Fit and Comfort

Seen above is the Ploopy headphones placed on a mannequin head, to help show how these headphones would look on the human head. Note that the head is slightly under average sized, so account for the discrepancies accordingly. As with all headphones, getting a good fit and seal is crucial, so make sure to properly use the headband for vertical sizing in addition to the swivel/rotation of the ear cups themselves. This section is mostly a summary of the points expanded upon in more detail on the previous page and I should say right away that the Ploopy headphones are far larger than the average set of headphones, and I have reviewed some massive headphones already! Some of this has to do with all the smaller parts that come together with screws and pins meaning there has to be some tolerance accounted for throughout. You might also be expecting this to be on the larger side once you found out this uses planar magnetic drivers but in practice those drivers are relatively tiny compared to the usual suspects. Ploopy also lists the mass of these headphones at 420 g and my unit weighed in at 413 g—close enough. This ends up being one of the lighter headphones for its size thus thanks to the use of 3D printed plastic and foam. It's also quite comfortable owing to the use of that oversized plush headband and the ear pads having plenty of room to accommodate even larger ears easily. That side, I would have liked the clamping force to be higher. Those with smaller heads may end up having seal issues even with the smaller headband.

Audio Performance

Audio Hardware

If you are contemplating making one-off headphones yourself, it's generally considered easier to make your own planar magnetic headphones compared to, say, a dynamic driver set. The latter is easier to scale up once you have things set up but it should not be surprising then that Ploopy went this route for its headphones. Given also the need to keep everything open-source, these headphones use parts that can be readily made/found in the future too. For example, the actual diaphragm here is just a flex PCB with traces already etched on it. It's extremely thick compared to your usual ultra-thin planar diaphragms and quite small in size too, this is why the Ploopy headphones are so hard to drive due to this low sensitivity driver. The flex PCB is glued in place to a driver jig and foam applied to keep it protected on the ear pad side. The magnets are six bars glued together again and placed behind the driver such that they sit in the recess of the driver jig seen in the middle photo above. The various parts are listed on Github but it will be easier to get Ploopy's kit and assemble yourself if you are short on time, or simply get the pre-assembled version as I did which at least gives you a higher probability of having similarly tuned drivers on each side. Ploopy does not share any driver specs but I measured an average impedance of 20 Ω for both sides, which is fairly typical for such planar magnetic drivers, but then an ultra-low sensitivity of <= 70 dB/mW. In fact, I ended up getting a spare driver to play around with and that came in at 67 dB/mW. Either way, even if you give Ploopy the benefit and say every driver gets as loud as 70 dB per mW fed, things are not as simple as just finding a DAC/amp that can give you a few mW at 20 Ω. As you will see soon, the driver modes and resonance are so high that EQ is almost a must. This in turn involves needing a preamp negative gain to avoid clipping and distortion which means there is now a higher impedance in place and the drivers need a lot more power to get audibly loud.


This is where the provided DAC/amp comes into the picture. It's considered part of the Ploopy headphones, for all intents and purposes, and the Raspberry Pi-based system is automatically recognized by Windows as an audio source that can output 16-bit 48 kHz stereo sound. It's not the fanciest DAC in the world by any means but, as is the trend in this article, it does the job well enough in this regard for someone who simply wants a working solution.


In addition to working as a DAC/amp for the headphones, the board also gets support from Ploopy community member George Norton. His toolbox, also on Github, is the easiest way to play around with the EQ filters already on board. Depending on when you get these headphones, it may or may not already have the latest firmware but it's easy enough to find the firmware of your choice and flash it using the toolbox or via a forced bootloader mode as explained on this page. Keep in mind that the firmware releases have been coming up frequently and the toolbox itself is still in a beta stage.


The toolbox gives you a visualizer for full parametric EQ, which is quite neat considering how easy it is to tinker around and upload to the board. Once done, it is the new firmware saved on the DAC/amp and presents that EQ to anything connected to the 3.5 mm output. The issue with using this with other headphones is there is no easy gain or power setting, let alone volume, so you may end up damaging the drivers of other, easier-to-drive headphones. On the other hand, this DAC/amp board isn't the best fit for the current firmware of the headphones anymore, at least in my opinion. You will see below how the Ploopy headphones are tuned directly and the older EQ that was shipped on the DAC/amp board. That was a far less demanding preamp and the headphones got to 75-80 dB at most even then. With the latest firmware, I can barely get it to 60-65 dB at the ear gain and I urge Ploopy to re-design the DAC/amp board with more powerful op-amps sooner than later.

Frequency Response 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 current headphones test setup uses a set of two custom in-ear microphones for the two channels. These microphones closely adhere to the IEC711 class, but have been tweaked to be more reliable in the >10 kHz frequency range, the precise issue with my previous setup, that is otherwise still very good and will continue to be used for IEMs and earphones. Two soft silicone pinnae are installed on the sides, separated by a distance matching my head, and multiple "height" adapters have been 3D-printed for further customization, based on fit, head size and shape. Each set of microphones has an XLR output I separately adapted to 3.5 mm. I first used a transparent source—the FiiO K9 Pro—which has enough power to drive the headphones and help me measure the raw frequency response before I used the DAC/amp board with the various different EQ-based firmwares tested separately. This artificial head simulator feeds the microphone lines into a reference USB sound card, which in turn goes to a laptop that has ARTA and REW running. I begin with an impulse measurement to test for signal fidelity, FFT to test for headphone seal, 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 1/12th setting, netting a good balance of detail and signal to noise ratio. The default tuning was used for testing, and no app or program-based EQ settings were chosen, unless specifically mentioned. Each sample of interest is measured at least thrice with separate mounts to account for any fit issues, and an average is taken of the individual measurements for statistical accuracy.


As per usual, you can find my headphone frequency response measurements on VSG.squig.link, along with all the earphone measurements. Scroll to the bottom and choose different targets there, including two from Harman Kardon, developed after years of R&D. The Harman 2018 over-ear target in particular is a reference curve many headphone makers aim for now, but I find it too bass-boosted—especially for open-back headphones. As such, I am opting for the Harman 2018 curve with the bass target from the Harman 2013 curve, which is what is being referred to as the "Harman Combined" target there. Before we get talking about the sound signature of the Ploopy headphones, I want to first talk about the channel balance achieved here. You will notice how the left and right channels are extremely close to each other all the way from 20 Hz to 20 kHz, which is the region of interest for human hearing. I did not pick up any channel balance when I first listened to the set before measurements were taken and I still don't perceive anything after seeing the well-matched measurements here, which isn't surprising given the drivers were assembled on the same day by the same person using the exact same parts and methodology. This is also why Ploopy says there is no warranty support for driver mismatch or a different frequency response from the published one if you go for the kit since there are so many variables involved there. I will also mention that using the headphones for ~30 hours didn't change anything either for those who would undoubtedly be curious about burn-in.


At this point I should mention that Ploopy sent over a sample each to me (for review) and audio community member Oratory1990 who works in the industry and maintains a very helpful collection of frequency response measurements done on an industry standard rig as well as EQ profiles for all of them to fit the Harman curve. For headphones, this means the Harman 2018 over-ear target which I mentioned above isn't my preference for open-back sets such as the Ploopy headphones. The latest non-beta firmware release (PM16) does EQ the Ploopy to the Harman 2018 OE target if you do want to try it out, but I am more partial to the PM12 firmware that I helped develop and is more compliant to the combined target. It's also an 8-band EQ setup rather than the 15-bands on the newer one which can be slightly more taxing on the microcontroller in the DAC/amp board, but the good thing is it's quite easy to try out the different firmware/EQ options and see what works best for you. I actually ended up testing the Ploopy headphones on a variety of different settings, including as-is without the DAC/amp board (no EQ) out of the FiiO K9 Pro ESS where it actually triggered over-current protection when I tried to get it as loud as possible for distortion measurements—the first time this has happened! PM11 is the default firmware that shipped on the board which relied on Ploopy's MiniDSP EARS measurements and a relatively simple EQ profile—you can see how it's still quite rough compared to PM12 and everything thereafter which used better, more reliable measurements. PM15 is a beta release that allows for separate output gain control relative to EQ preamp which I feel is a must to get the headphones loud enough for most people but unfortunately seems limited by the DAC/amp board in that it ends up putting out a muddy bass that's also distorted. It's a beta release for a reason that also needs a separate beta release of the toolbox but hopefully Ploopy can get this improved enough to be a working solution with the current DAC/amp hardware for many who are willing to put up with a slightly boomy sound that at least gets loud enough throughout.

I suppose there isn't much point to talk about PM11 anymore but the bare frequency response of the drivers is why the Ploopy headphones have become a de-facto poster child for the importance of EQ. The tuning without the DAC/amp board is quite frankly unbearable with driver resonance peaking at ~40 Hz so sharply and then the upper mids and lower treble feel like knives digging in the ears. It's one of the worst things I've listened to and there is no way I would have recommended anyone try the Ploopy, let alone actually buy a kit or pre-assembled set without EQ. While there is still a distortion and loudness issue with EQ—most of which can be resolved if you use your own EQ filters and a more powerful headphone amplifier rather than the provided DAC/amp board—the Ploopy headphones now become a viable, comfortable, open-source design you can use for years thanks to the easily available refresher kit that gives you a new headband and ear pads. You can also tinker with the firmware and hardware/design yourself and make your own Ploopy headphones the way you like it, and that's the main selling point here.

PM12 results in a more U-shaped sound that has decent bass extension until ~50 Hz before it dips down, but honestly this was never going to be a sub-bass monster anyway. It doesn't have the cleanest mids in the world since all the EQ filters make for a jagged response that you can feel when discerning instrument classes—especially an orchestral recording when brass instruments and strings play over each other. It works surprisingly well for vocals, be it male or female, and I know the two people behind Ploopy use these headphones for online communication and general media consumption. It works well enough for country, R&B, hip-hop, pop genres too, as long as you know this is still a DIY set at the end of the day. Treble extension was quite good already so that actually helps a lot in maintaining a good tonal balance. PM16 adds more mid-bass and sub-bass extension but I can't get over the increased distortion here; your mileage may vary. Also, having thought about it hard, I don't think having a comparison section makes much sense here given the whole point of these headphones relies on EQ and I don't have anything else that has it built into the chain. There are of course open-back headphones in this price range which are nicely tuned out of the box, including the Sennheiser HD 650/6XX and even the MOONDROP VOID, both of which are safer options to go for, but the Ploopy headphones are a completely unique offering that is meant for the open-source community or someone wanting a weekend project maybe.