auxetophone

from The Century Dictionary.

• noun A device for increasing the loudness of the sounds produced by a phonograph. See the extract.

from the GNU version of the Collaborative International Dictionary of English.

• noun obsolescent A pneumatic reproducer for a phonograph, controlled by the recording stylus on the principle of the relay. It produces much clearer and louder tones than does the ordinary vibrating disk reproducer.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun historical A pneumatic type of sound-playback device used in the early part of the twentieth century.