1995 BMW 740 Stereo Speakers Crackling

First of all, switch the two rear speakers side to side, then wait to see if the same speaker crackles on the right side, or if the one you put on the left crackles now. If the crackling is still coming from the left rear, it's not the speaker. If the crackling comes from the right rear now, it's that speaker.

When you pull them out, look on the back of them to see if there's an amplifier bolted next to the magnet. If there is, it may be repairable. You might also notice if you tip the speaker over into different positions while it's playing, the popping might clear up or get much worse. That's also proof the speaker is the problem.

Sometimes changing the volume changes the vibrations in the amplifier causing the static you're hearing. This is real common on older high-end Chrysler systems from the 1980s and '90s. These speakers can cost over $130.00 new. Repairs are $45.00 and are usually permanent.

Caradiodoc

I had the same problem with my 98 740I, I fixed it by removing the radio tuner from the dash, and cleaning out the volume knob with some electronic cleaner, you can only buy that form a electronic distributor it's what the professionals use to clean electronics.

It is probably the unit in the dash causing this issue. The speakers should be inspected as well, the previous posting was correct.