GSMArena has now uploaded the the 5s test and claims it sounds even better than the 5c.
"
Apple smartphones have never disappointed when it comes to audio quality and the iPhone 5s makes no exception. In the active external amplifier part of the test, the iPhone 5s did perfectly and even outdid the iPhone 5c with lower stereo crosstalk. Its volume levels were just as high as on the 5c, which makes them one of the best in business, second only to the HTC One and Butterfly.
The second trial produced equally impressive scores. The iPhone 5s again managed to beat its lower-tier brother by the virtue of its better stereo and was overall as close to perfect as it get."
German test site Fokus.de/handy thinks the 5s is the only phone to date to mach the 4s.
They write:
"Der Klang hat sich im Vergleich zum Vorgänger minimal gemausert: Konnte der Sound des
iPhone 5 dem
4S nur sehr nahe kommen, aber nicht hundertprozentig gleichziehen, weil die Höhen eine winzige Spur weniger klar und spritzig ertönten, so ist nun mit dem Referenz-Hörer, den Ultimate Ears Reference Monitors, kein Unterschied mehr zwischen 4S und 5S herauszuhören. Somit darf sich auch das 5S des besten Klangs aller Smartphones rühmen, mit kristallenen Höhen, entspannt-wuchtigen Bässen und einem ausgewogen-natürlichen Gesamteindruck. Klasse!"
A rough English rendering for those who don't speak German:
"Audio quality has slightly improved when you compare it the the old model: While the old iphone's audio quality was only close to that of the 4s, the treble being a tiny bit less clear and lively, we now cannot hear a difference between the 4s and 5s,listening with our reference cans UE. Thus, the 5s can pride itself having the best audio quality among all smartphones - crystalline treble, relaxedly powerful bass and a balance and natural overall impression. Awesome!"
Does not sound to bad, does it?