Bought a PRR S2 some time ago and was dissapointed that the sound volume was very low even though it was cranked. The horn was especially low. Decided to see if I could replace the speaker and decided to try drilling out the approximately 1/8" hole in the speaker box. Experimented with larger bits and stopped at 1/4," as it didn't need any more volume. Sound about doubled, and now run it with reduced CV's. Very pleased with results. Horn was distorted with old settings, but now is not with lower setting even though it is much louder. Bill