Crackling from bass combo when I hit low notes

You are probably overdriveing the unit... In a 20 foot square room, if *********** could not stand to stay in the room, it is too loud and likely driving the voice coil outside the linear range. This makes a very nasty noise.

There are two likely causes for this. One is much, much easier to fix than the other.
1) You are turning up the volume too much. Headphones, especially non-top of the line headphones, are not meant to be listened to at very loud levels. In this case, the crackling you are hearing is the speaker trying to reproduce a bass sound that is "clipping", or exceeding the maximum output level for that system. Remember - headphone speakers are very small; they have a harder time producing low sounds accurately. The solution is to just turn them down a little.
2) Assuming problem 1 is not the problem, the other likely issue is that they came with some sort of mechanical defect built in. If you are not playing them loudly, but you are still getting a crackle, especially if it is only on one speaker, they probably are broken. It is probably the jack itself, or the wiring leading up to the earpieces. Either way, it is not a terribly hard fix if you have some electrical know-how, but if you don't, there are plenty of people who can rewire them for much cheaper than it would be to buy a new set. However, if this has been happening since you got them, I would call the manufacturer first and see if they will replace them. Sennheiser tends to pride themselves in the quality of their equipment, so I would not be surprised if they sent you a replacement set.
Hope this helps!

Power sound amplifier output transistor push n pulls are dead and the q point is off the scale.
Either it is a modular amp or discreet top hat xistors

That's because explosions are pretty much only low frequencies, otherwise known as bass. Your tv crackles because the low frequency emitters of your tv are either of low quality or malfunctioning. If you lower the volume of your tv it should fix the problem.

Information I find online says it an Active Subwoofer, so that introduces its own amp as a possible source of the symptom. If there is another version of this model that's passive, all the more reason to believe the amp is the problem because passive speakers don't spontaneously emit sounds.

If there was a physical reason for the crackling I would think more power would make it worse or blow it up.

A poor sub signal cable connection might explain low current anomalies if random noises are entering the signal path.

Make sure the signal, speaker and power cables are not aligned parallel and close to each other.

Either the control is damaged (happens if they get hit) or it is possible the circuit board it is mounted on has broken solder OR worse, a crack near the control. The unit will require servicing. Parts are readily available.

The crackling sound on the left port of the bass box, indicates vibrating foreign matters inside it. Just open the box and clear it up. Put the sounds on. Listen if the crackling sound is audible. If the result is ok, then, close the box, and everything is alright..
However, if the result is otherwise, then, it is due to a defective speaker that needs to be replaced.

Hello Rachel, I use my QC3 for 2.5 years Mon-Fri for 3 hours a day. I have the same problem when battery is weak and/or it is cold outside. The cracking nose stops for me if battery fully charged. This is known problem andBose put it in the manual.
Vlad

Make sure all songs are in the right format. If the headphones move even slightly , you will get crackles - this is a common problem with mp3 players - the headphone jacks are sensitive.

Yea, now its time to replace it! the magnetic effect is weaken which makes the very bass low frequency sound to be distorted! You should re engergise the magnet of the subwoofer or should buy the new!