Saturday, 30 April 2022

REVIEW / MEASUREMENTS: CCA (Clear Concept Audio) C12 IEM - 1 Dynamic + 5 Balanced Armature Drivers - are more drivers better? (Plus new analogue disc technology, cable-maker Russ Andrews interview.)

Earlier this month, as I was preparing the final write-up for the KZ ZSN Pro review, I was impressed enough by the performance of those very inexpensive IEMs (less than US$25) to go ahead and grab these CCA (Clear Concept Audio) C12 (US$50) earphones to see how an upgrade at twice the price would perform in both listening and measurements. Note that CCA is a related company to KZ so when we look at the open-box image above, we see that the contents are similar. We have this time a braided ear-loop cable (that's still easy to get tangled), also 1.2m in length, a couple of info pamphlets, 3 extra sets of silicone ear pieces, same as the KZ ZSN Pro.

At twice the price of the KZ, the hope here is that these would represent a significant sonic upgrade across a number of domains. On the surface, a major talking point for these headphones is that they consist of a more complex arrangement of drivers which in theory could provide more accurate coverage across the audible frequencies. Drivers in each earphone include a single larger 10mm dual-magnet dynamic/moving coil driver, and 5 small balanced armatures (two of which are reported as Knowles 30095, not sure the others). So that's a total of 6 drivers per ear piece, 12 both sides - hence "C12".

"Professional HiFi" printed on the body.

The ear pieces look similar to the ZSN Pro. As you can see, I have the amber/gold-brushed zinc model here. The construction is good, feeling solid in the hand with the metal and transparent plastic allowing a peek inside. Weight of the ear pieces and wiring is 26gm (0.9oz), slightly lighter than the ZSN Pro.

Connector for the detachable cable is the same as the ZSN Pro - they call it the 0.75mm 2-pin "Type C". Obviously if one tugs too much the cable can detach but so far in use the connections have been secure.

Again, I have the model with the inline single-button play/mute and microphone for use with mobile devices like phones. Like the KZ ZSN Pro, the microphone works well for calls, in general better clarity than wireless headphones that I have tried (including the AirPods Pro and some Jabra Elite 75t). As mentioned above, the wires can tangle quite easily; not sure there's much one can do about this given the design. With the ear loops, the ear pieces are well supported when out for a run, and the wires are only mildly microphonic.

I. Measurements

Let's get to it, here's the "big graph" of data on these earphones, measured with the "average" size silicone ear tips they came pre-installed with:

Starting with the top left, we can see that the frequency response is in some ways (perhaps as expected) similar to the KZ ZSN Pro. It's V-shaped but if you compare this to the previous KZ ZSN Pro measurements (also see below), the main difference is a reduction in the 5-6kHz peak. Notice the reduction in resonant energy as seen in the waterfall plot in the bottom left compared to the KZ as well. Bass response is strong and maintained down to 20Hz and below. In these measurements we see quite a bit of >10kHz content. Most of this I believe is a result of the artificial ear canal of the measurement rig; not an audible issue in actual use. In general, results >10kHz are unreliable when looking at most headphone measurements with artificial couplers. The specs sheet on these earphones state a frequency response of "7-40,000Hz" (no specification around whether this is -6dB) so I assume some of the high frequency bump I'm seeing is a result of these drivers extending the upper range beyond headphones like the single-BA Etymotic ER-4B which I used to customize my target curve with.

The top right graph is the impedance of the earphones across the audio spectrum. These are rated at 24Ω which is essentially what I'm seeing with just slightly over 23Ω from 20Hz-1kHz. Above that, there are some small irregular increases up to 24.5Ω and then above 6kHz, it starts to dip and goes down to about 13Ω by 15kHz. Basically we have low-impedance headphones here and it's recommended that your headphone amplifier has 2.5Ω output impedance or lower. Thankfully, these days, many headphone amps have <1Ω impedance.

Sensitivity is quite high with 107dB SPL/0.1V at 1kHz. This works out to 111dB/mW, which is in line with the spec sheet's 112dB/mW. With this amount of sensitivity, it's easy to drive these headphones to headache-inducing levels. Make sure your headphone amp has very low noise level.

I mentioned the waterfall graph already. This looks significantly better than the KZ ZSN Pro where we saw quite a bit of 6kHz resonance. With this model, while there's still some energy up at 6kHz, -40dB decay overall is better, dropping off by 2ms from 1.5kHz up.

As for harmonic distortion, this is pretty good. At 1kHz, 95dB SPL output, THD is at 0.125% with the CCA C12; this is compared to 0.21% with the KZ ZSN Pro. The "family resemblance" here is the similar high 2nd order harmonics throughout the audible spectrum. Overall, the distortion is still a little bit higher than the more expensive 1MORE Quad Driver IEM previously discussed across the midrange (at around 0.1% THD).

CCA C12 IEMs on the miniDSP EARS.

For another look at some time-domain performance, let's have a peek at the 100Hz Square Wave (95dB SPL at 1kHz level):

No overshoot nor nearly as much ringing at the leading edge of the square transitions we saw with the KZ ZSN Pro. The bass frequency response with these earphones are good and the overall shape is that of a squarish waveform.

I didn't bother testing the leakage or isolation for these earphones as functionally they felt about the same as the KZ ZSN Pro. Overall I would say there's good isolation (enough to attenuate traffic noise a fair amount when walking down the street) and minimal high-frequency leakage in use; maybe not as good as the Etymotic ER-4B with triple-flanged ear tips.

II. Listening Impressions

As usual, I had a listen to the device when it arrived before I stuck them on my measurement rig. As I had commented previously, I don't believe little IEMs need any significant time to "break in". I did not notice any significant change in the sonic character from that first hour of cracking open the box to now, which is daily use over the last 20+ days or so. In fact, I ran some measurements and did not notice anything other than the usual inter-test variation in frequency-response over the weeks.

I like the comfort of these around-ear IEMs. No problem listening to music for hours at a time in the evenings with the phone, laptop or desktop. As mentioned above, be mindful of noisy headphone amps. For example, my Huawei ultrabook headphone output was noticeably staticky. Turning up the volume on these beyond comfortable listening levels did not result in any noticeable distortion.

Compared to its cousin, the KZ ZSN Pro, the sound signature is more refined and notable from the first time I put these on. What is most obvious is that the accentuated, at times excessive (depending on the music) high frequency harshness on the KZ has been tuned down with these. I mentioned for example Jennifer Warnes' "Way Down Deep" (on The Hunter) having an accentuated ringing of what sounds like a triangle strike has now been toned down to more natural levels in line with the rest of the music. Bright sounding albums like Donald Fagen's The Nightfly has become much easier to listen to without the same amount of fatigue as before (although still too "thin" for my taste). Female vocal sibilance was also noticeably reduced through these earphones; for example cantopop star Faye Wong's (王菲) early album Coming Home (DR13, 1992) sounded nicer with less "ssss".

Other than a reduction in the relative high frequency amount, there is a subjective improvement in "smoothness" as well. For example over the years, I've used the sound of the pipa on Zhao Cong's "Moonlight on Spring River" (The Dali CD, Vol. 3, 2012, DR9) as a showcase of "speed" and detail retrieval; you should be able to hear the vibration of each string during the rapid strums (plus the low bass which should not sound bloated or monotonic). There's also a nice decay trail to the strings which subjectively sounds more natural on the CCA C12 compared to the KZ ZSN Pro. As a general recommendation, check out the the series of "Dali CD's" as audiophile test recordings of very high quality - I see they're up to Volume 5 these days.

For those who like their '80s synth pop nostalgia, have a listen to The Future Kids' 80s Dreams (2022, DR6). Yeah, quite a bit dynamically compressed compared to real '80s sound, but the synths used and melodies are certainly very reminiscent of the "decade of excess" - well, the hair was big in those days although price tag for audiophile gear much more excessive these days! I enjoy the track "Remembering" with its syrupy sweetness.

I've seen IEM / headphone reviewers often describing soundstage in their writeups. I dunno guys and gals, assuming that crosstalk isn't an issue (not that I have noticed), I find it hard to discuss this in a review simply because I rarely even hear an actual 3D soundstage with headphones and IEMs! Other than binaural material, most stereo albums (without crossfeed applied) just sounds like it's mainly "in the head" with relative panning right/left and little illusion of the sound being in front, behind or around me. As such, with the good bass extension and not-as-harsh treble, binaural YouTube audio like The Tucker ZoneVirtual Barber Shop, or the Dolby Atmos for headphones demo sound really good with the impression of being in a virtual space.

Although I would describe the sound quality as being very good with excellent clarity and detail, I think there's still an opportunity to improve on the "smoothness". At times, I can hear a bit of "grain" in the treble which seems a little unnatural and I don't hear this on my more expensive headphones like the Sennheiser HD800. Of course, the price differential here is enormous and we're talking about very different technologies.

III. Summary

So then, would "upgrading" from the KZ ZSN Pro to this CCA C12 with even more drivers and at twice the price result in an improvement in sound quality? Yes, absolutely.

US$50 is still a very low price for "high fidelity" playback - a nice example of where price and fidelity do not necessarily correlate strongly these days even if "luxury" and price might! I believe that the sound quality of this earphone is very good and believe will compete with others many times the price in the audiophile and "high end" world. The price increase buys what I perceive and measure as a more "refined" sound compared to the ZSN Pro. The "V-shaped" EQ curve is not as extreme on the upper frequencies, does not sound as harsh; this seems to be correlated with a cleaner waterfall graph, and less ringing in the 100Hz squarewave plot. As such, they're "more neutral" which of course may or may not be what one might be looking for.

I've heard some subjective-only audiophiles claim that "measurements don't matter" or that "measurements don't tell me how something sounds". Obviously this is not true if one has even some modicum of experience with correlating measurements and listening! I find it fascinating how some people (often older magazine reviewers) make comments like this but they seem to have no experience with performing measurements and hearing the objective differences.

To demonstrate, here's a comparison of the frequency response for the 4 IEMs I've measured on this blog site thus far:

As you can see, I've matched the frequency responses for each IEM to be at 95dB SPL @ 1kHz on the graph. The curves represent the average frequency responses for both stereo drivers, with the same custom IEM Diffuse Field target that I typically use.

Looking at these overlays, we can indeed say with good confidence approximately how each IEM sounds once we have some experience using one of them. As I mentioned previously, the Etymotic ER-4B (black, dashed line) is a "standard" for me that I have used for the last 20 years. It sounds smooth, quite neutral in the treble, but as we can see from the graph, it lacks bass extension compared to the others. What is most notable with the 1MORE Quad Driver (green) is the mid-bass hump with relative accentuation between 100-200Hz but doesn't give us the deep <50Hz authority. To be honest, I don't quite like this kind of tonality as much mixed with the relatively recessed mid-range between 1-3kHz as it sounds "warm" but a bit dull and diminishes vocal clarity (hence the EQ I suggested in the review).

The inexpensive KZ and CCA IEMs are examples of the "V" EQ curve which accentuates both the low end and the treble frequencies. Notice that the KZ ZSN Pro accentuates the "Presence" frequencies especially 5-6kHz more than the CCA C12. It is this relative increase that is the cause of the "harshness" and "brightness" described; in comparison, the CCA C12 backs off a bit in the Presence frequencies and even though it's only 2-3dB lower into the "Brilliance" spectrum from 6-9kHz as well, this does make a significant difference when listening.

As for an EQ setting for these earphones, yeah, I guess one could tame the 5-6kHz range with another -3dB and maybe a -3dB high shelf from 9kHz or so. Some pop recordings might sound a bit too bassy on these if you're not a big bass-head; feel free to do something like a 250Hz, -3dB, Q 0.8 low shelf to tame it. Honestly, I'm quite happy with this earphone's frequency response as is so I'm fine with not fussing with anything especially when I'm listening on the go.

Finally then, let's for a moment discuss the question - Are more drivers better? Well, obviously we can't just directly correlate sound quality with "bigger/more is better"! In general, we can say that with more drivers, the device can be fine-tuned by the manufacturer to cover the full range of audible frequencies. How well the drivers "split" the frequency band, and how well they integrate (risk of smearing, frequency cancellation) would be dependent on the company's engineering abilities. And ultimately whether the final frequency response fulfills the desire of the listener's ears/brain would be to some extent idiosyncratic to the user (psychologically, emotionally, and physically depending on how well the IEM fits in the ear).

Having said this, I see that these Chinese IEM manufacturers have models like the CCA C16 (8 balanced armatures per ear piece), the CA16 Pro (1 dynamic + 7 BA), KZ ZAX (1 dynamic + 7 BA), and KZ ASX (10 BA each ear piece). Anyhow, you get the idea! Hopefully with even more drivers, the sound is even better tuned. The only way to know is to listen and test individually. I think the record for most number of drivers is 24 balanced armatures per ear piece - the Ambient Acoustics MAD24 (~US$3000).

I'm good with a US$50, high-value IEM with 6 drivers/ear for now at least. ;-)


In the "What in the world are they thinking?" news file, has anyone heard more about this "New Analog Disc Technology" that is supposedly being introduced by T Bone Burnett with apparently some Dylan content!?

First of all, it's a little odd to have Dylan re-record his "classic" tracks, don't you think? His voice sounds more than a little shot these days so I'm not sure I want to listen or buy re-recorded tracks or versions of material like Bringing It All Back Home, or Blonde on Blonde, or Highway 61 Revisited, etc. Does anyone honestly think there's a need for something better than vinyl, CD, and digital streaming these days?

The fact that they're turning to Dylan suggests the market here is for the old Boomer collector rather than average music lovers. To suggest a new physical music format in 2022 is both silly and at the same time obviously aiming at collectors who might see this as a kind of "investment". Indeed, if we further explore the company NeoFidelity, Inc. and these "Ionic Originals", we see articles like this which is even more direct in linking this concept with being collector's items (even a link to NFT's!?).

Anyhow, I'm guessing T Bone's trying to catch a bit of the vinyl action we're seeing with Record Store Day and the guys lining up to grab unique "RSD Exclusive" and "RSD Limited Run" items. Good luck with that; as a business venture this makes no sense other than a cash grab, unlikely to gain any traction especially if there's also a special type of turntable that one needs to purchase for this.

BTW, this LP-looking disk format is described as "lacquer painted onto an aluminum disc, with a spiral etched into it by music"... Hmmm, isn't this literally the description of an LP lacquer? The kind of stuff some vinyl collectors like to own but never really play because of fragility? Regardless, there's absolutely no way this kind of physical medium would be better in sound quality compared to CD (frequency, time, noise level, and distortion domains), just as vinyl is not equivalent in resolution. Let's not kid ourselves, there is zero chance that this is "the pinnacle of recorded sound"; the laws of physics have something to say about a spinning disc with "spiral etched into it by music".

T Bone's description of the sound is classic nonsense similar to Neil Young's anti-digital rants back in the day. A quote from the article:

“Analog sound has more depth, more harmonic complexity, more resonance, better imaging,” says Burnett. “Analog has more feel, more character, more touch. Digital sound is frozen. Analog sound is alive.”

This analog vs. digital divide is a bit silly anyways because all "sound" is analog ultimately. The difference is whether the resolution of the source is any better. And in that regard, for high fidelity, digital data trounces analogue media any day if we're comparing the same source mastering. Yeah, I know, some people will still like the playback of vinyl which has gone through various RIAA EQ transformations and the distortions the system adds. T Bone at one time championed the ill-fated XOΔE (CODE) digital format back in 2008 with Mellencamp's Life, Death, Love & Freedom (2008, DR9) I think being the only album in this "format" - basically DVD disc with hi-res 24/96 stereo content, "virtually indistinguishable from the original master tapes" and with "resonance, warmth, and presence... unprecedented in the digital era". (Here's an interesting article with a bit more detail on CODE.)

Anyhow, I kept looking at those articles to make sure this wasn't some kind of April Fools joke! :-)

Saw this patent link on AudiophileStyle (noted by Iving) with Joseph Henry "T Bone" Burnett's name on it. "Methods and Coatings for advanced audio recording and playback" (US Patent No: 10,629,227, April 20, 2020). Looks like basically a lacquer with hardened coating applied on it; described as quartz, sapphire, or diamond-like carbon over the aluminum + nitrocellulose cut lacquer disc.

Couldn't resist, here's the "money shot" of the benefit from the hardened coating:

See... Even analogue LP-type technology must be objectively verified for playback fidelity and not just subjectively designed "by ear". As in this spectrogram assessment. ;-)

As we know, every time an LP is played (especially lacquers, less resilient than vinyl), there will be accumulation in degradation. This is what we see in the 203rd pass in the figure on the left. They're showing that the hardened coating (right) maintains playback quality even after 203 passes/playbacks.

Reminds me of the harder Durabis scratch-resistant surface layer used with Blu-Ray discs compared to the easier-to-scratch polycarbonate CD and DVDs. Optical discs don't have contact with a read head so this is even more important with a physical medium like an LP lacquer and the needle that glides over the grooves! Wonder if similar coating technology can be applied to vinyl to make them even more durable? (BTW, did the Blu-Spec CDs also use Durabis polymer?)

Will be interesting what the final product is like, assuming this comes out, and whether it follows closely to the "embodiment" of what's described in this patent. I would be very surprised if this thing isn't basically compatible with LP playback turntables (33.3/45 rpm), phono cartridge, and RIAA preamps! Can't imagine anyone wanting to create a whole new (likely expensive) playback ecosystem in the 2020's!


SuperKord Signature + Andrews running measurements.

Finally, to end, I just wanted to repost a comment I made on the Steve Hoffman Forum; a discussion on cables (yet again). I know that these discussions over the years tend to get shut down and sometimes even scrubbed even if things don't get too argumentative. This comment was made in response to yet more talk about power cables, how supposedly companies like AudioQuest "voice" their cables, and more specifically about this "interview" with cable maker Russ Andrews:

Suppose for a moment that in fact cables (say power cables) are meaningfully "voiced" by the manufacturer. And that it made a big difference. Why are the manufacturers not also providing recommendations for users on the kinds of systems they should try pairing the cables with?

I have never seen recommendations like - "The Everest" should be paired with amplifiers capable of >200W output... "The Fuji" is meant for ~100W amps. Then you can try "The Mitchell" for low-power <10W amps.

Obviously this doesn't need to be correlated with power output. Maybe something else like Class A, A/B, D, digital source component, analogue source, etc... Or maybe length of wire you might need.

Point being, if there is something rational about this and the manufacturers are indeed tweaking something worthwhile instead of just providing "luxury" products that might be meant to look good with fancy claims like geometry and conductor material, wouldn't it be good for consumers to be aware and make informed choices in line with the tweaking?

Otherwise, it's just about price tags, appearance, and trial-and-error with the eyes/ears of faith.

So Russ Andrews in his interview (linked above), there's a picture of him with an oscilloscope "measuring a cable's performance". Wouldn't it have been nice for the interviewer to have just asked him "So Russ, what are you measuring there so I can explain this to my readers?" I think the answer would have been way more interesting and useful than knowing that he sold "55,000" power cables or that he likes rock climbing.

He quotes Feynman: "If you can't explain something on one side of a sheet of paper so that your grandmother can understand it - you don't really understand it yourself." I'd like to see him try explaining how his power cables can make a big difference based on this claim - like that SuperKord with the wooden thingies.

One more thing - "My 10% rule is that you should spend 10% of your budget on the electronics and 90% on the infrastructure to get the very best out of it!" What's that supposed to mean? If it's spending 90% to buy a house with a good sound room, maybe that's OK. I certainly hope it doesn't mean we're supposed to hand 90% over to him for some unsubstantiated "infrastructure" power cords?! Seems more than a little... unwise...

Guys, IMO, these are not serious "journalists" writing articles, nor are these serious manufacturers with actual products based on "sound" R&D.

Some audiophiles seem to love their esoteric "heroes". Articles like these seek to glorify the knowledge/experience/abilities of guys like Andrews. Without actual substance in articles of this nature to suggest that Andrews is producing anything of special value, I think the reasonable audiophile should be cautious, recognizing that the only reason this article exists is to put the name out there for advertising purposes. Notice that we have learned nothing at all about these cables when reading the article!

Over the years, I have seen other unusual audiophile websites like this Notice in the article that there is no publication date, and no author attributed (not even a pseudonym). All we are told in the "About" page for the site is that this is "India's first technology blog dedicated to audio."

This article feels like it's coming from a "fake blog", a "flog" or "flack blog" created by a company acting as marketing - in the case of this article, for Russ Andrews and his products, appearing as if from an independent source. From my perspective, mainstream audiophile media mainly exists in the service of advertising products to consumers anyways. I guess a "flog" is just as direct a method to get straight to the infomercial advertising without making any pretensions that a certain respected "golden ear" performed the interview and the lack of a publication date I guess just makes the article "timeless". Not much difference between this kind of stuff and, IMO, Michael Lavorgna's hyped vacuousness at Twittering Machines as a contemporary example.

Take care audiophiles... Remember that 50% of all Internet transactions these days consist of non-human agents ("bots") and then there are fake reviews (some have suggested up to 60% Amazon reviews fake!). There's a lot of artificiality out there which I think also includes many levels of "manufactured content".


  1. There are reports in the web saying specially these two mfr with IEM with 3 or more driver saying that only one or two really are connected and the rest of 3-4 driver are glued and not emitting sound.

    1. Thanks for the note Read,
      Interesting and would be highly fraudulent if so! This is something that will need a good 'ol "teardown" of the ear piece to see and measure what's going on!

      I see this interesting article with ongoing discussions on this issue and various earphones:

      Will be good to see how this shakes out! I think it is important to remember that measurement rigs have significant limits as well and subtle differences may not be clear. Best to somehow isolate each driver and look at their frequency response individually to be clear if they're making sound and how much. Not an easy job for the hobbyist given the small size!

  2. Agreed that there is a lot of audiophile crap being peddled out there. Interestingly, more "angry" audiophiles are coming forward in an attempt to knock some sense into long-time audio cultists.

    Here is a guy who is more of a "common man" ranting about the crap he's been putting up with. No audio science or fancy charts here folks, it's just an angry guy who's come to his senses and not drinking the Kool-aid anymore. I actually find him quite hilarious. He goes by the YouTube handle "cheapaudioman" and has that affable blue-collar and half intoxicated demeanor in contrast to the more academic posturing of Audiosciencereview and this blog site.

    1. Hey there AudioPhil,
      Oh yeah, the Cheap Audio Man. Hilarious dude.

      Yeah, a broad-based recognition of the silliness of the beliefs and myths of audiophilia is important. At an academic level, clearly the audiophile snake oil will not fly among researchers. Technical audiophiles like on ASR and here have been increasingly aware of the lack of evidence for much of the silly claims for years and building a case with measurements. And good to see a general no-nonsense attitude permeating to the general audiophile audience like this.

      Still lots of work to do I think but over time I hope the attitude of being able to show critical thinking, and be open about this in public forums and comments will serve the hobby well.

      Of course some manufacturers and certain magazines might disagree about such alternative voices!

  3. Assuming the drivers are actually connected... Is there an electronic crossover of some kind?

    1. When I read the article cited above, I saw that there is a crossover network of some sort.

    2. Hey guys,
      Looking at the boards on those pictures, appears that these are just SMD resistors changing the relative voltage going to the various drivers in order to control frequency response. Doesn't seem to be true crossovers but rather taking advantage of the relative FR for each type of driver they incorporate into the IEM.

      The advertising material for the C12 seems to suggest that the 5 BA's in each earpiece consists of a single 30095 mixed with 2 pairs of presumably custom drivers that subserve "mid" (maybe something similar to the Knowles 29689) and even higher frequency drivers.

      BTW, if we look at the FR of the 30095 (here:, we see that it naturally has peaks around 5kHz and 13kHz. Maybe the custom BAs are there to complement some of the valleys to smooth things out compared to the KZ ZSN with its single 30095 without accessory BAs.

      Anyhow, just speculation on my part without input from the manufacturer or a proper teardown to have a good peek. As with most things, it's probably best not to get too "greedy" with the number of drivers we ask for and more/bigger isn't often better. ;-)

  4. I thought that one of the advantages of headphones is that it's possible to use a single driver that covers the entire audible range without serious compromises. Being the objectivist that you are, you should be asking for measurable evidence that the use of multiple drivers confers real advantages. I don't think that the fact that the CCA isn't as bright and harsh as the KZ counts. The single-driver Etymotics are also less bright.
    It's possible to make a really good case for multiple drivers in loudspeakers, but I'm not at all convinced that there's a compelling case for multi-driver headphones.

    1. Hey Errant,
      Yeah, would certainly be great to have a single driver do it all. A driver that can achieve the full FR evenly would be ideal as well in the time domain. Alas, not sure this is achievable to find a single driver of such flat response with low distortion across the spectrum. Also, my feeling is that subjective preferences such as adding a bit of bass boost are important for consumers which again probably makes some kind of multi-driver system necessary.

      Of course we can achieve frequency changes with EQ but it's an extra step for many consumers who will not bother... Plus "hard core" audiophile purists will have their opinions on using EQ/DSP.

      Certainly not saying we need anything more than maybe 2-4 drivers to achieve adequate tweaking; but I can see the power and benefits of doing so in the service of preferred FR.

  5. There are a lot of single-driver 'phones on the market, using a number of different technologies (dynamic, electrostatic, planar magnetic, balanced armature). Seems to me that at least some of them achieve a reasonably flat response (or a response that closely matches a reasonable target) and low distortion over the audible range.

    For loudspeakers, of course, it's a completely different story.

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