Bass leaves after amp warms up?


I don't understand-after my Musical Fidelity M6i amp warms up for about an hour I notice the deep bass & kick drum aren't the same.
They sound less musical with loss of weight/depth.The notes are there but the moving of air have left.Sound is has much less impact and boreing.
I had the same problem with Bryston amp so there is no defect with amps nor with the rest of my equipment/
PSB Synchrony one speakers,AQ cables,Bryston CD Player.
My question has anyone heard similar & is there a plausable reason?
fishing716
IMO, It sounds like you have about the same bass energy in both good and bad recordings. It seems to be the character or quality of the bass that is changing. Tight and defined when amp cool, loser and woolier when warmed up. The Bryston amps I've used in the past had this quality to them. If you do not have the plugs installed in the lower vents I suggest you try them. The speaker will have an overly tight or lean bass until the amp gets warm upon which the bass should take on a more normal "Q".
It sounds like you have about the same bass energy in both good and bad recordings. It seems to be the character or quality of the bass that is changing
Exactly!
I do have one of the bass plugs installed
Have you tried the speakers without the plugs? If so and it is even worse than I'd say we are on the right track. When you add the plugs you are lowering the "Q" of the speaker. Some speaker companies included different lengths of plugs so that the owner could tailor the speaker for the "Q" that works best for his room/amp combination.

The only other possibility is using a whisper fan on the amp so that it never warms up.