SVS PB-4000 Ported Subwoofer Review

The SVS PB-4000 is the latest evolution of a powerful subwoofer design that has stood the test of time. This design started out as the PB13-Ultra which was launched in 2007 and has gone through a number of changes since its introduction. Up until the recent PB16-Ultra, it was SVS’s flagship subwoofer. It was hugely popular and found its way into thousands of sound systems with legions of happy owners. While the PB-4000 and PB13-Ultra have many similarities, the technologies implemented in the PB-4000 make it a radical enough redesign that it is rightfully considered a new subwoofer model rather than a mere iteration of the now classic PB13-Ultra.

The PB-4000 uses many of the advances made from the 16-Ultra series, chiefly from the unprecedented level of control the user now has with SVS’s Subwoofer control app. The amplifier also sees a major redesign with a build that uses essentially the same design as the 16-Ultra subwoofers. The cabinet has also been enlarged, and the benefits of the additional cabinet volume have been leveraged for improved performance. Like the 16-Ultras, the PB-4000 has an inset LED display with controls on the front baffle. Enhancements have been made to the driver for improved performance. The PB-4000 can also be controlled by a credit-card sized remote control that is supplied with the sub. The PB-4000 is more than just the PB13-Ultra with a few new features, but what is it exactly and what can it do? SVS has loaned us one for review, so let’s try to answer those questions right now.

Unpacking and Appearance

With a 172 lbs. shipped weight and a 153 lbs. unpacked weight, moving the PB-4000 around is not an insignificant task for most people. Thankfully, SVS has made unpacking the PB-4000 a lot easier than unpacking most large and heavy appliances. Unpacking directions are printed right on the box. The user simply needs to open the sides of the box and slide the inner-packed sub out. The inner packing slides out from underneath the sub very easily, so the PB-4000 does not need to be turned on its side at any point during unpacking. All you have to do is place the box in front of its intended placement and slide it out, since the internal packing can be pulled out from underneath the sub very easily. Unpacking the PB-4000 could have been a real chore, but SVS has devised a very clever packing system that made unpacking and placement relatively easy for the end user. 

  

Once unpacked, the PB-4000 reveals itself to be both very attractive and also a bit intimidating. It is a gleaming, black, oblong cabinet that houses a sleek cone and three large ports. I frequently liken subwoofers to automobiles in aesthetics, but the PB-4000 really does beg the comparison, as it does resemble some high-end luxury SUV: brawny yet streamlined. I received the gloss black finish which really accentuates the automotive stylization since it is like an automotive finish. I suppose the black ash finish would not bring to mind an automotive aesthetic nearly as much. The PB-4000 is large, but SVS has tried to make it as living-room palatable as possible for all household occupants. This is about as nice as a large ported subwoofer can be made to look. The curved edges, angled display inset, satiny cone, and posh gloss-black finish all help to make the PB-4000 acceptable to those who might not otherwise tolerate a large black subwoofer in their living space.

In my opinion, the gloss black finish is well-worth the $100 upcharge. It’s a small fee for a such a beautiful finish. There are downsides to gloss finishes such as readily visible fingerprints and dust, and it may also be potentially more vulnerable to scratches than the black ash finish. Those are considerations that potential buyers have to deal with, but the quality of the black gloss finish is terrific for the such a modest premium. The grille definitely takes away some of the splendor of the PB-4000 though, so if it is not needed, I would advise it be left off. The grille does not look terrible, but it does look more utilitarian, not as slick. The PB-4000 cone is just too pretty to obscure without good reason. It has a satiny luster that might be the nicest looking subwoofer cone I have seen to date.

The front LED display is using a blue segment display type, sort of like a digital alarm clock. There is something oddly retro about it, but I think it looks cool. The angle of the inset really helps to make the sub look as good as it does. If the display had simply been mounted on the horizontal or vertical edge face of the PB-4000, it would have looked a bit cheesy. By mounting the display at an angle, SVS made it look 110% nicer, and I think that the added complexity of manufacturing the PB-4000s to get that look was well worth the effort.

Design Overview

At first glance, the aspect that will likely leap out to most people about the PB-4000 is its large size. That size is needed in order to achieve the type of deep bass performance that it offers. There isn’t an easy way to generate prodigious amounts of deep bass from a small enclosure, hence the necessity of mammoth subwoofers like the PB-4000. As a comparative example, the PB-4000’s smaller sealed sibling, the SB-4000 which uses a similar driver and amplifier, would be able to essentially match the the PB-4000 in upper bass output, but in deep bass, the PB-4000 can have as much as four times the output of the SB-4000. So, with everything else being equal, cabinet size and construction can play a huge role in determining subwoofer performance, and SVS leverages that fact to make this a deep bass monster.

The key to making a large cabinet so efficient in producing deep bass is the ports. In a vented (or ‘ported’) subwoofer, the air in the ports can be made to vibrate very precisely by the way the motion of the cone pressurizes air inside of the subwoofer cabinet. This is called “Helmholtz” resonance, and it is the same physical principle that, when you blow air over the top of a bottle or jug, a clean ‘note’ is produced. The size of the port and size of cabinet determine the behavior of the port-generated output. Large cabinets and long ports will reproduce much deeper bass frequencies than small cabinets and short ports. The lowest frequency that the ports will effectively resonate its air volume is called the tuning frequency. Below that point, ported subwoofers generally stop producing any significant output.

The PB-4000 has three ports with the ability to seal any of these ports thereby shutting down that particular port’s output. By sealing the ports, the tuning frequency is altered- and deepened. While output at deeper frequencies can be gained by sealing ports, the cost is headroom at the original port frequencies. In other words, once a port is sealed on a multi-ported sub, the output capability at its tuning frequency is lessened. This design is called a “variable tuning” and is a key feature about the performance of the PB-4000. The lowered extension can be seen in the frequency response specifications from SVS: with all ports open (what SVS calls “Standard Mode”), the low end of the +/- 3dB point is 16 Hz, but with one port sealed (what SVS calls “Extended Mode”), the low end of the +/- 3dB point is 13 Hz. We will examine the trade-offs of sealing ports when we measure its performance in the “Measurements and Analysis” section of this review.

     

In order to achieve such extreme deep bass extension, a large cabinet is not enough; the driver must also be up to the task of moving a lot of air. The 13.5” diameter cone driver that SVS has employed in the PB-4000 is a high performer. It is mostly the same driver used in the PB13-Ultra, but with some minor improvements. The cone is made from a laminated glass fiber that is layered over a paper composite for a very stiff yet light cone. As I mentioned before, it looks gorgeous as well. The basket is a very tall, cast aluminum thing that provides the motor and suspension system with all the room they require to make huge excursion possible. The suspension consists of two good-sized nomex spiders and a large rubber surround. Dual spiders looks like a good idea in this driver, since the former is so deep compared to typical formers. Dual spiders can help restrict motion to keep the former centered for a single direction of travel; a long former such as in the PB-4000 driver is at greater risk of alignment issues otherwise, so it benefits from more tightly controlled movement.

The motor is an underhung design, meaning that the voice coil does not extend outside the top plate gap at rest, so the coil spends a lot of its excursion in a very constant magnetic field. This can help maintain linearity in long throw excursions, although the cost is that, unlike overhung designs, much of the flux of the field of magnetic force from the permanent magnet does go unused, so a very beefy permanent magnet is needed to create a powerful field all throughout the gap. SVS has provided this with stack of two 8.5” diameter, 1” thick ferrite magnets. Needless to say, this makes the driver very heavy, nearly 50 lbs, with the motor comprising 40 lbs. of that. The motor contains a copper shorting sleeve to reduce induction effects, a necessary measure to get a motor with this much coil to maintain a linear behavior. The coil itself is a 3” diameter, 8-layer, aluminum winding and is hidden by an additional collar extending from the top plate for its underhung design. SVS claims an astonishing 53mm Xmax for this driver, or 2 full inches of one-way linear excursion, however, I am thinking they mean geometric Xmax for the coil vs gap depth, since I don’t think the surround or spider would actually allow for that kind of linear throw. The motor is vented at the bottom through a flared pole piece.

As was mentioned before, the PB-4000 uses an amplifier design that is basically the same as the 16-Ultra amplifier platform and is very different than the amplifier used in the 13-Ultras. It is a ‘Sledge’ amplifier, but ‘Sledge’ is more like an SVS brand name and not so much a design platform. The PB-4000 uses a Class-D amp with a discrete MOSFET output stage that uses 32 Amp 600 Volt MOSFETs, which supposedly results in lower EMI and higher efficiency. It has an active Power Factor Correction that pre-regulates the incoming electrical power to 360V DC regardless of the power coming out of the outlet, so that the subwoofer is not affected by erratic voltage from less-than-perfect power sources. SVS says that an isolated circuit also eliminates the potential for ground loop hums, so the PB-4000 should not be subject to that common problem. Analog-to-digital conversion and signal processing is handled by a 50Mhz Analog Devices Audio DSP with double precision 56-bit filtering for very precise and extremely low-latency processing. Such processing power allows users to control the PB-4000 with an extraordinary level of depth and exactness.

    

As with the 16-Ultras, the users can control the sub with the SVS app for iOS and Android devices, or a remote control that is provided with the sub, or the front panel control buttons. With these array of controls, the user can control the volume down to a single dB of precision, low-pass filter behavior from 30 Hz to 200 Hz down to individual hertz frequency precision and also with a choice of slopes of 6, 12, 18, and 24 dB/ octave, phase control from 0° to 180° selectable down to individual degrees (or you can just flip the polarity from positive to negative), room compensation response curve selectable from 25 Hz, 31 Hz, or 40 Hz with a choice of a 12 or 6 dB/ octave slope (this is very handy for taming low-end boominess for those who get a lot of room gain), port tuning configurations, and front panel display brightness and time-out for those who don’t want it on at all times. One neat things that is especially easy to use with the SVS app is a 3-band parametric equalizer with which the user can adjust the bass response to their taste. It can also help tame peaks in the response that are produced by room acoustics. Altogether, the level of control that is given to the user over the PB-4000 by SVS is a enough to satisfy even the most hardcore system tweaker. Nearly every aspect of the sub’s performance can be controlled to a remarkably fine degree.

The PB-4000 cabinet is a burly and well-thought-out enclosure. It uses 1” thick MDF all around except the front baffle which is 2” thick. There are two 1” thick window braces inside the cabinet, and one of them is shaped to support the driver and ports. The ports need to be so long to achieve extreme deep frequency tuning points that they take a right-angle turn inside the cabinet. There is a healthy amount of stuffing lining the enclosure walls which can help to effectively increase the size of the enclosure via isothermal conversion. The PB-4000 comes with a very heavy-duty steel mesh grille which, unlike most subwoofer grilles, is actually able to protect the driver from incoming harm. It could block most thrown objects from impacting the driver, although I am not suggesting that owners throw things at their subwoofer. Those who have rambunctious children or guests can rest easy with this subwoofer when the grille is on.

One small complaint I have about the build is that the feet are shallow plastic cones that do not give the cabinet very much clearance from the floor, only half an inch. I get the reasoning for these feet: visually, it looks nicer when the subwoofer is closer to the floor. However, it doesn’t provide fingers with much room when lifting and lowering the sub, and with a 150 lbs. weight, that can be a safety concern. I would recommend that SVS replace the stock feet with something more substantial, like feet which give a 1” clearance.

Listening Sessions

The best placement for a single sub in my room gives me a relatively flat response for an un-EQ’d single subwoofer, with a window of +/- 4 dB from 25 Hz to 100 Hz with no broad dips in important ranges. This location trades low-end room gain for a relatively flat response, a worthwhile trade for my tastes. Receiver used was a Pioneer Elite SC-55 with a handful of different speakers, and the crossover was used mostly at 80 Hz and also 100 Hz at times. Since room acoustics have a huge effect on low frequencies, the way this sub sounds in my room at my listening position is not necessarily going to be the way it sounds anywhere else for anyone else, so readers would do well to keep that in mind, and not just for this subwoofer in this review, but for any subwoofer in any review. Most listening was done with one port sealed in the ‘Extended Mode’ configuration.

Music Listening

I decided to start a close listen to the PB-4000 with something traditional that would have a significant quantity of low-frequency bass, and what better instrument for that than a pipe organ recording? For this task, I selected a collection of works from Bach performed by Kei Koito, an acclaimed performer of Baroque organ music, in an album entitled ‘Organ Masterworks Vol.1.’ Not all pipe organ music digs into subwoofer frequency territory, but when it does, it can really make the sub justify its existence. On some tracks in this album, the sub is only lightly used, but other tracks make the subwoofer shake the very ground beneath it. While I did play this album at a loudness level that was just short of fatiguing (so therefore pretty loud), the PB-4000 was not challenged by the low-frequency content. It transported the listener to the Martinikerk, a very large church in Groningen, Netherlands where the album was recorded, and certainly conveyed a larger space than my family room. While the PB-4000 is relatively large for a subwoofer, it is still impressive how much bigger it sounds than its actual size. From my experience of listening to ‘Organ Masterworks Vol.1,’ I would say buyers looking at a subwoofer for pipe organ recreation have a pretty safe bet with the PB-4000. Indeed, with a response that is flat to 16 Hz (in extended mode), this sub is ideal for pipe organ since many of the larger pipe organs have 32’ stops, which produce a 16 Hz note. 16 Hz is about as low as any sound system needs to dig for musical content, since human hearing cannot really discriminate individual tones below that frequency.

After the traditionalism of pipe organ compositions by Bach, I decided to listen to something other-worldy yet laden with deep bass. A perfect album for this purpose is ‘Luciana’ by Juno Reactor. ‘Luciana’ is a strange one for Juno Reactor; it is a purely ambient, deep soundscape, but Juno Reactor is known for their brand of electronic dance music in the ‘psychedelic trance’ genre (a type of techno music). ‘Luciana’ does not sound like anything Juno reactor has made before or since. It is like a slow dive into the deepest trenches of an ocean on an alien planet. Rhythmic rumblings, reverberant whirs, pulsating drones, and distant buzzing are the sounds that make up this psychoacoustic atmosphere. This sonic palette suggests bizarre objects and a strange setting that are left to the listener’s imagination, but the music is evocative enough that there are some aural clues as to the shape of the sources of all of this sound. Low frequencies are used nearly continuously, and many of the sounds have a strong bass component, and these sounds can often be playing simultaneously. A lower-fidelity subwoofer could very well blend all of these low-frequency noises into a single ambiguous rumbling noise, and, in fact, I would say that accurate, good low-frequency playback is critical to capturing the essence of the music here. The PB-4000 neatly delineates these different sounds, and there is no confusion at all in bass frequencies. This soundscape is subterranean and cavernous, and the weight that the PB-4000 adds to the sound creates the feeling of being in a mine thousands of feet underground. This music needs a deep-digging subwoofer, and it needs a good one; the PB-4000 makes for a great fit for ‘Luciana.’

I turned my attention to a more pop culture music genre that is still heavy on bass, and toward this end I fired up some dubstep, namely the album ‘Repercussions’ by the acclaimed dubstep producer Distance. ‘Repercussions’ is a now classic 2008 double-disc set release of what was then some very heavy-duty dubstep; sparse but sharp percussion rhythms, desolate lead electronic melodies, twisted atmospherics, and bass-lines so thick you could cut them with a knife. The sound of dubstep as a genre may have changed since the release of this album, but it still sounds as fresh as ever. Perhaps good music just doesn’t age. At the higher volumes at which I listened to ‘Repercussions,’ the PB-4000 gave the music a palpable physical sensation as much as aural bass sound. Low-frequency transients such as kick drums were executed with an articulation that gave these sounds a more tactile feel than a lesser sub might have conveyed, since less capable subs often exhibit overhang that can smear such brief sounds. The bass lines were reproduced cleanly and clearly, and the PB-4000 gave this music a rock-solid foundation no matter what the volume level was set to. The PB-4000 had absolutely no troubles getting very loud. No matter how hard I pushed it, it did not complain, as in there were no mechanical or otherwise untoward noises. It will simply stop getting louder when you max it out, which is ideal behavior. It will not allow itself to be driven into any audible distortion that I could hear, at least for this content. It produces nothing but clean bass. Users who want strong, uncolored bass that doesn’t change its character at all with varying loudness levels can have that in the PB-4000. Distance’s ‘Repercussions’ and the PB-4000 proved to be a great match. I can strongly recommend this subwoofer for electronic music enthusiasts.   

Movie Listening

I had not seen the 2010 remake ‘Clash of the Titans,’ and, given the subject matter plus an SVS PB-4000 in my possession, it seemed an opportune time to correct that oversight. ‘Clash of the Titans’ is an epic adventure about the gods of ancient Greece and their displeasure with mankind. This movie has all manner of large-scale mayhem that is a feast for a capable subwoofer, from fierce thunderstorms to gigantic scorpions, and, of course, the Kraken, which is the real star of the movie despite its limited screen time. Ramin Djawadi, whose music is well-known to fans of ‘Game of Thrones,’ adds a pounding orchestral soundtrack to accompany the onscreen action, which gives the subwoofer even more to chew on. At the loud volume levels at which I watched the movie, the PB-4000 handled this sound mix with aplomb. When the Kraken attacked Argos, the massive beast’s destruction was recreated with verve as the city crumbled. It didn’t sound like the mere playback of a movie. Instead, it sounded like the city was falling down all around me. The same is true with the giant scorpion attack or the battle at Medusa’s lair. The PB-4000 more than just reproduced the sound mix, it transported the listener into the middle of the action. If subwoofers could be said to be ‘laid-back’ in the same sense that loudspeakers are, this sub would not qualify for that description. It tears into bass, and the deeper the frequency, the more energetic it gets.

Another movie that I watched with the PB-4000 was the 2016 superhero epic, ‘Batman Vs. Superman: Dawn of Justice.” This film was met with a middling reception at the time of its release, but I still managed to enjoy it, even though I generally do not even care for the superhero genre. But anyone who has seen this movie will know why I viewed it for the purpose of a subwoofer evaluation: powerful deep bass is abundant throughout the sound mix of this film. There are a multitude of action scenes in ‘Batman Vs. Superman’ that have loads of deep frequency sound in them, in fact every time Superman flies into the air there is a sonic boom. Batman has his share of boom too, where every punch lands with a visceral thud, and his hovering batplane throbs with a low-frequency humming. The final battle is, of course, a buffet of low-frequency sound effects. Hans Zimmer’s characteristic emphasis on bass is present in the film’s musical score as well. For those who wonder why subwoofers need to be so large, movies like this are why. This kind of sound mix can’t really be fully reproduced by a small subwoofer. To competently reproduce deep bass with low distortion, a lot of air displacement is needed, and anything that has to move a lot of air necessarily needs to be physically large. The difference can be heard in a movie like ‘Batman Vs. Superman’; a subwoofer like the PB-4000 changes the experience. It makes the fantastic seem more plausible by adding depth and grandeur to the soundscape. The PB-4000 gave ‘Batman Vs. Superman’ all the bombast that was intended by the sound engineers.

SVS PB-4000 Subwoofer Measurements and Analysis

 

The SVS PB-4000 was tested using ground plane measurements with microphone at a 2-meter distance in an open setting with well over 100 feet from the nearest large structure. The sub was tested with woofer and port side facing the microphone. The subwoofer’s gain was set to maximum, phase was set to 0, and the low pass filter was left off. Weather was recorded at 73°F and 70% humidity.

 

Frequency responses for the operating modes of the SVS PB-4000 

The above graphs are the base frequency responses for the different operating modes of the PB-4000. Each graph depicts how the port configurations with their corresponding tuning mode setting affects the response for the PB-4000. As usual, SVS delivers a phenomenally neutral response in all modes of operation. This is an extremely accurate subwoofer. Extended Mode grants the user about 3 to 4 Hz deeper extension. 3 to 4 Hz might not sound like a lot, but at these deep frequencies, it adds up to a 25% longer wavelength, so, in terms of physics, it is a very significant difference. As was explained before, it does make a difference in the experience of content that can take advantage of frequencies that deep as well. The sealed mode takes on the kind of response that we would expect to see versus the ported modes; the elimination of the port output greatly reduces output around their respective tuning points, but there is an increase in infrasonic bass, ie. frequencies so deep that they are essentially inaudible. I wouldn’t run the PB-4000 sealed unless the room acoustics created so much low-frequency gain as to make the subwoofer sound too ‘rumbly’ due to excess deep bass. There isn’t much sense in getting a large subwoofer like the PB-4000 for a sealed type response when a smaller subwoofer like the SB-4000 could do just as well in that respect and perhaps even better while saving you floor space.

As with other SVS subs, we see good upper frequency extension up to 200 Hz, so users have the option of higher than the typical 80 Hz crossover frequency if they want. This can be a big advantage in multiple subwoofer systems, because it can increase headroom in the extra mid-bass frequencies, and it can also help to smooth out the response for that extended frequency band. Furthermore, some smaller speakers do not quite reach down to 80 Hz, so higher-frequency extension from a sub can fill in the gap that would be left otherwise.  

SVS PB-4000 CEA-2010 Tabulated Measurement Results

The above CEA-2010 measurements are short-term bursts that show the subwoofer’s clean peak SPL before heavy distortion sets in. Our measurements have been referenced to 2-meter RMS, which is 9 dB down from the standard requirement for the measurements to be shown at 1-meter peak. However most publicly available CEA-2010 measurements are shown at 2-meter RMS, so we followed that convention.

The PB-4000 puts up some impressive numbers, especially in deep bass. 107 dB at 16 Hz is indicative of some serious air displacement in ‘Extended Mode,’ and it is accomplished with relatively low distortion as well. ‘Standard Mode’ boasts 112.3 dB at 20 Hz with a maximum of 8.3% distortion; that is stellar deep bass performance. Distortion is held low in the ported operating modes and does increase in sealed, but this is pretty much expected. To be sure, distortion quantities are not bad in the sealed operation, but this driver and enclosure are really intended for ported operation. Maximum distortion levels in the ported operating modes seem to average around 10%, and that is very unlikely to be audible. This is very clean bass. Keep in mind that distortion rises dramatically as we near the maximum output levels of the subwoofer and backing down just a few decibels with likewise dramatically lower distortion, so users aren’t likely to ever see distortion levels outside of the single digit range. We can see the driver does lose some efficiency above 80 Hz, but that isn’t likely to be noticeable to most users and it does still packs a punch in that region, just not quite as much as 50 Hz, where it seems to be the most efficient. That is not too surprising, since the moving assembly of the driver is sure to be a bit heavy in order to achieve a lower resonant frequency. SVS was correct to chase deep bass performance at the expense of headroom in the 100 to 125 Hz range, since people buy a sub like this for the deeper bass rather than mid-bass. The bottom line to this measurement set is that the SVS PB-4000 can move a lot of air and does so in a very controlled manner.

The above graphs show the measured frequency spectrum of the increasing CEA-2010 burst tests. Essentially, they depict the behavior of the subwoofer reproducing short burst tones at successively louder levels, with each test tone raised by boosting the input gain by 1 dB until no more output was to be had from the subwoofer. The frequency marked above the graphs note the fundamental tone being tested, and this can also usually (but not always) be discerned in the graphs by the horizontal axis frequency point of the “main ridge,” the highest levels on the vertical axis. The noise below the fundamental (that random spikiness to the left of the main ridge) should be ignored. What should be looked at are the smaller ridges to the right of the fundamental; these are the distortion products of the fundamental, and it is here where we see how cleanly the subwoofer handles a given output level. These are mostly harmonics: whole number multiples of the fundamental. This testing was done with the PB-4000 in ‘Standard’ mode.

From this testing, it can be seen that the PB-4000 remains very clean at every drive level until it hits it maximum limits. At the last dB, it looks like some kind of limiter kicks in and does add some harmonic components that weren’t there at just one tick under that gain setting. It does not appear to be distortion generated from the driver, as that normally occurs more gradually. Up until that last dB however, distortion is so low that it would be inaudible. The 16 Hz testing here does show more significant quantities of distortion, but that is because 16 Hz is below the tuning frequency of the PB-4000 in standard mode and therefore outside of its intended operational range. There is some 16 Hz output here but not much, and not enough to worry about distortion products at that frequency. At every other point, and at all but the highest drive level, the fundamental absolutely dwarfs and distortion products. As was said before: the bass that the PB-4000 produces is extraordinarily clean.

 

 

SVS PB-4000 long-term output compression for each operating mode

Testing for long-term output compression was done by first conducting a 20-second sweep tone where 50 Hz hit 90 dB with the subwoofer 2 meters from the microphone. We then conduct further 20-second sweeps by raising the gain by 5 dB until no more output could be wrung out of the subwoofer. These tests show us the long-term continuous headroom that this subwoofer is capable of. If we averaged the maximum amount of output the PB-4000 can produce across its listening modes, it looks to hover around 110 dB which is, needless to say, loud. The PB-4000 holds its response shape pretty steady until the last 5 dB where a small peak emerges centered around 45 Hz or so. I would guess it’s due to some induction effects, and, if so, it is relatively mild for that type of effect. It is also a bit too low in frequency to add some coloration to most music, since most musical recordings do not dig that low, and of course, it would only emerge when the subwoofer is driven to its maximum drive level.

If we look closely we can see the cost of plugging a port has on low-frequency headroom; from 20 to about 40 Hz the ‘Standard’ mode (all ports open) has a nearly 5 dB advantage in output, nearly doubling the headroom of the ‘Extended’ mode’s capability in that range. Of course, ‘Extended’ mode has considerably more capability below 20 Hz. Those interested in the most overall output should run the PB-4000 in ‘Standard’ Mode. ‘Standard’ mode would be a bit more appropriate for situations where, to name one example, a single PB-4000 has to tackle a large room.

 

SVS PB-4000 Total Harmonic Distortion per operating mode and output level 

The above graphs show the corresponding total harmonic distortion to the long-term output graphs. Essentially, they depict how linear the subwoofer remains for the corresponding drive level seen in the long-term sweeps. The quantity being measured is how much of the subwoofer’s output is distortion and is shown here as a percentage. The measurements posted here are not unexpected results given all that we have seen with this subwoofer thus far: vanishingly low distortion up until near the maximum possible output levels. The cleanest operating mode is ‘Standard’ mode, which again is not surprising since there is more port assistance and less long-throw driver excursion needed in that mode than ‘Extended’ mode. In ‘Standard mode,’ the PB-4000 is reluctant to go over 5% THD until it is pushed to the limit where it can be made to produce 10% THD. 10% THD is still a very low quantity of distortion, not still not likely to be audible considering it is mostly 2nd and 3rd order products. The ‘Extended’ mode distortion graph looks much like a cone excursion graph, which, of course, is no coincidence. The greater the excursion, the more mechanical stress that the driver will undergo with corresponding lowered linearity. Naturally, the same is true of the sealed distortion graph; as the cone is pushed to longer excursions just to maintain the same SPL level, distortion will increase.

Note: As a reminder, a sealed woofer must quadruple its excursion to maintain the same SPL when the frequency is halved. 

Component harmonics of the SVS PB-4000 for each operating mode 

The above graphs depict measurements of the constituent harmonics from the long-term output sweeps and is what the total harmonic distortion measurements are composed of for the 2nd and 3rd harmonics. These individual harmonics can give us a clue as to what might be the cause of some quirk or non-linearity. We are only showing the 2nd and 3rd here because they more or less reflect the higher even-order and odd-order behaviors, although higher-order harmonics will not be as abundant in quantity as the 2nd and 3rd harmonics. One thing that is readily apparent is that there is quite a bit more 3rd-order harmonic distortion than 2nd, and also that the 3rd-order products do not really pick up until the PB-4000 is pushed hard. That indicates a good deal of optimization since it shows the moving assembly doesn’t have a ‘preferred’ direction of travel where one direction has some kind of inhibition. That means that the moving assembly of the driver reaches the edge of its linear throw in both directions of travel at about the same time, so the engineering has squeezed out as much linear excursion as possible for a balanced design.

  

SVS PB-4000 group delay per operating mode 

Group delay is the measurement of how much time it takes for individual frequency bands of an input signal to be produced by the speaker. It can indicate that some frequency components are developing slower than others or are taking longer to decay. It is generally thought that 1.5 sound cycles are needed for group delay to be audible at bass frequencies, although there is an argument that group delay should remain under 20 ms to be completely unnoticeable, but that is likely meant for mid and upper bass frequencies. Regardless, the PB-4000 keeps group delay under 20 ms above 40 Hz for all operating modes. Below 40 Hz is bass so deep that human hearing isn’t likely to have the acuity to discern a delayed cycle or two. The PB-4000 keeps group delay down to a very well controlled levels where it counts. This subwoofer is not “boomy” nor does it smear sound in the time-domain. This bass does not linger where it would be audible. This is another measurement that explains why the PB-4000 performed so superbly in any type of music that I threw at it. Sealed mode has the best latencies here, but it isn’t enormously better than the ported modes, which is doubtlessly due to some filters that the amp is using. Using this subwoofer in sealed mode just does not hold many advantages.

 

Effects of different ‘Room Gain Compensation’ settings of the PB-4000

The above graph shows the effects that the ‘Room Gain Compensation’ control has on the response of the PB-4000. Smaller rooms can dramatically boost deep bass frequencies to the point where the bass sounds bloated. This is due to an acoustic phenomenon known as ‘pressure vessel gain’ but is more commonly referred to as ‘room gain’. Reducing the deep bass output can help achieve a more natural sound in these situations, and SVS has made it easy to do that with this control. Low frequencies can be reduced by 12 dB or 6 dB per octave slope at either 25, 31, or 40 Hz. 

Conclusion

As with so many other of my reviews, I will begin the summation of this product by going over its strengths and weaknesses, and, as usual, I like to start with the weaknesses. This section will be brief, because the PB-4000 has few weaknesses. One aspect about the PB-4000 that might be an issue for some is its weight. This sub weighs 153 lbs. That is so much that even two adults in good health would have difficulty lifting it. Users who want to move it around will need furniture sliders at the very least. What compounds this dilemma is the finish (in gloss black) is so nice that those need to handle it at some point will want to be extra careful so as not to scuff or scratch the finish. What’s more, the gloss black makes it difficult to get a grip on the sub, so it’s like trying to handle a 150 lbs. bar of soap that you do not want to come into contact with anything that could scratch its pristine surface. However, furniture sliders make it easy to move around, so I recommend users have a set handy when faced with the task of having to move the PB-4000.

Another problem related to the ergonomics of the PB-4000 is one I have already mentioned: the feet do not give enough clearance off of the floor to safely lift and set down this sub. Furniture sliders would help here too, if the user can set it down on the sliders, which will give it a bit of extra elevation. However, the ½” height of the feet just isn’t sufficient clearance for fingers that have to get underneath the sub to lift it. One potential solution to this is to use SVS’s SoundPath Isolation System. Users who want to add the SoundPath Isolation System will want to buy the 6 feet pack since the PB-4000 has 6 feet. The SoundPath Isolation Feet would make the PB-4000 much easier to deal with for those who need to move the subwoofer frequently. However, my hope here is that SVS decides to add more substantial stock feet to the PB-4000 that give it more clearance going forward.

One aspect about the PB-4000 that I want to mention at this point is not really a complaint about the sub but more of a heads-up for users; the sealed mode is simply not very useful. In some variable-tuned subwoofers, a sealed mode can be useful in small rooms where the ‘room gain’ can boost deep frequencies of a subwoofer with a flat response so much that the extra deep bass makes the sub sound flabby. Sealing the ports can reduce the low-end response to eliminate that effect. However, on the PB-4000, that can be addressed in the amplifier with its ‘Room Gain Compensation’ setting. Users can reduce the low-end by a 12 dB per octave slope, thereby emulating a sealed-type response if they wish. What’s nice about this feature is that it brings down the deep bass without losing the headroom that occurs when the ports are physically plugged. So there really isn’t any good reason to use this subwoofer in a sealed configuration. As we have seen in the group delay measurements, there isn’t much of an advantage that sealed has in the time-domain related performance, but, as we saw in the distortion measurements, it does significantly increase the rise of distortion in deep frequencies as the output is increased. I’m not complaining about the inclusion of support for a sealed mode, because it’s always nice to have more options. I am saying that with the PB-4000 has a better way of dealing with taming the low-end than sealing the ports, and there is no sense in buying such a large sub if its deep bass capability is going to be eliminated- the deep bass capability is the point of a subwoofer like this!  

With those minor quibbles out of the way, let us now recount some of the highlights of the PB-4000. First things first, the overall performance is admirable, in deep bass especially. This sub has a superbly neutral response with very low distortion. It reproduces the incoming signal without adding or subtracting anything. SVS’s performance target is clear here: accurate bass down to the thresholds of human hearing. Of course, its sound can be altered to suit the user’s taste with features like the variable tuning, the onboard parametric equalizer, and the room gain compensation control. However, these features are also there to better achieve a neutral response in room, since pretty much every domestic room will have an adverse effect on a response as immaculate as the PB-4000’s. The PB-4000 not only delivers a natively accurate response, it also gives users a way to cope with the inevitable havoc that room acoustics will commit on that response. Its performance qualifies it for Audioholics’ Bassaholic ‘Extreme’ room size rating in both of its ported modes, meaning that it is powerful enough to tackle a room size of 5,000 cubic feet. In its sealed mode, it merits the ‘Large’ room rating for rooms of a 3,000 to 5,000 cubic foot size, although I would not encourage users to run this sub in a sealed configuration in a room of that size range.

My second favorite aspect about the PB-4000 is that for a large subwoofer, it looks really nice (in gloss black). As we said before, subwoofers that aim for powerful deep bass must be large. Truth be told, most subwoofers of that type are not very pretty. SVS has styled their big, deep bass bruiser to look good, and that is no small feat. This is a more specific compliment for the gloss black finish without the grille. The grille is a very effective protector for the cone but does no favors for the aesthetics of the sub. I have not seen the black oak finish, but from the pictures that I have seen, the extra $100 surcharge for the gloss black is a no-brainer. That is a very minor surcharge for such a premium finish. If you need a subwoofer that has stellar deep bass performance but still has to look nice, the PB-4000 is a great choice. 

Another cool feature of the PB-4000 is the level of control that SVS gives to the user and also all the different ways to control it. The level of precise fine-tuning ability that is available for this subwoofer is enough for keep those who enjoy tweaking their equipment busy for weeks. Of course, the user doesn’t have to dig into every control to get a great sound; they can simply run an external calibration on the sub in its default settings and get good results. But the ability for perfecting the sound to taste is there for those who enjoy that. The SVS app is the best way to adjust the sub, but the remote control and front display controls work well too. One of the really nice things about the SVS app is that it explains what all of the controls do and how to use them on the control panels themselves, so novice users do not have to constantly refer to a manual to figure out what all the different settings mean.

Another feature that is handy for less knowledgeable users is the protection that the PB-4000 has against very hard use. The amplifier will not allow the subwoofer to be over-driven. This subwoofer wouldn’t be easily damaged from being played loudly. This is true of all the SVS subs I have reviewed, but it’s still an important and very valuable feature. There will be users who have the propensity to blast their sound systems as loud as possible, and the good news for them is that the PB-4000 can take it. Of course, leaving the sub at full blast all the time will reduce the operational life of the sub, but if users wanted to see how loud the PB-4000 can get for a short stretch, it will survive with no problem. 

One more key feature of the PB-4000 is its extraordinarily high build quality. Every component of the build of this thing is rock solid. If anything, it is overbuilt, and the penalty is the very heavy weight, but the reward is a sub that has virtually no cabinet resonance or vibration at all. It has the feeling of something that is built to last. The complete five-year warranty definitely adds to that feeling of reliability. It’s an expensive subwoofer, but with the PB-4000 you are getting your money’s worth. There is no question about where the manufacturing budget went for this sub, since everything is built to such a high standard.

To sum up the PB-4000, the phrase that comes to mind is ‘well-rounded’ when considering the cost. There is nothing disproportionate about it. It is big, but not too big to be a problematic in many households. There are more powerful subwoofers out there, but the fundamental performance of the PB-4000 is excellent, and it is still very powerful. It looks as nice as any subwoofer that can dig as deep could look. The controls are extensive yet accessible for inexperienced users. The extras that buyers get that are not a part of the subwoofer itself are all top notch, such as the intelligent packing, renowned customer service, free 45-day risk free in-home trial period, and an above-average warranty. It is well-rounded subwoofer where real consideration was given to every aspect of not just the subwoofer itself, but the customer’s overall experience.

The Score Card

The scoring below is based on each piece of equipment doing the duty it is designed for. The numbers are weighed heavily with respect to the individual cost of each unit, thus giving a rating roughly equal to:

Performance × Price Factor/Value = Rating

Audioholics.com note: The ratings indicated below are based on subjective listening and objective testing of the product in question. The rating scale is based on performance/value ratio. If you notice better performing products in future reviews that have lower numbers in certain areas, be aware that the value factor is most likely the culprit. Other Audioholics reviewers may rate products solely based on performance, and each reviewer has his/her own system for ratings.

Audioholics Rating Scale

• — Excellent
• — Very Good
• — Good
• — Fair
• — Poor

Metric	Rating
Bass Extension
Bass Accuracy
Build Quality
Fit and Finish
Ergonomics & Usability
Features
Dynamic Range
Performance
Value