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Open-back Planar Headphone Suggestions?


New Member
Jul 18, 2022
Hi all! Short-time lurker, first time poster here.

For a while I've been enjoying my Sennheiser HD 660s for streaming hi-fi through Qobuz. Adding the Oratory EQ profile to it was a world-changer.

I recently bought a pair of Dan Clark Audio x Drop Aeon Closed X headphones, though, and they're hands down the best headphones I've ever heard. The imaging and clarity is unlike anything I've ever experienced with headphones, and it feels like I'm hearing favorite albums for the first time again.

I'm totally bought into planar magnetic drivers now, and I'm wondering on whether I should look for an upgrade for my HD 660s for some planar magnetic open-backs. So a couple of questions:

1.) In your opinion, what would the benefits be of having open-back planars in addition to closed-back planars? Right now the main thing I can think of is it'd be nice to be able to better hear if something is happening while I'm in my home office (e.g. doorbell rings).
2.) What would be a good upgrade from the 660s for an open-back planar magnetic headphone if it's worth getting one (other than maybe the obvious answer of open-back Aeons)?

For reference, I've got a Hidizs S9 Pro for streaming off USB Audio Player Pro (Qobuz) on my Android, and an ifi hip DAC for streaming through Qobuz + Peace EQ on my computer (soon to be upgraded to a Monoprice Monolith 887 + SMSL SU-8s, just waiting for the SU-8s to ship). I also added a bit more bass to the Oratory EQ for the DCA Aeon Closed Xs since I like a bit more bass than Oratory's EQ provided.



Major Contributor
Forum Donor
Feb 13, 2018
Laguna, Philippines
I recently heard the Aeon 2 Noires and currently have the Aeon Open X. The Open X has elevation in FR in the upper bass but have less subbass than the Noires (this tuning is what I prefer) due to FR curve. To me the Open X tonality and clarity sans soundstage (no EQ whatsoever) is right up there with kilobuck headphones including the HD800S, Celestee, Clear OG, Dan Clark Noires, etc. I haven't heard the 660S but definitely you can EQ the Open X to your liking and it'll be close to the Closed X sound (you would have to lower the upper bass frequencies and significantly boost the subbass to make it sound like the Closed X).

If you crank up the Open X to my reference 85-90 dB SPL, you would literally drown out almost all noises (including your doorbell rings and even phone calls) so you'll only have the open back advantage at quiet volumes (60 dB or less)


Active Member
May 30, 2022
Open (& semi-open) backed planar magnetic headphones are my preference over closed back designs. Planars' sound waves come off both the front and rear (back) surface of it's diaphragm.

As Tyll Hertsens explains: "There is a significant amount of trapped air in volumes of various sizes that must be moved before sound is released out of the driver. The springiness and resonances that may (my italics) exist in this trapped air volume can cause problems. Quite a bit if design effort ... [is] ... spent getting just the right damping."

Planar resonance that occur are mostly in treble frequencies and of relatively low amplitude. Good designs incorporate some material to slow down that energy heading to the back of an ear cup (yet too much/dense isolation material concentrates that treble energy). Open back planars give more treble resonance a way to get out of the ear cup, reducing the potential for resonance reflecting forward off the interior surface of the ear cup.

The less resonance, whether from designer's interior damping material or open backs, the smoother the roll-off of frequencies. Then overall sound entails notes that are not congested with one another; there will seem to be some space between instruments playing (what some call the better "sound stage" of open backed headphones).

Closed back planar must be designed so the wave reflected from the ear cup interior back surface does not interfere with the front wave. Resonance depresses the fundamental frequency's sound pressure wave, while enhancing the sound energy at certain frequencies. The ear cup damping material used should compress the air column moving through it ideally quickly; which creates friction force on those fibers (movement of individual material fibers by sound pressure does not have acoustical importance).

Using the right material ensures a speedy (quick) response of heat and just a small temperature rise between fibers. It is a small temperature rise between damping material fibers which decreases the air column pressure. This makes the air less compressed (sound waves are compressed air) and that lowers the resonance frequency; controlling planar treble resonance.

Best planar designs take into account that frequency compressibility among different damping materials can be relatively low/lower/less at high frequencies and high/higher/more at low frequencies; more expensive material installed can have higher compressibility at high frequencies to deal with any planar treble resonance better. The best material designers might use for planars' resonance is that material where, as frequencies rise, friction occurs in the boundary layer close to the fibers because that produces more resistance quickly to the air flow.
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