A couple of years ago another member had a similar symptom. But he described it as a screech/scratching sound in the mids (vocals). He also had a V70SE (by that time I upgraded to the V110). He contacted Dynaudio and they thought it was a problem with his V70SE. They gave him a sweet deal on a new V110. When it arrived same problem. He said he took the C1's to his local dealer who confirmed the speakers caused it. Turns out both woofers coils had swollen up and were rubbing. This only happened at high volumes with bass heavy tracks and affected mostly female vocals.
If that is the case what you can try is with the system off push the woofer drivers by hand and both listen and feel for smooth movement. If you hear a scratchy sound or feel uneven movement the coils could have swollen.
That person bought his C1's used and really had no idea how the original owner used/abused them. I never found out if he had them repaired or just gave up on them.
To me it sounds like the woofers are bottoming out. When I had either the original C1's or MKII/Sig the bottoming out was a POP kind of sound. I personally heard that and made sure I never turned it up that loud again. It also happened with music that was very compressed.
If that is the case what you can try is with the system off push the woofer drivers by hand and both listen and feel for smooth movement. If you hear a scratchy sound or feel uneven movement the coils could have swollen.
That person bought his C1's used and really had no idea how the original owner used/abused them. I never found out if he had them repaired or just gave up on them.
To me it sounds like the woofers are bottoming out. When I had either the original C1's or MKII/Sig the bottoming out was a POP kind of sound. I personally heard that and made sure I never turned it up that loud again. It also happened with music that was very compressed.