Speaker Popping

[Johk]

Is the problem new or did it started recently?

If it's only your right speaker that does this, check if the level of your right and left are the same. If they are the same, then I'd say most probably that your right speaker has suffered some damage (maybe your crossover frequency is set too low, this could damage your speaker over time).

If it's only one speaker I don't think that the amp is the problem to check this your could plug the left speaker in the right speaker out from your receiver. If you don't have the popping sound, then you know for sure that it is the speaker.