The Sennheiser HD 490 Pro is a studio-grade headphone introduced in January 2024. It is equipped with a driver featuring a 38 mm diaphragm, a customized version of Sennheiser’s Sys38 driver, found in other variants in several headphones like e.g. the HD 560S. The headphone has an impedance of 130 ohms and a sensitivity of 105 dB/V. It is priced at around 400 USD before tax.
The HD 660S2, released in 2023, is the latest addition to a proud lineage of headphones that began with the HD 580, followed by the HD 600 and HD 650. Both the HD 600 and HD 650 remain in production since their respective launches in 1997 and 2003, continuing to enjoy strong popularity among professionals and audiophiles. They feature drivers with 38 mm diaphragm, like the HD490PRO. Like its older siblings, the HD 660S2 is a 300-ohm high-impedance headphone. It has a sensitivity of 105 dB/V, and the price is typically around 500 USD before tax.
SENNHEISER HD 49O PRO SPECIFICATIONS
- Type: Over ear, open
- Dynamic driver with 38 mm diaphragm
- Impedance: 130 Ohms
- Sensitivity: 105 dB/V, 96 dB/mW
- Total Harmonic Distortion: < 0.2 % 1kHz, 100dB
- Detachable cable: 180 cm
- Headphone connector: 4 pin mini XLR
- Cable termination: 3.5 mm
- Included 3.5mm to 6.35mm adapter
- Weight: 260 grams without cable
Current price and availability:
- Amazon: HD 490 PRO
SENNHEISER HD 660S2 SPECIFICATIONS
- Circumaural open-back design
- Dynamic driver with 38 mm diaphragm
- Impedance: 300 Ohm
- Sensitivityl: 104 dB/1V
- Frequency response: 8-41,500 Hz
- Distortion factor: <0.04% (1 kHz, 100 dB)
- Weight: 260 g
- Velour ear pads
- Cables: 1.8 m (6.3 mm stereo jack) + 1.8 m cable (4.4 mm balanced) + 6.3 mm to 3.5 mm stereo adapter and carrying pouch
- Made in Ireland
Current price and availability:
- Amazon: HD 660S2
BUILD AND COMFORT
Both headphones are very lightweight at 260 grams, built with a mix of metal and plastic, but Sennheiser is known for using durable plastic components.
They both come with velour pads, but the HD 490 Pro includes an extra pair made with a woven fabric, which sounds a bit different (see below).
The headphones have similar clamping force and are both comfortable to wear, unless the clamp feels too strong, a problem that seems to be relatively common.
With the HD 660S2, it is easy to adjust the clamp by extending the metal parts of the headband and gently bending them to your preference. The HD 490 Pro, however, has plastic along the metal parts of the headband, and I have not taken the risk of testing this out, but there are apparently people who have tried it with success of you search around.
Each model has detachable cables but with different connectors. The HD 660S2’s cable connects to both earcups using Sennheiser’s heritage HD6** series two-pin plugs, while the HD 490 Pro uses a four-pin mini XLR connector on the left side only.
The HD 490 Pro includes a 1.8 m cable with a 3.5 mm plug and a 6.35 mm adapter, while the HD 660S2 comes with two 1.8 m cables, one single-ended (6.35 mm) and one balanced (4.4 mm). Longer cables are available for the HD 490 Pro; the HD 490 Pro Plus version adds a 3 m cable.
The HD 490 Pro can fold flat with rotating earcups, whereas the HD 660S2 cannot fold at all.
HD 490 PRO PADS
The HD490PRO comes with two sets of pads: “Producer Pads” made of velour and “Mixing Pads” made of a denim-like fabric. In this review I will be using the velour pads but would like to comment a bit on the difference nonetheless.
Different pads always affect the sound, and in this case Sennheiser have made a very conscious decision of giving the headphone two different pairs of pads that give two different sound signatures.
The producer/velour pads give more bass and slightly less pronounced upper midrange and are tuned to be warmer sounding, the mixing/denim pads are designed to be somewhat more neutral.
The pads use a proprietary 6 pin fastening design. To swap the pads you have to grab the mounted pads on the inside and rip them off, then you align the new pads correctly and press them firmly into place. Both sets are washable.
Here is an excellent introduction video from Sennheiser that discusses the pads.
AMPLIFICATION
Both headphones are designed with dedicated amplification in mind. While many portable DAC/amps can power them sufficiently, most users will likely be pairing them with a desktop amplifier, especially in professional settings.
The HD 490 Pro’s lower impedance makes it easier to drive with portable gear, whereas the 300-ohm HD 660S2 offers more flexibility in another direction: It pairs especially well with equipment that has higher output impedance, such as the Lehmann Black Cube Linear or OTL tube amplifiers like the Woo WA2. This also makes it a strong match for older gear with higher output impedance.
For this comparison, I used the Topping A90, which performs well with both models. Still, the HD 660S2 can sound extra nice with e.g. the Black Cube Linear or OTL tube amps.
Anyway, the A90 drives both headphones very well, and after testing multiple amplifiers, I don’t believe the core differences between the two headphones would change much with other setups.
NOTE ON TUBE AMPLIFIERS
That said, I did compare the HD660S2 on the Woo WA2 tube amplifier with the HD490 Pro on the A90. The WA2 definitely elevates the HD660S2, enhancing all its strengths, though it doesn’t fundamentally change its character. The HD490 Pro, however, didn’t benefit in the same way when paired with the WA2.
COMPARISONS
Associated equipment:
- Amplifier: Topping A90
- DAC: RME ADI-2 DAC FS
White Elephant by Lebowski
This instrumental Polish prog rock really shines on the HD660S2, with a balanced, rich, and dynamic presentation and a well-present midrange. The HD490 Pro sounds leaner, offering more space between instruments and better imaging. Tonally, they’re quite similar in bass and treble, but the HD660S2 delivers thicker mids.
Land of Plenty by Bill MacKay
These steel-string guitars in instrumental folk avant-garde bring plenty of midrange energy. The two headphones sound quite similar, both leaning warm. The HD490 Pro comes across a bit crisper and slightly clearer, while the HD660S2 is richer and rounder yet maintains a comparable level of detail.
Hello Dave by Michael Wollny
On this jazz piano trio, the two sound quite similar, but the HD660S2 has more body, delivering a fuller and more energetic presentation. The HD490 Pro is a bit thinner, though it offers better imaging. Detail retrieval and bass energy are very comparable between them.
Stay On These Roads MTV Unplugged by a-ha
The HD660S2 delivers its characteristically richer midrange, making vocals sound more engaging, while the HD490 Pro offers a similar overall presentation but with better instrument separation.
Jambi by Tool
On the HD660S2, guitars come across larger and fuller, with vocals sounding closer, warmer, and richer. Bass is almost the same on both. The HD490 Pro has a slightly crisper edge in the midrange and gives the sense of being seated a few rows back, while the HD660S2 feels like you’re right on stage with the band.
Smile by Pearl Jam
The HD660S2 sounds warmer and fuller, while the HD490 Pro is a bit more spacious. It has slightly more pronounced sibilants, though still very tolerable.
As Before by Olga Konkova
They’re very close here, though the HD660S2 sounds a touch more intimate. The cajón drum comes through warm and punchy, the piano is crisp, and the vocals feel natural and smooth, but not laid back.
It Could Be Sweet by Portishead
Bass performance is very similar, but vocals are a bit warmer and richer on the HD660S2.
Young Vivaldi by Modo Antiquo
They share very similar tonality and instrument timbre, though the HD490 Pro may sound a tad cleaner here.
Spontaneous Compositorius by Thomas Agergard
The percussion on this track is excellent for assessing treble, and the HD660S2 and HD490 Pro handle the high frequencies equally well. They also capture the liquid character I always listen for on this track, which not every headphone reproduces.
The saxophone sounds good on both, though slightly more distant on the HD 490 Pro, while bass response is very similar.
WRAPPING IT UP
Sound Signature
The HD660S2 and HD490 Pro have very similar sound signatures, both balanced and slightly warm. The HD660S2 offers a bit more warmth, smoothness, and richness, but overall, their sound character remains quite comparable.
Treble
Both perform very well in the highs and sound pretty much the same. The HD 490 Pro might be slightly crisper and more spacious, while the HD 660S2 is smoother with even less pronounced sibilance.
Midrange
The HD 660S2 has a bit richer, fuller mids, making vocals and instruments sound warmer and more engaging. The HD490 Pro is slightly leaner but offers better instrument separation.
Bass
The bass is very similar on both in most scenarios, though with the HD490 Pro using the velour producer pads, which I have used for this review, it delivers slightly more bass on certain tracks and, if anything, a bit more detail.
NOTE: With the alternative denim mixing pads, measurements show that the HD660S2 and HD490 Pro perform very similarly below 100 Hz, but there are differences in the rest of the spectrum as well that are not insignificant, and I cannot comment further at this point.
Soundstage and Imaging
Neither of these headphones has a huge soundstage, and the differences are relatively subtle in the large scheme of things. Still, the HD490 Pro offers a more spacious presentation with better imaging, while the HD660S2 feels more intimate.
Detail, Dynamics, and Timbre
I find both headphones equally revealing, though they present detail a bit differently: the HD660S2 delivers it more smoothly, while the HD490 Pro is a touch crisper. Macrodynamics are strong on both, with microdynamics slightly better on the HD490 Pro.
As for timbre, both share very similar tonality and a natural presentation, but there are distinctions: The HD660S2 is generally warmer and smoother, while the HD490 Pro leans slightly crisper.
CONCLUSION
In conclusion, the HD490PRO and HD660S2 share a similar sound signature and have comparable performance. The HD660S2 is slightly smoother and more intimate, while the HD490PRO is a bit crisper and more spacious. It’s evident that they use similar drivers and housings and originate from the same manufacturer.
I think both are successful at bringing the “Sennheiser sound” a step forward in technical terms, without losing the signature characteristics.
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- Amazon: HD 490 PRO
- Amazon: HD 660S2
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