Systems ListJTR SpeakersCaptivator 118HT

Measurement Details

AmplifierClosed Loop
Outside Temperature76 F
Date TestedMay 17, 2017
Settings & EqualizationInput: At maximum
Delay/Phase: At zero
Low Pass Filter: Maximum / Off
Low frequency Adjustment: Middle setting


The measured half-space frequency response of the JTR Captivator 118HT is variable depending upon the settings of the low pass filter and the low frequency adjust control. That being the case it was measured with a variety of settings to determine their effect. The low frequency adjust control appears to be centered at about 17Hz where it can vary the output by about 14dB from minimum to maximum. The overall effect broadly extends from about 10-40Hz but the majority of the change is in the 12.5 to 25Hz octave. With the control at minimum the response rolls off sharply below 25Hz which could be useful for smaller rooms with appreciable low frequency gain. With the gain at maximum the response is very flat and extends well down to the 15Hz range in a half-space environment. This setting would be best employed in larger rooms or spaces typically without much low frequency boost. The low pass filter adjustment appears to be a 24dB per octave slope and is adjustable from flat out to 185Hz with it off to negative 3dB at about 60 to 65Hz with it at the minimum setting. The flattest response for the 118HT is achieved with the low frequency adjust at maximum and the low pass filter at maximum or bypass. With these settings the response is within a 6dB total window from about 17.5 to 190Hz. This is just a hair better than the JTR spec of 19 to 190Hz. We see a notch in the output at 200Hz which is likely related to the vents pipe resonance and a sharp roll off above that point towards 500Hz. The Cap 118HT should be useful up to the 130 to 140Hz range if required to meet small speakers and should be able to be matched to most situations with a combination of the low frequency adjust control, the low pass filter and the phase adjustment if needed.

During setup the Cap 188Ht was measured in both the normal vertical orientation with vents at the bottom and in a horizontal orientation on its side. The difference between the two was a very slight amount of extra low bass in the normal vertical orientation and a slight amount of extra output above 40Hz in the horizontal orientation. The difference was negligible either way with less than a single decibels difference in either orientation so the Cap 118HT was tested in the normal vertical orientation for all other measurements.

The group delay and waterfall charts for the 118HT indicate no issues to be concerned with. The response will change depending on the settings of the low pass filter and low frequency adjust controls, as will any subwoofer or speaker with adjustable signal processing built in. The group delay for the minimum, middle and maximum settings of the low frequency adjust control are shown. The group delay increases with the low frequency control turned higher as expected. Even with the control at maximum the group delay doesn’t reach 1 cycle until below 24Hz and doesn’t exceed 1.5 cycles until below 18Hz. This is very unlikely to be audible at such deep, slow frequencies. The waterfall decay shows much the same story.

For the long term output sweeps the low frequency adjust control was placed to its middle position as this is most likely to be the setting closest to flat in many rooms and is also likely to be closer to the native low frequency response of the driver and cabinet design. As usual the output was set to produce about 90dB at 50Hz, measured at 2 meters ground plane, as the starting point. Things proceed uneventfully from there, on through the 110dB measurement sweep where the 118HT is still exhibiting very little compression of the output. The next 5dB increase in signal, corresponding to a 115dB sweep, finally gets the 118HT to exhibit a slight amount of output compression where it reaches about 2.5dB near the vent tuning at 18Hz. Another 5dB increase in signal to the 118HT for a nominally 120dB sweep finally reaches its limits over the 20 to 40Hz octave. The output did not increase, or barely increased over this octave and we can see in the compression magnitude graph that the output has compressed by 5 to 6dB over much of that range indicating that the subwoofer is at maximum output in this area. Additionally the woofer produced some distorted sounds due to over excursion at the beginning of the sine sweep below 15Hz and some additional tonal changes in the upper bass during parts of the measurement indicating that distortion was getting high. There was also some audible vent noise around 15 to 20Hz during the sweep where air speeds had gotten high. As usual this is normal behavior for most powered subwoofers, not just the Cap 118HT. The final long term measurement is always a bit beyond what the subwoofer can actually reproduce comfortably and is essentially seeing whether the subwoofer will become damaged when driven at maximum and just how loud it will go with an unrelenting signal. The Cap 118HT seems to be well protected no matter what signal is sent to it and managed to muster up about 105dB at 17Hz, 110dB at 23Hz and greater than 115dB above 38Hz during this torturous test.

The harmonic distortion results captured at the same output levels as used for the long term testing show that the Cap 118HT is quite clean at the more moderate drive levels. The 100dB sweep shows THD that is about 5 percent or less from 17 to 200Hz. The 105dB sweep shows THD to remain low at around 6 percent or less from 15 to 200Hz. The 110dB sweep shows an increase in THD as the driver is driven harder with THD now reaching 10 to 11 percent from 25 to 35Hz. Still it remains at about 11 percent or lower from 15 to 200Hz. The 115dB sweep shows another jump in THD maxing out at 22 percent at 30Hz in the bandwidth of interest. The loudest 120dB sweep produces the most distortion from the Cap 118HT which tops out at about 24% in the bandwidth of interest, 17-200Hz. Looking at the harmonic makeup of the distortion, indicates that the relatively benign second harmonic is the primary offender and the third harmonic makes up the bulk of the rest of it.

Short term burst testing of the JTR Cap 118HT Shows that the system is capable of producing a bit higher output with short term signals. CEA-2010 style distortion limited results show the 118HT to be a capable system down to about 15 to 16Hz. Being a vented system tuned to about 17Hz, the 118HT could not produce a result with passing distortion down in the 10 and 12.5Hz bands. At 16Hz the 118HT was able to muster up 105.7dB at 2 meters ground plane with the distortion threshold just being met by both the third and fourth harmonics. This was accompanied by some vent air noise as well. The amp was also out of power at this level so the fail point and the maximum output regardless of distortion occurred at virtually the same time. At 20Hz the 118HT was able to produce just under 110dB which is a good showing. The output steadily climbs at each frequency band above that point until reaching a bit over 116dB at 40Hz and about 122dB at 63Hz and above. 

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