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JBL 708i Monitor Review (Passive: Part 1)

amirm

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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.

JBL 708i Speaker Active Monitor Review.jpg

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:
JBL 708i Speaker Active Monitor  Amplifier Warning.png


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:
JBL 708i Speaker Active Monitor Frequency Response  measurements.png


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:
JBL 708i Speaker Active Monitor near-field Frequency Response  measurements.png


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:

index.php


We can see good attempt at correcting those peaks.

Early window shows a strong dip once tweeter takes over:
JBL 708i Speaker Active Monitor Early Window  Frequency Response  measurements.png


That messes up any applicability of predicted-in-room response so please don't run with it:

JBL 708i Speaker Active Monitor predicted in-room  Frequency Response  measurements.png


The sweeps sounded very clean n the lab and you can see why from the very low distortion figures:
JBL 708i Speaker Active Monitor Relative THD Distortion measurements.png


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:
JBL 708i Speaker Active Monitor Woofer Distortion measurements.png


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:
JBL 708i Speaker Active Monitor Horizontal Beamwidth measurements.png


JBL 708i Speaker Active Monitor Horizontal directivity measurements.png


Vertically is as you would expect:
JBL 708i Speaker Active Monitor Vertical directivity measurements.png


Waterfall measurements lights up the resonances which we already know about:
JBL 708i Speaker Active Monitor CSD Waterfall measurements.png


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:
JBL 708i Speaker Active Monitor Impedance and phase measurements.png


Finally, here is the step response:

JBL 708i Speaker Active Monitor Step Response measurements.png


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/
 

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617

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This review is pretty narrowly appealing, but for those of us who advocate for hybrid active/passive crossovers it is very interesting. Extra channels of DSP and Amplification are not necessarily expensive, but they are clunky, and this speaker goes to show that you can get great performance with a passive network if you only ask it do to do the basic HP/LP, and get the response correct in the region where both transducers are interacting. Above and below that, one channel of DSP can handle everything else, and you only need one amplifier. One pair of speaker wires, too.

I really like these 70x models. Truly a professional speaker, and I like that the industrial design somehow blends the look of a 'studio monitor' and 'PA speaker' into one unique product category.
 

sarumbear

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According to the user manual, these are passive speakers. The only difference to a standard passive speaker is that these require custom equalisation. There is an option to bi-amp them (using 2 power amplifiers fed by an DSP acting as an active crossover and EQ) but that is not mandatory. EQ via a DSP is required though.

4F26D9F5-162A-491A-90EE-A80AA70AE3C1.jpeg


JBL positions these as baby brother of M2.
 
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MAB

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This review is pretty narrowly appealing, but for those of us who advocate for hybrid active/passive crossovers it is very interesting. Extra channels of DSP and Amplification are not necessarily expensive, but they are clunky, and this speaker goes to show that you can get great performance with a passive network if you only ask it do to do the basic HP/LP, and get the response correct in the region where both transducers are interacting. Above and below that, one channel of DSP can handle everything else, and you only need one amplifier. One pair of speaker wires, too.

I really like these 70x models. Truly a professional speaker, and I like that the industrial design somehow blends the look of a 'studio monitor' and 'PA speaker' into one unique product category.
Agreed that it may not be everybody's cup of tea, but it looks really appealing to me.
 

sarumbear

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ctrl

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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:
And typical port/cabinet resonances in a few hundred hertz which would need to be dealt with using DSP
Sorry this is not entirely correct. It should be said quite clearly that the BR port is a faulty design and that no DSP can correct this. You can correct the FR which reduces the audibility of the BR port noise, but it does not solve the problem.
Especially when used as a monitor, the BR port resonances will be audible - with DSP (less) or without (clearly).

If one realizes that the near-field measurement of the BR port is not baffle-step corrected and roughly draws in the correction (blue line), it becomes clear that JBL absolutely has to improve it - IMO.
1672442260645.png
 

valerianf

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Question: why the base speaker without DSP has a flawned design?
It remember me the first car with AWD system that were not staying on road if the electronic was inhibited!
A sane base would be the beginning of a good design.
Nobody needs a BR port that has unneeded resonance.
 

sarumbear

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Will be interesting to see part 2. Does the price shown include the DSP unit?
There’s no separate DSP. These are speakers which are designed to be used only after they are equalised. The EQ is done either with the DSP, which is integral to a certain model Crown power amplifier, or a BSS processor.

I think @amirm is confusing the product offering. This part 1 test is a test of the speakers without EQ applied. That’s all. EQ can be applied on a single channel amplifier feeding this speaker. Or, you can use 2 amplifier channels and use the internal DSP to act as an active crossover and EQ.
 
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amirm

amirm

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Question: why the base speaker without DSP has a flawned design?
Because they know they will make corrections in DSP. Otherwise it would require more complex crossover to correct.
 

restorer-john

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It's a "fix it in the mix" product. Screw a few drivers with potential in a PA-looking box full of flaws, resonances etc and use the magic of PEQ to make it listenable.

Not my cup of tea, especially at US$3800 pair, but let's wait and see what the end result is, after part 2 testing.

:)
 

stunta

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Is it safe to say that the only reason someone would go down this 708i route versus the 708p is for potentially higher SPL and easier repairability?
 

MAB

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Sorry this is not entirely correct. It should be said quite clearly that the BR port is a faulty design and that no DSP can correct this. You can correct the FR which reduces the audibility of the BR port noise, but it does not solve the problem.
Especially when used as a monitor, the BR port resonances will be audible - with DSP (less) or without (clearly).

If one realizes that the near-field measurement of the BR port is not baffle-step corrected and roughly draws in the correction (blue line), it becomes clear that JBL absolutely has to improve it - IMO.
Interesting.
If I put the 708p and 708i side by side, the port resonance looks identical. So nothing new, but not well controlled.
From the two reviews, adjusted for similar y-scale:
1672446551474.png

edit: I assume after DSP the woofer response will match and the port response will have identical responses. Perhaps I assume too much...
 
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Palladium

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Is it safe to say that the only reason someone would go down this 708i route versus the 708p is for potentially higher SPL and easier repairability?

I dunno but both look pretty awful from a value for money PoV if you don't need a lot of SPL?
 

Blumlein 88

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My main complaint with actives that measure well on the Klippel is SPL limiting. In limited experience even inexpensive Revel's sound better than the active offerings in the LSR line. In essence you don't really have a very good speaker design without DSP. DSP lets you obtain some results that are good and has some advantages in an active. Here you are getting the most expensive way to get there with the only gain being more SPL (which can be important).

I wonder if a passive that needs less DSP is why for instance the Revel Salon's scored better than the M2 in the big listening session over at AVS forums. DSP necessary designs are a lesser base upon which to add DSP than well done passive designs.

Also a request that might be of interest to do for one or two good candidates. Take an excellent or very good passive speaker, apply DSP derived from in room measures (maybe Dirac software is a good candidate). Then run that corrected speaker on the Klippel a second time and see what the result is. A heck of an intensive review for Amir to do, but I bet it would be interesting to almost everyone.
 

Mr. Widget

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I wonder if a passive that needs less DSP is why for instance the Revel Salon's scored better than the M2 in the big listening session over at AVS forums. DSP necessary designs are a lesser base upon which to add DSP than well done passive designs.
I am unaware of that listening session. Assuming it was well done, that is a very interesting comparison.

I like your premise. It certainly makes sense to me.
Another possibility is that we need additional tests or other interpretations of our speaker measurements.

FWIW: Not too long after the M2 was released I was talking with Kevin Voecks and he had taken a pair of M2s home to listen to them in his own listening room. He spoke very favorably of them. I never heard him speak that favorably about any of the other JBLs at any price point. Of course in his position at Harman, he had to speak favorably about all of them, but reading between the lines, he was extremely impressed with the M2s. I did not ask and he did not volunteer a comparison between his own Salon2s and the M2s.
 

dfuller

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I'm sorry but this is objectively flawed. That port is a mess. That kind of midrange ringing is exactly what Toole considers the worst offender for sonics (if I'm remembering correctly).
 
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