Help My Nautilus B&W 804's 'pop' at loud volumes.


When listening to loud volumes for long periods of time (around 2 hrs), my left speaker has begun to make a loud 'popping' sound during a stressful point on the speakers (example: Explosions near the end of 'The Dark Knight' Batman movie, or a tight bass hit during play of the new music Blu-ray version of Rush's 'Moving Pictures'. There's no evidence of a tear in the speakers dust caps, cone or their surrounds.

It doesn't seem to happen earlier during my listening experience. This leads me to believe it may be Amp or 'heat related'. But I'm still curious why it only happens to the left side speaker.

The speakers are driven by an Anthem AVM-20 pre/pro and MCA-50 amp. I'm using RSC Prime BiWire speaker cables by Tara Labs.

Thoughts?
bw_elite
As Raquel stated, get your speakers repaired if necessary. You didn't say, but it sounds like you are not using a sub for the bottom end. If you aren't, you should consider getting one (or two) to reproduce the bass frequencies. If you don't change your listening habits, or get speakers that are made for that kind of punishment, you will continue killing speakers.
Sounds to me like you may be bottoming-out the voice coil. A loud transient can push the speaker out pretty far and the recoil can cause the piston to hit the motor assembly.
It would be worthwhile to verify that the speaker polarity is in phase with the amp. In other words that the positive output from the amp is connected to the positive lead on the speaker. You can watch the cone to make sure that it is pushing air on the initial attack of a note. If it seems to be moving inward on the initial attack you are more likely to bottom out on transient peaks and damage the voice coil.
I agree that the pop may be from your amp clipping. From what I can see on my 804's is that they are total power hogs. I have a Mac 7150 (150 watts per ch) and I pegged the meters once and it wasn't all that loud. So unless you have a monster amp on those babies, you may have to lower your level.