Syzygy Acoustics SLF870 Subwoofer

Technology Serving Music

Equipment report
Syzygy Acoustics SLF870
Syzygy Acoustics SLF870 Subwoofer

Setting Up and Using the SLF870
Like a tonearm, much of the success of a subwoofer depends on how you set it up. Since the SLF870’s technology is new and unfamiliar, I started by reading the well-written and well-illustrated 11-page manual. Most subwoofer set-up suggestions are based on home-theater applications, where the goal is to flex the walls and dump as much bass energy as possible into the room. For an audio system, what’s important is seamlessly merging the output of the subwoofer with the output of the main speaker. You shouldn’t be able to tell there’s a subwoofer in the system; instead, it should sound like the main speaker has just added an extra octave or two of bass. If the subwoofer’s response isn’t relatively flat, the challenge of matching its output to that of the main speakers is a lot harder. Then there’s the matter of speed. I tried for years to find a subwoofer that would integrate with my Affirm Audio Lumination horn-loaded main speakers, which start to roll off below 50Hz. It wasn’t until I tried the original JL Audio Fathom f110 subwoofer that I found an adequate match for my Luminations. In choosing it, I went for speed and integration rather than bass quantity. I initially used two f110s, but found I could get a better integration with a single subwoofer.

The SLF870’s truncated rubber cone feet came screwed to the bottom panel, so that the drivers faced forward, which is how I wanted them. I placed the two subwoofers just inside my main speakers, a position dictated by available space more than anything else. My JL Audio subwoofers have a continuously adjustable phase control, which I can use to compensate for different positioning, and I was pleased to find that the SLF870 also have adjustable phase, built into the app. The relative lightness of the SLF870s made the cabinets easy to manhandle into the desired positions. The transmitter offers a choice of either right and left channel inputs on RCA jacks, or a single combined low-frequency effects (LFE) input for amps or receivers designed for 2.1-type speaker systems (two main speakers and one subwoofer). Syzygy thoughtfully provides a set of RCA interconnects, though I suppose an audiophile will toss those and the flimsy power cord in the drawer and use audiophile-approved cables/cords. I did. My linestage provides right and left channel outputs, so that’s how I connected it to the transmitter. I checked to be sure my preamp’s output impedance could drive the transmitter’s 20k-ohm input impedance. It could, just barely. (How hard would it be to design, say, a transmitter with a 50k-ohm input impedance that would be compatible with a wider range of equipment? Just asking.)

Now came the opportunity to try the Syzygy set-up technology. I downloaded the Syzygy sub app from Apple’s App Store onto my iPhone 6. (An Android version of the app is available from Google Play.) I made sure the transmitter was plugged in but not connected to the output of the linestage—that would come later. I ran into several problems setting up the stereo pair of SLF870s, and finally had to call Paul Egan, President of Syzygy Acoustics, for help. It seemed that the manual’s instructions were probably OK for a single SLF870, but connecting to a pair of them was more involved. The secret proved to be setting them up one at a time. Plug one SLF870 in and set it up; then unplug it and go through the same set-up routine for the other. The subwoofer you unplug will retain the set-up information. Next, pair the transmitter with the subwoofers, which involves pushing buttons on the subwoofer and the transmitter. If that sounds easy, it is, but it could be even easier if the amplifier controls and connection weren’t underneath the subwoofer when the driver is pointing forward. Finally, use the app to mute the subwoofers and plug the RCA interconnects from your linestage, preamp, or integrated amp into the transmitter. I’d strongly suggest buying SLF870s from a dealer who can help install them. Once installed, all you have to do is play music, not fiddle with the subs. They can be set to turn on when a signal is received, or can be left on at all times—they only consume 1/3 watt when quiescent. If you set them to turn on when a signal is received, the SLF870s will emit a very low frequency whomp when they activate. It’s not loud, but it gets your attention. I rather liked the reminder that the SLF870s were operating.

After the SLF870s are set up to work in your room and are connected to your main system, you still have to match their output level with the output of the main speakers. Although Syzygy doesn’t provide a tool to help with that task, I again turned to my iPhone, using an app called OctaveRTA. This is a spectrum analyzer which uses the iPhone microphone to pick up the sound from your room. I played a recording of pink noise from, and also a low-frequency sweep, which covers the range from 10Hz to 200Hz. Final tweaking of the adjustments was done by ear. The Syzygy Sub app serves as a really flexible remote control, allowing you to adjust levels, crossover frequency, phase, and several other parameters. It also lets you apply a DSP adjustment, so even after the app has equalized the response for your room, you can still adjust it if you want a different bass response. Think of the DSP adjustment as a super tone control.

Syzygy recommends 25 hours of break-in, but that’s 25 hours playing bass notes—not just turned on. That’s one break-in process I don’t want running 24/7! The subs do loosen up after breaking in.

I found the subwoofers matched my main speakers when set for a level of around 50 on the app. Other speakers and rooms will require different settings. Adjusting the level with the app was easy—just move a slider. When I adjusted the level for one subwoofer, the other one was also adjusted to the same level. Of course, my initial setting was too high, but I confess I listened to several albums that way, just enjoying the bass energy washing over me. (Does that mean I’m a closet bass-head?) Anyhow, after enjoying the surfeit of bass for a while, I forced myself to act like a responsible reviewer and dialed the sub-level back to match the output of the main speakers. You should be aware that the SLF870’s internal crossover is just a low-pass crossover, which keeps the higher frequencies out of the sub. It has no effect on the main speaker, which continues to run full-range. It would be interesting to use an external crossover like the JL Audio CR-1 reviewed by Jonathan Valin in Issue 254. A fully active crossover like that will also filter low frequencies from the signal driving the main speakers, relieving the speakers of reproducing bass and thus increasing the speaker’s dynamic range.

If you had just installed new subwoofers in your system, what would you play first to show it off? Being a classical music geek, I thought of organ music, specifically Saint-Saëns’ Third Symphony (Organ Symphony). Although my local symphony orchestra doesn’t enjoy a concert hall that sports a pipe organ, a few years ago they managed to stuff the orchestra pit with an electric organ on steroids, which could and sometimes did generate a 32Hz note that shook the concert hall and occasionally overwhelmed the entire orchestra—a memorable experience. Anyhow, I selected an album that contained the Organ Symphony and Poulenc’s Organ Concerto, as well as Barber’s Toccata Festiva, with Christoph Eschenbach leading the Philadelphia Orchestra, ripped to AIFF format from the CD layer of Ondine ODE 1094-5. Although it’s probably not my favorite recording of the Organ Symphony (I still prefer the one by Charles Munch and the Boston Symphony on Living Stereo), it’s the best-sounding recording of the symphony I have. I played the last movement, the Maestoso-Allegro, which has lots of spectacular organ fireworks. The SLF870s didn’t quite flex the walls of my room, but they still shook me. There’s a passage about 5:15 into the movement where the orchestra, which has been pretty rowdy, drops off into silence leaving the organ playing a very low sustained note. The SLF870s did full justice to that note, reproducing it with excellent pitch and lots of power. Yet the SLF870s validated the success of my efforts to integrate them seamlessly with the main speakers—I never heard them sounding like separate speakers.

Since it has bass extending to the mid-20Hz range, of course I had to try “Folia: Rodrigo Martínez” from La Folia 1490-1701, played by Jordi Savall and his band of Renaissance music specialists and ripped to AIFF from Alia Vox AFA 9805. The SLF870s projected substantial impact and power, yet integrated with the main speakers to project an impression of a realistic drum. Since the main speakers were still being powered by the normal amplifier, from the midbass upwards the system still sounded the same.

Another fave is Shelby Lynne’s album of Dusty Springfield covers Just a Little Lovin.’ On the Acoustic Sounds DSD64/DSF download, there’s a strong bass underpinning throughout. The title track opens with the bass guitar growling menacingly. The SLF870s played those lower-octave notes with excellent pitch, and although I suspect the bass on the downloaded track is overdone (the LP sounds more realistic), it was a kick to listen to it via the SLF870s—further substantiation that I really am a bass-head. Who knew?