Loudspeakers

Our last experience of the Manger Sound Transducer (MST)was with the Zerobox 109 [HFN Aug '07] since which time our measurements suggest it has been improved, achieving higher sensitivity and a somewhat smoother response – although it is still far from flat. Manger claims 89dB sensitivity for the P2 but our measurements only achieve this when the FFT data is averaged, giving the P2's shelved-up treble undue influence. Adjusted to pink noise, the sensitivity drops to 87.1dB.

The claimed 8ohm nominal impedance is also a little optimistic for we measured a minimum modulus of 4.1ohm and low-frequency phase angles sufficiently large that its EPDR (equivalent peak dissipation resistance) drops to twin lows of 2.4ohm at 76Hz and 116Hz. So while not a notably difficult load to drive, the P2 is not as benign as its specification suggests.

Forward frequency response [Graph 1, above], measured at 1m on the MST's axis, is characterised by the aforementioned treble shelf and narrow notches at about 1.7kHz and 7kHz which suggest resonances. (Ignore the roll-off below 400Hz which is a measurement artefact.) Together these features make for high response errors of ±5.4dB and ±6.0dB respectively to 20kHz, and a pair matching error also on the high side at ±1.7dB, although up to 12kHz it was better at ±1.0dB. Our diffraction-corrected nearfield bass measurement recorded an early if gradual roll-off below 130Hz reaching a mere 85Hz (–6dB re. 200Hz) but this can be bettered in practice by careful placement relative to room boundaries. Given the uneven frequency response, the cumulative spectral decay waterfall [Graph 2] is unexpectedly clean, with fast decay of the expected resonances. KH