Electroacoustic Measurements & Technical Analysis
Editor’s Note: Once again, we’re indebted to speakerphone’s @farbic amazing work. We spent a good number of hours discussing and troubleshooting measurement artifacts, in addition to discussing technical details. This effort, though, would not have been possible had it not been for DUNU‘s incredible support, providing us with two different copies of the DN-2000J to perform analyses on, as well as affording us absolute full reign over our test parameters. They want to gain as much constructive criticism from us as they can, whether it be with respect to sound signature tuning or quality control. This type of forthcoming attitude is to be applauded and set as an example to all manufacturers in the audio industry.
Once again, all measurements follow an acquisition protocol as close to IEC 60268-7 as possible. While insert earphones are normally to be used at the reference plane of ear simulator couplers, the DN-2000J was placed at a “realistic” distance away from the reference plane — about 5.8 mm. This ensures a practical response of ear canal resonances for most ears, given the larger diameter housings of the DN-2000J. Please bear in mind that, as with all ear simulator measurements, these results are only a representation of what can be currently modeled with current methods.
Left and right channels are well-matched, almost always within ±0.5 dB of one another, and mostly inside of ±0.2 dB. Our first test unit exhibited a ~4 dB bass response mismatch at 20 Hz in the right channel, accompanied by increased overall harmonic distortion (mostly due to increased 4th order harmonic distortion), suggestive of a partial blockage of the pressure excursion vent, as channel matching above 200 Hz was near perfect (within ±0.2 dB). Through lengthy discussions, DUNU decided to send us a second test unit, which tested without any mismatch issues.
The first resonant peak has a locus of approximately 3.2 kHz. Traditionally, earphones have had a large, broad peak centered between 2.5-2.7 kHz, in order to compensate for ear canal resonance, but it is also well-known that the loci of peak canal resonance differ from person to person, deviating between 2.5-3.5 kHz. Thus, it should still be acceptable for most people. Depending on the style, depth of wear, and choice of ear tips, this first resonant peak may also shift slightly.
The DN-2000J takes on a distinctively U-shaped sound signature response — moderately boosted lows, centered between 80-125 Hz, and boosted highs. This is a common acoustic treatment for earphones that attempt to adjust for Fletcher-Munson volume thresholds, making the DN-2000J especially good for low volume listening. As noted in our review, the DN-2000J does sound especially remarkable at very low volumes.
This type of U-shaped tuning is especially apparent when target equalization is applied, either for Diffuse Field or the Harman International target by Drs. Sean Olive and Todd Welti. When the bass extending silicone ring is applied, the bass of the DN-2000J is nearly on par with the Olive-Welti target curve for flat equalization below 200 Hz.
The treble response, however, is contrary to perfectly linear, and may pose problems for users that prefer smooth highs. The main treble resonances are deemed to be too strong when normalized to a equalization target such as the Olive-Welti target curve.
However, bandwidth on the DN-2000J is quite good, reaching most targets end to end.
Effects of Differing Ear Tips on Perceived Response
Being the first DUNU product to actively advertise a strategic partnership with Comply Foam, the DN-2000J seems to have been designed for these tips, taking advantage of foam tips’ tendency to smooth out peaky treble. With Ts-500 foam tips, the DN-2000J is smoother across the board, de-wrinkling most issues people might have with the capricious nature of the TWFK tweeter response. It does sound a little more prosaic as a consequence, but for long-term listening, I wouldn’t hesitate to recommend a pack of Comply tips to any individuals wishing to use the DN-2000J for longer listening sessions.
The plethora of ear tips included yield slightly different measured responses in our measurement tests. While the silicone ear tips mostly yielded identical results (more later), the different Comply foams yielded some surprising results. Surprisingly, the T-500 tips managed to attenuate treble even more than the Tx-500. The circular Ts-500 tips attenuate treble the least. All the Comply tips seem to smooth out the response of the treble, lessening resonance peaks.
The final resonant peak is attenuated a lot more greatly than is the resonant peak at 6.5 kHz, correlating with the subjective experience that the Comply foam tips control harsh treble and sibilance. The resonant peak at 6.5 kHz also shifts downward in frequency, suggestive of an improvement in sibilance control while maintaining clarity.
The measurements also show that absolute bandwidth decreases with Comply foams, but the subjective experience a posteriori doesn’t corroborate these findings. The different silicone tips, made largely of the same material, hold the frequency response similarly.
However, there are signs that the tips have differing resonant frequencies, as shown by the bass artifacts that show up. Although the effect was not measured, I found that wide bore, bi-flange silicone tips also tend to help facilitate both insertion depth and resonant peak smoothness.
Effects of the Silicone Ring on Bass Response & Spacer Rings on Treble Response
The silicone bass rings included with the packet are intended to raise the bass extension of the DN-2000J, at the expense of driver flex (caused by the inability for the earphone to equalize pressure between the sealed interface of the ear canal and the rear chamber of the earphone).
While the rings clearly show improved bass response below 250 Hz, increasing approximately +4 dB at 100 Hz, +6 dB at 50 Hz, and +8 dB at 20 Hz, the subjective experience suggests a more sluggish sounding bass response compared to the response sans occluded vents.
Spacer rings are a carryover from both the DN-1000 and DN-2000 — originally intended as novel means of solving fit issues some people had with wider housings, they also modify perceived treble response on the principle that residual ear canal volume affects resonant quarter-wave frequencies in the treble region.
As measured, with the spacer rings lower the final resonant peak indicative of (approximate) treble extension by a minor amount, but seems to affect other frequencies in relatively minor ways. Perhaps the most pronounced effect would be that the overhang of the ear tips is increasingly greater, but ear tips’ effect on frequency response is not convincingly measurable given our current testing methodology.
Measurement Artifacts with Differing Ear Tips
When measured with translucent, white, frosted silicone tips (red trace), there is a distinct bass artifact centered at around 150 Hz, while the foam-less grey silicone tips (blue trace) exhibit a similar one closer to 200 Hz. The foam-filled (for isolation) grey silicone tips (green trace) do not exhibit any artifacting.
The figure below zooms in on the region in question:
We have a possible explanation for these artifacts: sound waves are longitudinal waves, and are therefore subject to interaction with compliant materials such as silicone ear tips. The pulsatile response of sound waves will “bounce back” and create a distinctive pattern when earphones are measured inside an IEC711 coupler (and perhaps others).
The best analogy for this phenomenon would be in the human circulatory system. The aorta, the largest artery of the human body, is composed largely of elastic fibers that serve to provide the circulatory system a “reservoir” of sorts to buffer the flow of blood across all tissues of the body — a phenomenon known as the Windkessel Effect. Reflected blood flow will impress on the aortic semilunar valve and create a “dicrotic notch” very similar in pattern to what is shown here.
Thus, it’s reasonable to assume that the artifacts seen in our measurements are manifestations of destructive/constructive bounce-back due to varying elastic compliance of tips of different materials and shapes. It’s furthermore reasonable to surmise that silicone tips of different varieties (which a multitude of companies sell aftermarket) will affect users’ sonic experiences considerably.
We recommend any and all users to continually search for the best pair of tips for their personal ear size/shape, but also for tips of varying materials, as they may very well impact sound quality, both negatively and positively. At the same time, ear tips size and wear depth factors to be a much more significant variable. As we tested larger-sized ear tips that forced an increasingly shallow position in our ear simulator with respect to the reference plane, we noticed the expected downward shifts in quarter-wave resonances for treble frequencies.
Electrical Impedance & Source Matching
The DN-2000J is probably one of the lowest impedance earphones on the market currently in existence. Measuring at just over 5.5 Ω at the low end of the audio spectrum, it rises to just over 6 Ω at 1 kHz and to only about 11 Ω even at 20 kHz.
With such low load impedance, the DN-2000J will be ironically a dramatically challenging load for most headphone amplification sources, despite its high sensitivity. While it would take very little voltage/power to get the DN-2000J up to listenable volumes, expect the earphone to require great transient control, thus demanding a source that delivers adequate current swing.
We also suggest an amplifier of very low output impedance for the finest damping control over the bass driver, as the frequency response will drift by about +1.5-3 dB in the upper midrange and treble frequencies when 5-15 Ω of extra serial resistance is added to the output amplifier.
Luckily, the change won’t alter too much from there; even with an extra 400 Ω of serial resistance, the DN-2000J deviates by only a maximum of an extra 2-3 dB — no small amount, but nothing serious to write home about.
Perhaps because of the immensely low impedance (probably a little too low) voice coils of the dynamic and balanced armature drivers, the THD response of the DN-2000J isn’t as clean as we had hoped, but is still pretty good in the grand scheme of things, and is by far the least distorting hybrid design we’ve seen aside from the AKG K3003.
We’d be more concerned about THD variance from unit to unit, as the two we received and tested exhibited fairly different results, though both were never in the realm of danger for audible distortion, even under loud conditions. The subjective experience is certainly not hurt by these readings, as the DN-2000J is one of the most cleanly resolving universal-fit IEMs we’ve ever had the pleasure of experiencing.
Cumulative Spectral Decay (CSD)
From the CSD plot, we see that the treble contains typical ringing of the TWFK driver. We’re not thrilled with it, but it’s expected from anything sporting that driver family.
The more important area to notice is the bass — nearly all of the bass decay is neatly confined to frequencies below 250 Hz, with the DN-2000J‘s gentle mid-bass hump decaying away fairly quickly and giving way to sub-bass decay. These results hint at what we’re hearing from the truly excellent bass characteristics of this earphone.
Like the 911 Turbo meeting Godzilla on the proving grounds of the Nürburgring, the AKG K3003 has met its East Asian counterpart in the DUNU DN-2000J. At an MSRP of $349 USD, the DN-2000J has made true flagship-level hybrid sound available to the public at way under $500.
At the time of its release, the $1299 AKG K3003 was widely considered “overpriced”, but even its harshest critics (like me) pegged it at least at a value of $799. That the DN-2000J comes very, very close to the performance of the K3003 in the midrange and treble, while noticeably surpassing it in the bass — for less than half the price, no less — is nothing short of astounding. DUNU should be very proud of what they’ve accomplished; their ability to create such advancement in performance at the $350 price point is nothing short of astounding. If you’re a “clarity head” or anyone who craves immense levels of resolution, the DN-2000J is basically a no-brainer purchase.
- Flagship-level bass and overall sound quality for $349
- Retains resolution and clarity even at very low volumes
- Improved fit and well-rounded accessory kit
- Brighter, analytical, resolution-driven sound signature won’t please everyone
- Some may perceive treble to be harsh
- Extremely low impedance, will be very picky with sources for hiss/hum/rub/THD/IMD
Special thanks goes to the incredible support of Mr. Hsiao and Mr. Wu of the DUNU team in their New Taipei City office; without their many hours of assistance and accommodation, we would not have been able to test the DN-2000J so early and so extensively, both subjectively and objectively.
Furthermore, we thank DUNU for their extremely forthcoming attitude and willingness to troubleshoot technical snafus, regardless of how small they were. Their investigative, assiduous spirit will only enable them to raise the bar on their future products ever higher.
For more information about the DUNU DN-2000J, please visit:
About Mr. T
Mr. T is an in-ear fanatic by day, and writes SOAP notes by night. He pities the fool who actually has the patience to read through his stuff. (Full Author Bio)