lAB­o­RA­ToRy TEsT RE­PoRT

Australian HIFI - - ON TEST -

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.

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