I’m stumped, shorting speaker?

I've been trying to problem solve this one for months & I'm stumped.

The setup - an older SS class A amp running a pair of Focal K2P's (stereo, 4 ohm each).

The problem - As the system heats up after a few minutes, louder volumes (50%+) produces static in the speakers (both of them equally).

Checked the inputs, does it with multiple sources identically.  Checked the wiring - bomber.  Switched the amp to another identical amp, same problem.  Sent one amp back to SS to be checked, they returned it saying it's OK.  Still does the same things. 

Tried 2 other different amps, PROBLEM SOLVED, but cannot turn gains very high without excessive clipping - almost like protect mode, it just cuts out entirely momentarily.  Tried all amps on the rear speakers (Quart components), they all work fine.

So now I'm thinking it has to be something downstream of the amps - speakers or wiring?  The problem is identical in each speaker.  Each speaker sounds fine at lower volumes.  When the system is cold, maybe the first minute, it will tolerate high volumes well & sounds great.  After a minute of burn-in the static/clipping occurs.  Beyond that it will be fine at lower volumes only.  What the hell? 

I think the difference with the class A amps is that when see a short they can deal better than the other conventional amps, they're just much beefier & rated to a 1/4 ohm each, so maybe that's why they make static rather than protect.

It seems odd to me that if there's a fried VC it would only occur when the system is warm.  Also seems odd that the problem is symmetrical across the speakers.  Tested the speaker leads at the amp & found 3 ohms DCR - consistant with what it should be.  Is it possible that something in the X-overs are dying? 

Sorry such a long read, trying to give you as much info as possible to work with.  Any ideas are welcome, I'm clueless.

I don't get the part where you said "but can't turn gains very high without..." when you were referring to the two amps that worked okay, sort of.

You've been around for awhile here so I believe you would be setting gains according to the Rules of Setting Gains

What's your procedure?

I think it's unlikely that the same problem would manifest itself in both crossovers at the same time.  Should we assue that this system played properly for some time before the problem occured?  Or should we not?

Bypass the crossover if you want to get that part of it out of the way.  Connect the leads from the amp directly to the mid driver for testing.  See if the static occurs.  Do this to only one side at a time...see if the static still appears in the properly wired side as well.

OK, good strategy, I'll bypass the X-overs & report back.

Yes, the system worked well for a good 3-4 months before the problem started.  The gains were set using the clip indicators on the amps themselves & set low enough that they never should have gone into clip unless a particular track was recorded absurdly loud, but I almost never run the system that hard anyway. 

The reason I focused on the amps initially was b/c they're in an enclosed space with 2 fans forcing a good bit of air over them.  One of the fans got blocked for I don't know how long, but given that they're class A I know they were cooking in there.  As the weather warmed up the problem started.  I think that's just coincidence at this point tho.

About having to set the gains lower, I tried using a class a/b SS (normally on the sub) on the problem speakers, it plays fine but the gains have to be set considerably lower than expected, consequently the output from what is normally a 75 wpc amp is more like 25 wpc.  Increasing gain yeilds clipping & momentary shutdown - normal behaivor from that amp at clip is SQ degradation, not shutdown.  Connecting that amp to the rear speakers produces a lot more volume before clipping.

OK, update.  It appears the obvious has eluded me again.  Just one mid driver causing the problem, not both.  I don't have a balance control so I just never did that test, and the problem was so sonically ugly (and my soundstage so supreme  ) that it sure did appear to be both sides.

Bypassed the x-over, still there.  So this driver will be going in for warranty, finger's crossed.  It's still a bizarre character to the problem, the driver sounds great at lower volumes & then causes mad clipping at higher volumes, but only after a few minutes of burn-in time.  If anyone knows what that's about...

thanks for the help.