This is a follow up to my part 1 review of the JBL 708i speaker (monitor) using active DSP amplification. A Crown DCI 4/300n four channel amplifier with built-in DSP and profiles for 708i was used in bi-amp configuration.
The process of configuring the amplifier DSP with the profile for 708i is not overly complicated but made more tedious by missing information in the manual and even bad links. It you can survive through it, you will face a problem in that the gain for the Crown amp is set using analog trim pots. These are notoriously inaccurate. In the normal course of using the amplifier for stereo or multichannel use, this is not a big problem. But when using one channel for woofer and another for tweeter, such mismatch completely messes up the frequence response of the speaker. This is made more complicated by the fact that near-field measurements are highly impacted by where you place the microphone, i.e. the distance relative to each driver. Through some trial and error, I managed to get it close but I think it may be off by 1 dB or 2. I don't know how an end customer can perform the matching without proper instrumentation.
Another problem is the loud fan in the Crown amp. During setup, it seemed to shut off after being powered on. Alas, once testing was done, I realized it had was running (I could not hear due to my hearing protection). This may have impacted the measurements a bit.
I was also disappointed that Harman has locked the EQ settings for the speaker. I see that others have figured out a way to display this but out of the box, the icons are grayed out and the manual tells you the same.
All in all, I think you are buying yourself fair amount of grief here relative to 708p which comes as a packaged deal, ready to go.
Note that the passive crossover is active at all time, whether you use the speaker in one-wire or bi-amp mode.
JBL 708i DSP Speaker Measurement
Here is our frequency response measurements: (actual SPL = 86 dBSPL@1 meter)
I must say, I expected flatter response. The boost in the treble region of 5 kHz is out of place and seems to be caused by corresponding EQ boost in the DSP. Looking at the Harman measurements, we don't see this:
Both measurements share a distinct sharp dip but their frequencies are different. Mine is at around 780 Hz whereas Harman's is at 600 Hz. I am wondering if there are differences in production of speakers vs the original samples/design. If we look at the 708p with its integrated amplifiers/DSP, we don't see the error in treble:
And the dip is at 600 Hz which matches Harman measurements. I would imaging in the case of the 708p, the whole package is tested and measured at the factory to generate the desired result.
Another error is lack of bass extension/flattening in my 780i DSP. I expected this to be resolved as well.
Anyway, moving on, here is our near-field response:
Compare this to the passive measurement:
We see that the area around the bass resonance is pulled down as it should be. But there is an extra boost around 5 to 6 kHz that should not be there.
Unfortunately both early window and predicted-in-response look unrefined:
Distortion as before remains excellent at 86 dBSPL but tweeter gets unhappy at 96 dBSPL:
Overall directivity and beam control in horizontal axis remains superb:
Vertical is not but it is to be expected in 2-way design:
Finally here are CSD and step responses:
I have not listened to the speaker yet. When I do, I will add a section to this review.
Conclusions
At high level, the 708i provides more flexibility compared to integrated 708p. In practice, at least in the setup I tested, it proved fussy and rather difficult to optimize. Worst part is that it seems that the EQ profiles as provided by Harman are not accurate/representative of actual speaker samples. I wonder if the production of speaker takes into account its response variations and whether they match what the equalization attempts to do. If not, it is basically an impossible task to optimize as I don't see how end-users are capable of creating anechoic measurements for every sample.
Another miss is not having true active operation with crossovers in the amplifier rather than speaker. More efficiency can be had by doing that.
I leave slight possibility that there is a pilot error here, or an odd sample. But with 708p standing by, ready to go, I am not sure it is worth our while to keep testing and testing another configurations.
As is, I can't recommend the JBL 708i active DSP speaker. I really enjoyed the 708p which produced more correct objective measurements.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
The process of configuring the amplifier DSP with the profile for 708i is not overly complicated but made more tedious by missing information in the manual and even bad links. It you can survive through it, you will face a problem in that the gain for the Crown amp is set using analog trim pots. These are notoriously inaccurate. In the normal course of using the amplifier for stereo or multichannel use, this is not a big problem. But when using one channel for woofer and another for tweeter, such mismatch completely messes up the frequence response of the speaker. This is made more complicated by the fact that near-field measurements are highly impacted by where you place the microphone, i.e. the distance relative to each driver. Through some trial and error, I managed to get it close but I think it may be off by 1 dB or 2. I don't know how an end customer can perform the matching without proper instrumentation.
Another problem is the loud fan in the Crown amp. During setup, it seemed to shut off after being powered on. Alas, once testing was done, I realized it had was running (I could not hear due to my hearing protection). This may have impacted the measurements a bit.
I was also disappointed that Harman has locked the EQ settings for the speaker. I see that others have figured out a way to display this but out of the box, the icons are grayed out and the manual tells you the same.
All in all, I think you are buying yourself fair amount of grief here relative to 708p which comes as a packaged deal, ready to go.
Note that the passive crossover is active at all time, whether you use the speaker in one-wire or bi-amp mode.
JBL 708i DSP Speaker Measurement
Here is our frequency response measurements: (actual SPL = 86 dBSPL@1 meter)
I must say, I expected flatter response. The boost in the treble region of 5 kHz is out of place and seems to be caused by corresponding EQ boost in the DSP. Looking at the Harman measurements, we don't see this:
Both measurements share a distinct sharp dip but their frequencies are different. Mine is at around 780 Hz whereas Harman's is at 600 Hz. I am wondering if there are differences in production of speakers vs the original samples/design. If we look at the 708p with its integrated amplifiers/DSP, we don't see the error in treble:
And the dip is at 600 Hz which matches Harman measurements. I would imaging in the case of the 708p, the whole package is tested and measured at the factory to generate the desired result.
Another error is lack of bass extension/flattening in my 780i DSP. I expected this to be resolved as well.
Anyway, moving on, here is our near-field response:
Compare this to the passive measurement:
We see that the area around the bass resonance is pulled down as it should be. But there is an extra boost around 5 to 6 kHz that should not be there.
Unfortunately both early window and predicted-in-response look unrefined:
Distortion as before remains excellent at 86 dBSPL but tweeter gets unhappy at 96 dBSPL:
Overall directivity and beam control in horizontal axis remains superb:
Vertical is not but it is to be expected in 2-way design:
Finally here are CSD and step responses:
I have not listened to the speaker yet. When I do, I will add a section to this review.
Conclusions
At high level, the 708i provides more flexibility compared to integrated 708p. In practice, at least in the setup I tested, it proved fussy and rather difficult to optimize. Worst part is that it seems that the EQ profiles as provided by Harman are not accurate/representative of actual speaker samples. I wonder if the production of speaker takes into account its response variations and whether they match what the equalization attempts to do. If not, it is basically an impossible task to optimize as I don't see how end-users are capable of creating anechoic measurements for every sample.
Another miss is not having true active operation with crossovers in the amplifier rather than speaker. More efficiency can be had by doing that.
I leave slight possibility that there is a pilot error here, or an odd sample. But with 708p standing by, ready to go, I am not sure it is worth our while to keep testing and testing another configurations.
As is, I can't recommend the JBL 708i active DSP speaker. I really enjoyed the 708p which produced more correct objective measurements.
------------
As always, questions, comments, recommendations, etc. are welcome.
Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
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