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SVS SB13-Ultra Subwoofer Review Measurements and Analysis

By Joshua Ricci

The SVS SB13-Ultra subwoofer was measured while placed outdoors on the ground in a large field with the nearest large objects a minimum of 60ft or farther away from it, with the driver facing towards the microphone element. The left XLR input was used and an Earthworks M30 measurement microphone was placed on the ground at a distance of 2 meters from the nearest enclosure face of the subwoofer and pointing towards the driver. The grille was left off of the SB13-Ultra. The amplifier was set to maximum gain, the phase was set to zero and the low pass filter was set to bypass for all measurements unless otherwise noted. The internal PEQ, RGC and other DSP controls were also disabled unless otherwise noted. For more info on the testing equipment and procedures please see the article here.

Powered Subwoofer Testing Outline and Procedures Overview

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SVS SB13-Ultra: Effect of Low Pass Filter Settings on Frequency Response

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SVS SB13-Ultra: Effect of Room Gain Compensation Settings on Frequency Response

Above are the frequency response measurements of the SB13-Ultra subwoofer showing how adjustment of the internal low pass filter frequency and slope affects the top end response shape and also how the RGC or room gain compensation setting affects the low frequency extension. The low pass filter setting is selectable as either 12dB/octave or 24dB/octave and is variable at 7 frequencies from 31 to 125Hz. The indicated slope and frequency of the slope were in very close agreement with what was measured. The RGC setting primarily cut back the low bass frequencies a bit with the 6dB slope being a bit less aggressive and the 12dB setting being more so. This would primarily be used in a smaller room, with near field placement or with corner loading of the SB13-Ultra. The parametric equalizer function was not measured because it has been previously with the larger vented PB13-Ultra review and should perform identically. The 2 bands available give a wide array of options for combating room resonances at the listening position or for affecting broad adjustments to the response shape. Needless to say when the PEQ bands are combined with the low pass filter function and the RGC controls there is a huge amount of adjustment that can be made to the SB13-Ultra’s response. I could see the flexibility afforded by the internal DSP and the extensive input and output options being handy in dedicated 2-channel systems where a receiver with automatic room correction and bass management is not being used. I have a 2-channel garage system for casual listening while working on things and I have to use a separate active crossover unit to blend my B2031A’s to whatever bass system I’m using with them at the time. I could likely eliminate the active crossover unit if I were using the SB13-Ultra.

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SVS SB13-Ultra: Frequency Response as Tested

Above is the frequency response of the SB13-Ultra as tested with the all of the internal DSP functions that would affect the frequency response shape disabled. Judging by the shape of the response and some of the other measurements taken, there is likely a bit of bass boost centered at around 20-25Hz to extend the deep bass response. This is very common for small sealed units. Overall the response shape fits within a 6dB total window from 22-360Hz. SVS specs the response as 20-460Hz within a 6dB window. The top end is nice and extended on the SB13-Ultra so it could easily be used up as high as 150-200Hz if needed to blend with small bass-limited speakers.

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SVS SB13-Ultra: Group Delay

As expected of a sealed subwoofer system the group delay and other time domain measurements for the SB13-Ultra are well mannered and show nothing of consequence. The delay never approaches 1 cycle at any point over its entire useful bandwidth.

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SVS SB13-Ultra: Long-Term Power Compression

The long-term output compression tests for the SB13-Ultra show that it maintains excellent linearity with good tracking of the output demands and little changing of the response shape up through the 105dB sweep. The 5dB louder 110dB sweep indicates that the SB13-Ultra was already at its output limitations near 25Hz in the 105dB sweep and this is further reinforced with an even louder 115dB sweep which shows near zero increase in output in the deep bass. The SB13-Ultra managed to produce around 98dB at 20Hz, 105dB at 30Hz and greater than 110dB from 45Hz on up during the loudest 115dB sweep. Of note is that despite being driven some 5 to 10dB into compression in the deep bass and the driver cone moving a massive amount, the SB13-Ultra was stoic during this and emitted nothing more than a bit of suspension noise from the driver below 20Hz. No cabinet vibration or panel resonances were noted either. SVS has always shown an aptitude for preventing gross overload artifacts from their subwoofers and once again did the job well. Also interesting is that the repeat 90dB measurement, which was taken after the rest of the measurements in order to display any long term heating effects on the driver, indicates that there is very little shifting of parameters or heat built up in the voice coil. This is impressive considering that gusting winds on the day of ground-plane testing necessitated re-running some of the sweeps multiple times to get a clean measurement. This meant that the SB13-Ultra driver took a few more 23 second long sine wave sweeps than usual during this test.

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.


SVS SB13-Ultra: Output Compression Magnitude

Looking at the chart above, which shows only the amount of compression occurring in the output of the SB13-Ultra as the output level is increased, indicates that the SB13-Ultra is linear and responds to increased output demands with negligible compression of 1dB or less up through the 105dB referenced to 50Hz level. Increasing the output another 5dB to the 110dB nominal level again shows little compression above 35Hz where it is 1.5dB or less but the output in the deep bass has started to be limited and reaches 5dB from 20-25Hz. This indicates that there is likely to be some boost equalization used to shape the SB13-Ultra’s deep bass response which is centered in that bandwidth. Increasing the output demands another full 5dB to what would be an [email protected] nominal level pushes the SB13-Ultra into heavy limiting over the entire bandwidth.

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SVS SB13-Ultra: CEA2010 2 Meter Ground-plane RMS Results

CEA2010 Results

The CEA2010 maximum-distortion-limited-short-term output results for the SVS SB13-Ultra indicate it has a lot of muscle for a unit of this size and alignment. It is neck and neck with the excellent JL E112 for the most part which I also recently reviewed. At the 40Hz band and above the SB13-Ultra is capable of greater than 112dB of output and tops out at a loud 117dB over the 63-125Hz octave. At the 31.5Hz band and above the output is limited by the available amplifier power. As with any sealed subwoofer the low end output diminishes gradually into the deeper octaves as the driver is asked for more and more displacement. By 20Hz the maximum recorded output with passing distortion is 96.5dB which drops to 92.6dB at 16Hz. The SB13-Ultra was able to produce enough output with low enough distortion to get down into the lowest couple of bands as well and while not with pant flapping output, in room the boundary reinforcement will typically provide a noticeable lift to the lowest bass frequencies below 30Hz, while also boosting the fundamental of the waveform compared to the harmonics, which lowers distortion. This was the case in my room. At the 25Hz band and below the SB13-Ultra output was limited by distortion, the 3rd harmonic to be exact. If distortion is ignored completely the SB13-Ultra could produce output levels about 4dB higher in the deep bass but with greatly elevated distortion levels.


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