Fit and Comfort

The HarmonicDyne P.D.1 comes with several ear tip options, but they are all silicone tips. Seen above is the right ear bud installed with the size M Type A and B tips inside an artificial ear mold, which works well in representing my own experiences. The Type A tips are softer, so they can be more conducive to going in at a weirder angle if need be. This means the Type A tips are more universal in that regard, but if the Type B tips fit you, they will likely do the job better. I found the Type A tip flange just as easy to fit into the ear canal as it was to have folds in the middle, which can disrupt the seal. HarmonicDyne recommends the Type A balanced tips in general, but the size M Type B tips were my go-to for listening here. I suspect a nice set of Comply foam tips would prove handy with these if foam tips work well for you. The design of the P.D.1 is also fairly comfortable owing to the ergonomic design and average size, and the 6.5 g mass per ear bud without the cable also helps with longer sessions. The use of four vents adds to this, which does not interrupt the seal much but provides for ears that don't get too hot either. Passive isolation could be better, and perhaps this is where foam tips will benefit you further.

Audio Performance

Audio Hardware

I have a few bones to pick with HarmonicDyne/Linsoul, but one of the biggest ones is the complete lack of details when it comes to the audio hardware used with the P.D.1 on the product page. I had to rely on the badge that comes with these IEMs for more technical details, which of course I only knew since I had the sample already. This is why reviews come in handy, even if solely for such information. Funnily enough, third-party vendors provide more information about the P.D.1, including HiFiGo, as seen here. Marketing and product awareness go a long way, especially for this hybrid driver setup that is far from the norm, too. Indeed, the HarmonicDyne P.D.1 uses two different drivers but not the usual combination of a dynamic driver and a balanced armature driver. Instead, the P.D.1 uses a 10 mm custom dynamic driver with a diamond-like carbon (DLC) diaphragm with a carbon nanotube coating on the edges to handle the bass and upper mids, I'd imagine. Then there is a crossover to a 10 mm planar magnetic driver associated with a high magnetic flux magnet system for the mids and highs. This is quite intriguing and left me wanting to know more. For those more curious about planar magnets in IEMs, refer to my review of the Audeze Euclid.

Driving these won't take much power since these have a rated total impedance of just 16 Ω @1 kHz. I will give HarmonicDyne props for actually providing useful parameters here, including the sensitivity and THD rating, also measured at 1 kHz, and using appropriate units—in this regard, ThieAudio can learn a lot. Speaking of units, people may look at the 110 dB/Vrms sensitivity and expect the P.D.1 to be highly sensitive, but it in fact works out to 92 dB/mW, which is slightly under average for IEM sensitivity. This means the P.D.1 will benefit from an amplifier, and a portable DAC/amp or even dedicated DAP might be nice to have on the go, especially with the lack of a 3.5 mm jack on most phones today. If not on the go, space is less of an issue, but the cable length at 1.4 m might be a potential handicap if connecting to a PC as the audio source. HarmonicDyne also rates the frequency response to be 10 Hz–40 kHz, but good luck making use of that!

Frequency Measurement and Listening

I will mention that I have a general preference for a warm neutral signature emphasizing a slightly elevated bass and smooth treble range with detailed mids and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that ear buds can feed into enough for decent isolation similar to real ears. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through the sound card. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/6th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the ear mold that fits to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry and not just the audio coupler by itself. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the HarmonicDyne P.D.1, or at least the useful part of it. The left earbud was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how the two channels are pretty much spot on most of the way through the bass and mids. There is a weird dip past 1 kHz in the right channel, which is not a measurement artifact, and then things once again are consistent before the roll off the cliff in the highs. This is of course considering that the IEC711 isn't all that reliable at higher frequencies, but the difference between the two channels can't remotely be called an issue compared to the actual one. But before we get there, I will also mention that there was no discernible break-in period or effect, so there is overall good reproducibility and consistency since the average response for each channel is basically the same across the three repeated tests.

"We wanted to present a sound that was both accurate, and musical yet natural, HarmonicDyne has uniquely tuned the P.D.1 to provide a soothing experience with good sparkle and energy. The pair produces a natural bass response with lovely full-bodied vocals and smooth well-extended treble frequency response."

This is a quote straight from HarmonicDyne on the P.D.1 tuning, and I want you to remember it because the actual product experience unfortunately does not back the marketing talk. I am not going to mince words here—the HarmonicDyne P.D.1 has overall poor tuning. Let's dissect things further, shall we? The 10 mm dynamic driver indeed caters to the lows with a pretty good bass response for those preferring it. There's a clearly elevated response going down from ~200 Hz itself, and it continues upward to allow for rumbling sub-bass with detail retention. Mid-bass hits equally hard, especially with EDM, but bass guitar notes in funk and soul music do get hurt somewhat. We then get to a relatively smooth transition into the upper mids to where things things are still quite good. Male vocals are on the warmer side, but this can benefit some genres, including country music, if you wanted more energy. But "full-bodied" is certainly not what I would describe the vocals as here, and instrumental mixes unfortunately get muddy and hazy to where imaging is also fairly poor.

There is decent range in this otherwise U-shaped signature to theoretically allow the mids to shine. But I suspect a combination of the micro-planar driver and tuning is to blame here. If you have seen other IEMs described as "colored" in the sound signature and were not sure what it meant, listening to these will clarify it. A significant veil is added over what could be recessed tones in some segments, but accurate and and neutral it is not. The further you go past ~1 kHz, the stronger this blanketing effect gets. I don't know what is going on at that 1–2 kHz rise, but it gets really bright and shouty there, so much so that you will go from a veil draped over vocals and some instruments to suddenly energetic responses for female vocals and a loss in clarity. In fact, some female vocals sound deep because of the dark treble energy here. I am not an audio engineer and won't pretend to know how to set micro-planars up for a neutral response, but this is clearly not the way to do it. The inner ear resonance compensation also gets fatiguing before things roll off a cliff in more ways than one. There's really no extension in the highs, which made me laugh when I read of a well-extended treble frequency response in the quote above. It is a sad laugh, though, since HarmonicDyne sets the bar really high with the packaging, unboxing, accessories, and ear bud build quality before there is a big let-down where it matters the most.

I will give credit where it is due—in addition to the good bass response, the P.D.1 has a sufficiently wide soundstage. You can indeed close your eyes and imagine being in a recording room with instruments playing, it's just that those instruments don't get dealt the justice they deserve here, and the lack of good imaging hurts further. HarmonicDyne needs to get an EQ profile out as soon as possible, with some effort capable of improving your listening experience a good amount before scaling becomes an issue. I was originally thinking of which other IEMs to compare these to for a further discussion, but pretty much all other IEMs I have that cost as much or even less in some cases end up being a better listening experience fairly consistently.