Axel Grell has been an innovator in the audiophile world for decades. From the revolutionary HD600 series that began all the way back in the 90s, to the newly released OAE2, Grell has continued to lead designs on great headphones throughout his career. I recently gave the OAE2 a positive review and stand by it. Today, I wanted to take a look at the work that Grell contributed to over at Sennheiser before forming his own company: the HD650.
Released in 2003, many view the HD650 to be the pinnacle of the 600 series and the model headphone for the mid-range price bracket. While the headphone industry is ever changing, with many releases and discontinuations each year, the 650 has remained as a staple for over twenty years now. Considering that Grell was a leader in the designs of both of these headphones and that they both sit at roughly the same price point (when neither are on sale), I think that comparing them is a worthwhile exercise. Has Grell and his team outdone themselves, or are they outmatched by their own creation?
Build, Comfort, and Feel
Both headphones are fantastic in this department, both when comparing to each other and in the market as a whole. They both look great from a design perspective, with a nice black, silver and grey color scheme. Each feels great to hold and is very sturdy; with fully replaceable parts, both are products that will last for many years after purchase.
For comfort, I would say the HD650 comes out on top. It’s one of the most comfortable headphones I’ve ever worn. It’s light, has great pads, and just the right amount of pressure around the head. I forget I’m wearing them after a while. The OAE2 feels a bit heavier; I find myself having to move it around every once in a while for my head to not get sore. It’s not uncomfortable, but less comfortable than the HD650 for sure.
Technical Specifications
| Specification | HD650 | Grell OAE2 |
| Design | Open-back, circumaural | Open-back, circumaural |
| Driver Type | Dynamic | Dynamic |
| Driver Size | ~40 mm | ~40 mm (custom Grell driver) |
| Frequency Response | 10 Hz – 39.5 kHz | ~10 Hz – 40 kHz |
| Impedance | 300 Ω | 32 Ω |
| Sensitivity | ~103 dB (1V) | ~115 dB/V (approx.) |
| Total Harmonic Distortion (THD) | <0.05% | <0.1% (approx.) |
| Weight | ~260 g (without cable) | ~330–350 g |
| Cable | Detachable, 3 m (6.3 mm jack) | Detachable, modular system |
| Connector Type | Dual 2-pin (Sennheiser proprietary) | 3.5 mm dual entry |
| Build Materials | Plastic frame, metal mesh grille | Aluminum + polymer construction |
| Ear Pads | Velour | Memory foam (replaceable) |
| Clamp Force | Moderate (known to loosen over time) | Moderate (more ergonomic tuning) |
Sound Comparison
Both the OAE2 and the HD650 go for an honest, reference-quality sound. Despite having similar goals, they do sound quite different in many areas.
Soundstage
For those who want an extra-wide soundstage, the OAE2 is the clear winner. Its soundstage is a top-tier contender not just for headphones at this price point, but for headphones in general. Grell has really innovated in pushing the technology in this department. However, the HD650 also performs very well in this category. Its soundstage is also quite open and clear, and it may even be a better fit for those that don’t like an ultra-wide soundstage. However, the HD650 is just outmatched by what Grell has managed to do with this new headphone by a significant margin.
Bass Frequencies
Neither headphone is known for their sharp bass. Both are definitely mid-heavy headphones.This is not to say that the bass is missing from either headphone, it’s just not something they are known for. To my ears, the bass is a bit stronger on the OAE2. The kicks hit harder, it’s got more rumble, and there’s just a bit more of a punch to it, especially in genres like EDM. The HD650 bass rolls off a bit more and isn’t quite as present. For a more laid-back or clarity-focused listener this could actually be more ideal, I am a bit of a bass head myself, so I’d go with the OAE2 here.
Mid-Range Frequencies
This is where both of these headphones really shine. Vocals, guitars, snares, and strings all ring with exceptional clarity and depth. The width of the headphones assist greatly in this area, especially in the OAE2. Because the width is so extreme, there is room for the mids to breathe in what can often be the most crowded section of the frequency spectrum. The HD650 is more of an upfront headphone in this department, with a much more boomy sound especially in harder tracks.
Highs/Treble Frequencies
Both headphones are very competent in this department even if not exceptional. They don’t have the brightness of say a Hifiman, but the highs are crisp and never grading. I wouldn’t say either headphone is marginally better in this department, and I didn’t find myself having a clear preference with my ears.
Verdict/Final Thoughts
Grell had an incredible legacy to live up to with the OAE2, and I’d say he’s matched himself quite nicely. While some will still definitely prefer the HD650’s classic sound, I deeply appreciated the OAE2’s innovation in soundstaging. This quality alone sets it apart from the competition to great effect, and it holds its own in just about every other area as well. As someone who has listened to an ever growing number of headphones, I just find the OAE2 more interesting for its uniqueness. I know saying that may be blasphemous to many long-term audiophiles, but it’s just my personal preference in this case. I still love the HD650, it was actually the first audiophile headphone I ever bought and it will always hold a special place as the headphone that got me into the hobby.
Grell and his team’s talent really does speak for itself, and I hope that they continue to outdo themselves in the future in the ever-evolving audiophile space.
You can buy the Grell OAE2 and the Sennheiser HD650 at Audio 46.
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