SVS SB12-NSD Subwoofer Review Measurements and Analysis
The SVS SB12-NSD subwoofer was measured outdoors sitting directly on the ground with the M30 microphone placed 2 meters from the front lip of the cabinet with the grill removed. The driver was facing directly toward the microphone. The LFE input was used so that the internal low pass filter was disabled, the phase was set to 0 and the subwoofer volume was set to maximum. All tests were conducted in this configuration, except for those tests purposely conducted to examine the effects of the built in functions or different operational modes.
The overall approach to this testing along with the equipment and software used is outlined in the article here.
SVS SB12-NSD: Effect of Low Pass Filter Settings
Above is the measured effect of various settings of the low pass filter on the SB12-NSD’s response. The roll off exhibits a textbook 12dB/octave slope and the corner in the response matched up well with the indicators on the control dial.
SVS SB12-NSD: Basic Frequency Response as Tested
In the chart above is the basic response measurement of the SB12-NSD as it was tested. SVS claims a frequency response of 23-270Hz +/-3dB in the same type of measurement environment. This measurement actually betters the claimed response by fitting into a 6dB total window size from 21-300Hz. This is a very flat and extended response which indicates that there will be no problems blending the SB12-NSD to even the smallest bass shy speakers. A crossover point of 250Hz or slightly higher would not be out of the question if needed. Looking at the basic response shape another thing that jumps out is that there is obviously some signal processing involved to shape and flatten the SB12-NSD’s response. This is very common with small sealed subwoofers which otherwise would exhibit a shallow roll off starting somewhere above 35-40Hz in most cases. In the case of the SB12-NSD the outdoor response measurement indicates some amount of low frequency boosting and a high pass or rumble filter near 20Hz.
SVS SB12-NSD: Waterfall Decay
SVS SB12-NSD: Group Delay
Looking at the SB12-NSD’s response in the time domain indicates that there is some delayed energy below 35Hz. This is probably due to the DSP signal manipulation going on inside of the amplifier namely the rumble filter and boost EQ employed as sealed subwoofers usually have very uniform and clean energy decay unless there is some sort of processing of the signal involved. The group delay does break through 1.5 cycles between 20-35Hz but during the listening sessions I never noted any overhang or sense of booming or ringing from the SB12-NSD at all. A little perspective here… In my experience there can be some audible issues that show up as delayed energy in these measurements but in the few cases where it has been clearly audible, the amount has been far above normal and perhaps more importantly also high Q in nature indicating a severe amount of ringing or a resonance of some sort. It has also been higher up in the frequency range. Another thing to keep in mind is that even with a quickly, cleanly decaying subwoofer system once you place it inside of a room the acoustics will wreak havoc with the response including in the time domain. Many times it will completely swamp the subwoofers raw contribution all together.
SVS SB12-NSD: Long Term Output Compression
The maximum long term output compression test for the SB12-NSD shows that it maintains good bandwidth uniformity through the 100dB sine sweep but with compression setting in at the higher output levels. The output starts being limited near 25Hz first which indicates that is the likely center of the boost equalization used to extend the response. The boost equalization will chew up driver excursion and amplifier headroom much more quickly than the rest of the response range, so that the system will run into output limitations in the frequency range where the boost is centered first. By the 110dB sweep level the SB12-NSD is clearly out of gas. Running an even hotter 113dB sweep through it confirmed that the limiter was fully engaged at that drive level over almost the entire response range. Overall bandwidth uniformity is still pretty good even after the low bass range compresses though.
Note on Output Compression Testing: This is by far the most demanding measurement type conducted on the subwoofers during our testing and will reveal any issues with overload, port compression, port noise, driver distress, creaks, rattles, buzzes, etc. Additionally the test is conducted outdoors with just the subwoofer operating so there will be no nearby walls or objects to vibrate and no upper frequency content from other speakers in operation. These would normally help to cover up or mask any objectionable noises from the subwoofer in a typical room. Any sort of audible distress or issues with the subwoofer are readily apparent in this environment.
The SB12-NSD was completely unfazed by even the highest level sine wave sweeps and emitted no more than a bit of an over tone to its sound when cone excursions were highest, which was probably excessive harmonic distortion. I’m not sure that I would have noticed it indoors or with masking information from other speakers. For all intensive purposes this test is the subwoofer being thrashed for all it is worth outdoors while you listen for any signs of it crying “uncle”. Subjectively, a bit of extra “warmth” to the lowest frequencies at the absolute maximum drive levels indicates that the protections and limiting circuits are doing their jobs very well. It takes a surprising amount of deep bass distortion for it to become offensive. I also thought that I detected just a hint of cabinet rock at very low frequencies when driven to maximum output which would not be surprising considering the small enclosure and light weight. This can occur with high power subwoofers in lightweight, small enclosures, but is not a serious concern usually. There were no notable noises or issues with the cabinet or amplifier otherwise. As with the other SVS subwoofers tested, the protection and limiting circuits employed in the SB12-NSD are extremely effective at limiting any chance of damage to the unit and preventing offensive overload noises.
SVS SB12-NSD: Output Compression Magnitude
Above we have another way of looking at the results from the output compression test. This shows only the amount of compression of the signal that is occurring at each drive level. This graph clearly shows the EQ boost used to extend the response mentioned previously. It is centered at about 23 or 24Hz. This type of compression behavior is typical of a deep bass boosted sealed subwoofer.
SVS SB12-NSD: Maximum Long Term Output Level
Looking at the maximum long term output achieved during a sine wave sweep by the SVS SB12-NSD shows that, while it is certainly no SPL juggernaut, it does have generous output capabilities for a sealed subwoofer of its size and cost maintaining a respectable 100dB SPL capability or more from about 30Hz on up and reaching over 91dB at 20Hz.
SVS SB12-NSD: Total Harmonic Distortion
SVS SB12-NSD: 110dB Sweep Distortion by Component
Evaluating the distortion performance of the SB12-NSD shows very low distortion levels above 40Hz never breaking 10% THD even at the highest output levels and well below 5% THD above 50Hz. Below 40Hz the distortion spikes up to a maximum near 23Hz which as mentioned previously is the center of the boost EQ used. This behavior of rising distortion towards the lowest frequencies is typical of a sealed subwoofer alignment where the driver excursion alone produces all of the output. Looking at the harmonic makeup of the distortion shows that it is dominated by the second harmonic above 55Hz where distortion is already very low to begin with. In the deeper bass frequencies the third harmonic dominates which is not unusual for a driver being asked to produce long excursions.
SVS SB12-NSD: CEA2010 2 Meter Groundplane RMS Results
SVS SB12-NSD: CEA2010 2 Meter Groundplane RMS Comparison
The results for CEA-2010 short term burst testing show that the SB12-NSD possesses good peak output capabilities for a subwoofer of its size. Over 101dB is available from the 31.5Hz band on up. 105dB is available above 40Hz and the SB12-NSD manages to muster up almost 92dB at 20Hz with passing distortion results. Not bad at all for a single 12” driver in what amounts to a 14” cube. At 25Hz and above the output is amplifier limited. At 20Hz and below the SB12-NSD can eke out a little more raw output before the limiter clamps down but not without greatly increasing distortion levels.
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Recent Forum Posts:
the CEA-2010 measurements presented here are taken at 2 meters outdoor groundplane and are “rms” not peak values. This is equivalent roughly to a 1 meter anechoic (free space) SPL measurement.
The indoor SPL levels are considered to be a corner loaded subwoofer which puts the sub in 1 meter 1/8th space which adds +18dB over a 1m anechoic (free space) measurement. We are considering the listening distance from the subwoofer as being roughly 4 meters in most cases which drops the spl by 12dB (18-12= +6dB at this point.) A peak SPL report of the same signal reported via an rms calculation method will produce about 3dB higher numbers. (Add 3+6= +9dB) So that is why we are adding 9dB to the reported CEA-2010 numbers to compare them with the indoor peak SPL numbers required.
Note that if a sub just barely misses in one frequency band by a single dB or less, for example falling short by 0.7dB at 31.5Hz only, we will go ahead and give it the benefit of the doubt as long as it meets the other criteria since it is a drastic 6dB drop back to the next smaller room size.
I'm sorry but now I'm a little confused on this issue as well.
From what I understand, the sb12 scored a raw score of 96.3db at 25hz. From there, are you adding in the +12db from putting it in the corner as well as adjusting it +6dB for the conversion?
Is its total score 102.3 or 104.3?