SVS Prime Wireless Pro SoundBase Streaming Integrated Amplifier Measurements

Link: reviewed by Dennis Burger on SoundStage! Access on January 15, 2023

General Information

All measurements taken using an Audio Precision APx555 B Series analyzer.

The SVS Prime Wireless Pro Soundbase was conditioned for 1 hour at 1/8th full rated power (~9W into 8 ohms) before any measurements were taken. All measurements were taken with both channels driven, using a 120V/20A dedicated circuit, unless otherwise stated.

The Soundbase offers one RCA line-level analog input, RCA pre-amp outputs, one RCA sub-out (no bass management), one S/PDIF TosLink optical input, one HDMI input, one Bluetooth input, built-in streaming via ethernet or Wi-Fi, two pairs of speaker-level outputs, and one headphone output over a 1/8″ TRS connector. For the purposes of these measurements, the following inputs were evaluated: TosLink optical, RCA analog.

Most measurements were made with a 0.9Vrms line-level analog input and 0dBFS digital input. Our standard 2Vrms analog input needed to be reduced because of excessive distortion at the Soundbase’s input.  The Soundbase digitizes incoming analog signals with an 88.2kHz sample rate, and even an analog signal at 1Vrms caused significant distortion. The signal-to-noise-ratio (SNR) measurements were made with the same input signal values, but with the volume set to achieve the 1% THD output power of 88W (8 ohms). For comparison, on the line-level input, a signal-to-noise-ratio measurement was also made with the volume at maximum, where only 0.517Vrms was required to achieve 88W into 8ohms.

The volume control does not offer a numerical display. Based on the high accuracy and repeatability of the left/right volume channel matching (see table below), the Soundbase volume control operates in the digital domain. The Soundbase offers 6dB to 2dB volume steps for the first five steps. Most of the volume range yields volume steps between 0.5dB and 1.5dB, randomly distributed across the range. Overall range is -34.4dB to +34.3dB (line-level input, speaker output).

Although the Soundbase uses a digital amplifier technology, a rise in the noise floor was only apparent at and above 100kHz or so, with the exception of the 88.2kHz sample-rate clock (see FFTs below). For this reason, our typical bandwidth filter setting of 10Hz-90kHz was maintained, with the exception of noise and THD+N measurements, where a 10Hz-80kHz was used, to ignore the 87.2kHz and 89.2kHz IMD peaks between the 1kHz signal and the 88.2kHz sample rate.

Volume-control accuracy (measured at speaker outputs): left-right channel tracking

Published specifications vs. our primary measurements

The table below summarizes the measurements published by SVS for the Soundbase compared directly against our own. The published specifications are sourced from SVS’s website, either directly or from the manual available for download, or a combination thereof. With the exception of frequency response, where the Audio Precision bandwidth was extended to 500kHz, assume, unless otherwise stated, 10W into 8 ohms and a measurement input bandwidth of 10Hz to 80kHz, and the worst-case measured result between the left and right channels.

Our primary measurements revealed the following using the line-level analog input and digital optical input (unless specified, assume a 1kHz sine wave at 0.9Vrms or 0dBFS, 10W output, 8-ohm loading, 10Hz to 80kHz bandwidth):

For the continuous dynamic power test, the Soundbase was able to sustain 148W into 4 ohms (~1.5% THD) using an 80Hz tone for 500ms, alternating with a signal at -10dB of the peak (14.8W) for 5 seconds, for 5 continuous minutes without inducing a fault or the initiation of a protective circuit. This test is meant to simulate sporadic dynamic bass peaks in music and movies. During the test, the top of the Soundbase was only slightly warm to the touch.

Our primary measurements revealed the following using the analog input at the headphone output (unless specified, assume a 1kHz sine wave, 0.9Vrms output, 300 ohms loading, 10Hz to 80kHz bandwidth):  

Frequency response (8-ohm loading, line-level input)

In our frequency-response plots above, measured across the speaker outputs at 10W into 8 ohms, the Soundbase is within 0.5dB of flat in the audioband (20Hz to 20kHz). The Soundbase is -1.5dB at 10Hz and -0.4dB at 20kHz, not quite corroborating SVS’s claim of 10Hz-20kHz (±1dB), but it’s very close. There is also a brickwall-type attenuation behavior around 44kHz, indicating that the Soundbase is digitizing incoming analog signals with a 88.2kHz sample rate (further evidence of this is provided in the FFTs below).  In the graph above and most of the graphs below, only a single trace may be visible. This is because the left channel (blue or purple trace) is performing identically to the right channel (red or green trace), and so they perfectly overlap, indicating that the two channels are ideally matched.

Phase response (8-ohm loading, line-level input)

Above are the phase response plots from 20Hz to 20kHz for the line-level input, measured across the speaker outputs at 10W into 8 ohms. The Soundbase does not invert polarity and exhibits, at worst, 40 degrees of phase shift (at 20kHz) within the audioband.

Frequency response vs. input type (analog and 16/44.1, 24/96, and 24/192 inputs with 8-ohm loading, left channel only)

The chart above shows the Soundbase’s frequency response as a function of input type measured across the speaker outputs at 10W into 8 ohms. The green trace is the same analog input data from the previous graph. The blue trace is for a 16-bit/44.1kHz dithered digital input signal from 5Hz to 22kHz using the optical input, and the purple trace is for a 24/96 dithered digital input signal from 5Hz to 48kHz, while the pink trace is for a 24/192 dithered digital input signal from 5Hz to 96kHz. It appears that the Soundbase’s optical input resamples all incoming digital data at 44.1kHz, which is why all three digital input frequency response curves perfectly overlap and look as one. The -3dB point for the optical input is at 20.9kHz, with brickwall-type attenuation.

Digital linearity (16/44.1 and 24/96 data)

The chart above shows the results of a linearity test for the optical digital input for both 16/44.1 (blue/red) and 24/96 (purple/green) input data, measured at the line level output of the Soundbase. The digital input is swept with a dithered 1kHz input signal from -120dBFS to 0dBFS, and the output is analyzed by the APx555. The ideal response would be a straight flat line at 0dB. Both data were essentially perfect as of -105dBFS down to 0dBFS. At -120dBFS, all data are roughly +6dB above reference.

Impulse response (24/44.1 data)

The graph above shows the impulse response for the Soundbase, fed to the optical digital input, measured at the line-level output, for a looped 24/44.1 test file that moves from digital silence to full 0dBFS (all “1”s) for one sample period, then back to digital silence. We find a non-symmetrical response with no pre-ringing but significant post-ringing.

J-Test (optical input)

The chart above shows the results of the J-Test test for the coaxial digital input measured at the line level output of the Soundbase. J-Test was developed by Julian Dunn the 1990s. It is a test signal: specifically, a -3dBFS undithered 12kHz squarewave sampled (in this case) at 48kHz (24 bits). Since even the first odd harmonic (i.e., 36kHz) of the 12kHz squarewave is removed by the bandwidth limitation of the sampling rate, we are left with a 12kHz sine wave (the main peak). In addition, an undithered 250Hz squarewave at -144dBFS is mixed with the signal. This test file causes the 22 least significant bits to constantly toggle, which produces strong jitter spectral components at the 250Hz rate and its odd harmonics. The test file shows how susceptible the DAC and delivery interface are to jitter, which would manifest as peaks above the noise floor at 500Hz intervals (e.g., 250Hz, 750Hz, 1250Hz, etc.). Note that the alternating peaks are in the test file itself, but at levels of -144dBrA and below.  The test file can also be used in conjunction with artificially injected sine-wave jitter by the Audio Precision, to show how well the DAC rejects jitter.

The optical input exhibits low-level peaks at low frequencies, at -100dBrA and below. This is a good J-Test result, indicating that Soundbase DAC should yield good jitter immunity.

J-Test with 100ns of injected jitter (optical input)

The optical input was also tested for jitter immunity by injecting artificial sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at the 100ns jitter level.

J-Test with 500ns of injected jitter (optical input)

The optical input was also tested for jitter immunity by injecting artificial jitter sine-wave jitter at 2kHz, which would manifest as sidebands at 10kHz and 14kHz without any jitter rejection. Jitter immunity proved exceptional, with no visible sidebands at a very high 500ns of injected jitter. Above this level of jitter, the Soundbase DAC lost sync with the signal.

Wideband FFT spectrum of white noise and 19.1kHz sine-wave tone (coaxial input)

The chart above shows a fast Fourier transform (FFT) of the Soundbase’s line-level output with white noise at -4dBFS (blue/red) and a 19.1 kHz sinewave at 0dBFS fed to the optical digital input, sampled at 16/44.1. The steep roll-off around 20kHz in the white-noise spectrum shows the behavior of the Soundbase’s reconstruction filter. There are no aliased image peaks within the audioband. The primary aliasing signal at 25kHz is at -100dBrA, while the second and third distortion harmonics (38.2, 57.3kHz) of the 19.1kHz tone are at -115 and -85dBrA.

RMS level vs. frequency vs. load impedance (1W, left channel only)

The chart above shows RMS level (relative to 0dBrA, which is 1W into 8 ohms, or 2.83Vrms) as a function of frequency, for the analog line-level input swept from 5Hz to 100kHz. The blue plot is into an 8-ohm load, the purple is into a 4-ohm load, the pink plot is an actual speaker (Focal Chora 806, measurements can be found here), and the cyan plot is no load connected. The chart below . . .

. . . is the same but zoomed in to highlight differences. Here we find the deviations between no load and 4 ohms to be almost 0.2dB, which is an indication of a mid-level damping factor, or fairly low output impedance. When a real speaker is used, deviations are within about 0.15dB.

THD ratio (unweighted) vs. frequency vs. output power

The chart above shows THD ratios at the output into 8 ohms as a function of frequency for a sine-wave stimulus at the analog line-level input. The blue and red plots are for left and right channels at 1W output into 8 ohms, purple/green at 10W, and pink/orange at 60W. The power was varied using the volume control. At 1W, THD ratios ranged from 0.1% at 20Hz, down to 0.004-0.005% between 200Hz and 5kHz, then up to 0.01% at 20kHz. At 10W, THD ratios ranged from 0.05% at 20Hz, down to 0.004-0.005% between 200Hz and 2kHz, then up to 0.02% at 20kHz. At 60W, THD ratios ranged from 0.2% at 20Hz, then a slow decrease down to 0.03% at 20kHz.

THD ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms

The chart above shows THD ratios measured at the output of the Soundbase as a function of output power for the analog line-level input for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). THD ratios were lower into 8 ohms (compared to 4 ohms) at around 0.003-0.004% from 50mW up to 10W, then a steady rise up to the 1% THD value at 88W. THD ratios into 4 ohms ranged from 0.005% at 50mW up to 0.01-0.02% between 3W and the “knee” at 100W, then up to the 1% mark at 151W.

THD+N ratio (unweighted) vs. output power at 1kHz into 4 and 8 ohms

The chart above shows THD+N ratios measured at the output of the Soundbase as a function of output power for the analog line level-input, for an 8-ohm load (blue/red for left/right channels) and a 4-ohm load (purple/green for left/right channels). Overall, THD+N values for both loads were similar up to 50W, ranging from 0.05% to 0.02%.

THD ratio (unweighted) vs. frequency at 8, 4, and 2 ohms (left channel only)

The chart above shows THD ratios measured at the output of the Soundbase as a function of frequency into three different loads (8/4/2 ohms) for a constant input voltage that yields 10W at the output into 8 ohms (and roughly 20W into 4 ohms, and 40W into 2 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the 4-ohm load the purple trace, and the 2-ohm load the pink trace. We find similar THD values of roughly 0.05% at low (20-50Hz) and high (5-20kHz) frequencies across all three loads. Between 200Hz and 3kHz, the 8-ohm data (at 0.005%) is roughly 10dB lower than the 4-ohm data, which, in turn, is roughly 5dB lower than the 2-ohm data. This is a very good result for such a small, affordable integrated amp, and shows good stability even into 2-ohm loads.

THD ratio (unweighted) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows THD ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All THD data are roughly the same across all three loads. Starting at 0.1% at 20Hz, down to nearly 0.003% from 200Hz to 3kHz, then up to 0.01% at 20kHz (nearly 0.02% for the three-way speaker). This is another strong result, showing how the Soundbase will yield consistent THD results for different real-world loads.

IMD ratio (CCIF) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows intermodulation distortion (IMD) ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here the CCIF IMD method is used, where the primary frequency is swept from 20kHz (F1) down to 2.5kHz, and the secondary frequency (F2) is always 1kHz lower than the primary, with a 1:1 ratio. The CCIF IMD analysis results are the sum of the second (F1-F2 or 1kHz) and third modulation products (F1+1kHz, F2-1kHz). The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). At high frequencies (10-20kHz), there is roughly a 5dB differences in IMD values between both the dummy load and two-way speaker (-90 to -85dB) and the three-way speaker (-85 to -80dB). Otherwise, all three plots are very similar below 7-8kHz, at -90 to -85dB, or 0.003 to 0.005%.

IMD ratio (SMPTE) vs. frequency into 8 ohms and real speakers (left channel only)

The chart above shows IMD ratios measured at the output of the Soundbase as a function of frequency into an 8-ohm load and two different speakers for a constant output voltage of 2.83Vrms (1W into 8 ohms) for the analog line-level input. Here, the SMPTE IMD method is used, where the primary frequency (F1) is swept from 250Hz down to 40Hz, and the secondary frequency (F2) is held at 7kHz with a 4:1 ratio. The SMPTE IMD analysis results consider the second (F2 ± F1) through the fifth (F2 ± 4xF1) modulation products. The 8-ohm load is the blue trace, the purple plot is a two-way speaker (Focal Chora 806, measurements can be found here), and the pink plot is a three-way speaker (Paradigm Founder Series 100F, measurements can be found here). All three plots yielded roughly the same IMD values, between 0.02% to 0.03% up to 500Hz, then a drop to 0.01%.

FFT spectrum – 1kHz (line-level input)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input. We see that the signal’s second harmonic, at 2kHz, is at -90/-100dBrA (left/right), or 0.003/0.001%, while the odd harmonics at 3 and 5kHz are at -65dBrA, or 0.002%. There are low level power-supply-related noise peaks at the fundamental (60Hz) at -105dBRa, or 0.0006%, and the third (180Hz), fifth (300Hz) and seventh (420Hz) harmonics at -110dBrA, or 0.0003%, and below. The peaks seen at high frequencies at 87.2kHz and 89.2kHz are the IMD results between the signal (1kHz) and the sampling frequency of 88.2kHz. This is more evidence that analog signals are digitized at 88.2kHz.

FFT spectrum – 1kHz (digital input, 16/44.1 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 16/44.1. Signal harmonics are very similar to the analog input FFT above, except for the left channel’s second signal harmonic (2kHz), which is 5dB lower here, and the right channel’s third signal harmonic (3kHz), which is 5dB higher here. Power-supply-related noise peaks are barely visible here, and are below -110dBrA, or 0.0006%.

FFT spectrum – 1kHz (digital input, 24/96 data at 0dBFS)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the optical digital input, sampled at 24/96. The FFT is essentially identical to 16/44.1 FFT above.

FFT spectrum – 1kHz (digital input, 16/44.1 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 16/44.1 input sine-wave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and extremely low level power-supply related peaks below -130dBrA.

FFT spectrum – 1kHz (digital input, 24/96 data at -90dBFS)

Shown above is the FFT for a 1kHz -90dBFS dithered 24/96 input sine-wave stimulus at the optical digital input, measured at the output across an 8-ohm load. We see the 1kHz primary signal peak, at the correct amplitude, and extremely low level power supply-related peaks below -130dBrA.

FFT spectrum – 50Hz (line-level input)

Shown above is the FFT for a 50Hz input sine-wave stimulus measured at the output across an 8-ohm load at 10W for the analog line-level input. The X axis is zoomed in from 40Hz to 1kHz, so that peaks from noise artifacts can be directly compared against peaks from the harmonics of the signal. The most significant non-signal peaks are from the signal’s second (100Hz) and third (150Hz) harmonics, at -80dBrA, or 0.01%, and -75dBrA, or 0.02%, respectively. Power-supply noise-related harmonics can be seen at the fundamental (60Hz), at -105dBrA, or 0.0006%, and higher-order harmonics and IMD products can be seen at and below -110dBrA, or 0.0003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, line-level input)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the analog line-level input. The input RMS values are set at -6.02dBrA so that, if summed for a mean frequency of 18.5kHz, would yield 10W (0dBrA) into 8 ohms at the output. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -100/-110dBRa (left/right), or 0.001/0.0003%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 16/44.1)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 16/44.1. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110/-100dBRa (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

Intermodulation distortion FFT (18kHz + 19kHz summed stimulus, optical digital input, 24/96)

Shown above is an FFT of the intermodulation distortion (IMD) products for an 18kHz + 19kHz summed sine-wave stimulus tone measured at the output across an 8-ohm load at 10W for the digital optical input at 24/96. We find that the second-order modulation product (i.e., the difference signal of 1kHz) is at -110/-100dBRa (left/right), or 0.0003/0.001%, while the third-order modulation products, at 17kHz and 20kHz, are just above -90dBrA, or 0.003%.

Squarewave response (10kHz)

Above is the 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms. Due to limitations inherent to the Audio Precision APx555 B Series analyzer, this graph should not be used to infer or extrapolate the Soundbase’s slew-rate performance. Rather, it should be seen as a qualitative representation of the Soundbase’s limited bandwidth. An ideal squarewave can be represented as the sum of a sine wave and an infinite series of its odd-order harmonics (e.g., 10kHz + 30kHz + 50kHz + 70kHz . . .). A limited bandwidth will show only the sum of the lower-order harmonics, which may result in noticeable undershoot and/or overshoot, and softening of the edges. In this case, because of the digital nature of the amplifier, we see a 400kHz switching frequency (see 1MHz FFT below) riding on top of the squarewave.

Squarewave response (10kHz, restricted 250kHz bandwidth)

Above is the same 10kHz squarewave response using the analog line-level input, at roughly 10W into 8 ohms, this time with a 250kHz input bandwidth on the analyzer to filter out the 400kHz switching frequency. We can see significant over/undershoot and softening in the corners of the squarewave, a consequence of the Soundbase’s limited bandwidth, which is capped at half the sampling frequency (88.2kHz) used to digitize the incoming analog signals.

FFT spectrum (1MHz bandwidth)

Shown above is the fast Fourier transform (FFT) for a 1kHz input sine-wave stimulus, measured at the output across an 8-ohm load at 10W for the analog line-level input, with an extended 1MHz input bandwidth. This enables us to see the high-frequency noise above 100kHz reaching almost -90dBrA at 200kHz. We also see a clear peak at 400kHz, reaching -50dBrA, and its harmonics (800kHz, 1.2MHz). These peaks, as well as the noise, are a result of the digital amplifier technology used in the Soundbase; however, they are far above the audioband—and therefore inaudible—and so high in frequency that any loudspeaker the amplifier is driving should filter it all out anyway.

Damping factor vs. frequency (20Hz to 20kHz)

The final graph above is the damping factor as a function of frequency. We can see the left channel outperforming the right channel, with values ranging from 155 at 20Hz down to 90 at 20kHz. The right channel ranged from 112 at 20Hz down to 72 at 20kHz. These are good damping factor results for digital-amplifier-type technology, and do not show significant reductions in damping factor at high frequencies, which can be the case with other digital amplifiers.

Diego Estan
Electronics Measurement Specialist