When, in June 2019, I reviewed SVS’s SB-3000 active subwoofer for Soundstage! Access, I liked it enough to buy the review sample -- and we gave it a Reviewers’ Choice award. I noted that in my room, the sealed-box SB-3000 ($999 USD in Black Ash, $1099 in Piano Gloss Black) effectively equaled the quantity and quality of sound produced by my reference sub, SVS’s own sealed-box SB-4000 ($1499 in Black Ash, $1599 in Piano Gloss Black). The following July, the SB-3000 earned a slot on the Recommended Reference Components list of SoundStage! Hi-Fi.
Then, in August, Kevin East reviewed the SVS PB-3000 subwoofer for Soundstage! Access -- and it earned a Reviewers’ Choice award. The ported PB-3000 ($1399 in Black Ash) is the SB-3000’s sole companion in SVS’s 3000 series. (In SVS model names, SB stands for sealed box, PB for ported box.) Two foam port plugs and a sealed-mode setting configurable through SVS’s downloadable app allow the listener to effectively turn the PB-3000 into a sealed-box subwoofer. According to SVS, sealed mode improves the PB-3000’s transient response, at the cost of reduced output in the lowest octaves. Kevin preferred the PB-3000 in sealed mode while listening to music, but for movies, ported mode won the day: “For me, the very real improvements in LF sound quality for, alternately, music and movies, was worth the negligible hassle of handling a couple pieces of foam and pushing a couple buttons on my iPhone.”
Kevin’s belief that sealed subs are better for music and ported subs are better for films is widespread among audio enthusiasts. However, in my interview with Smith Freeman, SVS’s chief designer, Smith intimated that this is not necessarily true of current subwoofer designs -- or, at least, that the differences in performance between sealed and ported subs has narrowed.
I wanted to test this for myself, using the most rigorous listening tests I could muster in my listening room. Would I hear a significant difference when listening to music between an SB-3000 and a PB-3000, if both subs’ output levels were matched, and both were calibrated to the same Dirac Live target frequency-response curve? And when I listened to film soundtracks, would the PB-3000 trounce the SB-3000?
Setup: two-channel music
My two-channel system occupies a dedicated 15’L x 12’W listening room in the basement of my home, with carpet over concrete slab, the front and sidewalls treated with broadband absorption, and homemade bass traps in the front corners. I removed from its spot to the left of my right-channel speaker my reference SB-4000 sub, and replaced it with the SB-3000 I’d been using in my home theater. Then I replaced my second SB-4000, to the right of the left-channel speaker, with the review sample of the PB-3000. While some may argue that the fairest comparison would be to have both subs under review occupy the same location in the room, the time required to swap such heavy beasts between musical selections would take longer than I can retain precise recollections of sound quality -- especially when we’re talking about low bass, a region of the audioband and below in which what is felt all through the body is just as important, if not more important, than what is heard through the ears. My listening room is symmetrical from left to right, and the two subs were placed along the long front wall in positions that made those halves of the room mirror images of each another, each sub at one-third the distance from the nearer sidewall.
Of course, I left the PB-3000’s ports unplugged for these tests -- otherwise, I’d have been comparing two sealed boxes, when the entire point of this comparison was to evaluate the audible differences between sealed and ported subs.
The first order of business was to play bass-heavy music through the PB-3000 for a few days, to make sure it was well broken in. I connected Output 1 of my McIntosh Laboratory C47 preamplifier to the SB-3000, and Output 2 to the PB-3000, using generic unbalanced (RCA) interconnects. The balanced (XLR) connections of the C47’s Output 1 remained connected to my Marchand Electronics custom passive balanced high-pass filter (HPF, 120Hz corner frequency at 24dB/octave), which in turn was connected to my McIntosh MC302 power amplifier. The MC302 drives a pair of Bowers & Wilkins 705 S2 minimonitors perched on dedicated B&W stands.
I then performed full Dirac Live calibrations for the SB-3000/705 S2 and PB-3000/705 S2 combos. For those of you trying to match subs to your main speakers without an HPF, remember this rule of thumb: Use a 24dB/octave slope on the LPF in the sub’s settings for ported main speakers, and 12dB/octave for sealed mains. Both SVS subs had their low-pass filters (LPF) set to 130Hz at 24dB/octave. Switching between combos was as easy as using the C47 to switch between Outputs 1 and 2 -- always remembering to turn off the sub I wasn’t listening to. Dirac Live calibration involves taking measurements at nine different microphone positions. I took measurements at each mike position for both combos, first measuring one sat-sub combo, then the other, and then moving the mike to the next position. Repeat eight times. This ensured the most consistent results: each sat-sub combo was measured at precisely the same nine mike positions.
The plot below shows the averaged in-room response of the SB-3000/705 S2 combo (blue), against my current target curve (orange). Note the relatively smooth response from 20 to 50Hz.
Below is the averaged in-room response of the PB-3000/705 S2 combo (blue), against the same target curve (orange). Note that in my relatively small room, the PB-3000 exhibited significant boom around 20Hz -- this is what room EQ is for. The green traces in both plots represent the frequency responses Dirac Live projects to attain post-calibration.
My first impression when listening to the SB-3000 and PB-3000 post calibration was how close their bass responses were. This should come as no surprise; after all, both systems were calibrated to have the same in-room frequency response. It would be unfair to proclaim that ported subs aren’t suitable for music -- both subs were satisfying to listen to, providing me with deep, punchy, room-filling bass. But with both sub-sat combos’ levels matched, I could hear differences when I listened to one sub, then listened to the same passage through the other sub, when I kept the time it took to swap between the two to within 30 seconds.
Listening: two-channel music
I first wanted to listen for any differences in pace, drive, and punch, using two tracks: “Run-Around,” from Blues Traveler’s Four (16-bit/44.1kHz FLAC, A&M); and “Carousel,” from Buckcherry’s 15 (16/44.1 FLAC, Eleven Seven). I chose these tracks not necessarily for their bass output, but for the speed, rhythm, and timing of the drumming.
With both tracks, I first noticed that while the initial attack of the kick drum was the same through both subs, the drumstrokes’ decays seemed to last a bit longer with the PB-3000, which made the bass sound as if it had slower pace and rhythm than through the SB-3000. My second observation, surprisingly, concerned the midrange, specifically the voices in “Run-Around.” The slight lingering of bass notes through the PB-3000 seemed to ever-so-slightly obscure the clarity of the voices, as compared to the SB-3000. There was also marginally better separation of singer and drums on the soundstage with the SB-3000.
Next I cued up “Peel Me a Grape,” from Diana Krall’s Love Scenes (16/44.1 FLAC, Impulse!). Christian McBride’s quick fingerings on double bass were conveyed with a greater sense of control by the SB-3000. With the PB-3000, his notes seemed to linger just a little too long. The sealed SB-3000 started and stopped just a bit more quickly, again giving me an impression of faster speed.
When evaluating subwoofers, one must never forget to listen to very low synthesized bass. “She Will,” from Lil Wayne’s Tha Carter IV (16/44.1 FLAC, Cash Money), provides some seriously deep, powerful bass. For the same reasons I felt the PB-3000 lost out to the SB-3000 in my first listening comparisons, this time the PB-3000 edged out the SB-3000 in terms of pure musical enjoyment. A good sub should make listeners feel the deep, pulsating, sustained bass notes in “She Will.” Both subs did this, but with the PB-3000 I could feel the notes just a bit more, and for a bit longer. It was very impressive.
To confirm my findings, I asked my wife, a hip-hop fan and bass enthusiast, to descend to the listening room for some single-blind comparisons. Without her ever knowing which sub was turned on, her observations perfectly matched mine. She preferred the PB-3000 with Lil Wayne’s “She Will,” and the SB-3000 with Blues Traveler’s “Run-Around,” both for essentially the same reasons I describe above. But when she finished her comparative listening session by listening to “She Will” at loud volumes, and having chosen the PB-3000 as her preference, she said, “There’s still not enough bass.”
Personal preferences in the amount of bass boost can vary wildly. The target curve I use offers +6dB of bass boost from 16 to 50Hz relative to 2kHz. Many would find this pleasing, but many audiophiles might find it too much. In the past, I’ve experimented with increasing levels of bass boost, trying to find the amount that will satisfy my wife. For these sessions, we discovered that the SB-3000 and PB-3000 were both capable of meeting her demanding bass needs in our room. But what she finds acceptable sounds, to me, insane: about 15dB of bass boost relative to 2kHz. Her preferences might go a long way toward explaining why bass-heavy Beats headphones so quickly grew popular among hip-hop fans, who tend to prefer big bass.
Setup: 7.1-channel movies
I didn’t go to the same lengths to control variables in my 7.1-channel home theater as I had with the music comparisons in my 2.1-channel listening room. I did consider performing a full Audyssey XT-32 calibration for both subs, using my Denon AVR-X3400H receiver, but decided against it -- I wasn’t sure I could avoid overwriting my default calibration.
My home theater is not a dedicated space, but occupies a portion of an open 21’L x 15’W basement rec room. I placed the PB-3000 in my SB-3000’s usual spot in my home theater, and then the SB-3000 atop the PB-3000. I entered the Denon receiver’s menu, disabled my second sub (an older SVS PB10-NSD), and played the Denon’s internal subwoofer test tones to match the levels of the SB-3000 and PB-3000. I used my miniDSP UMIK-1 calibrated mike at the main listening position (MLP), and used Room EQ Wizard’s (REW) SPL meter function. With the receiver’s sub output set to 0dB, the two subs each produced a measured SPL of 78dB when the SB-3000’s volume was set to -12dB and the PB-3000’s volume was set to -13dB. Both subs’ LPFs were disabled (LFE mode engaged), and with both subs the Denon’s LPF was set to 120Hz, the main LCR speakers’ HPFs were set to 100Hz, and the height and surround speakers’ HPFs were set to 120Hz. To switch between subs, I swapped their interconnects (RCA) in and out of the Denon’s subwoofer output.
Listening: 7.1-channel movies
I chose the opening of Edge of Tomorrow (aka Live Die Repeat), starring Tom Cruise and Emily Blunt. Between the 23- and 37-second marks of chapter 1, some unholy bass notes are recorded at high volume. They change in pitch, sounding almost like test tones. They’re a torture test for any sub -- watching the extreme excursions of both subs’ cones during this sequence was funny and frightening at once.
After I’d switched between subs a few times, it was pretty clear that the PB-3000 was taking the prize: I could feel more rumble in my rump. The SB-3000 was no slouch -- but when with reckless abandon I pushed both subs to the same high volume levels, the PB-3000 consistently offered more output in the lowest octave.
To confirm this, I took a few measurements with my UMIK-1 mike, using REW to send 15-200Hz sweeps through the subs. In this case, the measurements were conducted with the subs in the same location, and mike behind the MLP, about 10’ from the subs. For the first measurement of each sub, I tried to normalize the bass output to 90dB SPL at 40Hz. For each subsequent measurement of each sub I increased the volume 3dB, using SVS’s app.
The plot below displays the SB-3000’s output. You can see significant compression from 15 to 30Hz with the loudest sweep, and a maximum output at 20Hz of just under 100dB SPL.
By contrast, the PB-3000’s plots (below) show far less compression from 15 to 30Hz for the loudest sweep, and a maximum output at 20Hz exceeding 105dB SPL.
Conclusion
It may seem that I’m stating the obvious, but given the same driver size and amplifier power, in home theaters ported subs have the advantage over sealed subs. After all, the raison d’être of ports is to increase the output at low frequencies, and more output will yield a more viscerally tactile listening experience of the demanding soundtracks of many of today’s films. Many people, however, must contend with other mitigating factors when choosing a sub, and may not have the luxury of making a choice based on performance alone. These factors may include cost, size, and décor. Since my home theater is also a communal rec room, I chose the SB-3000 over the PB-3000 for the former’s smaller size. I was stunned when I first unpacked the PB-3000 -- compared to the SB-3000, it’s imposing and BIG.
As for music, should I just repeat the old audiophile saw that sealed subs are better than ported subs? Well, yes, I must -- with a qualification. Sealed subs should sound slightly faster, and convey a better sense of rhythm and timing, than a ported sub of similar quality. But if you’re a big fan of hip-hop or other music with lots of heavy, electronically generated bass, you might prefer a ported sub -- as my wife and I did.
And if your budget is limited, perhaps only a ported sub will give you the bass output you want for what you’re willing to pay. The only way to know for sure is to listen and compare in your own space.
I’d be remiss if I didn’t end this piece with a nod to the SVS PB-3000. If you can tolerate its imposing, room-shrinking size, it can provide you with the best of both worlds: Its foam plugs allow it to be used as a ported or a sealed subwoofer.
. . . Diego Estan
diego@soundstagenetwork.com