Australian Hi-Fi

Laboratory Test Report

- Steve Holding

Readers interested in a full technical appraisal of the performanc­e of the Airpulse A100 Active Speaker System 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 tested the Airpulse A100 in its acoustic test laboratory using both in-room and anechoic test methods. Graph 1 is a composite graph where the lab has used post-processing to splice two graphs together to produce a complete picture of the Airpulse A100’s frequency response when the bass and treble controls are both set to 0dB.

The lower part of the graph (below 1kHz) is the in-room response measured by the lab, and the upper part of the response (above 1kHz) is the anechoic response it measured.

You can see from Graph 1 that the Airpulse A100’s frequency response is totally enclosed within a 6dB window from 48Hz out to 27kHz, so the normalised response that can be derived from this is 48Hz–27kHz ±3dB. This is selfeviden­tly an excellent response! However, you can see that the higher frequencie­s are, on balance, rather higher in level than the lower frequencie­s, so that below 3kHz, all frequencie­s fall below the 90dBSPL horizontal, whereas above 3kHz, they almost all sit above it.

In the normal scheme of things, we would expect the A100 to sound slightly bright in listening sessions. However, as these speakers have bass and treble controls, it is possible for users to alter the frequency response either to linearise it or tune it to their personal taste.

You can see how the treble control can be used to reduce the level of high-frequencie­s by looking at Graph 2. The 0dB response is the centre of the three traces, in dark blue. Note that the output level has been changed slightly from that used in Graph 1, so the two cannot be directly compared. The mauve trace shows the response when the treble control is at the +3dB setting, and you can see that it is, on average, about 3dB above the 0dB trace at frequencie­s above 5kHz, but diminishes below this frequency.

The brown trace on Graph 2 shows the frequency response with the treble control at the –3dB position and you can see that, on average, the response is about 5dB lower than the 0dB trace, rather than the 3dB it should have been. It would appear from this graph that the ‘flattest’ response from the A100 will be gained by positionin­g the treble control halfway between the –3dB and 0dB calibratio­ns on the rear panel.

Graph 3 shows how the A100’s bass control aˆects the output of the low-frequency driver. First, you can see that the control has no eˆect on frequencie­s above 200Hz (which is approximat­ely the ‘A’ below middle C). In this case, the eˆect on the response is about +3dB (blue trace) and –3dB (green trace). The response at 100Hz suggests that Airpulse is actually boosting the bass a bit in order to extend the low-frequency response downward so that the –3dB is actually the ‘flat’ response but results in a premature roll-oˆ below 100Hz — which is what you’d expect from such a small driver in such a small cabinet.

The output of the rear-firing bass reflex port is shown in Graph 4, and you can see that the control aˆects port output at around 55Hz to 70Hz by about ±5dB rather than ±3dB, which is all good: better more than less!

Graph 5 shows how the output of the port relates to the output from the low-frequency driver (note that the port output has not been compensate­d to adjust for radiating area), and you can see that although the low-frequency driver’s minima is at about 62Hz, the maximum output of the port is up at 70Hz, slightly higher

The bass went deep enough to be aurally satisfying. I didn’t feel the urge to connect a subwoofer

than you would expect. The port’s output is mostly controlled, but there is a significan­t resonance at 590Hz and an even-larger resonance at 1.4kHz. It would be better if neither of these was present, but you can see that although the effect of this resonance is visible on the main frequency responses shown in Graphs 1, 6, and 7, in the way the level is boosted across the 1–2kHz region, it doesn’t really adversely affect the linearity of the overall response.

The in-room response of the Airpulse A100, as measured by Newport Test Labs using a pink noise test signal and using a third-octave filter to smooth the resulting trace, is shown in Graph 6. This test method simulates what the human ear would hear in the listening room, and you can see that the response is superbly flat from about 60Hz out to 20kHz. Indeed, above 80Hz the response is within ±2dB out to 20kHz. This, again, is an excellent result for the Airpulse A100.

Graph 7 is a composite frequency response graph, where Newport Test Labs has overlaid the various different measuremen­ts so that you can see the ‘fit’ between them. This graph also shows that although the port resonance at 1.4kHz is slightly visible on the near-field output of the bass driver and has a fairly significan­t effect on the anechoic response (which is not smoothed, so shows the exact output of the A100 at each frequency), once the response is smoothed the effect of the resonance disappears.

Overall, the Airpulse A100 delivered excellent performanc­e in all of the tests conducted by Newport Test Labs, and exhibited a more extended bass response than we would have expected.

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