Bass leaves after amp warms up?

I wonder if the problem could be better addressed if the OP had a SPL meter and a test disc so he could actually measure the SPL's at the listening seat. That way he would know if it was in his audio system or in his head. It would also help to know at which frequencies this loss of bass occurs and the actual amount of the loss.

Not only credibility, which isn't too important unless you are running for some type of award, but more importantly it might lead to a solution.

I have not read all of the posts. This has probably been addressed, but I'll risk it. When using a SPL meter as a guide once your system has 'warmed up' you just might find that by moving the listening chair (I assume you do all your critical listening from a centered seat in a close to equalateral triange) backward or forward (as little as 6" can may a huge difference in the bass) or the speakers but not so much, and take advantage of nulls or nodes caused by your room and or speaker/listening chair placement.

Just a WAG, but judging from your system photos you might yet have something to learn about set up and room acoustics. Just a guess mind you.

If you need help learning how to use a SPL meter just ask.

Good luck.

Fishing, When you run your tests with the SPL meter, set up as Al suggested and using your test disc, be sure to chart your results on a graph. This will allow you to have visual evidence of the changes you experience and will serve as an easy reference if you try moving your listening chair or speakers which you should also note on your graph. This will serve you well on your current problem, but it will also serve as a base in the future should your start to move your stuff about. It's a bit tedious, but considering all of your efforts so far it's worth while to solve or rule out possible issues.

Also, room temps can affect sound levels at some frequencies somewhat so I would note the room temp when the tests are made so you can compare them to later tests at different temps.

Another thing you can do is to disconnect one speaker. Then set up your mic/SPL meter about 3ft from the center of the connected speaker. Then run your test and chart it. Then disconnect that speaker, connect the other speaker and run the same test. This will help you rule out problems with the cross over in either of the speakers because they won't measure the same. (I once had a new pair of speakers with a bass problem in one speaker created by the manufacturer's mis-wiring a cross over. One speaker was flat to 32hz, the other rolled off starting at 100hz.)

Hope that helps a bit.

Krellman, Well said. FWIW, I agree with I with you on all three points.

One of the reasons I recommended the SPL meter was for the OP to see for himself that his problem was not with absolute volume level of the bass. He just likes his system's sound when it is cold and the HF's dominate the sound and the sense of speed that can impart to the bass. Most of us, I think, would not consider this to be a balanced sound, but he does and that is why most folks couldn't really figure out his problem or how to solve it, we just don't listen to things with his ears nor his preferences. We have just assumed that he listens with our ears and priorities.

As someone suggested, if that is a sound he really wants, he needs to evaluate his components after they have warmed up and select components that will give him the overall sound he is seeking. A daunting task I suspect.