Fluctuations of the loudness of speakers???


I've just discovered something that has me concerned. Sometimes while listening to music, either of my two speakers (that are probably not broken in yet)suddenly loses volume (not all the way but still very noticable)...it's like they lose juice suddenly. It's more noticable at lower volumes but happens at higher regardless. I don't know if to blame speakers, or cables, or if my power outlet has a problem with my 250 wpc amplifier. Sometimes a simultaneous "crackling" sound occurs. I have no idea if the problems are related but at keeps me up at night :-( Any ideas greatly appreciated...
branislav
What you're describing are the classic symptoms of a bad speaker relay in a power amp. That is:
- Can appear in either or both channels
- Changes if the amplifier is cycled on and off
- Much more pronounced at low volume levels
- Cranking up the volume for a few seconds fixes it at lower volumes for awhile
- tapping or pounding on the unit can cause or alleviate the problem

Of course if you don't have a solid-state amp with a speaker relay . . . then that's not the problem, in which case I'd second others' suggestion of bad cable connections, or loose solder connections inside a component.
It seems like I'm going to have to borrow an amplifier for a day from somebody (nobody I know has any) and see if the problem continues...then I can apply the process of elimination. What a drag...I'll be sure to post results when I figure it out or even as I get closer. Thanks everybody for their suggestions...
Another observation, problem is more common when the system is cold than warmed up...
To change a tube, open the case, just pull out the tube when cold,,,pull straight up - don't twist it... and replace with the same tube type and number. You might have some dirt on the pins of the old tube, so I would remove and replace the same tube to see if the problem goes away.
Well, it's not my speakers...just borrowed generic receiver and none of the problems described above occured. The music sounds like from behind a curtain though, all the details are lost. Made me realize that apart from the possible problem with my amp (tube?)it blows the generic Best Buy stuff out of water :-)