Wilson Audio’s Sasha returned sets of flat and extended frequency responses in all tests conducted by Newport Test Labs. Graph 1 shows an averaged result of nine individual frequency sweeps, measured at a distance of three metres from the Sasha, with the central grid point exactly
on-axis with the Sasha’s tweeter. As you can see, the frequency response over the region graphed is very linear, being within ±2dB from 52Hz up. More importantly, you can see that the overall response is very balanced, and that even below 52Hz, where the frequency response falls away, it doesn’t plummet, but just drops to around 5–7dB below the average response. The only characterising trait on the response is a slight, wideband ‘droop’ between 100Hz and 500Hz.
Graph 2 shows the Wilson Audio Sasha’s high-frequency response in detail, and also with and without the grille fitted. The first thing to note is that you should ignore the ‘wiggles’ in the response at the extreme left of the graph, which are artefacts of the measuring technique used (gating). You can see that the graphed response extends from 500Hz to 22kHz ±2.5dB, and that the response is marginally ‘smoother’ when the grille is not used, though the only real difference between the two traces occurs at 5kHz. Although the response shows peaks centred at 1.8kHz, 4kHz and 20kHz, the Qs are so high that they would not be individually audible as peaks and thus can safely be ignored. The peak at 20kHz is most likely the tweeter resonance. Graph 2, when considered in conjunction with Graph 1, shows that Newport Test Labs measured the overall frequency response of the Wilson Audio Sasha as 48Hz to 22kHz ±3dB. This is, self-evidently, an excellent frequency response.
Low frequency performance has been graphed using the standard near-field technique, and you can see that Wilson has tuned the bass reflex port so it’s delivering its maximum output somewhat lower-down in frequency than the driver’s minima, which is the reason for the superior performance at the extreme low end. The port’s output peaks at 23Hz, whereas most designers would have it peaking at 26Hz. This graph shows the output of both of the woofers and you can see that they’re perfectly matched, which is indicative of excellent QC procedures at Wilson. The slight variations in the response above about 180Hz stem from the fact that the woofers are located at different positions in the cabinet, and it’s the difference in rear-loading that causes these slight variations.
Graph 4 is an extension of Graph 3, this time ‘adding in’ the output from the midrange driver, and the output from the ‘port’ in the head of the Wilson Sasha. You can see that the port is acting more like a real driver than a ‘port’, with a very flat response between 60Hz and 200Hz that’s virtually a ‘mirror’ of the output at the front of the midrange driver, except that it’s shifted downwards in frequency. The midrange driver’s response is very flat for the most part, though it appears to show a rise above 1kHz.
The impedance/phase graph (Graph 5) shows that the Wilson Audio Sasha presents a difficult load for any amplifier. Although the curve shape looks conventional, check the graph scale—the top of this graph is only 10 ! Indeed over the range 20Hz to 20kHz, the Sasha’s response never rises above 8 and at its lowest point drops to around 1.6 (at 85Hz). The phase angle at this same frequency is around –15°, but this is up from around –45° at 55Hz. Signifi- cantly, the impedance is at or well below 4 over the region 55–375Hz, so the speaker will be demanding extraordinarily high current delivery from the amplifier—particularly at higher SPLs. Since I’ve mentioned SPL, I should note at this point that Newport Test Labs measured sensitivity at 91dBSPL at a distance of one metre, using a 2.83Veq input level, which exactly met Wilson Audio’s specification. Not only is this an excellent figure in its own right, it’s also excellent because Newport Test Labs’ methodology for this test is so stringent that most speakers fall well short of 90dBSPL. The fact that the Sasha exceeds it by a full dB is highly creditable.
The final graph (Graph 6) that has been selected for inclusion with this review is a composite one that combines all the previous traces (except those for impedance modulus and phase angle) on the one graph. You can see that the various different test methodologies do give an excellent and completely cohesive picture of the Wilson Audio Sasha’s overall measured performance, which is excellent. The Sasha has a smooth, well-balance and well-extended frequency response—with particularly good bass extension—and is also highly efficient, so it will make good use of amplifier power. Its only real Achilles’ heel is that it’s likely to be a bit difficult to drive, which means you will need to pay careful attention to your choice of amplifier.