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1.
These are the absolute worst speakers someone can have in their car. They can also refer to speakers in general such as in a boombox. Granny Blasters are named such because they are only worthy of being owned by your grandmother. Any music coming out of them will sound like shit either because they are really old, or just really poorly made - like I said, something your grandmother would own.
Kid #1- Yo, man I just got a new car!
Kid #2- Fuckin sweet man, now we can drive around town and pump music like the badasses we are!
Kid #1- Nahh man, shit's got Granny Blasters on it, we got to hook it up first.

Radio Raheem in Spike Lee's "Do the Right Thing" did not have a Granny Blaster. His boombox was crisp as it blasted Public Enemy.
by Boston Glitch Pigeon August 03, 2009