Unconventional headphones: Sonic response consistency, albeit cosmetically ungainly

Back in mid-2019, I noted that the ability to discern high quality music and other audio playback (both in an absolute sense and when relatively differentiating between various delivery-format alternatives) was dependent not only on the characteristics of the audio itself but also on the equipment used to audition it. One key link in the playback chain is the speakers, whether integrated (along with crossover networks and such) into standalone cabinets or embedded in headphones, the latter particularly attractive because (among other reasons) they eliminate any “coloration” or other alteration caused by the listening room’s own acoustical characteristics (not to mention ambient background noise and imperfect suppression of its derogatory effects).

However, as I wrote at the time, “The quality potential inherent in any audio source won’t be discernable if you listen to it over cheap (i.e., limited and uneven frequency response, high noise and distortion levels, etc.) headphones.” To wit, I showcased three case study examples from my multi-headphone stable: the $29.99 (at the time) Massdrop x Koss Porta Pro X:

$149.99 Massdrop x Sennheiser HD 58X Jubilee:

and $199.99 Massdrop x Sennheiser HD 6XX:

I’ve subsequently augmented the latter two products with optional balanced-connection capabilities via third-party cables. Common to all three is an observation I made about their retail source, Drop (formerly Massdrop): the company “partners with manufacturers both to supply bulk ‘builds’ of products at cost-effective prices in exchange for guaranteed customer numbers, and (in some cases) to develop custom variants of those products.” Hold that thought.

And I’ve subsequently added another conventional-design headphone set to the menagerie: Sony’s MDR-V6, a “colorless” classic that dates from 1985 and is still in widespread recording studio use to this day. Sony finally obsoleted the MDR-V6 in 2020 in favor of the MDR-7506, more recent MDR-M1 and other successor models, which motived my admitted acquisition of several gently used MDR-V6 examples off eBay:

One characteristic that all four of these headphones share is that, exemplifying the most common headphone design approach, they’re all based on electrodynamic speaker drivers:

At this point, allow me a brief divergence; trust me, its relevance will soon be more obvious. In past writeups I’ve done on various kinds of both speakers and microphones, I’ve sometimes intermingled the alternative term “transducer”, a “device that converts energy from one form to another,” for both words. Such interchange is accurate; even more precise would be an “electroacoustic transducer”, which converts between electrical signals and sound waves. Microphones input sound waves and output electrical signals; with speakers, it’s the reverse.

I note all of this because electrodynamic speaker drivers, specifically in their most common dynamic configuration, are the conceptual mirror twins to the dynamic microphones I more recently wrote about in late November 2022. As I explained at the time, in describing dynamic mics’ implementation of the principle of electromagnetic induction:

A dynamic microphone operates on the same basic electrical principles as a speaker, but in reverse. Sound waves strike the diaphragm, causing the attached voice coil to move through a magnetic gap creating current flow as the magnetic lines are broken.

Unsurprisingly, therefore, the condenser and ribbon microphones also discussed in that late 2022 piece also have (close, albeit not exact, in both of these latter cases) analogies in driver design used for both standalone speakers and in headphones. Condenser mics first; here’s a relevant quote from my late 2022 writeup, corrected thanks to reader EMCgenius’s feedback:

Electret condenser microphones (ECMs) operate on the principle that the diaphragm and backplate interact with each other when sound enters the microphone. Either the diaphragm or backplate is permanently electrically charged, and this constant charge in combination with the varying capacitance caused by sound wave-generated varying distance between the diaphragm and backplate across time results in an associated varying output signal voltage.

Although electret drivers exist, and have found use both in standalone speakers and within headphones, their non-permanent-charge electrostatic siblings are more common (albeit still not very common). To wit, an excerpt from a relevant section of Wikipedia’s headphones entry:

Electrostatic drivers consist of a thin, electrically charged diaphragm, typically a coated PET film membrane, suspended between two perforated metal plates (electrodes). The electrical sound signal is applied to the electrodes creating an electrical field; depending on the polarity of this field, the diaphragm is drawn towards one of the plates. Air is forced through the perforations; combined with a continuously changing electrical signal driving the membrane, a sound wave is generated…A special amplifier is required to amplify the signal to deflect the membrane, which often requires electrical potentials in the range of 100 to 1,000 volts.

Now for ribbon microphones; here’s how Wikipedia and I described them back in late 2022:

A type of microphone that uses a thin aluminum, duraluminum or nanofilm of electrically conductive ribbon placed between the poles of a magnet to produce a voltage by electromagnetic induction.

Looking at that explanation and associated image, you can almost imagine how the process would work in reverse, right? Although ribbon speakers do exist, my focus for today is their close cousins, planar magnetic (also known as orthodynamic) speakers. Wikipedia again:

Planar magnetic speakers (having printed or embedded conductors on a flat diaphragm) are sometimes described as ribbons, but are not truly ribbon speakers. The term planar is generally reserved for speakers with roughly rectangular flat surfaces that radiate in a bipolar (i.e. front and back) manner. Planar magnetic speakers consist of a flexible membrane with a voice coil printed or mounted on it. The current flowing through the coil interacts with the magnetic field of carefully placed magnets on either side of the diaphragm, causing the membrane to vibrate more or less uniformly and without much bending or wrinkling. The driving force covers a large percentage of the membrane surface and reduces resonance problems inherent in coil-driven flat diaphragms.

I’ve chronologically ordered electrostatic and planar magnetic driver technologies based on their initial availability dates, not based on when examples of them came into my possession. Specifically, I found a good summary of the two approaches (along with their more common dynamic driver forebear) on Ken Rockwell’s always-informative website, which is also full of lots of great photography content (it’s always nice to stumble across a kindred interest spirit online!). Rockwell notes that electrostatics were first introduced in 1957 [editor note: by Stax, who’s still in the business], and “have been popular among enthusiasts since the late 1950s, but have always been on the fringe as they are expensive, require special amplifiers and power sources and are delicate—but they sound flawless.” Conversely, regarding planar magnetics, which date from 1972, he comments, “Planar magnetic drivers were invented in the 1970s and didn’t become popular until modern ultra-powerful magnet technology become common in the 2000s. Planar magnetics need tiny, ultra powerful magnets that didn’t used to exist. Planar magnetics offer much of the sound quality of electrostatics, with the ease-of use and durability of conventional drivers, which explains why they are becoming more and more popular.”

Which takes us, roughly 1,200 words in, to the specifics of my exotic headphone journey, which began with two sets containing planar magnetic drivers. Back in late May 2024, Woot! was selling the Logitech for Creators Blue Ella headset (Logitech having purchased Blue in mid-2018) for $99.99, versus the initial $699.99 MSRP when originally introduced in early January 2017. The Ella looked (and still looks) weird, and is also heavy, albeit surprisingly comfortable; the only time I’ve ever seen anyone actually using one was a brief glimpse on Trey Parker and Matt Stone’s heads while doing voice tracks for South Park within the recently released Paramount+ documentary ¡Casa Bonita Mi Amor!. But reviewers rave about the headphones’ sound quality, a headphone amplifier is integrated for use in otherwise high impedance-unfriendly portable playback scenarios, and my wife was bugging me for a Father’s Day gift suggestion. So…

A couple of weeks later, a $10-off promotional coupon from Drop showed up in my email inbox. Browsing the retailer’s inventory, I came across another set of planar magnetic headphones, the Drop + HIFIMAN HE-X4 (remember my earlier comments about Drop’s longstanding history of partnering with name-brand suppliers to come up with custom product variants?), at the time selling for $99.99. They were well reviewed by the Drop community, and looked much less…err…alien…than the Blue Ella, so…(you’ve already seen one stock photo of ‘em earlier):

Look how happy she is (in spite of how big they are on her head)!

And of course, with two planer magnetic headsets now in the stable, I just had to snag an electrostatic representative too, right? Koss, for example, has been making (and evolving) them ever since 1968’s initial ESP/6 model:

The most recent ESP950 variant came out in 1990 and is still available for purchase at $999.99 (or less: Black Friday promotion-priced at $700 on Amazon as I type these words). Believe it or not, it’s one of the most cost-effective electrostatic headphone options currently in the market. Still, its price tag was too salty for my curiosity taste, lifetime factory warranty temptation aside.

That box to the right is the “energizer”, which tackles both the aforementioned high voltage generation and output signal amplification tasks. Koss includes with the ESP950 kit, believe it or not, a 6 C-cell battery pack to alternatively power the energizer (therefore enabling use of the headphones) when away from an AC outlet. Portability? Hardly, although in fairness, the ESP950 was originally intended for use in live recording settings.

But then I stumbled across the fact that back in April 2019, Drop (doing yet another partnership with a brand-name supplier, this one reflective of a long-term multi-product engagement also exemplified by the earlier-shown Porta Pro X) had worked with Koss to introduce a well-reviewed $499.99 version of the kit called the Massdrop x Koss ESP/95X Electrostatic System:

Drop tweaked the color scheme of both the headphones themselves (to midnight blue) and the energizer, swapped out the fake leather (“pleather”) earpads for foam ones wrapped in velour, and dropped both the battery pack and the leather case (the latter still available for purchase standalone for $150) from Koss’s kit to reduce the price point:

Bad news: at least for the moment, the ESP/95X is no longer being sold by Drop. Good news: I found a gently used kit on eBay for $300 plus shipping and tax (and for likely obvious reasons, I also purchased a two-year extended warranty for it).

And what did all of this “retail therapy” garner me? To set the stage for this section, I’ll again quote from the introduction to Ken Rockwell’s earlier mentioned writeup:

Almost all speakers and headphones today are “dynamic.”

 Conventional speakers and headphones stick a coil of wire inside a magnet, and glue this coil to a stiff cone or dome that’s held in place with a springy suspension. Current passes through this coil, and electromagnetism creates force on the coil while in the field of the magnet. The resulting force vibrates the coil, and since it’s glued to a heavy cone, moves the whole mess in and out. This primitive method is still used today because it’s cheap and works reasonably well for most purposes.

 Dynamic drivers are the standard today and have been the standard for close to a hundred years. These systems are cheap, durable and work well enough for most uses, however their heavy diaphragms and big cones lead to many more sound degrading distortions and resonances absent in the newer systems below.

By “newer systems below”, of course, he’s referring to alternative electrostatic and planar magnetic approaches. And although he’s not totally off-base with his observations, the choice of words like “primitive method” reveals a bias, IMHO. It’s true that the large, flat, thin and lightweight membrane-based approaches have inherent (theoretical, at least) advantages when it comes to metrics such as distortion and transient response, leading to descriptions such as “unmatched clarity and impressive detail”, which admittedly concur with my own ears-on impressions. That said, theoretical benefits are moot if they don’t translate into meaningful real-life enhancements. To wit, for a more balanced perspective, I’ll close with a (fine-tuned by yours truly) post within an August 2023 discussion thread titled “Is there really any advantage to planar magnetics or electrostats?” at Audio Science Review, a site that I regularly reference:

For electrostatics, the strong points are the low membrane weight and drive across the entire membrane. The disadvantage is output level. The driver surface area is big, which has advantages and disadvantages. On can play with shape to change modal behavior. Electrostatics are difficult to drive in the sense that they require a bias voltage (or electret charge) and high voltage on the plates, which necessitates mains voltage or converters. Mechanical tension is a must and ‘sticking’ to one stator is a potential problem.

 For planar magnetics, the strong points are the maximum sound pressure level (SPL), linearity and the driver size. The latter can be both a blessing and (frequency-dependent) downside. Fewer tuning methods are available, and it is difficult to get a bass boost in a passive way. The magnets obstruct the sound waves more than does the stator of electrostatic planars, which has an influence on mid to high frequencies. Planar magnetics are easier to drive than electrostatics but in general are inefficient compared to dynamic drivers, especially when high SPL is needed with good linearity. They are heavy (weight) due to the magnets compared to other drivers. They can handle a lot of power. They need closed front volume to work properly.

 Dynamics can have a much higher efficiency, at the expense of maximum undistorted SPL. They can be used directly from low power sources. There are many more ways to ‘shape’ the sound signature of the driver, and the headphone containing it. They are less expensive to make, and lighter in weight. Membrane size and shape can both find use in controlling modal issues. Linearity (max SPL without distortion) can be much worse than planar alternatives, although for low to normal SPLs, this usually is not an issue.

 Balanced armature drivers [editor note: an alternative to dynamic drivers not discussed here, commonly found in earbuds] are smaller and can be easily used close to the ear canal. These drivers too have strong and weak points and are quite different from dynamic drivers. They are easier to make custom molds for due to their size.

In closing, speaking of “balance” (along with the just-mentioned difference between theoretical benefits and meaningful real-life enhancements), I found it interesting that none of the electrostatic or planar magnetic headphones discussed here offer the balanced-connection output (even optional) that I covered at length back in December 2020:

And with that, having just passed through the 2,500-word threshold, I’ll close for today with an as-usual invitation for your thoughts in the comments!

—Brian Dipert is the Editor-in-Chief of the Edge AI and Vision Alliance, and a Senior Analyst at BDTI and Editor-in-Chief of InsideDSP, the company’s online newsletter.

Related Content

• Balanced headphones: Can you hear the difference?
• Microphones: An abundance of options for capturing tones
• Is high-quality streamed audio an oxymoron?
• Earbud implementation options: Taking a test drive(r)
• Teardown: Analog rules over digital in noise-canceling headphones
• Audio Perceptibility: Mind The Headphone Sensitivity

<!–

–>

<!–

div-gpt-ad-inread

–>

The post Unconventional headphones: Sonic response consistency, albeit cosmetically ungainly appeared first on EDN.