The A5 has some trouble with deep bass frequencies at top volumes. Whether using AirPlay or the Aux input connection, the A5 vibrated and slightly distorted at near-maximum volumes when playing the Knife's “Silent Shout,” a song with tremendously deep bass.
Since the system uses digital signal processing, this is a bit surprising, as DSP tends to squash challenging dynamic content at top volumes to avoid distortion. On songs with lesser low-end presence, the system still occasionally vibrates at maximum volume—not distorting, but audibly rattling due to the vibrations of its own drivers. Basically, the A5 can get louder than its frame can handle, but it seems unlikely that you'd regularly be listening at such high levels.
Happily, at moderate-to-very high (but not maximum) volume levels, these issues disappear, and we're left with a powerful speaker system. Low frequencies are robust, mids articulate, and the highs crisp and punchy. The A5 sounds excellent whether playing back dense rock mixes like the end sequence to Grizzly Bear's “Yet Again,” or more dynamic, instrumental material, like John Adams' “The Chairman Dances.”
On the classical piece from Adams, the mids seems to get the bulk of the spotlight, but high frequency content like the wooden percussion isn't muffled or hidden. The low frequency content, like the big drum hits at the end, is delivered with a focus more on the low-mids and the attack rather than the sub-bass frequencies. This means the A5 manages to sound powerful without being muddy, or overly weighted towards sub-bass frequencies, like many systems are in the Age of More Bass.