lABoRAToRy TEsT REPoRT
Readers interested in a full technical appraisal of the performance of the Krix Esoterix Altum Loudspeakers should continue on and read the LABORATORY REPORT published on the following pages. Readers should note that the results mentioned in the report, tabulated in performance charts and/or displayed using graphs and/ or photographs should be construed as applying only to the specific sample tested. Newport Test Labs measured the overall frequency response of the Krix Esoterix Altum speaker as extending from 38Hz to 36kHz ±3.2dB, which is an excellent result and is shown as the black trace in Graph 1. You can see that the trace is flattest across the range 100Hz to 17kHz, where it deviates by only around ±1.5dB. Below 100Hz there’s the expected roll-off while above 17kHz it appears there’s a rise in the tweeter’s output to a resonant peak at 20kHz, after which the response falls away but easily extends out to 40kHz and beyond. Note that the response is not spectrally skewed in a way that would indicate the speaker might emphasise one region of the spectrum at the expense of another, even given the ±3.2dB response envelope: the peaks and dips in the response are fairly evenly distributed. Experience leads me to suggest that the slight dip in the response between 70Hz and 100Hz would disappear when the speakers are placed in proximity to a boundary such as a rear wall.
Graph 2 shows a magnified view of the high-frequency section of the Krix Esoterix Altum’s frequency response, measured using a gating technique that simulates the response that would be obtained if the speaker had been measured in an anechoic chamber. Once again, the superb linearity across the midrange is clearly obvious.
The low-frequency response of the Krix Esoterix Altum (Graph 3) was measured by Newport Test Labs using a near-field technique that once again, simulates the response that would be obtained if the speaker had been measured in an anechoic chamber and, as noted on the graph caption, the two traces have not been scaled to compensate for the differences in radiating diameters between the port and the bass/midrange driver. You can see the output of the bass/midrange driver (black trace) rolling off smoothly from 100Hz to reach its minima (where it’s held still by the port) at 39Hz. The port’s peak output is a fraction lower, at 35Hz, and has a fairly moderate Q, so its output is 6dB down at 24Hz and 66Hz.
Newport Test Labs measured the impedance of the Krix Esoterix Altum (Graph 4) using the voltage drive technique and you can see that it will be fairly easy to drive, though the driving amplifier would have to be capable of driving 4Ω loads, as the impedance drops below 4Ω between 120Hz and 250Hz, and also above 13kHz. The low impedance at very high frequencies (below 3Ω at 22kHz) will
Bass and midrange frequencies are delivered by a 165mm driver that has a coated wood-fibre cone that is driven by a 38mm-diameter voice coil and a neodymium-iron-boron magnet whose size is much larger than one would usually expect on a driver of this cone diameter.