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SVS PB-4000 Subwoofer Measurements and Analysis

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pb4000 outdoor testing.jpg

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.

4000 response comparison.jpg 

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

The PB-4000 is an extremely accurate, phenomenally neutral, subwoofer.

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.  

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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.

CEA-2010 bursts_ 16 Hz.jpg CEA-2010 bursts_ 20 Hz.jpg
CEA-2010 bursts_ 25 Hz.jpgCEA-2010 bursts_ 31 Hz.jpg
CEA-2010 bursts_ 40 Hz.jpgCEA-2010 bursts_ 50 Hz.jpg
CEA-2010 bursts_ 63 Hz.jpgCEA-2010 bursts_ 80 Hz.jpg
CEA-2010 bursts_ 100 Hz.jpgCEA-2010 bursts_ 125 Hz.jpg

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.

4000 extended mode long term.jpg  4000 standard mode long term.jpg

 

4000 sealed mode long term.jpg

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.

 4000 THD Extended Mode.jpg 4000 THD Standard Mode.jpg

4000 THD Sealed Mode.jpg

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. 

4000 2nd 3rd HD Extended.jpg

4000 2nd 3rd HD Sealed.jpg

4000 2nd 3rd HD Standard.jpg

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.

4000 Group Delay.jpg  

SVS PB-4000 group delay per operating mode 

....this subwoofer is NOT boomy nore does it smear sound in the time-domain.

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.

4000 Room Gain Compensation effects.jpg 

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 re4000 cone.jpgviews, 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 th4000 front.jpge 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!  

Bassaholics ExtremeWith 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. 

...the PB-4000 performed so superbly in any type of music that I threw at it.

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.

4000 hero3.jpg

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-4004000 flash.jpg0 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

  • StarStarStarStarStar — Excellent
  • StarStarStarStar — Very Good
  • StarStarStar — Good
  • StarStar — Fair
  • Star — Poor
MetricRating
Bass ExtensionStarStarStarStarStar
Bass AccuracyStarStarStarStarStar
Build QualityStarStarStarStarStar
Fit and FinishStarStarStarStarStar
Ergonomics & UsabilityStarStarStar
FeaturesStarStarStarStarStar
Dynamic RangeStarStarStarStar
PerformanceStarStarStarStarhalf-star
ValueStarStarStarStarStar

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About the author:

James Larson is Audioholics' primary loudspeaker and subwoofer reviewer on account of his deep knowledge of loudspeaker functioning and performance and also his overall enthusiasm toward moving the state of audio science forward.

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