Plasticity or plastic city? The Sonorous III arrived in the type of fully branded/printed box which always command my respect for the art of paper folding and package engineering. Rather than conceal the fur-lined wooden presentation box of the X, this package had the Three sit in a plain folded cardboard cradle, 1-metre cord in a separate plastic sleeve. This time Final had thoughtfully included a 3.5/6.3mm metal adaptor. Again there was a small multi-lingual owner's manual and a credit-card sized warranty card. And—what more would you need?—that's all she said.

He on the other hand (that would be me coming off both the full-metal Ten and the €309 Romanian Meze 99 Classic, the latter with wooden cups and all'round noble materials) has to admit something more. At first, the full-on conversion to light plastics felt just a bit of a tweak. This piqued when one of the ear cushions seemed to have been punctured in transit. Closer inspection revealed that it was a deliberate circular hole right next to the ear cup's cable entry. It was dutifully repeated on the other cushion. Clearly these were deliberate tuning bores.

This warrants a brief paragraph on transducers, cabs and airflow management. As most hifi nutters know, putting the same drivers into otherwise identical cabinets (same dimensions, same internal braces, same panel thickness) made from MDF, Plywood, aluminium, glass, Panzerholz, PMMA, solid wood or any other conceivable stuff results in sonic differences. More perplexing is that the same holds true for amplifiers. The late Eduardo de Lima, of Brazilian firm Audiopax, had compared his original Model 88 valve amp in stainless steel, aluminium and brass enclosures. Without understanding why—his engineering brain had no real explanation—the brass casing sounded best by far. Back to headphones. Ear-cup materials particularly for sealed variants like our Final influence the sound just as happens to speakers.

What's more, the ear-cushion-driver-cup assemblies become your very private dual-mono listening rooms. If the cushions leak, it's like opening French doors right behind your speakers. The bass could disappear. If internal reflections aren't controlled or managed, a sealed headphone could sound like a nearly empty hard room. Think lots of glass, tile floors and no absorptive materials like curtains, carpets, pillows and overstuffed furnishings. You'd expect a very bright sound. It's only at first glance then that the notion of headphone ear pads being sonically critical seems silly or perverse. Once you realize how they're an intrinsic part of your temporary double 'rooms' to help define their composite shape, volume and relative lossiness or absorptive index of the walls, it all makes perfect sense. Without getting nerdy, we'll thus say that the little pillion holes act as air-pressure-relief micro vents. Aside from manipulating the mix of their composite casing between polycarbonate and glass in a precise ratio, then cushion foam of just the right compliance, density and shape for their driver loading, Final use the small holes as final tuning features.

From all of that, it's a given. Despite the very same aluminium driver, the Three must sound different than the Ten. And despite what I said about the unreliability of memory-based A/Bs, that was certainly the case. This reminds me of our Swiss naturopath. Performing an iris diagnosis, he orders a very specific blood/urine test to be performed by an outside laboratory. Whilst his diagnosis tells him very clearly what's wrong—which organs work a bit too hard, what toxins might be present—it doesn't tell him precise values. It's only the laboratory chemistry test which locks in a precise vitamin D level, arsenic presence from tap water etc. Armed with your blood/urine test results, the naturopath can now prescribe exact dosages to take, of very specific supplemental compounds over a specific period of time. A subsequent blood/urine test then tracks/verifies your progress towards rebalancing your body.

Without a 'blood test' of a direct A/B, I couldn't tell you aural percentage points either. But I can certainly tell you that the X was the brighter-all-over performer with the snappier salutes, more extreme resolution and dynamic charge. By implication, the Three was the more forgiving. Think plusher family sedan to the X's sporty two-seater without external mirrors and far stiffer suspension that telegraphs every tiny bump in the road. Not only did the X look shinier, it also sounded it. By contrast, the black Three was less percussive. Like its light-absorbing colouring, it wa less lit up and intense. There goes my iris diagnosis. To get into the lab and spit out more specific things on the Three, we'll rely on actual A/Bs against some of our usual suspects.