Is the HD 660S2 worth the upgrade from the HD 650?

If you like the HD 650's tuning but wish it had more sub-bass and less treble roll-off, yes: published measurements show the HD 660S2 extends further at both ends. If the HD 650's warmer, more intimate character is the point for you, owners describe the 660S2 as different rather than strictly better: more extended and a touch less warm.

HD 660S2 vs HD 800S — which is the better Sennheiser?

The HD 800S is Sennheiser's flagship open-back, known for a much wider stage and more extended treble. The HD 660S2 is more forgiving of average recordings, per owner reports, and costs far less. For most listeners spending under $600, the HD 660S2 is the right choice.

Does the HD 660S2 need a balanced amp?

No. The included balanced 4.4mm cable is a bonus, but the power math shows a good single-ended desktop amp drives the HD 660S2 with plenty of headroom. Balanced outputs usually offer more voltage and better channel separation on paper; with a 300Ω headphone and a competent amp, the audible difference is small.

What amplifier pairs best with the HD 660S2?

Our current pick is the Topping DX5 II (~$299), a DAC/amp with a 4.4mm balanced output that uses the included cable. The FiiO K11 R2R (~$170) and Schiit Magni ($119) are cheaper single-ended options with plenty of voltage for 300Ω, and the Schiit Asgard X ($399) suits a separate-DAC stack. OTL tube amps like the Schiit Valhalla 3 are a classic match for 300Ω Sennheisers.

Sennheiser HD 660S2 Review 2026: Worth $100 Over HD 650?

Name: Sennheiser HD 660S2
Brand: Sennheiser

On sale the HD 660S2 costs about $100 more than the HD 650. Measurements show what that buys in bass and treble, and which amp suits its 300Ω load.

Research-based review, updated October 2026 · prices checked Oct 10, 2026. AmperHeads doesn’t bench-test or audition gear: this page combines published specs, our power math, third-party measurements and long-running owner reports. How we research and rate gear .

What Does a Modern Sennheiser 6XX Sound Like?

The HD 600 and HD 650 defined what a reference open-back headphone should sound like for nearly three decades. Sennheiser’s 300Ω line stayed largely unchanged from 1997 (HD 600) and 2003 (HD 650) until the HD 660S in 2017 and the HD 660S2 in 2022. The question the audiophile community asked straight away: is the new model better, or just different?

Published measurements and owner consensus give a fairly clear answer: the HD 660S2 extends further in the two places the HD 650 is criticised, sub-bass and treble, while keeping the natural midrange that made the series famous. It does not make the HD 650 obsolete.

Prices as of October 2026: Sennheiser US lists the HD 660S2 at $679.95, and it regularly sells for about $480. The HD 650 sells for about $380 on sale, so the real gap is roughly $100.

Design and Build

The HD 660S2 uses the familiar Sennheiser 6XX chassis with cosmetic changes: a darker finish and a slightly more premium look. Underneath it is the same proven platform: velour pads, a light frame and a dual-entry detachable cable with Sennheiser’s two-pin connectors. Pads, cable and headband cushion are replaceable with standard Sennheiser parts.

The notable addition is in the box: a standard single-ended cable plus a 4.4mm balanced cable. That lets you use a balanced amp output without buying an aftermarket cable, which the HD 600 and HD 650 require.

Owners describe the fit as essentially the same as the HD 650: a firm initial clamp, even pressure and plush velour pads that suit long sessions on most head shapes.

Sound: Measurements and Owner Consensus

The notes below summarise published frequency-response measurements and long-running owner reports on r/headphones and Head-Fi, not our own listening.

Bass

This is the HD 660S2’s most significant change. Where the HD 650 rolls off in the sub-bass, published measurements show the HD 660S2 extending noticeably deeper, and owners coming from the HD 650 consistently mention it first. Electronic music, film scores and bass-forward rock benefit most.

The mid-bass lift that gives the HD 650 its warmth is reduced. Owners describe a tighter, more controlled low end with less bloom. Some call that more accurate; others find it slightly leaner.

Midrange

The midrange is still the heart of the HD 660S2’s appeal. Owners describe the same natural timbre and organic vocals that made the series popular, shifted slightly toward neutral compared with the HD 650’s warmth.

Treble

The HD 660S2 directly addresses the HD 650’s “veil”. Measurements show more upper-treble energy than the HD 650, and owners describe more air and longer cymbal decay, without the sharp peaks that make some open-backs fatiguing. It’s not a bright headphone; it is simply less rolled-off.

Soundstage and Imaging

Owners generally describe the stage as slightly more open than the HD 650’s, with precise placement on well-recorded material. It is still a near-field Sennheiser presentation, not as wide as the DT 990 Pro or the HD 800S.

Amplifier Pairing

The HD 660S2 is a 300Ω headphone and needs real voltage, the same as the HD 600 and HD 650. Phones and most dongles fall short on loud peaks; any current desktop amp clears the requirement with headroom.

Topping DX5 II (~$299): our current pick. A one-box DAC/amp with a 4.4mm balanced output, so the included balanced cable gets used.
FiiO K11 R2R (~$170) / Schiit Magni ($119): cheaper single-ended options with plenty of voltage for 300Ω. The K11 R2R includes a DAC.
Schiit Asgard X ($399): for a separate-DAC stack with more power than this headphone will ever need.
OTL tube amps (Schiit Valhalla 3): output-transformerless tube amps remain a classic match for 300Ω Sennheisers.

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For every current amp ranked against the HD 660S2’s 2.0 V requirement, see the best amp for the HD 660S2 pairing guide.

The same 300Ω pairing logic, with the voltage math, is laid out in the best amp for the HD 600 and best amp for the HD 650 guides.

Is It Worth the Price Over the HD 650?

On sale, the HD 650 sells for about $380 and the HD 660S2 for about $480 (October 2026). The roughly $100 premium buys:

Deeper sub-bass extension
Less treble roll-off
A balanced 4.4mm cable in the box
An updated driver and housing

If the HD 650’s rolled treble and limited sub-bass were specific frustrations for you, the HD 660S2 addresses both. If you love the HD 650’s warm, intimate character exactly as it is, the upgrade is less compelling. At the full $679.95 list price, wait for a sale.

Final Verdict

Based on the measurements and the owner record, the HD 660S2 is the most complete 300Ω Sennheiser under $600. It keeps the proven 6XX formula and adds the extension the HD 650 was always missing. If you’re building a desktop system around a proper amp and can buy it near $480, it’s worth it. On a tighter budget, a used HD 650 still competes seriously at well under half the price.

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