JBL 708i Monitor Review (Passive: Part 1)

[Tangband]

The horn implementations that JBL typically has are significantly superior. So it's not flat out superior. This is showcased by the incredibly smooth directivity and lack of weird behavior in the highest octave.

Neumann doesn't even bother with horns or extensive waveguiding because they're not targeting the high-end PA world. This speaker is capable of 117 dB / 1m peak output from 80Hz to 20KHz. Something I'm sure the KH150 is not even close to achieving.

Pardon, but I dont see any superb behaviour of the horn implemententation of the JBL monitor. The distortion and the unneveness in frequency response at 96 dB is acceptable, but worse than Genelec 8030c .
At higher levels the horn in jbl will be better ofcourse.

 

[tomtoo]

This is very bad port. I wonder that jbl has not seen that by themself.

 

[Toni Mas]

This is very bad port. I wonder that jbl has not seen that by themself.

A loudspeaker designed to play at insane high spl ... An insanely too low tuned port... There can be no miracle and no free lunch, even for JBL...

 

[FeddyLost]

BR port is completely unprofessional. Such desigh is not acceptable at this price point.

 

[Toni Mas]

BR port is completely unprofessional. Such desigh is not acceptable at this price point.

Typical flaws of "profesional" gear...

 

[Dj7675]

When used in a bass managed system with a typical 80hz crossover, would the port resonance be reduced?

While it means almost nothing, I have listened to both they 708p and 705p full range and pretty high levels and did not notice any problems (although not sure I would know what to listen for). When testing full range, with both, I did have to make sure my subwoofers were off. The output on both scales up to loud volumes extremely well IMO.

 

[Dj7675]

There has been quite a lot of discussion through the years on AVSForum trying to apply the proper EQ to them outside of the crown amps and bss processors. This EQ pulled from the BSS processor, I believe provided the most complete settings (the ones pulled from the Crown amps seemed to not be complete if I recall correctly) LINK
I have no idea of course if it is correct or complete but seems interesting on how Harman chose to use EQ.

 

[dfuller]

Typical flaws of "profesional" gear...

No, not really.

 

[Robbo99999]

I don't think I was very impressed by what I saw of the 708p when it was reviewed, and this is the same. Has got some issues that shouldn't be going on, (& yes I know the peak at 900Hz hasn't been damped down with EQ yet).

 

[DevinCortno]

Seeing part 2 of the test and the EQs developed for this will be very interesting. It's be nice to get away from the Crown amps to something better. These always stood out as very capable in terms of bass and dispersion control.. great HT speakers I bet, and it's nice to only have to run speaker wire to them.

 

[DSJR]

I wonder - If the ports were blocked off, might that clean up the upper mids (assuming the main driver isn't over-damped mechanically when loaded this way)? The loss of bass extension could possibly be eq'd back with care?

Just guessing, but hopefully not a stupid comment.

 

[Toni Mas]

No, not really.

In my experience pro stuff justo pretend to play loud, at best loud and clean... Refined sounding, never heard...
If modest only spl required no need to spend thousands in pro studio speakers...Stay away...

 

[dfuller]

In my experience pro stuff justo pretend to play loud, at best loud and clean... Refined sounding, never heard...
If modest only spl required no need to spend thousands in pro studio speakers...Stay away...

Yeah, but you can get pro speakers that play loud without this kind of port nonsense. Big ATC 3 ways being the primary example first coming to mind. Do they have horns? No. But they don't need them. Neumann KH420s, same idea. Even the 310s when you cross them with a pair of subs to take the bottom couple of octaves off.

The principal use looks to be monitoring and in a mobile application as they state there will also be a need for simplicity, low weight, and ruggedness, not to mention tolerating high playback levels. Since its not being used for critical listening or purely for mixing its likely ok for a few boogers to be there that can then be tidied up later with some form of EQ or DSP. If you are looking for an end game speaker your princess is definitely in another castle, but for the usage case they offer acceptable performance for the intended application. For us it would be nicer if they didn't have those issues, but we are not the target audience for these.

The 708P is exactly the same in terms of cabinet, port, drivers - and those are absolutely marketed as professional monitors for critical listening.

Besides - these are meant for permanent installations (hence the -i suffix), and also why they're passive.

I wonder - If the ports were blocked off, might that clean up the upper mids (assuming the main driver isn't over-damped mechanically when loaded this way)? The loss of bass extension could possibly be eq'd back with care?

Just guessing, but hopefully not a stupid comment.

You'd clean up the midrange resonances for sure, but the driver isn't really meant for use in a sealed enclosure.

 

[Toni Mas]

I wonder - If the ports were blocked off, might that clean up the upper mids (assuming the main driver isn't over-damped mechanically when loaded this way)? The loss of bass extension could possibly be eq'd back with care?

Just guessing, but hopefully not a stupid comment.

Bass extention can be achieved with a closed box with eq, spl is sacrifyed though quality increases. Bass Reflex is always the prefered choice to provide more bass, though sacrifying quality

 

[sarumbear]

No, not really.

Agreed. Pro gear is often better than Hi-Fi gear. You maybe mistaken with cheap PA as pro gear. Besides, most Genelec speakers everyone loves are pro gear.

 

[changer]

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.
View attachment 253590

I agree this speaker has an issue with port resonance, but think your conclusion is incorrect: it appears to me that @amirm usually does not adjust the near-field measurements for size of the radiators. This leads to a higher than actual SPL level of the much smaller port.

To align woofer and port output at actual SPL level, the radiator surface SD for woofer and port opening must be used to calculate an offset. This offset is global, which means it also reduces the level of the port resonance in the mids, as opposed to baffle step.

I could be wrong, but an adjusted for size port measurement is usually lower in level than the woofer. Only when summed, they together create the higher in level, preferably flat response.

 

[sarumbear]

I agree this speaker has an issue with port resonance, but think your conclusion is incorrect: it appears to me that @amirm usually does not adjust the near-field measurements for size of the radiators. This leads to a higher than actual SPL level of the much smaller port.

To align woofer and port output at actual SPL level, the radiator surface SD for woofer and port opening must be used to calculate an offset. This offset is global, which means it also reduces the level of the port resonance in the mids, as opposed to baffle step.

Why?

 

[changer]

If you could restate your question somewhat more precisely, I’d happily answer.

 

[sarumbear]

If you could restate your question somewhat more precisely, I’d happily answer.

Why would there be an adjustment for the size of a sound emitter. That was the only premise in your post.

 

[jhaider]

I only cited the KH150 as an example of a good front BR port design. Did not mean to equate a 6'' woofer LS with an 8'' woofer LS - obviously

My point is the KH150 port was optimized under vastly different constraints.

Again, KH150 has basically equivalent bass output of the much smaller 705P (especially in install form; the powered one is comically deep) per SuR’s measurements, but with a much larger cabinet. So there's just more room to play with the port design. Furthermore, while this speaker is larger, if you accept JBL’s relative specifications 708 has 7dB greater output capability than 705, and thus a 7dB output advantage thus KH150.

It's also worth noting that none of this is new information. People have been kvetching about the 7-series port resonances for as long as I've been reading about these speakers, because JBL provided reasonable data from the start. Most of these kvetchers through all that time, it should be said, have not tried to personally evaluate the audible significance of these port issues. Dr. Toole often writes about features in graphs that are more offensive to the eye than the ear. I think this is one of those features.

I have no idea of course if it is correct or complete but seems interesting on how Harman chose to use EQ.

I’ve measured the frequency response of the hacked file screenshots as well as of the undisturbed tuning file, on a BSS BLU-50. The crack is complete as to FR (did not test limiting, etc.) on a BSS device. Caveat is BSS defines some filters differently from, e.g. miniDSP. So a plug and chug in a different processor will yield different results. That said, the differences do not manifest as severely on 708 as on 705. On that speaker one can basically ignore the hacked file screenshots, except as a trace of the target curve.