This is a partial review of the JBL 708i discrete active speaker but tested as a passive. It was purchased used by a member and kindly sent to me for testing. I *think* it costs US $1,900 each.
Sorry for the stock picture. The unit is still on Klippel NFS measurement stand to be tested in Part 2. The reason is that this speaker has mandatory drive requirement using a DSP or combo DSP+Crown amplifier from JBL:
Member and I were curious what its performance would be without the DSP and hence this set of measurements. I do have the Crown amplifier with the necessary filters loaded. But need to build some wiring harness to interface it to my measurement system (comes with binding posts rather than XLR). At first I thought all the crossover circuits were in the DSP unit but it seems when you drive it using the "Single Wire" interface, it has built-in passive ones as you see later.
So to summarize, this is NOT the measurements you would see as far as frequency response/distortion when used with appropriate front-end. Part 2 will address that. The purpose of this post then is education and somewhat a logical "teardown" of this active speaker system. Or if you want to build your own DSP solution for it.
The advantage of an outboard amplifier is that you can use much more powerful ones than what comes in the powered version (708p). The measurements are actually similar to that of JBL 709p which is all-in-one version of this system. But I suspect the limits will be higher. Certainly that is what I felt as I swept the speaker in the lab. It was one of the few times that I thought my very strong hearing protection ear muffs were not strong enough! This thing can get loud!
I should mention that while rather small, these are quite dense and heavy speakers. The massive motor on the woofer is likely contributing to this.
JBL 708i Raw (no DSP) Measurements
Let's start with our usual frequency response measurements to see what work is left for the DSP to do:
The peaking around a few hundred hertz needs correction in addition to some bass lift. We can see the reason behind the former in near-field driver measurements:
The front facing ports always mess with the response this way. Fortunately since they are resonances, DSP correction should be very effective to at least linearize the response (what distortion they have, will be reduced but not eliminated). Here is the response of the 708p by the way:
We can see good attempt at correcting those peaks.
Early window shows a strong dip once tweeter takes over:
That messes up any applicability of predicted-in-room response so please don't run with it:
The sweeps sounded very clean n the lab and you can see why from the very low distortion figures:
There is just a peak that is bothersome around 1 to 2 kHz which we can attribute to the woofer from near-field woofer response:
I put a question mark there though as it could be from port interference as well (although its distortion has a very sharp peak).
The star of the show is highly controlled beam width and directivity in horizontal dimension:
Vertically is as you would expect:
Waterfall measurements lights up the resonances which we already know about:
Not that you would normally see the impedance graph for a powered speaker but here it is in case you want to DIY your own solution:
Finally, here is the step response:
Conclusions
Not much to conclude here other than some excellent "bones" when it comes to directivity control and very low distortion. And typical port/cabinet resonances in a few hundred hertz which would need to be dealt with using DSP. Once there, I think it will be a more capable speaker than 708p-, albeit, at much higher cost.
Build quality is typical Pro speaker, i.e. indestructible, but pleasant enough to be usable at least in a home theater if not in a living room.
Not going to include a poll as this is not a finished review of the product as intended.
------------
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/
Sorry for the stock picture. The unit is still on Klippel NFS measurement stand to be tested in Part 2. The reason is that this speaker has mandatory drive requirement using a DSP or combo DSP+Crown amplifier from JBL:
Member and I were curious what its performance would be without the DSP and hence this set of measurements. I do have the Crown amplifier with the necessary filters loaded. But need to build some wiring harness to interface it to my measurement system (comes with binding posts rather than XLR). At first I thought all the crossover circuits were in the DSP unit but it seems when you drive it using the "Single Wire" interface, it has built-in passive ones as you see later.
So to summarize, this is NOT the measurements you would see as far as frequency response/distortion when used with appropriate front-end. Part 2 will address that. The purpose of this post then is education and somewhat a logical "teardown" of this active speaker system. Or if you want to build your own DSP solution for it.
The advantage of an outboard amplifier is that you can use much more powerful ones than what comes in the powered version (708p). The measurements are actually similar to that of JBL 709p which is all-in-one version of this system. But I suspect the limits will be higher. Certainly that is what I felt as I swept the speaker in the lab. It was one of the few times that I thought my very strong hearing protection ear muffs were not strong enough! This thing can get loud!
I should mention that while rather small, these are quite dense and heavy speakers. The massive motor on the woofer is likely contributing to this.
JBL 708i Raw (no DSP) Measurements
Let's start with our usual frequency response measurements to see what work is left for the DSP to do:
The peaking around a few hundred hertz needs correction in addition to some bass lift. We can see the reason behind the former in near-field driver measurements:
The front facing ports always mess with the response this way. Fortunately since they are resonances, DSP correction should be very effective to at least linearize the response (what distortion they have, will be reduced but not eliminated). Here is the response of the 708p by the way:
We can see good attempt at correcting those peaks.
Early window shows a strong dip once tweeter takes over:
That messes up any applicability of predicted-in-room response so please don't run with it:
The sweeps sounded very clean n the lab and you can see why from the very low distortion figures:
There is just a peak that is bothersome around 1 to 2 kHz which we can attribute to the woofer from near-field woofer response:
I put a question mark there though as it could be from port interference as well (although its distortion has a very sharp peak).
The star of the show is highly controlled beam width and directivity in horizontal dimension:
Vertically is as you would expect:
Waterfall measurements lights up the resonances which we already know about:
Not that you would normally see the impedance graph for a powered speaker but here it is in case you want to DIY your own solution:
Finally, here is the step response:
Conclusions
Not much to conclude here other than some excellent "bones" when it comes to directivity control and very low distortion. And typical port/cabinet resonances in a few hundred hertz which would need to be dealt with using DSP. Once there, I think it will be a more capable speaker than 708p-, albeit, at much higher cost.
Build quality is typical Pro speaker, i.e. indestructible, but pleasant enough to be usable at least in a home theater if not in a living room.
Not going to include a poll as this is not a finished review of the product as intended.
------------
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/
