The Sennheiser HD 600 remains a benchmark in the open-back, over-ear headphone category. For over two decades, it has been lauded for its accurate and detailed sound reproduction across diverse musical genres. Several successors have followed, including the Sennheiser HD 650, Sennheiser HD 660, and the subject of this review, the Sennheiser HD 660S2.
While similar in appearance and construction, the HD 660S2 is positioned at a higher price point than the HD 600. This review aims to determine whether the increased cost is justified or if the original HD 600 maintains its dominance. A recent review of the Sennheiser HD 490 Pro, a similarly priced contender, revealed that while it approached the HD 600’s performance in some areas, it ultimately fell short.
Technical specifications and box contents
Let’s begin with the specifications and included accessories. The HD 660S2 shares a similar design with its predecessors, featuring a metal-mesh exterior. The on-head feel is comparable to the HD 600, although the HD 660S2 exhibits slightly higher clamping force, likely due to its relatively new condition. Weighing in at 260 grams, they offer a comfortable fit. The package includes a 6.3 mm cable (1.8 m), a 4.4 mm cable (1.8 m), a 6.3 mm to 3.5 mm adapter, and a carrying pouch. With a 300-ohm impedance, the HD 660S2 can be used with a smartphone (if compatible), but it performs optimally when paired with a more powerful source. For this review, we utilized a Scarlet 6i6 2nd Gen audio interface. The drivers measure 38 mm in diameter, 4 mm smaller than those found in the HD 600.
It is important to note that these are open-back headphones, making them unsuitable for environments with noise or where sound leakage is a concern, such as airplanes or buses.
With the specifications covered, we can now delve into the primary aspect: the sound quality.
The Sound Experience Sennheiser HD 660S2
A detailed analysis reveals two immediate observations. The midrange performance is exceptional, a testament to the overall sound quality. Conversely, the low frequencies are somewhat underwhelming. As is typical for open-back headphones, bass response is inherently less pronounced. While the Beyerdynamic DT 900 Pro X surprised with its powerful and clear bass despite its open design, the HD 660S2’s bass response presents certain shortcomings. We will explore these aspects in greater detail, examining the frequency spectrum from high to low.
High Frequencies (High-range)
The high frequencies are present, but lack the sharpness and crispness necessary for certain genres. Tracks such as Etherwood – Lighthouse, and even Alan Jackson – Drive, sound slightly muted. While the level of detail is undeniably high, without EQ adjustments, there’s a perceived deficiency in treble response, where the HD 600 or Audio-Technica ATH-R70x offer superior performance. The difference is subtle, but noticeable in direct comparisons. However, the HD 660S2 excels in the treble range with hip hop music. Listening to Gangstarr – Family and Loyalty, the track sounded particularly impressive.
Mid Frequencies (Mid-range)
The HD 660S2’s midrange performance is exceptional, representing its strongest attribute. These headphones reveal nuances in familiar tracks, indicative of a high-quality listening experience. The width and acoustic properties are particularly noteworthy. The precise placement of sounds creates an immersive listening experience. While the Audio-Technica ATH-R70x provides a similar level of width and acoustic detail, determining a clear winner is challenging. Considering the price point, the ATH-R70x offers a more compelling value proposition.
Low Frequencies (Low-range)
While the treble response was considered somewhat subdued, the bass performance is disappointing. The bass feels thin and lacks the presence of its competitors. The HD 600 delivers a heavier and more substantial bass response, a feat the HD 660 S2 doesn’t quite achieve. The bass is certainly audible and balanced, but lacks the necessary impact or pressure when required.
The Overall Soundstage – Sennheiser HD 660 S2
While not the most expansive soundstage available, it provides an enjoyable listening experience across various genres. The overall sound quality meets expectations for headphones in this price range. However, the question arises: is the price justified when the HD 600 performs comparably, and in some cases better, for a lower cost? After extended listening with the HD 660S2, switching to the HD 600 reveals a noticeably narrower soundstage.
The overall sound quality is excellent, allowing for immersive musical enjoyment. The differences become apparent when critically evaluating individual frequency ranges and comparing them to other high-performance headphones.
Conclusion – Sennheiser HD 660S2
In conclusion, our overall satisfaction is tempered by the price point, considering comparable performance can be found at a lower cost. While no headphones are perfect, excelling in every aspect, the Audio-Technica ATH-R70x offers strong performance across the board, but its 470-ohm impedance and extremely open design may limit its versatility. The HD 600 possesses a remarkable cohesiveness and clarity that has stood the test of time. The Sennheiser HD 490 Pro, while sonically impressive, suffered from a design flaw where the ears made contact with the internal components, impacting comfort. Ultimately, the Sennheiser HD 660S2 does not clearly outperform its less expensive competitors, making its price a significant factor. This is unfortunate, as the midrange performance is genuinely exceptional, but the lack of consistent support from other frequencies prevents a higher overall rating.
Sennheiser provided a test unit for this review. The providers of review units have no editorial influence on our evaluations.
