Alta Audio Alec Loudspeaker Lab Report

Lab Report

Most listeners will be auditioning just off the top of the cabinet where there's both a slight loss in high treble (and substantially in ultrasonic treble) with a dip in midrange output too [green trace, Graph 1]. The ideal axis is just at the top of the 'ribbon' planar tweeter [black/red traces, Graph 1] where the Alec gains its 'brightest' high treble response. The grille is disruptive in the upper mid [blue trace, Graph 1] but, sans grilles, the Alec's ±2.7dB and ±2.9dB response errors and 0.7dB pair matching are fine (aside from a short-lived 2.1dB at the 2.3kHz crossover) but the 88.4dB/1kHz (and 86.6dB from 500Hz-8kHz) sensitivity figures are well short of the claimed 93dB. Bass? See below...

Distortion is higher than with contemporary speakers at ~2% through the bass rising to ~5% through the midrange where a broad spread of 2nd-7th harmonics persists until >2kHz, where the superior planar tweeter gets into its stride. The latter offers a tremendous ~55kHz treble extension – free of any debilitating resonance [see Graph 2]. This behaviour was consistent across both samples as was, at low frequencies, the 26Hz line/74Hz port-tuning (with extended 47Hz/–6dB output), but also showing pipe modes/harmonics at 173Hz, 365Hz, 575Hz and 975Hz. The nearfield response of the woofer shows distinct lobes at 55Hz, 92Hz and 148Hz, and nulls at 74Hz, 120Hz and 173Hz from a limited 330Hz bandwidth (–6dB re. 200Hz). The corrected LF extension [green shaded area, Graph 1] suggests 45Hz (–6dB re. 200Hz) but there are cancellations from 60Hz-120Hz. These resonances are clearly reflected in an uncommonly complex impedance/phase response. PM


Response inc. nearfield summed driver/port [green], freefield corrected to 1m at 2.83V [yellow], ultrasonic [pink]. Left, black; right, red; w. grille, blue


LF modes are revealed by resp. and impedance while driver modes at 1-3kHz are seen here

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 88.4dB / 86.6dB / 84.8dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 3.9ohm @ 25Hz, 25.8ohm @ 1.6kHz
Impedance phase: minimum & maximum (20Hz–20kHz) –27° @ 89Hz, +50° @ 1.2kHz
Pair matching/Resp. error (200Hz–20kHz) 2.1dB/ ±2.7dB/±2.9dB
LF/HF extension (–6dB ref 200Hz/10kHz) 45Hz / 56.9kHz/54.5kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 2.1% / 4.5% / 0.2%
Dimensions (HWD) / Weight (each) 1029x380x318mm / 34kg
Price £9000 (Piano Black); £10,000 (Rosewood or Beech)

Alta Audio LLC
Huntington, NY, USA
Supplied by: Sound Design Distribution Ltd, Cardiff
0800 0096213