Dahlquist DQ10 issues


I have a set of Dahlquist DQ-10 that sound great, but if I listen at moderate volume for 30 minutes or so the right one begins to fail. It almost sounds like a completely blown speaker.  when I turn the system off and go to use it again later, it seems fine. If I listen at lower volumes, it seems to work just fine for as long as I want.

I thought perhaps I had an amplifier issue, so I tested by listening until I started to hear the failure, then replacing with another speaker and it was fine (I will hook up to a different amplifier as well, but I’m fairly confident it’s the speaker).

is it possible there are components in the speaker that are overheating that are causing an issue?  i’ve never had symptoms like this with any other speakers.
jleluga
@rodman99999 , it sounds like a thermal issue. Don't you think that the most likely place for a thermal issue is the crossover? Certainly potentiometers and L pads are prone to causing problems. jleluga, you can clean the potentiometers with freon solvent which you can buy as electronics cleaner https://shop.advanceautoparts.com/p/crc-qd-electronic-cleaner-11-wt.-oz.-05103/7070074-p?product_cha...
You just point the tube at any open section and blast away.
Could be a rubbing voice coil on that woofer. Did you ever have the foam surrounds replaced on both woofers? 
"...so I tested by listening until I started to hear the failure...".                                                      Knowing how that, "failure" sounds would be most advantageous, to anyone attempting a diagnosis.      ie: A dead, complete speaker system (bad connection), rattling lows (surrounds & rubbing VC), highs gone (possibilities mentioned above), etc.