Loudspeakers

The axial response [Graph 1] shows a very slightly dished overall trend and a lift after the 2.4kHz crossover – a baffle step effect – coinciding with low-level driver modes from 2-4kHz and (from the MPD III tweeter) at 8kHz seen on the CSD waterfall [Graph 2].

These, and the uplift in high treble – peaking at +6dB/36kHz – account for the relatively modest ±2.8dB response errors (re. 200Hz-20kHz) while the poor 2.0dB pair matching is entirely due to a dip in output of one tweeter at 8kHz [red trace, Graph 1]. Pleated film diaphragms are notoriously difficult to build, with even small deviations in edge-clamping and positioning of the rear foam producing peaks and nulls in response. Excluding this (in all likelihood) inaudible dip, pair matching was a far tighter 0.8dB. Furthermore, the treble may be tuned very effectively by toeing the speakers away from your listening axis by 10-15°, the latter flattening the response above 10kHz [grey trace, Graph 1].

Sensitivity is bang-on MA’s 86dB spec. at 1kHz, decreasing very slightly to 85.4dB over 500Hz-8kHz (all re. 2.83V/1m) so the Studio 89s will need a big amp to deliver big sounds. Fortunately the 89’s 4.4ohm/202Hz minimum impedance – and modest ±43° phase angles through the bass, mid and treble – result in a relatively painless 2.2ohm/135Hz (and 20Hz) EPDR. Low sensitivity/small drivers means THD in the low bass increases to ~2% here (100Hz re. 90dB SPL/1m) and while the two drivers and ports are tuned symmetrically, the latter to 56Hz, there’s also a fairly strong (–10dB) quarterwave/port mode at 750Hz. Diffraction-corrected bass extension is 57Hz (–6dB re. 200Hz) but deeper is possible with rear wall reinforcement. PM