Once you've decided to splash out on some custom earphones - and paid your fee to do so - it's time to make an appointment with an audiologist to get your ear canal impressions taken. This means having those canals filled with silicone gel which is a slightly surreal experience. Especially as I arranged to have this done in a Starbucks on Baker Street and attracted more than a couple of strange looks.
Impression taken, the mouldings find their way to ACS and up to 21 days later a pair of custom tips should arrive for your hf2s. In the meantime you can use the hf2s with the standard tips which are supplied in the package.
There's no denying that the firm-ish, clear silicone tips supplied by ACS are wonderfully comfortable. Ease of fitting depends on just how twisty your ears are, although the method should be the same for everyone - a twisting action gently screwing the earphone into the canal. Don't worry; it's less violent that I just made it sound.
Once you have your hf2 Custom earphones in then be prepared to really learn the meaning of awareness should you dare to venture outside. I thought navigating Piccadilly Circus was dangerous enough when I could hear the traffic and people around me but the isolation afforded by custom-fitted earphones turns the usually simple act of crossing a road into a life-risking experience.
As you might hope, this isolation does make a tangible difference to the quality of music produced by the hf2 earphones. Or, to be pedantic, seeing as the drivers inside the earphones are the same as in the standard hf2s, the perceivable quality.