64 Audio A4s

The reviewer calls the bass response fantastic and says its low-frequency extension into the 20-30Hz range is exceptional. Sub-bass quantity is very high and slam is strong, though bass texture is described as somewhat dry.

The midrange is described as nearly as solid as the bass, with flat lower mids that avoid bloat. A measured upper-mid recession makes female vocals and electric guitars less biting, but supports a smooth, relaxed presentation.

Treble is the principal sonic reservation in the review, with insufficient energy around 5kHz and dips through the mid-treble. The tia-driven upper-air region keeps it from sounding fully rolled off, but lower-treble definition is still missed.

The A4s presents a convincing amount of immediate, surface-level detail and comes across as reasonably technical on first listen. Closer comparisons reveal limits in finer resolution, so it does not fully compete with stronger technical performers.

Imaging is judged above average, with reasonably reliable placement of instruments and voices. Larger, more enveloping note images give the presentation some scale, although localization is not described as best in class.

Bass punch gives the A4s satisfying physical impact, and the reviewer considers it more coherent than a comparison point. However, larger shifts in loudness are less convincing, with macro-dynamic contrast specifically identified as a weakness.

The reviewer identifies fit as an area where custom monitors make a meaningful difference and reports no difficulty keeping the A4s in place. The flush shell fit also supports stable positioning during ordinary use, although the supplied review does not directly discuss seal changes across different users.

The reviewer reports wearing the A4s for more than five hours without problems, falling asleep in them, and being able to lie on their side. The flush-fitting custom shells appear especially well suited to long sessions, though this is a single reviewer account.

Isolation is described as absolutely fantastic, with the APEX system avoiding the pressure buildup sometimes associated with highly isolating monitors. This combination should suit listeners who need strong passive attenuation without an overly occluded feeling.

The supplied review focuses on fit, isolation and sound rather than shell construction, cable quality, connectors, included accessories or long-term durability. The custom shells are said to sit flush in the ear, but reviewers say little else about ownership hardware.

At roughly $1,149-$1,199, the reviewer considers the A4s a solid recommendation for listeners specifically seeking a custom in-ear monitor. The review does not directly compare it with similarly priced custom-IEM peers, so its competitiveness against alternatives at this price is not fully established.