This is indeed Emperor Wilhelm II. speaking. However it is not one of his famous "balcony speeches" of July 31 and August 1, 1914, that he made from the top of the balcony of the Stadtschloss in Berlin to the crowd. The text here is actually that of a written appeal printed in the Deutsche Reichsanzeiger (the official journal of the German Empire) on August 6, 1914. However, the wording of all of the Emperor's speeches during the July crisis and the beginning of World War I is the same, just slightly adjusted.

Interestingly, the recording of the appeal of August 6 was done much later on January 10, 1918. It was part of a program by linguist Wilhelm Doegen, founding member of the Königliche Preußische Phonographische Komission ("Royal Prussian Phonographic Commission"), to record important speeches of recent years. Wilhelm's "appeal to the German people" was selected and released to the public in the hope of catching again the alleged vigour of the beginning of the war.

The Emperor was not familiar with recording devices and had to be trained to give his appeal as a fiery speech without corresponding audience like a cheering crowd. If you listen closely you might get the impression that in the beginning of the recording Wilhelm II. speaks rather calmly (like reading out directly from the paper) and then becoming more and more engaged over the course of the recording.

Source: Deutsches Rundfunk-Archiv (German Broadcasting Archive), you can also access a transcript of the appeal there.