MRM928

Hello , looking for some insight and ideas please. I recently picked up a pair of Quartets for my Marantz 2270. They sound fantastic until I push them past 50% volume. At that point I begin to hear a popping sound coming from the Mid area maybe. I originally thought they would be a great fit for my 2270 because they’re 8ohm and the older Marantz is better with 8. So does anyone know what’s going on here? Is it a bad combination ? Is it something with the speakers ? I’ve read it could be crossovers , my knowledge is not at that level. All information is appreciated.