Bass leaves after amp warms up?

Does the dealer you bought from still sell the PSBs?

Maybe go there, talk to the dealer, and listen to your speakers there off a few different amps if possible. Maybe even take yours in and see what happens there off various amps if possible. Maybe even take the amp in to test out. See if same thing happens there.

Some of the recent posters have, understandably, not read through all of the 130+ posts in this thread. So here is a summary of some of the key facts that have been stated:

The same problem has been exhibited with two different models of PSB speakers (the Synchrony One and the Synchrony Two), both having impedances that are specified as 4 ohms nominal and 4 ohms minimum. JA of Stereophile measured the impedance of the Synchrony One that is presently being used as being between about 2.7 and 4 ohms throughout most of the bass and mid-range regions. The OP does not play the speakers at high volume levels.

The same problem has been exhibited with three different integrated amplifiers. There is reason to believe that driving low impedances is not a forte of any of those amplifiers.

The same problem has been exhibited with two different sources.

Connecting only one speaker to the amplifier considerably increases the amount of time between a cold start and the appearance of the problem.

When the bass disappears, it can sometimes be made to reappear by switching between sources, disconnecting and reconnecting the speaker cables, or other seemingly innocuous things. The integrity of all connections appears to be good.

My suggestion, at this point, in addition to the planned electrician visit, and attempting to borrow different speaker cables: Try to borrow a separate power amplifier that is known to be able to deal with very low impedances, and drive it from the pre-outs of the integrated amp.

Regards,
-- Al

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.

Interesting, it is hard to account for all of the reported phenomena. It sound like the poster does not like the inherent sound of his system after all of the gear has properly warmed up. This would mean some kind of system tuning is in order-change in speaker and/or listener placement, room treatment, equipment change, whatever, and perhaps a change in listening habit--e.g., leaving the system on all the time so that it is warmed up from the get go.

Comparison with an amp well suited for the speakers, at least on paper, would seem to be the one thing to try with biggest upside. At a minimum, OP finds out if prime suspect, the amps ability to drive the speakers, is in fact an issue. At best, overall performance may well go up significantly and current problems would be but a memory.

I am hard pressed to imagine how power source would produce the pattern of sound deterioration over time described. Defective speaker wires might be a reasonable explanation. Replacing speaker wires with most anything else, even basic 12-14 gauge zip wire, should be enough to determine if current wires are defective in some way leading to deterioration of sound over time.