The blue trace, taken in Wide mode, is very similar to the Narrow-mode response in the middle and low frequencies, but there is less treble energy at the listening position, presumably because more energy is being directed to the speakers' sides and being absorbed by the room's furnishings. This mostly eliminates the room acoustic's effects.) The red trace was taken in Narrow mode despite the additional measurements that contribute to the averaging, it is very similar to the responses shown in fig.3. (I average 20 1/6-octavesmoothed spectra, individually taken for the left and right speakers in a rectangular grid 36' wide by 18' high and centered on the positions of the listener's ears. The sensitivity of human hearing decreases rapidly at low frequencies, and low-frequency sounds must be played at a much higher sound-pressure level to be perceived as being as loud as mid-frequency sounds (footnote 2).įor fig.4, I measured the BeoLab 90's spatially averaged response in each of its three modes of operation. Though this rise looks alarming (footnote 1), it was not as audible as you might thinkother than in the magnificence it added to the organ recording of mine mentioned by KR, which has significant energy below 32Hz. I suspect that the increase in level in the low bass arises from the usual boundary reinforcement in this regionKR had each speaker situated just 18' from its respective sidewall. There are still some room effects visiblethe lack of lower-midrange energy and the peak at 105Hz in the left channelbut these are mild, especially when you consider that there was no spatial averaging in this graph. Both sets of filters are applied simultaneously you can see that the amount of correction is relatively small, covering a range of +5 to ≦dB.įig.3 Bang & Olufsen BeoLab 90, Narrow mode, 1/6-octave responses of left (blue) and right (red) speakers with DSP correction at listening position. The responses of these filters, as set up by B&O's Geoff Martin, are shown in fig.1 (Mono and Side) and fig.2 (Left and Right). However, it differs from conventional correction solutions in applying not just individual filters for the Left and Right speakers, but also filters to correct the speakers' summed (Mono) output and the difference between their outputs (Side). (These were set to a sample rate of 96kHz for the measurements and I fed Fuzzmeasure's analog signal to the Master loudspeaker where it was converted at 192kHz.)įirst of all, as KR described in his review, the BeoLab 90 system uses digital signal processing (DSP) to correct the room's acoustic. I used SMUGSoftware's Fuzzmeasure 3 app running on my MacBook Pro, along with an Earthworks QTC-40 microphone and a FireWire-connected Metric Halo ULN-2, which combines a low-noise microphone preamplifier with A/D and D/A converters. The BeoLab 90 is so massive that, rather than having it shipped to my home, I traveled to Kal Rubinson's place to take some measurements.

Fuzzmeasure pro 3