tia™ - The Story of Tubeless In-Ear Audio is an article that delves into the development and innovation behind 64 Audio TIA (tubeless in-ear audio) technology.

64 Audio Fourth Patent

• In July 2020, after three years, 64 Audio was awarded its fourth patent for our groundbreaking technology dubbed TIA, which stands for tubeless in-ear audio.

• U.S. Patent #US10721549B2 was issued on July 21st, 2020 for the implementation of direct radiating drivers in microacoustic chambers.

The Beginning

The story of Tia is Fourté's story. In order to transmit sound from the driver's spout to the end of the IEM canal, balanced armature drivers (BA) must traditionally be mounted on a vinyl tube. Knowing that this tube has always had a detrimental impact on the drivers' natural, uncolored sound, the first step was to remove the tube to test if the BA performed more naturally—like a large-scale speaker, which doesn't use tubes in this application.

tia™ Driver

A positive result from eliminating the tube prompted 64 Audio’s R&D team to press into unlocking more of the potential of these BA drivers, quickly turning into a BA with an exposed/open face. Before sourcing what is now known as the Tia Driver, we initially cut the drivers open ourselves to test this; sometimes even sanding the side of the drivers off to expose the diaphragm. The results astounded the team and this open-face balanced armature driver was here to stay.

To see how these new drivers behaved in an earphone they were placed in various positions within an empty IEM shell. Upon first listen, although far from perfect, it had interesting sonic qualities that were obviously going to turn into something revolutionary.

The initial step involved eliminating a tube component from the design, which yielded a positive outcome. This success encouraged 64 Audio's R&D team to further explore the potential of the balanced armature drivers.

Open-Face Balanced Armature Driver

The team proceeded to experiment with the balanced armature drivers by transitioning to an "open-face" design.

In order to assess the behavior of the new drivers, they were placed in various positions within an empty IEM shell. This was done to evaluate how the driver's position within the housing affected the sound quality and overall performance. The drivers were experimented with extensively, even undergoing processes like cutting and sanding to expose the diaphragm, indicating a rigorous testing phase.

Despite not being perfect initially, the open-face balanced armature driver showcased interesting sonic qualities. These unique sonic attributes have the potential for revolutionary changes in the field of IEMs, suggesting that the new technology had the capability to significantly enhance the listening experience.

From The Shell To The Canal

The high-frequency Tia driver was initially positioned entirely outside of the ear canal based on our understanding of IEM pinna correction. The potential beauty of having open drivers in an open shell without tubes or dampers was highlighted, despite the fact that this swiftly changed. However, we shifted this Tia driver to boost the high-frequency (HF) extension and found that the extension and HF clarity improved with increasing distance from the canal stem. The objective was to get closer, to the point where the Tia high-driver got stuck in the IEM's canal or stem. This was a bittersweet finding because it exposed us to a wide range of production issues and potential manufacturing barriers, but the benefits outweighed the problems.

Tia Acoustic Chambers

It's fascinating to learn about the research and development process behind the design of the headphones. The team encountered a dip in the frequency spectrum around 3khz-6khz and found that the mid-Tia driver lost some extension in the lower treble due to its open and further back position in the shell. However, the team was determined to maximize the power of this larger Tia driver in the mids.

Through experimenting with different enclosures and structures within the shell, the team discovered that a small wall structure placed directly in front of the low-mid Tia driver's diaphragm yielded positive results. This wall acted as a divider within the shell between the Tia low-mid and dynamic low driver. Interestingly, controlling the gap between the top of the wall and the back of the faceplate allowed the team to find a sweet spot that extended the response of the Tia low-mid driver from 3khz to about 5khz.

One key aspect of this patent is the use of the shell, as well as the air inside the shell, as the transport medium for the sound waves. Unlike traditional designs that use tubes or the air inside those tubes, the acoustical impedance is derived directly from the shell itself. The structures, chambers, and air volume within the shell play a crucial role in shaping the frequency response of the headphones.

Tubeless BA Driver

Even with the positive results in the high-mid band, the upper mid/lower treble was still lacking between 2khz-6khz. An additional high-mid driver was required, to sit between the Tia Low-mid and Tia High drivers. Sourcing a fully open version of this very fragile high-mid BA wasn’t possible at the time, so it was implemented within the shell in its standard form; sound radiating from a spout but still radiating into the shell without the use of a tube. The design was finalized with two fully open Tia drivers, low-mid and tweeter, a tubeless upper-mid BA driver, and a tubeless dynamic driver for the low-frequency band.

[Source: tia™ blog 64 Audio]