Q Acoustics 3020i on a Cambridge AXA35: 6 ohms against an 8-ohm-only amplifier
Here the nominal figure already fails: 6 Ω against a required 8 Ω, with a 4 Ω minimum underneath. The calculator uses 86.75 dB per watt, not the printed 88, and returns 100.2 dB at 2.5 m.
Rejected on the label, not only on the dip.
The previous pairing failed because a nominally 8 Ω speaker dipped below the rating. This one fails one step earlier: the 3020i is a 6 Ω speaker and the AXA35 asks for 8 Ω, so the nominal figure alone is already outside the manual. Underneath it there is a published 4 Ω minimum, which is where the amplifier would actually be working. Verdict: thermal overload hazard, with 6 Ω nominal and 4 Ω minimum against an 8 Ω requirement.
Sensitivity is quieter than the sheet suggests. Q Acoustics prints 88 dB, measured at 2.83 Vrms / 1 m. Into 6 Ω, 2.83 V is 1.33 W and not 1 W, so the calculation uses 86.75 dB per watt. That gives 100.2 dB at 2.5 m from 35 W, 10.8 dB below the 105 dB reference peak, with 2 % cable loss on 16 AWG and a damping factor of 35. Against a genuinely 8 Ω speaker quoted the same 88 dB, this one is 1.2 dB quieter before anything else is considered.
Read the impedance line literally. The 3030i datasheet says «Average impedance: 6 Ohms»; the 3020i page for the same series says «Nominal impedance». Two pages, two words, one row — and an average is not a floor. The floor is the separate 4 Ω minimum, and the floor is what an output stage meets. This is why the catalogue stores both numbers and compares the second one.
What to do. With an 8 Ω-only amplifier, a 6 Ω speaker is not a marginal choice, it is the case the manual excludes. Either put the 3020i on an amplifier rated to 4 Ω — where its 25–75 W window is comfortably covered — or, if the AXA35 stays, accept that no bookshelf speaker in this catalogue meets its stated requirement and choose the mildest load you can verify rather than the one the shop pairs it with.