JBL 708P Review (Professional Monitor)

[wwenze]

Very similar behavior as 705P including that distortion at 1.7kHz

 

[Dj7675]

Yeah, looking back at the JBL LSR308P MkII review, it's clear that JBL might be eating its own lunch with that model at an 85% discount versus the 708P. The 308P MkII has smoother in-room response and better directivity, and the only sacrifice appears to be a bit more distortion.

I’ve had both (in different rooms). I had the 708P in our living room for about 6 months or so. I really liked them. Only reason I ended up going back to passives was the worry about longevity. I also had the 308p in my theater for a few months. Different rooms so not a direct comparison, but they sounded very different to me. Bass sounded different (much more clean) and 708p could play very loud and sound really good. I would agree, you could be done in one’s search with these.

 

[617]

So it's a tweeter and upper-midrange in one, it seems ("Dividing Network Transition Frequency 1,7 kHz") https://jblpro.com/products/708p (specifications).
Wow.

Pretty standard crossover frequency for a robust HF transducer. The use of a compression driver distinguishes this speaker from the likes of Genelec and Neumann and so forth.

 

[amirm]

I'm a bit surprised to see the distortion levels at 96db, although that is admittedly loud for a mid/nearfield type speaker. Am I correct in assuming 2.5% distortion on the tweeter wouldn't be audible in listening?

2.5% is a lot but it is a narrow spectrum which may be the reason it wasn't audible to me.

 

[respice finem]

Pretty standard crossover frequency for a robust HF transducer. The use of a compression driver distinguishes this speaker from the likes of Genelec and Neumann and so forth.

The "wow" factor for me is, there is no tradeoff in the form of elevated distortion in the upper midrange. I wouldn't expect this performance from a compact 2-way speaker. One can't outsmart physics of course, so distortion will rise quickly below 100 Hz, but at least for nearfield application this should easily do without a subwoofer, since our hearing becomes less sensitive to distortion with falling frequency.

 

[PaulD]

Yes indeed....a compression driver. These speakers are a significant step up from the 308 series.

Dave.

Indeed. We have some rooms with the 308s, and the 708s for the LCR trio in our Atmos room (20-odd 705s for the surrounds), and the 708 is a large step-up from the 308. Lower distortion, flatter frequency response, better dynamic ability. They are seriously good speakers. I would happily live with a pair in a smaller room.

 

[beefkabob]

No surprises here. Happy 705P and 708P owner. Cross them over at 80hz to a massive sub for eternal orgasmic splendor.

 

[Blumlein 88]

So several testimonies that these are obviously better than the 308 mk II by those who have both or have heard both. Yet the preference rating of the 308 is so much higher to nearly clear the range where you'd expect one to prefer it rather conclusively.

 

[jhaider]

Good to see the filters are correct here (my theory re your 705P sample is that the filters weren’t flashed to the DSP correctly, based on my measurements of the 705i without processing). This series of speakers is just ridiculously good when everything's sorted.

One reason PIR slopes down less than typical speakers - and the speakers don't present as bright as some might guess - is the exceptionally wide top octave dispersion. That is because of the tiny horn exit, along with JBL's trick phase plug and waveguide modeling. Top octave is similar to something like the 10mm Raal ribbon, but the compression driver on horn can play an octave lower.

So several testimonies that these are obviously better than the 308 mk II by those who have both or have heard both. Yet the preference rating of the 308 is so much higher to nearly clear the range where you'd expect one to prefer it rather conclusively.

Well, one key difference is a much longer throw woofer - I expect linear throw is >300% higher - along with much more power. So the speaker won't soon run out of gas. Note that per Sound und Recording's measurements 705P has about 2.5dB greater capability from 50-100Hz than 308. LSR708P, which is much much larger and has a commensurately high tech woofer, is going to be at the tippy-top of the class of 8" woofer speakers in terms of bass headroom.

 

[Maiky76]

Hi,

Here is my take on the EQ.

The raw data with corrected ER and PIR:

Score no EQ: 4.97
With Sub: 6.78

Spinorama with no EQ:

• Great Horizontal directivity
• Jaggy response that impairs the score (NBD and SM_PIR parameters)
• port!

Directivity:
Better stay at tweeter height
Horizontally, not critical up to 30deg

EQ design:
I have generated two EQs. The APO config files are attached.

• The first one, labelled, LW is targeted at making the LW flat
• The second, labelled Score, starts with the first one and adds the score as an optimization variable.
• The EQs are designed in the context of regular stereo use i.e. domestic environment, no warranty is provided for a near field use in a studio environment although the LW might be better suited for this purpose.

Score EQ LW: 5.55
with sub: 7.36

Score EQ Score: 5.86
with sub: 7.67

JBL 708p APO EQ LW 96000Hz
February022021-143409

Preamp: -1.7 dB

Filter 1: ON HPQ Fc 32.3 Hz Gain 0 dB Q 0.91
Filter 2: ON PK Fc 97.5 Hz Gain -1.5 dB Q 0.93
Filter 3: ON PK Fc 908 Hz Gain -3.35 dB Q 7.31
Filter 4: ON PK Fc 1381 Hz Gain 1.04 dB Q 1.07
Filter 5: ON PK Fc 7049 Hz Gain -1.1 dB Q 2.46
Filter 6: ON PK Fc 10000 Hz Gain 2.01 dB Q 3.95
Filter 7: ON PK Fc 13802 Hz Gain -1.5 dB Q 5.51

JBL 708p APO EQ Score 96000Hz
February022021-143236

Preamp: -1.4 dB

Filter 1: ON HPQ Fc 32.3 Hz Gain 0 dB Q 0.91
Filter 2: ON PK Fc 100.5 Hz Gain -1.5 dB Q 0.93
Filter 3: ON PK Fc 921.5 Hz Gain -2.9 dB Q 6
Filter 4: ON PK Fc 1604 Hz Gain 1.49 dB Q 1.57
Filter 5: ON PK Fc 7095 Hz Gain -1.53 dB Q 1.71
Filter 6: ON PK Fc 9965 Hz Gain 1.88 dB Q 3.45
Filter 7: ON PK Fc 13782 Hz Gain -2.13 dB Q 3.85

Spinorama EQ LW

Spinorama EQ Score

Zoom PIR-LW-ON

Regression - Tonal

Radar no EQ vs EQ score

The rest of the plots is attached.

 

[JohnBooty]

So several testimonies that these are obviously better than the 308 mk II by those who have both or have heard both. Yet the preference rating of the 308 is so much higher to nearly clear the range where you'd expect one to prefer it rather conclusively.

I forget -- does the "preference score" take distortion into account? If the scoring system ignores the higher THD% in the 308 vs the 708, that would certainly favor the 308. That, and the slightly wider horizontal controlled dispersion of the 308P (+/- 60deg instead of 50deg)

In reality, I doubt anybody would prefer the 308 over the 708.

I'm only speaking from my personal experience with the 306P, which to the best of my understanding has the same tweeter and amp section as the 308P. Distortion as you climb to 90dB and above is what keeps the 305/306/308 from being total world-slayers.

In my case, it's a rather small room and they are crossed over to subwoofers. So I'm generally not hitting those limits in an audible way and I actually consider it my "endgame" setup for the forseeable future. But yeah, they do run out of steam fairly quickly....

 

[Tks]

"The JBL 2409H high-frequency compression driver incorporates an innovative low- mass annular diaphragm to deliver smooth response beyond 36 kHz, with extraordinary output and very low distortion."

https://jblpro.com/products/708p

Anyone got a reason as to why companies bother making drivers do anything beyond 20kHz in this sector? I get perhaps if you're using singal generators to output some odd sounds in some scientific field. But 36kHz? I don't get it.

 

[thewas]

Technically and objectively, the JBL 708P is near perfect. There is a bit of port resonance which while there, is far better than what we see especially in front-ported speakers.

Don't agree there, for that category and price range the jaggedness in the whole critical mid region between 500 Hz and 2 kHz due to the not optimal port design is disappointing and so high that it even gets punished by a comparatively low Harman score. A well designed front port can be seen for example on the Neumann KH80 which has almost no jaggedness at all and gets huge 1.2 point higher Harman score despite less deep bass (with sub the difference is even larger with 1.6 points).

 

[amirm]

Anyone got a reason as to why companies bother making drivers do anything beyond 20kHz in this sector? I get perhaps if you're using singal generators to output some odd sounds in some scientific field. But 36kHz? I don't get it.

They have to as otherwise the whole "high-res" music thing becomes a farce if the speaker can't go above 20 kHz. It is also good to have extended response so that we know there are no resonances around 20 kHz.

 

[amirm]

Don't agree there, for that category and price range the jaggedness in the whole critical mid region between 500 Hz and 2 kHz due to the not optimal port design is disappointing and so high that it even gets punished by a comparatively low Harman score. A well designed front port can be seen for example on the Neumann KH80 which has almost no jaggedness at all and gets a 1.2 point higher Harman score despite less deep bass (with sub the difference is huge 1.6 points).

KH80 is not remotely in the same planet as this speaker. It blows its brains out at a fraction of power.

 

[thewas]

KH80 is not remotely in the same planet as this speaker. It blows its brains out at a fraction of power.

Of course, its 4" vs 8" so almost 4 times less bass radiating surface and we are talking about fidelity, not SPL... With that logic a ragged FR PA loudspeaker would be even better...
I used the KH80 just as an example of a well designed frontal port.

 

[Tks]

They have to as otherwise the whole "high-res" music thing becomes a farce if the speaker can't go above 20 kHz. It is also good to have extended response so that we know there are no resonances around 20 kHz.

I thought this was a professional monitor? Pro's taken for fools as well, or are they actual fools in the first place?

 

[beefkabob]

It doesn't matter. Plus some pros think they can hear to 192khz.

 

[pierre]

They do react very well to EQ. If you push a bit the number of PEQs, you get a score of 6.7 which is as good as Genelec 8341.

Eq is:

EQ for JBL 708P computed from ASR data
Preference Score 5.0 with EQ 6.7
Generated from http://github.com/pierreaubert/spinorama/generate_peqs.py v0.4
Dated: 2021-02-02-07:53:25

Preamp: -1.1 dB

Filter  1: ON PK Fc  1126 Hz Gain -3.77 dB Q 0.10
Filter  2: ON LS Fc  1961 Hz Gain +2.87 dB
Filter  3: ON PK Fc   905 Hz Gain -3.77 dB Q 4.41
Filter  4: ON PK Fc 14315 Hz Gain -4.04 dB Q 1.43
Filter  5: ON PK Fc  2295 Hz Gain +2.51 dB Q 12.00
Filter  6: ON LS Fc   509 Hz Gain -1.70 dB
Filter  7: ON PK Fc  7169 Hz Gain -1.59 dB Q 4.17
Filter  8: ON PK Fc 10339 Hz Gain +1.01 dB Q 4.57
Filter  9: ON PK Fc  4385 Hz Gain +0.92 dB Q 11.35
Filter 10: ON PK Fc   667 Hz Gain -1.31 dB Q 12.00
Filter 11: ON PK Fc   607 Hz Gain +2.47 dB Q 12.00
Filter 12: ON PK Fc   752 Hz Gain +1.48 dB Q 12.00
Filter 13: ON PK Fc  1562 Hz Gain +1.58 dB Q 12.00
Filter 14: ON PK Fc  5357 Hz Gain -0.54 dB Q 6.56
Filter 15: ON PK Fc  2494 Hz Gain -0.62 dB Q 12.00
Filter 16: ON PK Fc  1134 Hz Gain +0.80 dB Q 12.00
Filter 17: ON PK Fc   644 Hz Gain -1.77 dB Q 12.00
Filter 18: ON PK Fc  2742 Hz Gain +1.12 dB Q 12.00
Filter 19: ON PK Fc  1937 Hz Gain +0.91 dB Q 12.00
Filter 20: ON PK Fc  1759 Hz Gain -0.93 dB Q 12.00

The PEQs are not sorted by frequency on purpose. You can cut the filter where you want, the most effective PEQ being at the beginning.
Here is how the score evolved per iteration. For example, with 7 PEQs you get a score of 6.04.
After peq 5 you start to see a lot of high Q PEQs which are smoothing the frequency (and then boosting the score) but they may not be that audible.

(pid=98842) ITER  LOSS SCORE -----------------------------------------------------
(pid=98842)    0 +722.43 +4.97
(pid=98842)    1 +13.52 +4.34
(pid=98842)    2 +8.23 +5.23
(pid=98842)    3 +13.93 +5.34
(pid=98842)    4 +8.69 +5.80
(pid=98842)    5 +9.03 +5.91
(pid=98842)    6 +7.84 +5.93
(pid=98842)    7 +6.56 +6.04
(pid=98842)    8 +6.65 +6.03
(pid=98842)    9 +6.27 +6.09
(pid=98842)   10 +6.07 +6.15
(pid=98842)   11 +5.32 +6.23
(pid=98842)   12 +5.34 +6.36
(pid=98842)   13 +5.04 +6.52
(pid=98842)   14 +4.94 +6.54
(pid=98842)   15 +4.98 +6.56
(pid=98842)   16 +4.88 +6.58
(pid=98842)   17 +4.48 +6.58
(pid=98842)   18 +4.05 +6.65
(pid=98842)   19 +3.92 +6.71
(pid=98842)   20 +3.70 +6.72
(pid=98842)   21 +3.70 +6.72

and then the EQ version:

 

[beefkabob]

I'm done around 14.8khz.