When a guy in a garage brings a major corporation to its knees, it's David and Goliath all over again. All hail the underdog. Before things do go to the dogs, yelp, my phrasing is unmitigated exaggeration... but based on something true. Dan Clark's successively more and more comprehensive rebuilds of affordable Fostex planarmagnetic headphones had led the Japanese to eventually revisit their classic orthodynamic design. To stick to our version of the story, we'll assume—not that you'd expect them to admit it—that their new model was directly inspired by the clever upgrades our man in San Diego performed. For an original manufacturer, it'd be only natural to want to remain one step ahead of a particularly industrious and successful after-market mod man, especially one who rode coat tails by amassing an enviable collection of very enthusiastic global reviews. Cue up heavily modified Oppo universal decks from ModWright & Co.; or Alex Peychev-rebuilt Esoterics under the APL banner for parallel variants on this theme.

Not to be outdone by Goliath returning, Dan has since sharpened the thorn in Fostex's side called Alpha Dog by way of the new Alpha Prime. With his doggone theme escalating—it all started with the original $299 Mad Dog—the $999 Prime still looks like a $599 Alpha Dog. That's only fair. After all, Alpha remains part of its name. As such it inherits the 3D-printed ear cups* in burgundy-red or black lacquer which had one-upped Dan's original effort of just a rebuilt driver inside stock Fostex cups. It of course also gets his super-plush lambskin pads and sticks to the original Fostex head band plus Dan's signature leather strap below. How the Prime dominates the Alpha is invisible. It's back to the planar diaphragm. Now that undergoes an even more comprehensive disassembly and rebuild. Its sonic advances with Dan's complex maze cups and bass tuning were apparently significant enough to warrant a new model designation. At least theoretically then, an Alpha should be able to convert to a Prime by swapping driver assemblies. In practice, the process turned out unexpectedly complex and too time consuming to become viable.

* Cable giants AudioQuest are readying their first-ever headphone called NightHawk which is to sport liquid-wood cups and 3D-printed grills. That latter item suggests more inspiration from the Alpha Dog's pioneering use of a very fine maze pattern in which unwanted driver energies (in Clark's case the rear wave) exhaust themselves rather than reflect. As to the Prime looking identical to the Alpha—the surcharge would seem mostly labour-related—there's a written designator on the risers to distinguish the two; and the new leather band is now split in the middle for increased comfort.

If you feel lost already in the thicket of a plot which, very impolitely, assumed too much prior knowledge, simply revisit my review of the Alpha Dog. Today's assignment isn't about rehashing ground already covered. It's a continuation of the story focused on how the Prime exceeds the Alpha on sonics. Before we go there, here's what Dan said about what he does to an Alpha driver (obviously still a modified T50RP Fostex) to make it a Prime candidate: ... ear on tweeter, perfect silence... wow... absolutely nothing. To be honest, nothing was about the extent of my expectations. Why would Mr. Clark give secrets away to competitors? He's been at his Fostex mod/rebuild thing for years. His MrSpeakers™ outfit (so named because he started in speaker design) has grown into a nice full-time headfi business. Let someone else put in their own time to figure it out. But obviously, I did ask. As it turned out, the man wasn't quite as taciturn as he might have been. First for the benefits. "A really easy and fast sound, detailed but not zingy for a quicker more detailed presentation free of hardness or glare; better transition from bass to midrange and mids to highs for a darker and smoother tone topped by more organic highs; bass that goes lower, is more articulate, hits harder yet is more balanced with the rest of the music; lower distortion across the spectrum; improved transient response." Quite the lustful litany.

Next, illustration with measurements: "Since people requested to see our frequency response, here's our target curve. For those not familiar with headphone measurements, don't try to make sense of the data above 5KHz. There are too many interactions between test fixture and headphone. Generally, our measurements correlate pretty well with InnerFidelity's frequency response and THD but don't get carried away. You can't overlay our results on theirs and expect a direct match. A few notes for those not into measurements. The 'rolloff' around 1KkHz is not really rolling off. The headphones are very smooth on both noise and test tones. And yes, the bass on most units is that flat and yes, it's a closed headphone with one minor vent and the same isolation you've been used to with the Alpha Dog. The 'peak' at 7KHz does not result in sibilance, this is mostly a measurement artifact. We are going to publish the -3dB point as 15Hz but so far, every unit we've built has easily beaten that."