Why do high-end open headphone makers all still eschew active EQ?

Discussion in 'Headphones' started by riker1384, Jul 28, 2018.

  1. riker1384

    riker1384 Acquaintance

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    With the rise of noise cancelling and Bluetooth headphones it's becoming very common for mass-market headphones to have active electronics onboard. It's apparent that a lot of these models are also using active EQ to improve the frequency response. It can be readily seen in these measurements of Bose headphones and others in active vs passive modes:

    https://www.innerfidelity.com/images/BoseQuietComfort35WiredPassive.pdf
    https://www.innerfidelity.com/images/BoseQuietComfort35WiredActive.pdf

    https://www.innerfidelity.com/images/BoseQuietComfort25Passive.pdf
    https://www.innerfidelity.com/images/BoseQuietComfort25.pdf

    https://www.innerfidelity.com/images/SonyMDR1000XWiredPassive.pdf
    https://www.innerfidelity.com/images/SonyMDR1000XWiredNCActive.pdf

    https://www.innerfidelity.com/images/SantaCruzAudioSC1000Passive.pdf
    https://www.innerfidelity.com/images/SantaCruzAudioSC1000Active.pdf

    I'm wondering why none of the high-quality audiophile headphone companies are willing to do this on their open headphones. Obviously they don't have as many problems to correct, but they do clearly have some issues that could be addressed with EQ. Take the ubiquitous open-dynamic-headphone bass-extension problem. A properly designed EQ could greatly improve the bass extension when listening at moderate volume, while reducing the boost at higher volumes in order to reduce distortion and prevent over-excursion. Pretty much every portable Bluetooth speaker does this in order to get better extension out of a small box. It is frustrating that all the best headphones makers use an antiquated approach and won't do things that any modern $50 portable speaker can do.

    A lot of headphone enthusiasts spend tremendous amounts of time trying to physically tweak their headphones in order to fix problems that could easily be solved with some EQ. Adding damping materials to flatten the midbass hump on an HD650, or to to lower one peak in the treble on an HD800 and so forth.

    "Solderdude" over at DIY Audio Heaven has made headphone EQ available with his Kameleon headphone amplifier: https://diyaudioheaven.wordpress.com/headphones/kameleon/ It accepts EQ modules custom-designed for various high-end headphones. The HD650 module, for instance, extends the deep bass, flattens the upper-bass hump, and lifts the treble a bit, making it much more accurate overall. Unfortunately he doesn't sell it as a finished product, just a circuit board for DIYers to complete and build a housing for.

    Some high-end planar-magnetic manufacturers are boutique operations that might not have the resources to design and build electronics, but the larger companies should be able to do it as they already often do in their existing active closed headphones. Particularly Sennheiser, and others such as Focal or NAD/PSB.

    With an active EQ, the biggest question would be how to package it. Putting it onboard would add some weight, but modern electronics are pretty damn small and light. You would probably have to put them in the headband to avoid occluding the drivers. The main drawback in my mind is that adding onboard electronics would introduce more points of failure and potentially reduce the reliability and longevity of the headphones. But in a world where Sennhesier is capable of selling the HD58x for $150, I think the benefits of an active version could be worth the risk that it might not be a family heirloom guaranteed to work in 25 years.

    The reliability risks could be ameliorated if a big company like Sennheiser commits to proving replacement batteries and amplifiers. And they could add a hard amp-bypass switch to allow operation as normal passive headphones. This would allow the phones to keep working in case of an electronics failure, and also allow purist audiophiles to use them with their own electronics.

    The alternative packaging approach, having an outboard amp-EQ module such as the Kameleon above would reduce the portability and simplicity of use of the headphones. It is less desirable to me for this reason. And it might present a marketing problem as it would force them to admit that the headphones (along with the maker's other passive models) have "flaws" to be solved.

    Active EQ could offer additional benefits beyond just improving existing headphones. It might allow more flexibility in the driver design. I imagine designing a headphone driver and enclosure is like playing Whack-A-Mole. You make a physical change to solve one problem, and some other problem pops up in another part of the spectrum. And so we're forced to choose between different headphones, with new ones coming out all the time, and each one having its own major flaws. It's trivial to find speakers that are +/- 2 db or less over the entire spectrum or better, but there are only a few models of headphones that even come close. The overall fidelity level of headphones remains well below that of speakers and it doesn't seem to be improving that much.

    Active designs dominate the pro-audio speaker world, and even passive speakers have electronic filtering done in the crossovers and have for many decades, while headphones are stuck in an extremely primitive Lowther-style paradigm of just a driver and no filtering at all.

    With EQ available, the engineer could worry less about optimizing one thing-overall response flatness-which might allow them to better optimize other characteristics. There might be a driver design that has some advantages, such as lower bass distortion or less diaphragm breakup in the treble, but it has some slope somewhere in its response which is easily corrected in an active design but makes it unusable in a passive design.

    Probably the biggest objection to active designs are audiophiles who insist on using high-end electronics to drive the headphones. Personally I'm not in that camp. I don't hear much difference between electronics with speakers or headphones. I think any subtle drawbacks would be outweighed by the large advantages that EQ would bring. And I don't want to create EQ myself with computer software or some outboard EQ unit. I want to be able to pick up my headphones and plug them into any computer, TV, or stereo and have them work. And I think there must be other people who want the quality of a good open-back headphone but don't want to bother with audiophile tweaking. (There are dozens of us!)

    ============
    To sum up, WHAT I WANT specifically:

    What I am picturing is something like this: Either HD650 or HD58X drivers mounted in standard Senn 600-series frames. An amplifier/EQ module and Li-ion battery are built into the headband. The battery is user-replaceable and the amp section is either replaceable, or they sell entire replacement headband/amp assemblies. There are two inputs: a 3.5mm (or 2.5mm?) jack for audio, and a USB for charging and to also use for audio input when connected to a computer. There is a 3-position switch:

    -FLAT/accurate mode
    -A euphonic mode with something like the Harman target curve. It can simply be called BASS BOOST if necessary in order to avoid confusing the rubes. (Another benefit of active design-being able to choose different target curves.)
    -OFF/BYPASS mode simply bypasses the electronics completely and connects the drivers straight to the 3.5mm input. This is to be used in case of battery or amplifier failure, or for purist audiophiles to use their own amps.

    They could also make a budget version based on the HD500-series platform and drivers, and possibly a high-end version based on the HD800.
    ============
    I might post this at Head-Fi at some point in the vain hope that manufacturers read it and consider it. But I'd like to hear what you all think. Would you consider an active open audiophile headphone, or are you committed to traditional passive designs?
     
  2. m17xr2b

    m17xr2b Friend

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    I personally don't like eq on the HD650 with a TOTL setup. EQ is fun sometimes on some headphones but for reference listening even a 0.5dB adjustment with a DSP creates artefacts that I can hear and don't like. It's my opinion headphones need a setup with proper synergy that doesn't require eq.
    I'm kinda doing the same thing but with tube rolling for euphonious/accurate sound or as I please.
     
  3. Armaegis

    Armaegis Friend

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    A few points in no particular order:
    - if you're at the point where you can hear the difference in dacs, then you can probably hear the difference in EQ's (most of them are not very good; and they get worse the larger the changes become)
    - EQ doesn't do anything to ameliorate distortion and other fiddly things (oftentimes makes them worse actually)
    - with speakers, you don't just attack the room with DSP; you always work with room treatments and proper placement first before you start diving into corrections
    - it took active speakers a very long time before they were considered in the same league as passives; headphones will take time there as well
    - audiophiles like playing with components; it feeds the gear acquisition nervosa; sometimes that's half the fun of it
    - nothing you've said above is particularly groundbreaking; the changes are coming, we all know it, but the science is still relatively new and headphone measurements and standardizations are still a bit of a wild wild west scenario
    - at the moment, physical modding and measuring after is still faster/cheaper than EQ shenanigans; this will likely change in a few years as resources become more standardized and readily available
     
  4. maverickronin

    maverickronin Friend

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    The short answer is that most audiophiles have philosophical objections to EQ making it hard to market. In addition, starting with less efficient, higher fidelity drivers will require more supporting electronics for higher power or greater voltage swings making it harder fit into the headphone without making it weigh a ton.

    The Sonoma Model One is a recent example of this. It sounds excellent (at lower volumes at least) and is priced quite fairly against the entire TOTL 'stat rig that it would replace but it isn't very popular since no one seems to like the idea of such proprietary components.

    I do agree that active DSPs are the way forward for improved fidelity in headphones as well as speakers. Designs with internal microphones like noise cancelers use can even help correct non-linear distortion and time domain artifacts.

    Someone's going to have to come up with a marketable way to sell them though. Self contained electronics may be too difficult to implement, additional outboard electronics seem a bit inelegant, and people don't like being tied to proprietary AIOs
     
  5. Metro

    Metro Friend

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    Audeze is a proponent of DSP and equalization, as evidenced by their Lightning cables, Mobius headphones, and software.

    Overall, many of the things you propose have little appeal for audiophiles. Maybe for mid-level but not the high end. Fitting amps and DSP/DACs into headphone earpieces require compromises compared to the desktop components most of us have. For calibrated equalization, there are currently software solutions such as Sonarworks True-Fi/Reference.
     
    Last edited: Jul 28, 2018
  6. MF_Kitten

    MF_Kitten Banned per own request

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    I have a MiniDSP 2X4 HD running into my headphone amp, and a MiniDSP EARS to measure with. I make things act and behave the way I want :)
     

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