Thank you in advance for any advice; I’ll try to explain this as clearly as possible.

I bought the pictured speakers from Acoustic Energy and linked them up with a Marantz amp from the 80s gifted by a relative. Each time I’d use it, it’d work for a different length of time before inevitably cutting out in one speaker so sound would be coming out of only one speaker.

I switched the cables around to make sure it wasn’t the speakers themselves. I changed the inputs to check it wasn’t the cables. I bought new cables in case.

Then my partner bought me another amp to try to fix the problem: an Arcam Alpha 5 plus. The internet tells me this is from 1995. Thought everything was fine after trying it out the first time, but the problem keeps coming back. It always works for a little bit, then cuts out in one speaker, always the same speaker.

It’s not the input either as it does it for the phono, CD, and aux inputs. 

So: it’s not the speakers themselves, it’s not the cables, it’s not the input, AND it’s not the amp, as the problem has happened with two different amps - the exact same problem.

This evening I had the idea that it could be an incompatibility between the age of the amps (they were both old) and the newness of the speakers. 

I’ve looked on the internet and gathered that there can be a problem between new and old and something to do with 4 ohm; I have no clue what that is and the forums are people who know what they’re talking about. Please can someone explain in layman’s terms whether or not new speakers could be cutting out due to the amp’s age and it not being able to handle it. Could it be cutting out in one speaker due to some kind of over-powering in the amp?  
And could buying a more modern amp fix the problem? I’m happy to buy a newer amp as I’m not precious about my set up being vintage - I don’t need it to be perfect, I’m not an audiophile, I just want a system that doesn’t have my speaker cutting out every single time I try to play music or watch TV.

Sorry that was long but I hope I’ve covered it all, and thank you again to anyone who can offer any guesses.

Do new speakers not work with old amps?