The review focuses on the high-end Synchrony Series B600 from the Canadian brand PSB. Known for their unique approach to crossover tuning and speaker settings, PSB's philosophy has always stood out to me. This review delves into their latest bookshelf speaker model.
Impedance
Starting with impedance, it's noted that the unit's resonant point Q-value significantly changes when the input voltage is amplified from 0.1 to 2.83 V.
For a clearer comparison, offsets were applied to the X and Y axes, highlighting how low-frequency characteristics might alter at actual listening levels compared to the small-signal area. This complexity underscores the importance of considering impedance and TS parameters in speaker design, emphasizing the need for real-world testing to ensure performance at listening levels.
Additionally, the speaker harbors another peculiar aspect discovered post-performance measurement and during the packaging phase. I was urgently informed by the client that the speaker's designed frontal axis is not aligned with the tweeter but rather positioned 12 inches above the base. This oversight was unexpected, as I had not anticipated such an ambiguous point being chosen as the frontal axis.
Upon further verification, aligning the manufacturer's flagship model tweeter height with the bookshelf model indicated the exact point 12 inches above the base. This revelation led me to question whether this specification was merely for marketing purposes or had a deeper rationale. Left with no alternative, I proceeded to conduct direct measurements to explore this anomaly.
Frequency Response
Upon comparison, it was found that, considering the overall balance, the response at the manufacturer-claimed point (highlighted in blue) was surprisingly the most balanced. The intention behind this design choice remains unclear. It may be speculated that this was done to cater to consumers looking to set up a multi-channel system with the same series, by providing a consistent acoustic axis similar to that of the flagship models. This approach could ensure a uniform sound field and listening experience across different speakers within the same series.
Nearfield Measurements
Directivity
In terms of directivity, the speaker shows a smooth profile across mid and high frequencies, particularly at the recommended listening axis, with controlled excessive high-frequency responses thanks to structural elements obstructing the tweeter.
The vertical directivity is relatively unaffected by axis changes, maintaining a consistent character.
A nuanced comparison revealed that at the manufacturer-recommended listening height, the speaker exhibited smoother directivity characteristics. Furthermore, the directivity angle in the midrange frequencies is about 70 degrees, which is considered relatively wide.
Polar plot
Examining the polar plot further elucidates that directional characteristics depend on listening height, potentially highlighting a matter of personal preference. Notably, positioning the tweeter as the axis results in a smoother attenuation across various bands, particularly within a 30-degree frontal arc.
As for the vertical axis, similar to previous observations, it primarily reveals offsets dictated by axis configuration rather than introducing distinct characteristics or alterations in sound dispersion.
THD
The gradual increase in third-order harmonic distortion forming a peak towards the crossover frequency can typically be attributed to electrical issues with the woofer driver.
The low-frequency performance of the speaker is commendable. However, it's important to note that the Equivalent Input Harmonic Distortion (EIHD) plot is calculated under the assumption of a flat full-range magnitude response. Thus, if the response in a specific band is weaker or stronger than the average or the measured reference output, distortion may be under or overestimated. Typically, in my reviews, I trim the X-axis to the point where the low-frequency slope begins in the frontal frequency response plot. For this speaker, considering its conservatively tuned port, the same standard would require cutting off data around 100Hz.
Nonetheless, limiting the low-frequency data provided to you excessively would not be ideal, even considering corrections; therefore, I seek your understanding as I extend the provided range down to 50Hz.
In conclusion, the distortion displayed in the 50~100Hz range may appear lower than what might be expected from the speaker's consistent output performance in reality.
With an increase in output, a slight rise in High-Order Harmonic Distortion (HOHD) was observed across roughly an octave range in the mid-low frequencies, though this issue, detectable only at high output levels, was not easily audible. HOHD, representing harmonic distortion components of the 10th order and above, is indicative of noise generated not directly by the driver's motion but rather by internal components vibrating, experiencing friction, or unnecessary resonance. While lower-order harmonics (2nd to 5th) can contribute to a change in timbre, even a small amount of HOHD can be perceptibly irritating, differing significantly in its impact on sound quality.
Observing the characteristics near the resonance frequency (70-75Hz), it appears that a form of inherent protection operates through compression at large displacements. Given this speaker's Frequency Response (FR) characteristics, which show the low frequencies being conservatively output by about 3dB compared to the reference frequency of 1kHz, the performance is somewhat disappointing. While expecting large output and clean response from all speakers without considering the environment might be overly stringent, akin to expecting a car to perform well and stably without necessarily being designed for racing, the price range of this speaker raises expectations for superior performance, making its conservative low-frequency output more notable as a drawback.
Multitone test
Between 100Hz and 5,000Hz, the speaker presents an average Modulation Distortion (MD) of about 1.5 to 2%, peaking around 4%. This observation raises suspicions about port noise, especially considering the frequency band. Given the speaker's price range, these levels cannot be considered low.
Before even discussing whether these figures are absolutely high or low, it's clear they deviate from the expected performance of a bookshelf speaker in the 6.5-inch category. This indicates that, relative to its class and cost, the speaker's distortion performance might not align with typical expectations.
When the bandwidth of the measurement signal is limited, distortion across the board decreases. This suggests that a significant portion of the distortion components could be attributed to the woofer's displacement. Moreover, by cutting off the signal at 80Hz, thus minimally engaging the port, the peak shape observed around 1kHz disappears. This indicates that controlling the signal's frequency range can significantly impact the distortion profile, particularly by reducing the woofer's displacement and the port's contribution to the overall sound output.
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