about the JBL HT5
The HT5 are the surround speakers in the JBL HT Series. As surrounds, they are perfectly fine. However, as HiFi main speakers, I find the clarity is somewhat lacking. Vocals are not well isolated from the mix. On top of that, there’s some boxiness in the male voices whereas female vocals sound slightly nasal. This modification will resolve all these issues.
JBL HT5 5.25″ midwoofer Thiele / Small
Fig 1 – JBL HT5 midwoofer Thiele / Small Parameters
I was quite surprised with the 5.25″ midwoofer. The Fs is 166Hz. I believe JBL chose such a high Fs because they wanted an early roll-off.
Remember, the HT5 are surround speakers. In Home Theater systems, the surrounds are normally rolled off at 80Hz (-3dB) because bass is not required.
JBL HT5 RAW Frequency Response
Fig 2 – JBL HT5 RAW Response of the Woofer and Tweeter. Measurements below 500Hz include room reflections.
The Black plot in Fig 2 is the Raw response of the midrange driver. See how early the bass rolls off. Because of this, there’s no necessity to use a large value capacitor to roll off the low frequencies.
Higher up the frequencies, there is a 5dB rise from 500Hz ~ 2.5kHz. That’s the effect of baffle step. At 5kHz, the driver cone starts to breakup.
The Red plot is the Raw response of the bi-radial horn tweeter. It is exceptionally smooth. No peaks and nulls anywhere. Moreover, the roll-off from 3kHz to 15kHz is constant and linear. This is a very well designed horn tweeter.
JBL HT5 Modified Crossover
Fig 3 – Modified Frequency Response of HT5 Midrange and Tweeter
Fig 3 shows the modified midwoofer response (Blue plot) and the horn tweeter (Red plot). Acoustically, the two drivers are crossing at about 2.5kHz.
Modified JBL HT5 Frequency Response
Fig 4 – Modded and Original HT5 Frequency Response
The Blue plot in Fig 4 is my modified response to enhance the midrange. It is similar to the original JBL HT5 response (Black plot) except for a slight increase in SPL from 400Hz ~ 3kHz.
Modified HT5 Cumulative Sprectral Decay (CSD)
Fig 5 – Modded HT5 CSD. Window = 1.3ms (769Hz), Time Range = 1.0ms, Rise Time = 0.1ms
Modded HT5 Toneburst Energy Storage
March 23, 2018Projects