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VK-X Sound Signature (1/3)

Discover our work on the passive acoustic response


Hi everyone, Alexandre here, and I hope that my blog post finds you well 🙂

Today, we are very proud to finally unveil the first presentation of our work on the passive acoustic response of the VK-X.




Important Note !


Before I begin, I would like to point out that the response graph presented below was made with our custom measuring equipment, which simulates our head via a silicone stand and silicon ears. It does not represent the reality of what you will hear because many parameters can modulate your sound perception and the actual frequency response of the VK-X (our silicone device, your head, your ear canal, your audible or inaudible frequencies, the positioning of the headphones ). It is therefore a curve, which, like all the curves given by the manufacturers of headsets, must be interpreted with moderation for the above reasons, and which will change from one measuring device to another.

Nevertheless, it is a very practical tool at the workshop, which allowed us two things:

  • Obtain the desired real passive sound signature (ie by listening to the headphones) thanks to a constant back and forth between a real and qualitative listening of the headphones on the one hand, a work on the mechanical acoustics of the VK-X on the other hand, and finally measurable effects thanks to our measuring equipment.
  • Obtain a balanced sound between our Left and Right channels, which is very important for good listening comfort, and depends to a lesser extent on the measurement device used.





A frequency response of the VK-X according to our measuring equipment.



How to read this graph?


The curves show the gain plot (in dB decibels) as a function of the frequency (in Hz) of the signature of the left channel (in purple) and the right channel (in red). To achieve them, we sent in the headphones a signal consisting of all audible frequencies, from 20Hz to 20kHz, at a volume of 85 dB.


Passive sound signature: we have achieved our goal


At aëdle, we like balanced signatures, with accurate rendering of all frequencies, generous lows, but not exaggerated, just like what we produced with the VK-2 and the ODS-1:

We wanted a headphone with present and detailed lows, and that can deliver also very low frequencies such as sub lows, these frequencies that we feel more than we hear them.

We wanted a headphone with a “body”, which breaths, which feels open enough and have a great spatialization. The VK-X responds very well to this extent, just like what we did for the VK-2.

Finally, we wanted a headset that is clear and precise in rendering percussive and rhythm instruments.


We are extremely happy and proud of the passive signature of the VK-X: that is to say without any signal processing, the raw sound, without a filter, natural. Our first desire was to give the headphone a great sound acoustic basis, using only mechanical levers to act on the sound. This work has been achieved thanks to countless roundtrips between qualitative listening within the team and with our partners, mechanical modifications made to the VK-X (joints, the positioning of components, vents, speakers,. ..), and quantitative measurements via our measuring device.



Balancing Left and Right: excellent results


Balancing the left and the right was a long and meticulous work that we will detail in a future article. On this type of work, it is especially important to have the most identical paths possible in the low end of the spectrum, because it is here that the imbalance can be the most unpleasant, with a clogged ear sensation of a side for example. For the rest of the spectrum, we are a little more “flexible”, because these are frequencies that will come out especially in stereo, and which will, therefore, be usually voluntarily unbalanced between the left and right when recording. It’s a job we’ve achieved for the VK-X.

By observing the frequency response graph, you can see that the left and right channels of the VK-X are not superimposed perfectly. There are, in places, segments shifted by 1.5dB (with a maximum of 2.5dB at 6kHz). This is normal for headphones, and especially for a headphone like ours, with a strong artisanal component in its manufacture. The bottom line is that this shift is minimal and inaudible, and it is likely that your ears are far from hearing it.

Indeed, very good hearing ability can generally distinguish at best a difference of 3dB between the two ears, and the lower end of the spectrum, often the most embarrassing, is very well balanced. It is, finally, also a performance to match with your own difference in hearing sensitivity between your left and right ears, which is probably not quite zero for all frequencies!



What will be the active/electronic changes to this signature?


Obviously, we will treat the signal a little digitally thanks to the DSP (Digital Signal Processor) integrated into the VK-X. The passive signature is overall very good and we are very happy with the result. However, some local corrections will be made to improve “comfort”, ie to slightly rebalance the levels of certain frequency bands, or cut bumps. The good news is that the corrections will be minimal and will be only “attenuating”: we will not have to amplify or boost a slice of the signal since it is always above the measurement level at 85 dB. We will simply have to mitigate some slices of gains, which does not affect the quality of the signal, unlike amplification or boost.



Upcoming articles on the sound signature


I am currently writing 2 articles, always on the sound. The first will deal with the work we have done on the passive response of the VK-X, with before/after graphs, and details of how we proceeded. The second article will deal with the work done we have done next on the electronic side, ie on the active processing of the sound signature.

With Lucas and Baptiste, we are available to answer your questions, so do not hesitate to post your comments or to contact us by email!




PRIMO Noise Canceling Microphones received in Paris


Good afternoon everyone!


Lucas here. I hope my blog post finds you well. Last week, we received the microphones for the VK-X Noise Canceling system. I am happy to share some pictures of them and to present how we placed them. If you have any question, please post them below!



2,300 PRIMO Microphones



The Noise Canceling microphones are part of the components for which the sourcing was impacted due to this year’s electronic shortage. Luckily, Baptiste managed to find an identical reference from Japan-based and famous PRIMO brand and secured a 2,300 units stock that we received last week at the workshop. Each pair of VK-X headphones will house 2 PRIMO microphones for its Active Noise Canceling system. Those microphones are pretty small: 2mm wide and 6 mm round, – they did not clutter up the workshop yet, but we’re still counting 😉





How are they placed inside the VK-X?



Feed-Forward Noise Canceling microphones need to be perfectly isolated from the inside of the headphones to record properly the surrounding sound, which will be electronically canceled when playing your music. As you can see in the mechanical renders that Alexandre created for this post, we placed them on each earcup, behind the little 4 points grid located on the back side of the VK-X (the renders are showing the left side of the VK-X), which appeared to be an ideal compromise between design and recording position.


The ANC microphones are isolated from the inside of the headphone thanks to a custom Silicone Joint, itself held in the Internal Plastic Shell that fits inside the External Aluminum Cup.




How are they connected to the main Electronic Board?



Each ANC microphone is being soldered by hand at the workshop to its connexion cables as you can see on the close-up picture below. On the left side of the VK-X, the microphone is connected directly to the main “doughnut” electronic board. On the right side, the microphone is connected first to a small slave electronic board, that is then connected to the main electronic board through the headband.