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SVS PB16-Ultra Subwoofer Measurements and Analysis

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pb16 testingC.jpg

The SVS PB16-Ultra 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 ports facing the mic. The subwoofer’s gain was set to maximum, and the low pass filter was left off. Weather was recorded at 63°F and 63% humidity.

PB16-FrequencyResponses.jpg 

Frequency responses of the main operating modes of the SVS PB16-Ultra 

The frequency response graphs of the modes of the PB16-Ultra demonstrate it to be a very accurate subwoofer. One difference between our findings and SVS’s specs occurs in the high end, where SVS’s claims a +/- 3 dB point out to 280 Hz in the ported modes. We see a big drop right after 200 Hz, but that can hardly be a point of complaint for a subwoofer, since that is already an above-average high-end extension that isn’t likely to be taken advantage of as it is. Keep in mind the scale when viewing this response graph; that is a 2 dB tick marks for the vertical axis, which is a very unforgiving scale, and the response is not smoothed at all. The PB16-Ultra is such a high-performing and accurate subwoofer that I feel it can bear this level of scrutiny easily. What is shown is a highly linear response from below 20 Hz to just above 200 Hz in all modes; while this is standard M.O. for SVS, few other subs sport such a flat frequency response. There is a small uptick in output at the tuning points, but this is slight, and will likely only be perceived as beefing up the deep end of certain effects sounds. If room gain boosts the deep end too much for certain tastes and the sealed mode does too much to damp deep bass output, there are a variety of room compensation curve adjustments that can be accessed from the SVS subwoofer app. The frequency response is very malleable, thanks to SVS’s programming options. Some users may even want to boost the low end with the parametric equalizer to give rumble effects even more grunt. As will be seen in below measurements, the PB16-Ultra has the low-end headroom and built-in self-protection to sustain that kind of response. 

SVS PB16-Ultra CEA-2010 Burst Test Measurements

 

 Standard Mode (3 ports open)

Extended Mode (2 Ports Open)

Sealed Mode

Frequency (Hz)

SPL (dB)

THD + N (%)

Harmonic limit

SPL (dB)

THD + N (%)

Harmonic limit

SPL (dB)

THD + N (%)

Harmonic limit

12.5

-

 

 

89.1

16.1

3rd, 9th

89.8

15.1

3rd

16

100.0

20.3

3rd

109.1

8.2

 

97.1

21.5

3rd

20

113.8

11.8

 

112.3

15.5

 

103.2

23.9

3rd

25

116.9

2.7

 

115.5

5.4

 

109.7

22.2

3rd

31.5

119.5

7.6

 

118.0

9.7

 

114.7

17.4

 

40

120.3

11.5

 

118.8

9.3

 

116.1

13.6

 

50

119.4

11.3

 

118.4

11.9

 

116.6

13.5

 

63

117.7

7.8

 

117.1

7.1

 

115.7

6.6

 

80

115.6

3.9

 

115.0

4.9

 

114.0

6.3

 

100

113.9

6.1

 

113.6

6.5

 

113.0

7.5

 

125

112.8

5.4

 

112.7

5.4

 

112.2

6.0

 


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 publically available CEA-2010 measurements are shown at 2 meter RMS, so we followed that convention.

The frequency response graphs of the modes of the PB16-Ultra demonstrate it to be a very accurate subwoofer.

Some interesting features emerge in our CEA-2010 results. We see massive output potential at 63 Hz and below, topping out at a staggering 120 dB at 40 Hz in standard mode. The 109 dB measurement at 16 Hz in Extended Mode is also rather spectacular. When we compare the upper bass frequencies to the deep bass frequencies, we can see where SVS’s heart lay. While the mid and upper bass output isn’t bad, it is 50 Hz and below where the PB16-Ultra really shines. A subwoofer like this is especially comfortable with deep bass content as in the film ‘Tron Legacy’.

It is also interesting to compare these numbers SVS’s measurements for their former flagship subwoofer, the PB13-Ultra previously reviewed, to see if they achieved the performance gains they were after. At 50 Hz and below, we see a gain of 2.5 to 5 dB depending on frequency, which means a 33% to 80% increase in performance respectively. At 63 Hz to 80 Hz, the performance increase over the PB13-Ultra hovers around a 1 dB gain, and the PB13-Ultra manages to outperform the PB16-Ultra slightly in upper bass at 100 and 125 Hz, although those high frequencies are less consequential since few people will be using a crossover that high. I would speculate that the relatively high moving mass of the PB16-Ultra driver (the cone, voice coil, and former) in combination with the underhung design diminishes the upper bass sensitivity; this is the trade-off made for the enormous excursions needed for monster deep bass while keeping the size and weight of the unit manageable so as not to need a forklift to move. Readers considering the SB16-Ultra subwoofer should note that subwoofer uses an overhung voice-coil and lighter-mass driver, as opposed to the underhung driver of the PB16-Ultra, and that design type should have more upper bass capability than the PB16-Ultra, so they would be in error to judge the SB16-Ultra’s performance from our measurements of the PB16-Ultra.  

A couple more notable aspects of these measurements: we can see that the PB16-Ultra driver has a very large displacement advantage over the PB13-Ultra driver from comparing the low-frequency sealed measurements where the largest gains are made. Also, as is the norm with SVS, the harmonic distortion is extremely low. This is remarkably clean bass even though the subwoofer is being pushed to its maximum limits. Only a handful of these measurements are capped by the CEA-2010 distortion thresholds. It is a rare subwoofer that can churn out low frequencies this loud at such low levels of distortion.

10-20HzCEA-PB16c.jpg     25-50HzCEA-PB16c.jpg

63-125HzCEA-PB16c.jpg

Frequency Breakdown of CEA-2010 Burst Measurements for the SVS PB16-Ultra

The above graphs show the frequency spectrum of the increasing CEA-2010 bursts as reproduced by the PB16-Ultra in Extended Mode. Essentially, it depicts 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 either 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.

These graphs show us the extraordinarily low distortion that the PB16-Ultra produces at nominal to high drive levels. At the test frequencies below the port tuning, 10 Hz and 12.5 Hz, there is a lot of heavy distortion, but that would be expected as it is outside the subwoofer’s intended range of operation. Above those frequencies, we can see greater than 30 dB differences between the fundamental and the largest distortion product at medium to high drive levels, meaning the total harmonic distortion is lower than 3%. That is extremely low, well below anything remotely audible. The predominant distortion product is the 3rd harmonic, but, even at the highest drive level, it is still not that bad, and, from this, I would guess that the driver still has a bit more linear headroom for more power than what it is being given at many of these frequencies.

PB16sealedLTSc.jpg      PB16ExtLTSc.jpg

PB16standardLTSc.jpg

Long term output sweeps of the SVS PB16-Ultra in different operating modes 

These graphs show us the extraordinarily low distortion that the PB16-Ultra produces at nominal to high drive levels.

Testing for long-term output compression was done by first conducting a sweep tone where 50 Hz hit 90 dB with the subwoofer 2 m from the microphone. We then conduct further 20 second sweeps by raising the gain by 5 dB until no more output could be rung out of the subwoofer. Looking at the results, the PB16-Ultra doesn’t start really start losing its response shape until the 115 dB sweep. In the sweep above that, a bit more output can be had between 30 to 60 Hz, but everywhere else is tapped out. As with the burst tests, these long-term tests indicate the frequency band where the PB16-Ultra is the most capable: the region from 30 Hz to 60 Hz. While zero compression at all drive levels is the ideal, having extra headroom in this frequency band is not bad since it is where most movie sound effects lay. It should be noted that in this most brutal of subwoofer tests, the PB16-Ultra never made any straining noises or gave any indication that it was being badly stressed. It remained composed and in control of itself at all times.

PB16-sealed-THDc.jpg      PB16-extended-THDc.jpg

PB16-standard-THDc.jpg

SVS PB16-Ultra Total Harmonic Distortion per operating mode and output level 

The above graphs show total harmonic distortion, essentially depicting at what drive level and frequency the subwoofer loses linear playback. The performance on display here by the PB16-Ultra is superb. At 90 and 95 dB drive levels distortion wavers between 1% to 2% from 20 Hz to 100 Hz in the ported modes. In that same frequency range at the highest drive levels, distortion still remains below 10%, even when the sub is outputting 115 dB+ sound levels. 10% THD at these frequencies is not likely to be audible. Below the tuning points, distortion skyrockets, but output plummets as well, so that wouldn’t present a problem. Since the driver has to carry the entire output load in sealed mode, more distortion crops up in the lower frequencies there, but the sealed distortion profile is still quite good, with vanishingly low distortion down to 20 Hz up to the 100 dB sweep level. A limiter can also be seen in action in sealed mode where distortion goes back down below 16 Hz at the 100 dB sweep level and above. Like our other measurements show, the PB16-Ultra produces some remarkably clean bass.  

 CompDist-2nd-3rdC.jpg     CompDist-4rth-5thC.jpg

Component harmonics of the SVS PB16-Ultra 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 up to the fifth harmonic. There aren’t any surprises here; the third harmonic is the dominant harmonic, and, as the sub is pushed harder, more distortion is generated in the low end. One slight oddity is that the second harmonic actually decreases as a percentage at the highest sweeps, and I don’t know why that would be, except if maybe the limiter became more active above a certain output level. The third harmonic of the sealed mode graphs nicely illustrates how hard the driver is being pushed for the given output level, although we do see the high-pass filter in action in the lowest measured frequencies, as in the THD charts.

PB16gdc.jpg 

SVS PB16-Ultra 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. The PB16-Ultra presents nothing to worry about. Group delay does not even surpass 20 ms until 40 Hz, at which point it is much too deep in frequency to be audible. By the point that the group delay passes one wave cycle, the frequency is too deep to make a difference. For the range where it is important for group delay to be kept under control, the PB16-Ultra manages it very well. Stored energy is kept to a minimum where it would impact sound quality. This matches my subjective impression of the PB16-Ultra as having very tight bass with no overhang.

PB16-LP-settings.jpg 

Sampling of some of the effects of the PB16-Ultra low-pass filter

The above graph depicts just a few different effects that can be had on the frequency response of the PB16-Ultra’s low-pass filter. With a choice of any frequency from 30 to 200 Hz and a slope of 6, 12 24, and 48 dB per octave rolloff, the low-pass filter can be tailored to any upper-end rolloff shape. The PB16-Ultra can be tweaked to seamlessly cross over in any system that lacks modern bass management.

 

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Recent Forum Posts:

shadyJ posts on April 18, 2017 13:53
Interesting idea that port compression will make the driver behave as though it were in a sealed enclosure. It makes some sense though. Also an interesting idea that port compression will reduce port distortion relative to cone excursion at high output levels. A good way to investigate that would be to take a variable tuned sub out for a day and do much finer sweeps that what is in those charts, and then compare the 2nd HD vs 3rd HD for various port settings. I probably won't have time to do that myself, but maybe on a slow day during testing its worth a look.
Andron posts on April 18, 2017 06:23
:oops: I'd like to propose my answer for the phenomenon, James Larson noticed in the review, saying:

James Larson
One slight oddity is that the second harmonic actually decreases as a percentage at the highest sweeps, and I don’t know why that would be, except if maybe the limiter became more active above a certain output level.

I think it's because of the ‘natural limiter’ of the reflex alignment = port compression.
I read, the port produces 2nd order distortion.
When the port compresses, the Subwoofer becomes yet a bit more like a closed box around the tuning frequency.
Cone excursion increases which leads to increased 3rd order distortion BUT the air in this, now semi-closed box, actually decreases harmonic distortion relative to the cone excursion due to linearization of Kms(X) of the driver's suspension, due to the now more prominent air spring coming into play again.
So, while the fundamental output decreases compared to the driver's excursion, it's more than compensated by the reduced, port generted harmonic with further reduction of the said 2nd harmonic by the now prevalent air spring. I can be wrong. Just a curious thing.
shadyJ posts on January 11, 2017 20:17
It looks like a SB16-Ultra review will be happening but not until the spring, perhaps an April/May time frame. Sorry for the delay, but groundplane measurements are not possible in this neck of the woods until then.
Auditor55 posts on January 11, 2017 20:08
Still no update on SB16 review?
Auditor55 posts on January 01, 2017 15:39
shadyJ, post: 1163127, member: 20472
Hello David,

It would be great to review the SB16, but for myself, I will not be able to review subwoofers until the spring, sadly, so if that does happen, it won't be for awhile.

As for the group delay, I am guessing that the higher levels of delay in the PB16 are probably mostly due to the subsonic filters used to protect the driver. The nonstandard driver designs and somewhat larger enclosure might also be contributors. But, like is stated in the article, this delay should not concern you, it is far too low in frequency to be offensive or even audible.

I really would like to get a review of the SB16.
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