Running on DCS or Conventional? I have noted the potentiometer is bypassed when running on DCS, if you are in conventional mode, the volume setting would have an impact, kinda basic info but I didn't see it noted here.
As far as speakers, I have had great success with Google searches and have found exact size matches at far less than direct purchase from any of the manufacturers. Of note, a 2 inch Poly (plastic cone) has really improved the high frequency sounds, in my opinion. I have had significant paper cone failures here in the Florida humidity and so far my experience going to poly has been a success.
Search Veco-Round-Speaker-0-2W-50CS16G-M75ND/dp/B00IKN98BQ on Amazon for the 2 inch poly
Mark