In hi-fi, a typical subwoofer-satellite, or sub-sat, stereo system consists of a subwoofer and two small main speakers. Nowadays, this is also known as a 2.1 system—for two speakers, one subwoofer. The main speakers reproduce the highs, the midrange, and some of the upper bass frequencies, while the subwoofer delivers a bit of the upper bass and all of the deeper bass.
Some sub-sat history
The US loudspeaker manufacturer Miller & Kreisel Sound Corporation (aka M&K Sound, or just M&K) claims to have invented the sub-sat system in 1976, with the system it called “David & Goliath.” However, when I posted a link to the claim on M&K’s website onto my Facebook feed and asked for comments, several people pointed out that there are sub-sat systems that pre-date the David & Goliath. Regardless, M&K has laid claim for the invention, and in an ad from 1976 that you can find on the company’s website, you can see M&K’s large Goliath I subwoofer, accompanied by two small speaker models made by Heco Hennel & Co, a company based in Berlin, Germany. Consumers could choose which speaker model—the Visonik David 60 or the smaller Visonik David 50— to combine with the M&K sub.
So how can you get away with just one subwoofer to produce bass for both channels? The main reason for this is that at frequencies below about 200Hz, the wavelengths of the sound waves reproduced by the sub are so long that they radiate omnidirectionally in the room. As a result, your ear-brain hearing mechanism can’t easily identify where the sounds are coming from. In contrast, the higher frequencies coming from the smaller speakers are easily located, so your brain is tricked into thinking ALL the sound—including the deep bass—is coming out of the small speakers. This means that stereo reproduction of bass frequencies is not so important, which is something that M&K spelled out explicitly in that old ad. This might sound weird, but it’s true—providing the setup of the satellites and subwoofer is ideal, which isn’t always easy to achieve.
But a sub-sat system does not have to be limited to just one subwoofer. For example, you can use two subs, which makes it a 2.2 system, a configuration I’ve always liked. Even though I know that one subwoofer is enough to do the trick, it puts my mind at ease to know that each channel has its own subwoofer for bass. It’s the neurotic hi-fi purist in me that overrides common sense—but with that peace of mind comes a more relaxing listening experience, at least for me.
There is also a real advantage in using two subs—you have even more flexibility to place the subwoofers in the room precisely where they can deliver the best-quality bass. Numerous tests have shown that having more than one sub tends to deliver a smoother bass response, meaning you’d see fewer and/or smaller peaks and dips if you measured the in-room frequency response. In fact, I’ve seen home-theater setups with six subs, placed all around the room—though in a stereo system, I think two is likely to be the most anyone would need. With two subs, you can also place one very close to each main loudspeaker, something that’s not possible in a 2.1 system.
There are several reasons why taking the sub-sat approach rather than just having two larger speakers is appealing. But for me, two reasons matter the most. One is that you can achieve full-range sound (i.e., 20Hz to 20kHz), or close to it, from relatively compact speaker enclosures. The other is that you have the freedom to place the main speakers in the room for the best tonal balance, soundstaging, and imaging, while the subwoofer(s) can be placed to deliver the best bass response. You don’t have that kind of freedom when you only have two conventional speakers to move around.
While a sub-sat system with one or two subwoofers seems like the cat’s ass for audiophiles looking for topflight sound, this approach comes with some caveats, with the biggest one being that it’s not always easy to get the speakers and subwoofer(s) to blend seamlessly. Not so many years ago, this was particularly tricky, because the inexpensive measurement microphones and room-measurement software tools that are available today simply weren’t around. As a result, many people tried to tune the output levels, crossover slopes, and phase relationships of the speakers and subs by ear, oftentimes with poor sonic results. That’s one of the reasons why sub-sat systems, despite being available for nearly half a century, have been slow to catch on among serious audiophiles.
Diego Estan in April 2019, when his sub-sat system was based on Bowers & Wilkins 705 S2 speakers and two SVS SB-4000 subwoofers, plus a Behringer Super-X Pro external crossover
Another reason for sub-sat reluctance is that even with good measurement tools, getting that optimal balance between the speakers and subwoofers can be time-consuming. For example, when the SoundStage! Network’s Diego Estan first committed to the sub-sat approach for his reference system, about five years ago, he had two stand-mounted speakers, one subwoofer, a miniDSP UMIK-1 USB measurement microphone, Room EQ Wizard audio measurement software running on his laptop, an external crossover to split the signal differentially between the speakers and the sub, and a good understanding of what he needed to do. Yet when I recently asked him how long he had to tinker with his system until he was happy with it, he replied, “It took me at least three dozen hours of tweaking over a period of several months before I was really satisfied with the sound.”
The average consumer isn’t going to spend months fine-tuning his or her speakers to get them to sound right—and most audiophiles wouldn’t, either. But now, if you have the right equipment, you don’t have to. . . .
A sub-sat system made simpler
In March of this year, through a confluence of events, I had a group of cutting-edge components in my reference room that allowed me to create an outstanding, compact sub-sat system: truly full range, seamlessly integrated between the speakers and subs, and spectacular sounding. It was also—here’s the clincher—super-quick and really easy to set up. After I got it up and running, I knew I had to write about it here. Knowing that sub-sat systems of the past were difficult and time-consuming to get right, my hope is that my experience might encourage others to give a similar setup a try.
Vivid Audio Kaya S12
The speakers were Vivid Audio Kaya S12s, which sell for $6500 per pair (all prices in USD) in standard finishes, including the Pearl White finish that I used for this setup. I could’ve chosen other suitable speakers, but the S12s were a great fit, for reasons that’ll become apparent.
The S12 is a passive, two-way stand-mounted speaker with a 1″ dome tweeter and a midrange-woofer with a 4″ cone (the entire driver, with surround, is about 5.25″ in diameter). Both driver diaphragms are made from an aluminum-magnesium alloy, and the drivers are bespoke Vivid Audio designs. The bulbous cabinet is made from RIMCast polyurethane and is about 19″ high. The speaker’s shape provides a diffraction-free surface that helps it disappear sonically in the room. And it does—sound flies out of the S12, freely and clearly.
I used a pair of 24″-high Foundation stands for my setup. They worked well sonically, but as you can see from the photos, they didn’t match the aesthetic of the speakers. If this was going to be a permanent setup, I’d get the matching Vivid stands.
Vivid Audio specs the S12 down to 45Hz (-6dB), which is pretty deep for a speaker that small—I had tested the pair without a sub for a couple of weeks, which gave me a good baseline for their sound, and they sounded surprisingly robust in the lows. But like any small speakers, they benefit from a sub or two in order to achieve really deep and powerful bass.
KEF had sent me two KC62 subwoofers ($1499.99 each) for a video we published on our YouTube channel. One was in the Mineral White finish, the other in Carbon Black—the only two finishes available for the KC62.
The KC62 has a compact, extruded-aluminum enclosure that measures about 10″W × 10″D × 10″H. To move the air, it has two 6.5″-diameter woofers positioned on opposing sides of the cabinet. The drivers are wired in phase, so their movements are equal and opposite to each other. As a result, the forces they generate oppose each other, so resonances from the drivers that would normally travel into the cabinet are canceled out. This is known as a force-canceling driver configuration, something that we explained in another YouTube video. But this isn’t the first force-canceling subwoofer from KEF, or from other companies, for that matter—there have been plenty of others. What’s unique about the KC62 is KEF’s Uni-Core technology that allows the two woofers to share the same motor system. This is something of an engineering feat when you see how it works—watch our KC62 video linked earlier to learn more.
KEF pushes the envelope with the KC62 in terms of providing deep bass from a tiny enclosure. The company claims bass extension down to 11Hz, which is astoundingly low, as well as a maximum output of 105dB, which is really loud. The size of this sub also makes it a radical departure from the M&K David & Goliath days, when the main speakers might’ve been small, but the subwoofer had to be pretty big.
NAD C 298
Each KC62 is self-powered by two internal 500W amps, but for the passive S12 speakers I used the NAD C 298 stereo power amplifier, which Evan McCosham reviewed for this site in March. Priced at $1999 and able to deliver 185Wpc into 8 ohms, the C 298 is a game changer insofar as lower-priced amplification goes—it boasts incredibly low noise and distortion for an amp of any price, thanks mainly to the Eigentakt class-D amplification that’s onboard, which was developed by Denmark’s Purifi Audio. I could’ve used a variety of other amps for this exercise, but the price-performance of this one is off the charts, so it fit right in with what I wanted to achieve in a truly topflight sub-sat system.
Had I just used any ol’ preamp for this setup, I would’ve been saddled with the same problem so many others have had in the past. For example, I would’ve had to figure out how to drive both the amp and the subs from it, since few preamplifiers have dedicated subwoofer outputs. I also would’ve had to do what Diego did—use an external crossover to try to blend the speakers with the subs. However, I had Anthem’s STR preamplifier-DAC ($3999) on hand, which features, among many things, dual subwoofer outputs and a digital signal processing (DSP) section that runs Anthem Room Correction (ARC). The downloadable ARC Genesis software not only allows you to tame room modes and make the output from the speakers flatter (i.e., more neutral), but also makes the complete integration of one or two subwoofers with a stereo pair of speakers possible. Therefore, the STR, which debuted in 2018, negates the need for an external crossover. For creating a 2.1 or 2.2 system, the STR is a godsend, because, as you’ll see, it became the control center that tied my system’s speakers, subs, and amplifier together.
As I said before, I was stuck with the Foundation stands because that was all I had available. Similarly, I didn’t go out to find speaker cables, interconnects, or power cords that might suit this system better—except for the 15′ Monoprice 138085 single-ended RCA interconnects that I used to connect the KC62s to the STR. I didn’t have single-ended interconnects that long, so I bought the set off Amazon for only $21.80. Otherwise, I just used the usual assortment of cables that I keep for my review setups. So Crystal Cable Standard Diamond balanced interconnects ran from the STR to the C 298, QED Supremus speaker cables connected the C 298 to the S12s, and various Shunyata Research power cords juiced up the STR, C 298, and KC62s. I mention this because if you decide to replicate this system, feel free to switch the cabling up—what I used worked well with these components, but you may find other products that work better for you.
Configuring and listening
My room is big, measuring 36′L × 16′W × 8′H, with around one-half used for the system and listening area (so about 18′L × 16′W × 8′H). This means I can place speakers quite far from any of the walls, making soundstages deeper and the imaging more precise. So each speaker was about 5′ from the closest sidewall and about 7′ from the wall behind it.
I could have placed the subs in many locations in my room, but after talking about the setup with Laurence Dickie, cofounder and chief designer at Vivid Audio, and Jack Oclee-Brown, who oversees product development at KEF, I decided to start by placing each one on the floor, directly behind the stand of the speaker it would be working with. Dickie told me that although a subwoofer might work better at another point in the room further from its companion speaker, the two stand a better chance of blending when they’re spaced as closely as possible. Likewise, Oclee-Brown said, “Perfect. They basically become an extension of the main speakers. Only doable with compact stereo subs.”
ARC Genesis has to be downloaded onto a computer to work its magic with the speakers and the subs, so I used the Asus ZenBook UX303U laptop that runs my music server. I attached the measurement microphone that comes with the STR to one of the laptop’s USB ports and the STR to another with the long USB cables that Anthem also includes. I had to go into the STR’s onscreen menu to tell it that there were two subwoofers connected and that I wanted to have them operate as a stereo pair (you can also run two monaurally). But take note that you only need to connect the computer to the STR while ARC Genesis is calibrating the setup; once the calibration process is completed, the settings are uploaded to the STR and the computer can be disconnected.
The calibration process is prompted by the ARC Genesis software and involves following the onscreen instructions, selecting certain options as requested, and moving the measurement microphone to various positions at and around the main listening position. As you’re doing that, the ARC Genesis software feeds test signals to the STR, which then feeds them through to the speakers and subs. The microphone captures the transducers’ outputs to collect the data ARC Genesis needs.
You can choose from five to ten measurement positions, depending on how much data you want the software to collect. But although more measurement positions will provide ARC Genesis with more information to work with, right on Anthem’s website it says, “For most rooms, we recommend five measurement positions. More isn’t necessarily better.” With five positions, it takes less than five minutes to do. (However, I ran through the process many times to make sure I was doing it right and getting consistent results, so I took a little longer than necessary.)
I’d like to tell you that the process went swimmingly, and the speakers and subwoofers were ideally married to each other right off the bat—but that’s not what happened. During my initial ARC Genesis calibration attempts, I set the Mode switch on the KC62s to the LFE (low-frequency effects) position, which turns off the internal crossover. This basically lets the subs run wide open, producing higher frequencies than necessary, which I thought would give ARC Genesis the widest range of frequencies to work with. But the way LFE works on the KC62s meant that the ARC Genesis calibration process applied the crossover point to the subs at too low a frequency. And when I listened, the output from the subs was too low as well.
Setting the Mode switch on the KC62s to Manual allowed me to adjust the crossover setting, which, in turn, set an upper limit for the frequencies the subs would reproduce. First, I set them both to 80Hz (there’s a dial to do this), so the subwoofers would shelve off at this frequency and allow ARC Genesis to do its magic. The calibration results were night-and-day different. This time, ARC Genesis established a 70Hz crossover point from the speakers to the subwoofers, which seemed about right. It also showed much higher output levels for both subwoofers than when they were set to LFE, and when I compared the levels with the outputs from the main speakers, I saw a linear response from 20kHz all the way down to 20Hz.
The only thing I changed in the ARC Genesis–generated settings was what’s called Maximum Correction Frequency, which defaults to 5kHz. The STR’s onboard DSP only attempts to correct nonlinearities in the measured frequency response up to the frequency specified by this setting. Since the Vivids had a pretty linear response in the mids and highs, which I could see from the ARC Genesis measurements, I wanted to begin my listening with correction only operating below 250Hz. This would mean that the STR’s ARC system was really only affecting the bass region.
The sound I heard mirrored the data that ARC Genesis had presented. I began by listening to the Cowboy Junkies’ The Trinity Session (16-bit/44.1kHz WAV, RCA). This is a great subwoofer test track because it has bass output down to 20Hz, which you’ll hear and feel only if your system can reproduce it. And if your system produces bass that’s too loud, the low frequencies will cloud the midrange and Margo Timmins’s vocals won’t sound clear. It’s a sonic balancing act that provides a good litmus test for speaker-subwoofer integration. Playing The Trinity Session through this system, there was full bass output down to the lowest frequencies I could hear or feel; I couldn’t tell where the speakers were passing off to the subwoofers, or vice versa, which is exactly what you want in a sub-sat setup; and even though the subs generated much deeper bass than the speakers alone could produce, the super-clear midrange of the S12s remained intact.
I followed The Trinity Session with Bruce Cockburn’s The Charity of Night (16/44.1 WAV, True North Records), which doesn’t have nearly as much bass weight as Trinity, but has deep enough bass on many tracks, that, if it’s missing, results in a sound that’s too lean. Once again, the differences I heard with the subs in the system were only positive—in short, the bass output was noticeably deeper than what the S12s could produce on their own, the transition from the speakers to the subs couldn’t be heard, and all the good qualities of the S12s’ sound, such as the amazing midrange clarity and the beautifully extended top end, remained.
I could’ve left that setup alone, but I wanted to try one more thing—increasing the crossover setting on the KC62 subs from 80Hz to 90Hz, in order to make sure their outputs weren’t cutting off too quickly for the ARC. So, I turned their dials a little to the right, and when I ran the calibration process again, ARC Genesis bumped up the crossovers for the speakers and subwoofers from 70Hz to 80Hz, but the rest of the settings didn’t change. Once again, I manually set the Maximum Correction Frequency to 250Hz. Then I listened yet again. . . .
I can’t say this final calibration with an 80Hz crossover point sounded all that different from the 70Hz calibration, but it definitely didn’t sound worse. For instance, playing The Trinity Session and The Charity of Night again, they sounded the same as before, right down to how well the speakers blended with the subs. And there were no telltale signs of the point where the speakers trailed off and the subs came on. The integration still sounded perfectly seamless.
Next, I listened to Lana Del Rey’s Norman Fucking Rockwell! (16/44.1 WAV, Polydor Records/Interscope Records), an album I’ve played a couple of hundred times over the last year through my reference Revel Ultima2 Salon2 loudspeakers. The Salon2 is a 53.3″-high, four-way, six-driver floorstander that costs $21,998 per pair. Three of its six drivers are 8″ woofers, allowing the speaker to reach to the bottom of the audioband. It’s a full-range transducer with high output capability that I’ve used for many years now.
Norman Fucking Rockwell!’s first track is the title track, which, when I played it through my new sub-sat setup, generated a few pleasant surprises. One surprise was that the bass was as deep as the Salon2s could reproduce in my room. But far more surprising was that the KC62s’ bass seemed tighter and more detailed—I could hear textures within the bottom two octaves that I hadn’t heard before. In fairness to the Salon2s, I had never subjected them to ARC Genesis calibration, so it’s possible that they were exciting room modes, and, therefore, the bass region was getting blurred from all the low-frequency sounds bouncing around. But, still, what I heard from the Vivid S12s and the KEF KC62s demonstrated how a sub-sat system can reproduce full-range bass without compromise.
The midrange of the S12s also seemed slightly cleaner than I was used to hearing from the Salon2s, as well as more detailed—for example, I could hear some of the many production tricks applied to Del Rey’s voice a little more clearly through the S12s, particularly the ambience that gets added to it here and there. But where the Vivids and KEFs fell short of the Revels is in what I like to call effortlessness. The Salon2s can project sound into my room at high volumes without strain. When I pushed the S12s and KC62s to louder-than-normal listening levels, they delivered, but I got the sense that they were working much harder at it than the Salon2s. I chalk that up to the Salon2s having more driver surface area than the S12-KC62 combo.
I also played Del Rey’s latest album, Chemtrails Over the Country Club (16/44.1 WAV, Polydor Records/Interscope Records), which I’d already played a couple of dozen times on the Salon2s and on the S12s without subs. I love this new album, but, unfortunately, it’s marred by a bass-light sound on almost all the tracks. The exception is track 6, “Dark but Just a Game,” which has super-deep bass that seemingly comes out of nowhere. But on the album’s other tracks, I’d be surprised if the bass extends much below 60Hz.
“Dark but Just a Game” was obviously reproduced with more low-frequency energy than the S12s could muster on their own, but even the bass-light songs had quite a bit more heft and richness with the KC62 subs in the setup. But what was most striking with this album was the stunning clarity of the S12s’ midrange—Del Rey’s vocals were consistently projected with crystalline purity. Once again, the subs were extending the bass but leaving the amazing sonic qualities of the S12s alone.
Finally, I played Bruce Cockburn’s Humans (16/44.1 WAV, True North Records). On all the tracks, his voice was also more clearly reproduced than I’ve heard it through the Salon2s, but this time it was the bass presentation that stuck out. Based on what I know about the album after listening to it for 39 years, the firm-yet-bouncy drum sound on tracks such as “Rumours of Glory” and “What About the Bond” was reproduced by the S12s and KC62s with no hint of slop or overhang, which confirmed to me that the KC62 can reach low and do so with complete control, and that the integration between the S12s and KC62s was ideal.
Setting up this sub-sat system wasn’t flawless—as I mentioned, I had a hiccup along the way with how to set the controls on the subs. But, including the time I spent fiddling with the KC62’s Mode switch, the total time I took to set up the equipment and run the calibrations I needed to get topflight sound was about an hour, even with re-running the process over and over again to verify consistency. Granted, not everyone is fortunate to have a room large enough to be able to position the subs optimally close to the speakers, and they might take some time to find the best positions. But compared to the nightmares I know people have had setting up sub-sat systems in the past, I consider what happened here with this system to be something of a modern-day miracle. A lot of that miracle-working credit goes to Anthem’s STR and the ARC system that runs on it, which is a far cry from anything available when sub-sat systems first came out—or even what Diego had, just five years ago.
In closing, I encourage you to try setting up a similar sub-sat system yourself and see if you agree with my findings—and if, having tried it, you can go back to just having two loudspeakers in your room again. I have a feeling that if more people take up this challenge, many will find out how painless setting up this kind of system is—providing they have the right combination of components, as I did—and how extraordinary the sound quality can be. It’s been more than 40 years since they were first talked about, but, with the components and tools available today, I think that the sub-sat system has finally come of age.
. . . Doug Schneider