Conflicting pins between the PCM library and speaker and the NRF24L01 The PCM library uses pin 11 and the NRF24L01 also uses pin 11. I am using an Arduino nano, and don't know if there is any way to change the pins of either the speaker or the transceiver.
https://github.com/damellis/PCM
No, you can't just change pins. Both systems use hardware that is specific to pin 11.
The best you could achieve would be to use a software SPI implementation on other pins to drive the nRF24L01, but that would mean changes to the library you are using to remove the SPI library usage and replace it with your own software SPI implementation.