate with your system that sets them apart. When done correctly, the REL 212/SX doesn’t just allow your system to dig deeper, it transforms the entire experience to a level where you’d think that you upgraded everything from the preamp, to amps, to speakers. Strong claims? Yes. But when your system’s soundstage gets taller and wider, the music becomes more 3-dimensional, and even your midrange clarity and detail improve then you know that you’re onto something special.

Prior to adding the REL 212/SX pair, my system was very good. With the REL’s in place, it became even more magical with an entirely new delivery of space, depth, and detail from top to bottom. Want to experience just how good they are? Disconnect the subs from the system and listen to what you had before (and thought was very good), and immediately you’ll find that the entirely new dimension to the musical performance is now missing. To say that the 212/SX was completely transformational to my system would be an understatement.

My latest go-to for evaluating bass capabilities as well as spatial presentation is Make Us Stronger by Ghost Rider (off the album Part of the Dream – Compiled by Vini Vici, 2017). This track is perfect for determining just how good the low-level impact and details are in your speakers (and system in general). If you’re into deep, solid bass, this track has it. If you wish to test the speed and accuracy of the low-frequency drivers in your speakers and/or sub(s), this track will separate the men from the boys so to speak. If your speakers and system get it right, this track is magical. If there’s a weak link, or the drivers simply aren’t up to the task, it will come across as bloated and muddy as bass notes simply slur together. But when playing through the Sonus faber and REL 212/SX combo, it will literally make you laugh out loud because the presentation is so full, deep, tight, and fast. Once you really experience details and clarity in the bass, as you do with the REL 212/SX, you never want to go back! In addition to incredible bass, this track is also produced in such a way that you will swear that you’re listening to it in a full-blown Dolby Atmos setup because it is so enveloping. While the 3-dimensionality was impressive with the REL subs turned off, it was far more when they were turned on.

I’m a sucker for the Double Bass, and artists like Gary Karr, Brian Bromberg, and Christian McBride really showcase the capabilities of subwoofers and speakers that are capable of serious low-frequency reproduction. When played on the right system, these performers are transported right into your listening space, allowing you to fully experience every deep note as it hangs in the air in front of you. From the moody and dramatic sounds of Gary Karr’s bow gliding across the strings in Adagio in G minor (Adagio d’Albinoni, 1981), to Brian Bromberg’s finger plucks in The Saga of Harrison Crabfeathers (Wood, 2002), the REL 212/SX never skipped a beat and played them with more realism and clarity than I’ve ever experienced before.

A subwoofer review wouldn’t be complete without talking about their performance in a home theater setting, and I can confidently say that they ace this task just as well as they do with 2-channel music. One of the big benefits in my opinion is the way that they hook up with the rest of the system. By utilizing 2 separate inputs for each of the front channels (one receiving the full-range signal from the L or R speakers, and the other being the dedicated LFE input), I feel that this brings out far more details than simply allowing the HT processor to do all the work and cramming it all into just one input. One of my best demo scenes that I use for evaluation is during the main battle on the hill from Hacksaw Ridge. Not only do you have rapid-fire low frequency sounds coming at you from all directions from gunshots, hand grenades, artillery fire, and everything in between, but you also have some extremely low explosions that are capable of rattling windows in the house. Some subs may do the low frequency at high levels well but struggle a bit at the speed at which everything is coming at you. This speed and accuracy, combined with gut-wrenching low output capabilities are what really sets the REL 212/SX apart.

The REL 212/SX SUBWOOFERS have increased the overall performance level of my system(s) more than any other piece of equipment or acoustical room treatment I have ever made. Highly recommended!

The role of the subwoofer is far more than just filling in the low notes, and in the audiophile world, it faces many uphill battles given the challenges based on how well they blend into the system. Many have tried subwoofers in the past, and while they did wonders for the home theater environment, they simply stood out too much in the 2-channel configurations. I have tried a lot of subs in the past in my systems, and while they certainly added a “fun factor”, I never felt that they made my entire system better…until now! What REL is doing with their subwoofer design and development, particularly with how they utilize high-level input signals, they are single-handedly raising the bar in the audio industry on what can be accomplished in low-frequency reproduction. The pair of REL 212/SX subwoofers have brought a level of performance to both my 2-channel and home theater systems that I wasn’t expecting, which is exactly why I purchased the review samples!