Kroma Atelier Stella Xtreme Loudspeaker Lab Report

Lab Report

Measured above the AMT axis (in keeping with the likely listening position) this remarkable loudspeaker offers a smooth but slightly downturned mid with a +3dB 'step' above 5kHz exposing an equally uniform but boosted presence/treble. The latter contributes to the acceptable ±2.3dB and ±2.4dB response errors while Purifi's excellent QC ensures the Xtreme's fine 0.4dB pair matching up to 1.5kHz (the narrowband 1.6dB/1.9kHz and 3.3dB/17-20kHz errors are less significant). Sensitivity is on target at 88.8dB/1kHz and 88.6dB/500Hz-8kHz – both figures broadly in line with Kroma's 89dB rating – and achieved without hitching the partnering amplifier to a bruising load. Indeed, aside from a brief dip to 3.0ohm at 1.5kHz, the Xtreme's impedance lies comfortably above 4ohm across the audio band and while the biggest swings (impedance phase too) occur through the bass, the lowest EPDR of 1.75ohm also occurs at 1.2kHz and 2.3kHz as the AMT tweeter takes over at 2.75kHz.

Purifi's novel 'Neutral Surround' design evidently demonstrates less mistermination than we often see in our loudspeaker tests [see CSD Waterfall, Graph 2] leaving some discrete, low-level modes associated with the AMT tweeter above 3kHz. As promised in Purifi's literature, harmonic distortion is exceptionally low at just ~0.03% through the midrange (re. 90dB SPL). These 165mm bass/mid units work over a wide 48Hz-2kHz bandwidth while the main woofer, peaking at 73Hz, works over 48Hz-155Hz (all –6dB) and, together with the 33Hz tuning of both upper and lower ports, delivers a very respectable bass extension of 31Hz (–6dB re. 200Hz). PM


Response inc. nearfield summed drivers/ports [green], freefield corrected to 1m at 2.83V [yellow], ultrasonic [pink]. Left speaker, black trace; right, red;


Cabinet and bass/mid driver modes are well controlled, leaving some minor tweeter resonances

Sensitivity (SPL/1m/2.83V – 1kHz/Mean/IEC) 88.8dB / 88.6dB / 86.6dB
Impedance modulus: minimum & maximum (20Hz–20kHz) 3.0ohm @ 1.52kHz, 17.0ohm @ 24Hz
Impedance phase: minimum & maximum (20Hz–20kHz) –33° @ 27Hz, +42° @ 20Hz
Pair matching/Resp. error (200Hz–20kHz) 3.3dB/ ±2.3dB/±2.4dB
LF/HF extension (–6dB ref 200Hz/10kHz) 31Hz / 33.4kHz/33.5kHz
THD 100Hz/1kHz/10kHz (for 90dB SPL/1m) 0.25% / 0.03% / 0.5%
Dimensions (HWD) / Weight (each) 1150x260x450mm / 43kg
Price £28,800

Kroma Atelier
Andalusia, Spain
Supplied by: Boyer Audio Ltd, UK
0330 223 3769