Systems List › DIY › BMS 18N862 SEALED
NotesThe BMS 18n862 driver in the sealed test box boasts one of the more impressive sets of measurement that has been pulled from any driver. The impedance is incredibly flat up well past 500Hz with very little inductance rise and exhibits a system resonance of about 42Hz in the 4.2 cubic foot test enclosure. The sensitivity measurements show very good sensitivity also with a bit over 80dB at 1m with a 2.83 volt input at 20Hz which rises up past 90dB by 35Hz and reaches around 97dB by 100Hz. This combined with the relatively easy to drive 8 ohm nominal load mean that this should be an easy system to drive. The full range response measurements show that this driver could easily be used as a woofer in a 3 way system and crossed over up near 400 to 500Hz.
The high power measurements indicate that the 18n862 driver has a lot of excursion for a professional style driver and good power handling. The long term output sweeps show that this driver is very linear up through the 50.3 volt sweep, where it does not even reach 1dB of output compression at any point over the bandwidth of the measurement. During the 89.5 volt sweep which should push the driver another full 5dB harder, the driver made some distress noises in the deep bass frequencies, which indicated that it was out of clean excursion. However even at this level, the output compression is still barely 2dB which is quite good. The driver also happens to overload gracefully and distorts well before any mechanical limits can be reached. During the 89.5 volt sweep the output levels recorded at a 2 meter distance reached over 104dB at 20Hz, nearly 116dB at 40Hz and plateaued at 119 to 120dB from 60Hz-125Hz.
The distortion measurements are among the best that have been recorded. The driver exhibits high distortion levels in the deep bass during the 89.5 volt sweep but it is being driven past its excursion limits by this point. By moving down to the 50.3 volt sweep the distortion where the driver is within its linear excursion limits in the deep bass and still producing impressive output levels, it can be seen that the THD levels above 40Hz are very low indeed while the distortion never breaks 25% even down in the 10-20Hz octave. This is impressive considering the output levels during this sweep. Reducing the power further to 28.3 volts and looking at the THD measurement shows that the THD is 10% or below over the entire bandwidth. Indeed above 40Hz the THD levels are under 1%! This is a very clean driver as long as it is operated within its limits. A good part of this performance is without doubt attributable to the triple shorting rings in its motor design.
The CEA-2010 maximum short term burst output testing indicates that this is a high output driver. like most high sensitivity professional style drivers the output levels recorded via CEA2010 protocol over the 63-125Hz octave are very high indeed in the 130dB range before the Powersoft K10 starts running out of voltage swing. At 40Hz the 18n862 came it at just under 120dB but the testing had to be stopped there due to distress noise from the driver suspension. In the deep bass the 18n862 manages to produce output levels that are comparable or better than many heavy duty car audio drivers that claim a much longer excursion and produced just under 104dB at 20Hz and about 91dB at 10Hz. If distortion was ignored completely the 18n862 could burst output levels some 3 to 4dB higher than the distortion limited results in the deep bass which give an indication of just how much mechanical safety margin this driver has. Pushed for everything it was worth the sealed 18n862 could muster up over 107dB at 20Hz and an impressive 95dB at 10Hz.