Bass leaves after amp warms up?

Atmasphere I tried your suggestion of turning off the amp when the sound changes and my first try was successful!
I only waited 10 minutes and returned but the bass was back in full bloom.
I don't know how long it will last but will explore this development till I discern a pattern.
Something must be overheating?

Fishing, I can feel your frustration, but IMO nothing can be done w/o measuring the SPL. Wait for your friend to measure and then we'll have a more definitive diagnosis. (Underpowered amp as many of us believe). OK, my last post.

Fishing716 -

A couple of suggestions.
What I have found with some mosfet amps is they go through cycles. On turn on, very transparent, then after a while they go gluggy. However if you wait another hour then the transparency returns.
The other suggestion would be to get the amplifer checked over - get the "bias" checked to make sure it is in spec. The bias will determine the operating temperature to some degree and too high a bias can result in "gluggy" sound.

Just re read all of the Fishing716 posts to find a pattern. Please correct me if I am wrong but it seems that there is rarely a time that the bass sounds bad when first turning the system on for that day and also you have had marginal success by often fiddling with the cables. You also have mentioned that the bass leaves quickest with video sources.

Another "grasping at straws" would be to dermine if something in your speakers are getting so warm that the "Q" of the speaker increases enough that the bass no longer has punch, impact or definition to it. You could try losely filling your ports with spongy foam before you turn on your system to see if you can recreate the "flat" bass sound for us. It does not hurt anything to try.

Yet another "grasp" would be some kind of capacitance build up in your cables that can be dissipated with enough fooling with them, not that I know how that could happen.

I know that these are some pretty out there ideas but it is all I could come up with as the other posters have done an excellent job of covering the subject.

I've been following this post from the beginning but do not remember if the following has been asked. Do you know anyone else that has a similar system that you could spend some time listening to? I'm wondering if the problem is tied to a form of listener fatigue. I do not mean to offend. I ask only because somedays I can listen for hours on end with no perception difference and on others it goes quicker. Especially if I have had to mix sound for a band the day before. The patterns of the sound quality coming and going do not overtly suggest this but I thought I would throw in on the "grasping at straws".