DALI Oberon 1 with a Marantz Cinema 70s: the green verdict rests on a number DALI never published
DALI publishes 6 Ω nominal and no minimum at all. The calculation substitutes 4.8 Ω — 80 % of nominal — and only then says safe. Level: 50 W and 84.75 dB per watt give 99.8 dB at 2.5 m.
Safe — on an assumption, and you should know which one.
DALI publishes a 6 Ω nominal impedance for the Oberon series and no minimum anywhere. The catalogue therefore carries no dip figure for this speaker rather than a guessed one. But the calculation still needs something to compare against the Marantz’s 4 Ω rating, so it substitutes 80 % of nominal — 4.8 Ω — and returns a safe verdict on that. Read it as «nothing published contradicts this pairing», not as «measured and fine». Three speakers in this catalogue are in the same position: the Oberon 1, the ELAC Debut 2.0 B6.2 and the JBL Stage A130, all 6 Ω nominal, none with a published minimum. Every one of them receives the same synthetic 4.8 Ω.
Why that matters here. A nominal figure is an average over the band; real two-ways routinely fall well below it around the port tuning and the crossover. For the speakers in this catalogue that do publish a minimum, the gap between nominal and minimum runs from 2 Ω to 4.4 Ω. If the Oberon 1 behaves like its neighbours, its true minimum is below the 4.8 Ω the calculation used and possibly below the receiver’s 4 Ω rating. Nobody outside DALI can say.
Level. The Oberon 1 is quoted at 86 dB, 2.83 V / 1 m into 6 Ω, which is 1.33 W, so the calculation uses 84.75 dB per watt — the quietest speaker in this batch. With the Cinema 70s’ 50 W into 8 Ω at 2.5 m that gives 99.8 dB, 11.2 dB below the 105 dB reference peak, 2 % cable loss on 16 AWG and a damping factor of 35. DALI also prints a maximum SPL of 106 dB at 1 m, so the window between audible and compressing is not generous.
Worth knowing about the receiver. The Cinema 70s is a 110 mm slim chassis with seven channels inside, and its honest rating is 50 W + 50 W into 8 Ω, 20 Hz–20 kHz, 0.08 % THD. The 70 W in most shop listings is 6 Ω, 1 kHz, 0.7 % THD. A modest honest number is a consequence of the enclosure, not of a weak design — but it does mean this receiver should be kept away from low-sensitivity speakers, and 84.75 dB per watt is the lowest here. If the room is larger than this 2.5 m, that is the first thing to reconsider.