It's interesting but I can't say I am sure I can always relate it to frequency respons.... I auditioned the whole piega coax line up through the master series to the Master Line Source ... and I can't say I can hear the same issues here.... there are other things with Piega though, I am not sure I like the sound of a grand piano, a Steinway Model D sounds not fully real (that is my subjective opinion)
Maybe these are phase related issues, the harmonics may be out of phase ...
Piega Coax 711 also show this rising trend ....
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Piega writes on their webpage:
Furthermore: As our ribbon systems ensure that the direct sound components and the sound reflected from the surfaces of the room always reach the listeners in the correct phase
So much for that claim
I don't like when a "credible" speaker manufacturer tell me rubbish
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