Systems List › JTR Speakers › Noesis 212HTR
NotesMeasurements on the Noesis 212HTR were conducted only on the low frequency section. The passive crossover used for the pair of 12Ē drivers was in the loop. The measurements start with the impedance curve for the LF section. The Impedance shows a classic vented alignment and indicates a vent tuning of about 50Hz. The minimum impedance for the system measured about 2.9 ohms at the vent tuning and an average of about 3 to 4 ohms over the 100 to 300Hz range. The basic frequency response of the LF section of the system showed extension to about 50Hz in the bass range and about 300hz on the top end where the low pass filter section of the crossover rolled out the upper end frequency response of the 12Ē drivers. The ultimate slope of the low pass filter appeared to be 18dB an octave. Overall the on axis ground plane response of the Noesis 212HTRís low frequency section fit within a 6dB total window from about 56Hz to 320Hz. This is with no smoothing applied to the measurements, which would normally extend the range within the window a bit. Sensitivity measurements of the system showed excellent sensitivity of well over 100dB. The Noesis 212HTR low frequency section is a 4 ohm nominal design so a voltage of 2 volts was applied at 1m. The resulting response measurement shows a sensitivity of about 98dB at 50Hz which slowly rises above 100dB near 60Hz and crests 105dB at about 85Hz where it plateaus between 105 and 106dB from 90-165Hz. The 10 meter measurement with a larger input of 20 volts shows slightly less sensitivity but it is still in the neighborhood of 105dB over the same range. This is a very sensitive system which will still put out a lot of sound when connected to an amplifier with modest capabilities.
Since this is a vented system, with a relatively high tuning point, a high pass filter was engaged to protect the drivers during the high output testing. A 40Hz 18dB octave Butterworth filter was selected for this purpose. The long term output testing started with a drive voltage of only 1.93 volts which produced approximately 90dB at 2 meters at 50Hz. The Noesis 212HTR behaved well through each 5dB increase in level until reaching an input level of 34.3 volts where a slight bit of excursion noise was noticed from the drivers. The next measurement was increased by only 3dB and corresponded to an input voltage of 48.5 volts at which point the drivers clearly were reaching there excursion limits during some parts of the bass bandwidth. During the48.5 volt measurement the output level reached 115dB at 50Hz and steadily climbed passing 120dB at 60Hz and reaching a very loud 125dB above 80Hz. The repeat 1.93 volt measurement to gauge if there were any thermal effects in the drivers indicated that there was a modest amount of heat related parameter shift and a temporary loss of about 1 to 1.5dB in sensitivity over certain ranges of the bandwidth. This effect was almost entirely gone after a few minutes of cool down. By comparison we often see much larger shifting and heat buildup in heavy duty subwoofer systems. The amount of output compression occurring during these measurements indicates that the Noesis 212HTR is very linear through the 19.3 volt measurement with compression of 1dB or less. We can safely ignore anything below about 35Hz as that is below the system tuning and the high pass filter so the output is getting down into the noise floor. The maximum 48.5 volt measurement produced some vent and driver compression near 50Hz where it briefly reaches 4dB. Away from the vent tuning, above 60Hz the compression is between 1 to 2.5dB at this drive level.
Measurements captured at the same drive levels as those used for the long term output testing indicate that the Noesis 212HTR has commendably low distortion over itís useful bandwidth. When driven hard the THD does climb substantially below 50Hz but this is a little below the effective vent tuning of the system. A slightly more aggressive high pass filter at a slightly higher frequency near 50Hz would have cleaned a lot of that up. Above 55Hz the THD never reaches 5% during the loudest measurement. The harmonic makeup of the distortion is virtually all 3rd harmonic above 40Hz with a slight contribution from the 2nd harmonic though it is mostly well down in level.
The CEA-2010 burst output measurements conducted on the Noesis 212HTR were started at the 31.5Hz band. The lower bandwidths were too far below the system tuning to get any appreciable output. At 31.5Hz the system was able to produce a modest 95 to 96dB before the drivers ran out of excursion. This is a bandwidth that is well below the system tuning. At 40Hz things improve to just over 108dB as the signal is now closer to being within the Noesis 212HTRís useful bandwidth. At 50Hz the signal is finally within the systems reach and the 212HTR was able to produce just over 120dB with an input of 97volts. At 63Hz an input of 130v produced almost 128dB and the output climbed into the 132-136dB range above that point.