2x parasound A21
I presume this means that you have used the two A21s in bridged mode. The manual for the A21 states as follows:
You should not connect a speaker with an impedance of less than 8 Ω to the A 21 when it is configured for bridged mono operation....
... We strongly recommend against using speakers rated at less than 8 Ω when bridging.
The Maggie 1.7 has a nominal impedance of 4 ohms. The Harbeth 30.2 has a nominal impedance of 6 ohms. Both speakers are therefore not good matches for bridged A21s.
Also, given that a single A21 operating in stereo mode is quite powerful (spec’d at 250 watts into 8 ohms and 400 watts into 4 ohms), and given that both speakers have sensitivities in the vicinity of 86 db or so, I would think it likely that a single A21 operated in stereo mode would provide enough power anyway.
And, finally, I see that the Harbeth has a "power handling" spec of 150 watts "programme," which is to say that a single A21 operating in stereo mode can most likely supply more than twice as much power into its 6 ohm impedance than the speaker can safely handle.
Regards,
-- Al