Speakers

 A piece of music might sound like a masterpiece when played on a high quality speaker, while sounding terrible if played on a cheap pair of headphones. 

Likewise the gospel.

This has two implications:

1) If you've heard the message of the Christian faith preached in a distorted way (through a bad speaker) don't discard it. It's a masterpiece when played on the right speaker.

2) If you're sharing the gospel, make sure you use the best quality speakers you can to do so.