It's a Bird. It's a Plane.

It's SuperTrax.

Fyne Audio's new supertweeter will have you singing high praises.

By now, most of us appreciate what a well-integrated subwoofer does in a hi-fi system. We understand how it takes over from the loudspeaker's fading low-end response to seamlessly extend performance deep into sub-bass territory.

Did you know the same concept can be applied to the other end of the frequency range, by adding a supertweeter and extending linearity well past 20,000 Hz?

But you have questions... Of course you do. We all know we can hear, or at least feel, sub-bass notes, and as a result, few of us have quibbles with the "how" of subwoofers. With high frequencies though, it's common knowledge that only the youngest and healthiest of us can hear past 16,000 Hz, topping off at the human maximum of 20,000. So how can supertweeters work?

"Only Dogs Can Hear My Speaker's Extension!"

The common forum comment when anyone discusses any kind of frequency extension past 20 kHz, is that only dogs and cats can hear it. As usual with forum comments, this completely misses the point.

The overall linearity of a system past audible frequencies means greater linearity and fewer passed down artifacts in the audible range. The response graph of a speaker that drops by 6 dB at 20 kHz is likely to be more problematic in the audible frequencies than the graph of a speaker that drops by 6 dB way up at 55 kHz.

This point about a system's linearity doesn't fully explain the value of a supertweeter. If you have a loudspeaker that starts breaking up at 10 kHz, ruining the air frequencies, it is not going to be fixed by throwing on an ultra-high-frequency transducer. After all, there is no crossover so you aren't lightening the load on the speaker by adding a supertweeter.

The point here is that, like high-end subwoofers, a supertweeter is not intended to be a repair for bad loudspeakers, but more a fine-grit finish for good speakers. By masking and filling in over the natural decay and understandable non-linearities of a well-designed loudspeaker, both subwoofers and supertweeters bring improvements across the entire frequency range.

This graph shows just how much energy a trumpet has all the way to 100 kHz. Quoted by Dr. Paul Mills in his white paper on the SuperTrax, it is from a paper There's Life Above 20 Kilohertz! A Survey of Musical Instrument Spectra to 102.4 KHz by James Boyk, California Institute of Technology.

Non-Audible Doesn't Mean Non-Perceptible

Not only are we learning new things about how our bodies work, we are still finding structures and anatomies never before identified. While it's true we can't hear past 20 kHz, there are other ways to sense the air pressure changes we call sound.

Dr. Paul Mills, the genius behind Fyne Audio's designs, has peer-reviewed scientific findings to back his foray into the upper reaches of the audio band.

Japanese researcher Oohashi used brainwave activity to prove that frequencies up to 60 kHz are perceptible. A further paper by Lenhardt found that profoundly deaf subjects could sense ultrasonic frequencies. The mechanism for this is most likely bone conduction which is sensed by a small organ in the inner ear called the saccule.

It makes sense then much of our world is filled with sounds that extend far past what we consider the top end of our hearing. Musical instruments, for example, have plenty of energy in the ultrasonic regions. The Fyne Audio whitepaper on the SuperTrax cites a study that shows the spectral energy from a trumpet (see graph above). There is considerable energy above 20 kHz, and it's only at about 100 kHz that it drops into the noise floor.

"A similar result," writes Dr. Paul in the paper, "is found with instruments from other musical families, with the violin and oboe showing energy above 40 kHz. Even sibilants in speech were found to have energy above 40 kHz."

Percussion instruments were found to have even more high-frequency information, says Dr. Paul. "A cymbal crash has 40% of its energy above 20 kHz, "while the triangle was found to have a healthy output at 100 kHz."

But Is This Information Recorded?

We've established that instruments produce ultrasonics, and that we can perceive them, so the next question is, are these frequencies even present in recordings, which are frequently capped at 20 kHz? Also, CD-quality files cannot even store information above 22.05 kHz. (For any given sampling rate, the highest frequency that can be sampled is half the rate, so for CD, half of 44.1 kHz.)

"I suspect the ultimate performance will always be limited by the content," says Max Maud, sales & marketing director, Fyne Audio. "But of course, a lot of music won’t be that compressed or limited. Also, it's how these unattainable frequencies alter the stuff we can hear, allowing these frequencies more room to breathe."

Don't Miss the 360 Angle

Now, onto the specifics of the Fyne SuperTrax. As you can see from the photos, there's something different going on there, and it's groundbreaking enough that the design has been freshly patented.

The thin-ply carbon diaphragm driver of the SuperTrax fires upwards onto a tractrix profile cone that's modeled on the BassTrax used in Fyne loudspeakers. This allows for a 360 degree dispersion which makes the SuperTrax sound far more realistic than regular supertweeters, which have a very narrow dispersion.

Because the SuperTrax avoids "beaming" effect associated with higher frequencies "the spatial effect in the music is amazing," says Max. "Quite astonishing, in all honesty."

With its rich walnut finish and gleaming metalwork, you can see that the SuperTrax is a perfect match for Fyne's Vintage series of speakers. However, it will work with any flat-topped speaker up to 98 dB sensitivity. 

Are you convinced it's not just Fido and Mittens who'll appreciate a supertweeter, but you are hesitating because the SuperTrax's finish doesn't match your modern loudspeakers? Worry not, Fyne Audio will have a contemporary design later this year. And since Fyne's bestsellers are the F700 range with the sloping top, says, Max, "Our clever designers will factor in this adjustment too."