MMX 330 PRO
headphones
$349
Used market: $270*
Specifications
4 of 7 values have a recorded sourceExpert Audio Engineering Commentary
Tonal Profile
The open sibling of the MMX 300 PRO — same 48 Ω, same 5–40 000 Hz, same published sensitivity, different enclosure. Open backs leak in both directions: you hear the room, the room hears you, and the bass depends far less on how well the pads seal.
Amplification Warning
Identical electrical load to the closed model. If your source drives one it drives the other; the choice between them is acoustic, not electrical.
What the datasheet actually says
Quoted verbatim from the manufacturer’s own page, with the date we checked it. We state what is printed, not what anyone intended by it.
«Nominal sound pressure level: 96 dB»
No reference unit is printed. beyerdynamic names it on the PRO X pages — «100 dB SPL (1mW/500Hz)» — so we read this as dB/mW; read as dB/V it would mean about 81 dB/mW, which no 48 Ω headphone of this class measures. The same 96 dB also appears on the closed MMX 300 PRO page, so the figure does not distinguish the open model from the closed one.
checked 8/5/2026* Estimated with the depreciation fallback (~77% retained value). · checked on 8/5/2026