Specifications

Frequency response_ 16 — 20000 (Hz)
Resonant frequency (optional)_ 20 — 35 (Hz)
Impedance (with box)_ 4 (Ω)
Transducer principle_ ribbon, open, on-ear
Cable length_ 3,2 m
Connectors_ gx12 2pin,4pin, blinding posts
Weight_ 510 g

Included in the kit:
Durable case
Headphones
Box with resistive load
Cable
Papers

RUBY13 are handcrafted ribbon headphones available by pre-order with ultra-detailed sound and deep, powerful bass. They offer a great experience for music listening, as well as for music production and mixing.
A key strength of the RUBY13 is their ability to reveal the stark quality difference between various audio recordings.

When creating the RUBY13, my goal was to minimize the use of plastic. I opted for plastic only for the inner part of the earcups to reduce overall weight.
The rest parts of the headphones feature premium materials:
Aluminum
Structural steel
Stainless steel
Brass
Oak wood
Carbon fiber
Fiberglass
Hypoallergenic foam
Hypoallergenic velour

The current weight is 510 grams, but I have plans to further reduce it to 400 grams in future iterations without loss of quality. I am constantly refining and improving the RUBY13 based on valuable feedback from users.
The cable is hand-braided from copper acoustic wire. It features GX12 connectors, chosen for their higher current capacity and secure locking mechanism.

This headphones sound truly impressive with a good amplifier, DAC, and a high-quality audio recording. The ribbon transducers have an extremely low impedance. Therefore, they connect to a speaker amplifier via a dedicated load box with a 4-ohm resistive load.
For optimal performance, a Class A/B amplifier with a power rating of at least 100 Watts is recommended. Connecting ribbon headphones through a resistive load box provides the purest sound, unlike a transformer, which imparts its own coloration to the sound. I am currently working on finding acceptable transformer parameters. Once I test and achieve satisfactory results, I will immediately put the transformer-based adapter into production. This will allow the Ruby13 to be connected to a headphone amplifier.

!!!WARNING!!!

Before connecting the headphones to an amplifier, always check the amplifier’s volume level and turn it all the way down to zero. Protect your hearing!
Excessively high volume can also damage the ribbon driver. Although the driver is designed to prevent the ribbon from stretching or tearing, you must still exercise caution when using a powerful amplifier.
If you turn the volume up too high during listening, you will hear a crackling sound. This indicates that the ribbon is making contact with the fabric on the grille (the ribbon’s excursion range is ±5mm!!!). If this happens, immediately lower the volume to protect both your ears and the headphones.

Tuning

Straight out of the box, the RUBY13 have a emphasis on frequencies above 2000 Hz (The high frequencies are slightly elevated compared to the Harman target curve). Therefore, I strongly recommend using a software equalizer or, if available, an analog EQ on your amplifier.
I make measurement the frequency response of every single unit. The ribbon driver responds exceptionally well to equalization, allowing you to tailor the sound to your precise personal taste.

Personal HRTF

A head-related transfer function (HRTF) is a response that characterizes how an ear receives a sound from a point in space. I’m currently researching this topic and plan to help users get their personal HRTF in the near future. By purchasing the Ruby13, you enable me to expand my capabilities for experimentation and new developments.

Contact

I make it a point to answer all questions and provide assistance with EQ setup. I highly value user feedback as I am deeply committed to my product.
If you have any questions or suggestions, please feel free to email me at kaputski.audio@gmail.com. I would be glad to receive your email.