Stealth Sonics is the latest and one of the few local companies in the custom in-ear monitor business, but is already making a splash in audiophile circles.

The company offers three versions of custom in-ear monitors: the two-driver C2, the four-driver C4 and the C9, its most expensive product with nine drivers.

The C2 costs $699 while the C4 breaks into high-end territory at $1,099. The C9 costs $1,988 and, while it might be the flagship product, it does not mean it is the best choice for everyone.

A pop or rock music listener might be content with the C2, which has a smooth and punchy sound, while those who prefer a flat, studio-accurate response might opt for the C4.

The C9 is designed to present the best overall sound and has a clean, clear and balanced delivery, without sounding sterile or boring.

It is also able to present wonderful separation between the bass, mids and highs, and deftly handles a wide variety of genres.

I particularly enjoyed the C9's low-end capability, which reproduces strong, powerful bass that sounds natural. The earphones have excellent transient bass response, with each drum beat sounding fully alive and punchy. Listening to English rock band Slowdive's No Longer Making Time was a treat from start to finish, from the resonant drum introduction to the soft guitar licks in the background.

The C9 is made from a smooth, polished acrylic that is tough and sturdy.

The fit is snug and comfortable and I was able to pop them right into my ears with no trouble at all. In fact, as they are moulded exactly for my ear canals, they slipped right in like a key into a lock.

If the fit feels off in any way, the company offers a free 30-day refit. The earphones also come with a one-year warranty.

• Verdict: Shelling out almost $2,000 for the C9 will be out of reach for most casual listeners, but audiophiles who like the earphones' clean, clear and realistic sound signature can add Stealth Sonics to their list of established custom in-ear monitor makers.