Of course there is an interesting conundrum when buying a pair of T2s. If they are all custom made how do you try them first? Quite simply you can't. You pay your money, get some impressions made at an audiologist - ACS's dealer map will provide some suggestions (there are numerous partners nationwide) - and join the waiting list (manufacture and delivery usually takes two/three weeks). A 30 day return policy exists for unsatisfied customers and earpieces will be remade if there is a problem with the fit.
The first special thing you'll notice when you use T2s is the fit. ACS makes the custom moulds for Etymotic's HF2 and HF3 earphones amongst others and those moulds are roughly the same size as a regular earphone tip. For its own monitors things are rather different. The moulds are considerably larger filling the entire ear canal. The benefits to this are twofold. 1. You get a near perfect seal (27db of isolation) which loses the vast majority of environmental noise even before the audio starts and 2. The speakers are held entirely inside the ear resulting in a flush finish. This is convenient since you can rest your head against a pillow at the end of a long day and sleep comfortably when travelling long distances. The sheer level of sound isolation means without any audio T2s function as professional grade earplugs.
With such a snug fit putting the T2s in initially takes practice. A provided guide will walk you through it (an anti-clockwise twist works best) and you'll be a pass master in no time. Because they're made from medical grade 40 shore silicone they're durable yet flexible so they adjust with jaw movements to maintain comfort. The silicon also heats quickly to body temperature meaning you'll forget they are in within minutes. It's impressive stuff, but the real lasting impression (pun very much intended) comes when you press play.
It is hard to know where to begin describing such an experience. 'Ballistic', 'vast' and 'agile' would all be good adjectives, but the overwhelming impression is that of emotion. For all their manufacturing refinement they produce a sound that feels like it was formulated in the sweat shed from an Ozzy Osbourne stage dive and the fires of Jimmy Hendrix's burning guitar. In a sector split between some customers demanding surgical precision and others addicted to bass the T2s effortlessly please both. They are as much fun with Mozart, Pavarotti and Miles Davis as they are with Metallica, the Chemical Brothers and Eminem. Dual drivers provide incredible drive across low, mid and high ranges and two balanced armature transducers add exquisite detail with frequency response from 16Hz to 20KHz. The effect is like getting knocked out by a velvet boxing glove.