Two excellent planar dynamic single-driver IEMs compared
When it comes to single-driver planar magnetic IEMs, the two 7Hz Timeless versions and Letshuoer S12-series have been among the most popular. Last year, the Timeless was released in its second version, and this year, the S12 arrived in its fourth iteration. This is a comparison between the latest versions of both series: the Timeless II and the S12 Ultra.
Both have very large drivers that are almost identical in size. The Timeless II uses a 14.5 mm driver, while the S12 Ultra features a 14.8 mm driver.
The original 7Hz Timeless was launched in 2021 as one of 7Hz’s first offerings. The Timeless II followed in late 2024 and is priced at 229 USD.
The original S12 was also released in 2021. The S12 Ultra was launched very recently, in the autumn of 2025, priced at 169 USD.
The S12 Ultra includes a USB DAC/AMP dongle, the DT01 Pro.
7HZ TIMELESS II SPECIFICATIONS
- Driver: 14.5mm planar magnetic driver
- Impedance: 15.2 ohms
- Sensitivity: 108 dB/V@1KHz
- THD: <0.2%/1KHz
- Frequency Response: 5-40000Hz
- Weight per earbud: 5 g
- Connector type: 0.78 mm 2-pin
- Cable: ca. 1.2 m 7N 4-core single-crystal
- Termination: interchangeable 3.5 mm and 4.4 mm jacks.
- Included: metal storage case, cable with interchangeable 3.5mm/4.4mm jack, silicone ear tips
Current price and availability:
- Linsoul: 7hz Timeless II
- Amazon: 7hz Timeless II
LETSHUOER S12 ULTRA SPECIFICATIONS
- Driver: 14.8mm planar magnetic
- Impedance: 16 ohms
- Sensitivity：101dB
- Frequency Response：20Hz – 40kHz
- Cable：1.2 m Silver-plated copper
- Cable Connector IEM: 0.78 dual pin
- Cable termination: 3.5mm / 4.4mm swappable
- Shell material: Aluminum alloy
- Included: DT01 USB dongle (3.5 mm output), metal storage case, cable with interchangeable 3.5mm/4.4mm jack, silicone ear tips
- Available in two colours: Gunmetal and Mocha
Current price and availability:
BUILD AND COMFORT
Both are made of CNC-machined metal and are medium-sized with rounded inner shells, making them quite comfortable to wear. The 7Hz Timeless II has a decorative circular faceplate that protrudes slightly from the main housing, which may cause comfort issues for some users.
Other than that, both models come with excellent cables and puck shapes metal circular storage cases, which are rather heavy and better suited for keeping the IEMs on your desk rather than carrying them in your pocket.
As mentioned, the S12 Ultra also includes a small USB dongle, the Letshuoer DT01 Pro, which adds value if you need it.
COMPARISONS
Associated equipment:
- Amplifier: Topping A90
- DAC: RME ADI-2 DAC FS
Hello Dave by Michael Wollny
The S12 has fantastic bass; it’s snappy and smooth, natural and effortless. The Timeless II is very similar, but a tad clearer sounding, the bass might be a bit more powerful as well.
Yours by Bill Laurance
The Timeless II is wonderful, especially the bass is impressively full and tight, but the rest is well balanced and natural sounding. The S12 Ultra is very similar, but the background is slightly less black, making instrument separation a bit less impressive – but it’s still good.
Fuglefangeren by Maridalen
The Timeless II sounds wonderful, with extremely detailed bass that is rich and full. The saxophone timbre is very pleasant—slightly dark but natural. There is plenty of detail across the entire frequency range. The S12 Ultra sounds very similar, but the Timeless II comes across as a bit cleaner and has slightly more bass.
Seven Nation Army – live performance (Northern lights..) by The White Stripes
The S12 Ultra is wonderful, fabulous bass, slightly dark tuning, dynamic and detailed. The Timeless II is similar but not identical. It’s a bit brighter here, and there’s a tad less bass quantity. However, the differences are very small.
Jambi by Tool
But are excellent. Slightly dark, great bass. Vocals stand out in the mix. The Timeless II is a bit thicker and richer sounding.
Bored by Deftones
Again very similar, both are excellent. There are minor differences but they’re not really worth mentioning.
Escape Route by Boris Blank
They’re relatively similar, but the Timeless II is a bit meatier with a thicker sounding bass.
Spontaneous Compositorius by Thomas Agergard
Again, they are very much alike. Even the bright percussion is rendered very similarly; the treble performance and treble character is very close between the two.
Young Vivaldi by Modo Antiquo
Here they’re easier to distinguish. The S12 Ultra is smoother and darker, the 7Hz Timeless II has a somewhat crisper and brighter timbre, feeling airier and more aggressive – in a good way.
Midnight City by M83
They sound very similar, the S12 Ultra might be a tad darker.
Sunrise by Norah Jones
The Timeless II offers powerful bass and upfront vocals, good instrument separation and a high detail level. The S12 Ultra is quite similar, but it’s tuned a bit darker and feels a bit smoother.
WRAPPING IT UP
Sound Signature
The Timeless II and the S12 Ultra have very similar sound signatures. Both have powerful high quality bass, present, yet slightly dark mids, and clear highs.
Treble
They both offer great detail without sounding overly crisp or aggressive. They’re very similar but the Timeless II feels slightly more open and a bit brighter.
Midrange
The midrange is quite similar on both and has a slightly dark tuning. On some tracks the Timeless II is more upfront and energetic.
Bass
Both offer truly excellent bass performance. The bass quantity leans toward the powerful side. The quality is outstanding; there’s a great sense of detail and texture. There are some variations between them from track to track, and more often than not, the Timeless II has slightly more bass quantity than the S12.
Soundstage and Imaging
Both have a large soundstage and very good imaging that is comparable in most respects. However, the Timeless II has a slightly blacker background, which gives it a small advantage in imaging and overall clarity.
Detail, Dynamics, and Timbre
In terms of detail, both are excellent and quite comparable, but when there is a difference, it usually favors the Timeless II. Dynamics are essentially the same. The timbre is also similar—slightly dark and warm with a somewhat dry character—but when differences appear, the Timeless II tends to sound a bit more upfront and energetic.
CONCLUSION
By and large, I find the S12 Ultra and the Timeless II to sound very similar. Both offer excellent, powerful bass, present mids, and clear highs. They share a slightly dark presentation with a touch of dry warmth in their timbre. When I do notice differences, they are mostly in favor of the more expensive Timeless II, which can occasionally sound a bit clearer and cleaner, with a more energetic midrange. For the most part, though, they are very close and often difficult to tell apart.
Both the 7Hz Timeless II and the Letshuoer S12 Ultra come highly recommended.
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- Linsoul: 7hz Timeless II
- Amazon: 7hz Timeless II
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