The one that got away? In December 2015, I'd reviewed Final's flagship full-size Sonorous X headphone. By February 2017—I'm an Aquarius—I'd ordered my own. In the interim, the COS Engineering H1 had become my reference headfi deck. For its high-current balanced outputs, I'd gotten a balanced cable harness from ALO Audio's Ken Ball to experiment with the Sonorous III and VI. Driven balanced by the Taiwanese DAC/amp, those far more affordable models broke through into a different league of performance. It won them a well-deserved mention in my first 3 x 1 = 5¾ feature on the odd math of unexpected hifi synergies. Their leap was inspiring enough to lasso in their heavyweight elder with the very same leash that plugs then twists into the ear cups for a secure lock. The one that'd gotten away returned for good/gold.

This follow-up reports on the X squared, i.e. driven balanced via two XLR; and how it compares to the III and VI in the same mode. Source for my friendly sibling rivalry? The Soundaware A280 used as purist SD card transport into the H1 via coaxial S/PDIF. The memory card held .flac and .aiff files from 16/44.1 to 24/96 resolution. Despite the X's flagship pedigree and sticker to match, it doesn't come with a balanced harness, not even one terminated ¼". The two cables of different lengths included terminate in 3.5mm exclusively. It's a reflection on the design's high 105dB sensitivity. It happily runs off a generic portable player or smartphone without strap-on amplifier. Hence if you mean to take any Sonorous model into balanced overdrive, you must procure an aftermarket leash from another vendor. Given the X's price, size and massive weight, stationary not on-the-go use is really the most likely. Now sources and amplifiers of matching pedigree become justifiable mates to milk the maximum. And tapping such luxury is where it gets interesting.

Here we see the hardware context the X would drop into, Sonorous VI warming up the spot, III playing the desktop. In this type scenario, what would scaling Mount No Compromise net, from base camp One at €379/III to base camp Two at €649/VI to €4'599/X for the Sonorous Summit? The core driver and overall geometry remain consistent though the VI does add a balanced armature to the main dynamic. The primary changes are to the quality/density of the build. Where we might call the III the equivalent of an MDF speaker with plastic port and the VI the same box with an aluminium baffle, the X becomes an all-metal box as a kind of on-ear Magico. Of course those comparisons are only approximate. Still, they visualize Final's Sonorous theme: refine the III's starter platform across sundry models by using ever stiffer heavier materials to mount/damp their proprietary high-Tesla driver. Along the way, they gild the lily with fancier surface finishing. This turns the range topper into a gold/stainless sparkler to show off the company's fancy metal-work acumen. Those who'd cry bling step down the range into more and more black ABS plastic until their modesty sensibilities are met. Here we'll deal purely in sonics. Our question is, how do material changes translate to audible changes when the preceding hardware is of superior resolution and drive? The obvious idea is that maxing out those values will increase the gap between models.