JBL 708P Review (Professional Monitor)

[amirm]

Time to sell your Salon2's?

No. Salon 2s go way lower.

 

[Frank Dernie]

JBL pro is well represented in Europe. You can easily find all studio monitors (M2 included).

I can't get an audition in the UK and am not prepared to go abroad for one any more (I auditioned my Goldmunds in France but I was working there then).

 

[LTig]

Much better race. They both tonally sound wonderful. But I think I will give the nod to JBL for dynamics and power handling.

Interesting, since the KH310 has less distortion at 96 dB SPL than the 708p.

 

[LTig]

It was the 1234A SAM, with 2 x 12". I have no idea if it is the same woofer area as the 15"-16" M2 bass driver. I did like the shape more for soffit mounting.

Woofer area is close. I agree though that the 1234a is better suited to in wall mounting.

 

[thewas]

What about Neumann KH-310 vs JBL 708P?

Also the 708P is not happy at 96dB as Amir correctly wrote in his reviews:

I personally would rather prefer distortion in the lower bass where its less audible (plus you can lower it by subs and/or near front wall placement and according room filters) and not creating IMD mess at the very important and audible mids at a 3-way design. Also on sound quality aspects I prefer the KH310, which can be partially seen also on the FR and HD plots, unfortunately Sound & Recording has only tested the 705P as it would be interesting to compare its IMD plot to the one of the KH310.

 

[beefkabob]

Oh boy. I'm done at 7.mumble kHz. I would have guessed 10kHz. That's kind of humbling. Age: 66. left ear is worst than right ear by about a kHz. I've spent a moderate amount of time shooting 30 cal. rifles on a range with good ear protection. I know that I don't have "golden" ears, but this seems to be a case of tin-plated brass, at best.

I like to layer my ear protection when shooting more than a few rounds. In ear CIEM or plug plus over the ear muffs. That makes even 556 bearable, but only just.

Truth be told, not much happens over 7khz. If you couldn't hear anything 7khz and above, you'd just miss out on the top three piano keys, and I don't think those get used much.

 

[andreasmaaan]

The fact that there's such a large cancellation notch really makes me wonder about port design. It seems to me there's a fair amount of work to be done to get ports to truly behave themselves only as intended...

They're inherently problematic in 2-way designs, in which the port resonance frequency and the frequencies of internal standing waves in the enclosure are almost certain to be fall within the frequency range of the woofer (unless the port is made so small that it can't handle high SPLs without significant compression/distortion, which is the greater evil and best avoided).

In 3-way designs, ports are rarely problematic, or at least there's not usually any reason they must be so. The port can be made large enough to keep compression/distortion to within acceptable limits throughout the woofer's full range of linear displacement, while the upper frequency limit of the woofer tends to ensure that the frequencies of internal standing waves, and the port's own resonance frequency, all fall above the range of frequencies that the woofer reproduces.

 

[neph]

The thing that bugs me is that the JBL 708 costs ten times more than the JBL 308 and yet scores worse on the preference transfer function that the same company developed as a benchmark tool and implemented into their product design philosophy.

Secondly, i would argue that, excluding distortion, 308 measures better than 708. Any user able to highlight significant subjective improvements over 308 in the data department, please do so. Where does this duo of speakers stand in the circle of confusion theory of Harman?

Thirdly various owners and Amir report better resolution and performance attributed mainly to lower distortion. How is resolution quantifed by the % of lower distortion at high SPL? I would also argue that the 708 distortion performance is not that good, considering the compression driver.

Overall, i find it disappointing for a company that has concreted its design philosophy on scientific research, have their x10 more expensive product perform worse than their cheaper one on their own reference metric. An to maybe pre-emotively comment on excuses such as distortion, etc, this product should have better performance than 308 based on price alone. Any of the usual "boutique" manufacturers, would have been crucified in the name of the 308 messiah like for such performance.

 

[YSC]

They're inherently problematic in 2-way designs, in which the port resonance frequency and the frequencies of internal standing waves in the enclosure are almost certain to be fall within the frequency range of the woofer (unless the port is made so small that it can't handle high SPLs without significant compression/distortion, which is the greater evil and best avoided).

In 3-way designs, ports are rarely problematic, or at least there's not usually any reason they must be so. The port can be made large enough to keep compression/distortion to within acceptable limits throughout the woofer's full range of linear displacement, while the upper frequency limit of the woofer tends to ensure that the frequencies of internal standing waves, and the port's own resonance frequency, all fall above the range of frequencies that the woofer reproduces.

Well but at least in the very often mentioned Genelecs and Neumann (can’t see any for kh120 and 8030C) or even the 308P, Adam TxV don’t have such a nasty dip, resonance somewhere yes but don’t make this which looks bad for such an expensive pro line

 

[andreasmaaan]

Well but at least in the very often mentioned Genelecs and Neumann (can’t see any for kh120 and 8030C) or even the 308P, Adam TxV don’t have such a nasty dip, resonance somewhere yes but don’t make this which looks bad for such an expensive pro line

I don't believe Amir took nearfield measurements of the 8030C port. There are some anomalies in the nearfield woofer output that look fairly indicative of port misbehaviour though:

Resonances are clearly visible in the nearfield measurements of the 308P's port (orange trace):

Ditto for Adam T5V:

And T7V:

And has Amir measured the KH120? I must have missed it

 

[mhardy6647]

I am way late to this party (something about night-time and sleeping...), but two thoughts come to mind.

1) How are these in a big room (i.e., a "listening room" -- which some of us Luddites still maintain for... well... listening.)?

2) I was amused by this graph.

How the world has changed -- a JBL that's not happy @ 96 dB?! Not your father's JBL's, I reckon.

 

[Juhazi]

Well but at least in the very often mentioned Genelecs and Neumann (can’t see any for kh120 and 8030C) or even the 308P, Adam TxV don’t have such a nasty dip, resonance somewhere yes but don’t make this which looks bad for such an expensive pro line

It just tells about how that issue has ben taken care of. This might even reflect to how other issues in speaker design have been considered as well...
- port position on baffle and inside
- port tube material and shape
- enclosure design and material

Most Genelecs and most ADAMs have port on backside, so do small Neumanns. Then resonance peak is not so harmful.

 

[Bugal1998]

1) How are these in a big room (i.e., a "listening room" -- which some of us Luddites still maintain for... well... listening.)?

I may be less impressed than Amir with their output (could come down to differences in what we deem to be loud)... It's good, but even crossed over to subs it still get's unhappy in a larger room and my 12' listening distance... By "unhappy" I mean it starts to sound loud instead of powerful as playback levels increase beyond some still semi-reasonable output. I suspect the output would be sufficient for the vast majority of home users, but for me the difference between the 4367 or the M2 (whose limits I have never found) and the 708 is striking when the volume increases. Totally different league (and price tag).

I for one was not surprised by the 96db distortion figure. The output, dynamics, and resolution is imoressive for near or mid-field use or in a small room, but I steer folks to a speaker designed for a larger space and higher output if that's the intended use.

 

[Absolute]

Mind you that positive PEQ cause ringing in time domain which can be audible especially at higher Qs and such higher frequencies which is something that the Harman score doesn't take into account:
https://support.genelec.com/hc/en-u...-does-GLM-not-fix-dips-on-frequency-response-
Which is also obvious when taking into account that those are DSP loudspeakers, so if all problems could be fully corrected by DSP the experienced engineers who tuned them would have already done so.

This is related to room acoustics, not the speaker itself which is mostly a minimum phase device. I've not seen it mentioned for speaker correction anywhere, if it's true then flat measuring compression drivers in most horns will be the sound of ringing

Personally I've never been comfortable with high Q boosts and avoid it myself in my M2 clones even if the graph look less pretty.
For the longest time I convinced myself that a few of the high Q boosts around 9-16khz were responsible for the harsh metallic sound I experienced on my speakers.
Turns out there's something wrong in one of the tweeters with significant distortion around 500-700 that shouldn't be there.
Only obvious with loud sweeps and loud distortion testing, but clearly audible even at levels where the measurements looks ok.

At first I thought the tuning was too bright, maybe too much energy in the 7-10 khz range. But whatever I did I couldn't EQ the harshness away. Until I figured out during loud sweeping that the harshness came from tweeter distortion around 600 hz and that a PEQ or steeper crossover fixed that.

This example is one of those experiences where you find out that tonality is just one of the things that needs to be ok, resonances, ringing and distortion will contribute to sound whether we like it or not.

But still unsure whether a high Q PEQ introduce ringing in the driver.

 

[Bugal1998]

Another comment... Many listeners seem happy with the output and dynamics of speakers that are far less capable than the 708 when being used in larger spaces and long(ish) listening distances.

Do they not listen as loud? Have they not heard a truly high-output speaker with minimal dynamic compression (I. E. they don't know what they're missing)? I don't know... Always best to keep subjective comments from people like me in perspective and listen with your own ears whenever possible... which is admittedly challenging/impossible at times.

 

[thewas]

This is related to room acoustics, not the speaker itself which is mostly a minimum phase device.
...
But still unsure whether a high Q PEQ introduce ringing in the driver.

That has nothing to do with specifically the driver or room correction itself but is a result in the output of minimum phase PEQ filter system with positive gain, which in the end is a resonator, a reason also why a negative PEQ with the exactly inverse response (thus also center frequency and Q-factor) can compensate the resonance of anything (for example a driver or a room mode) if its also minimal phase (antiresonator).

Here it is demonstrated nicely:

 

[Robbo99999]

I'm not sure the differences between them is only about this. One has a compression driver, the other has not. Waveguides/horns are different. Dispersion characteristics have similarities, but are still different. I would be very surprised if trained listeners were not able to consistently pick these speakers apart in blind tests. Preference is another issue of course.

Yeah, perhaps.....it would take some serious testing to be confident in picking apart the differences with certainty. But certainly if you listen at very loud levels then you'd probably want to get the 708p rather than the 308p (well not too loud because even the 708p is unhappy at 96dB). If you don't listen at loud levels then it's probably a closer contest between them....and choosing the right one is more murky.....but lets face it there's a massive difference in price between the speakers so I'd be surprised if someone was umming & ahhing about which one to choose, I don't think they're in the same market bracket.

 

[Absolute]

That has nothing to do with specifically the driver or room correction itself but is a result in the output of minimum phase PEQ filter system with positive gain, which in the end is a resonator, a reason also why a negative PEQ with the exactly inverse response (thus also center frequency and Q-factor) can compensate the resonance of anything (for example a driver or a room mode) if its also minimal phase (antiresonator).

Here it is demonstrated nicely:

I'm too stupid to figure out what that video should show me, but I measured my tweet before and after two high Q peqs, one were the response were flat and the other where there was a dip.
5000 hz and 9270 hz;

CSD shows the same, but this was easier on the eye. Ringing at 5 khz and no ringing where I just fixed the dip?

 

[Tovarich007]

It just tells about how that issue has ben taken care of. This might even reflect to how other issues in speaker design have been considered as well...
- port position on baffle and inside
- port tube material and shape
- enclosure design and material

Most Genelecs and most ADAMs have port on backside, so do small Neumanns. Then resonance peak is not so harmful.

View attachment 110326

Small Neumann and most of Adams are front ported, not on the back side.

 

[Juhazi]

JBL 70x speakers have port noise interfence nulling around 900Hz, which is different from eg. cone resonance peak/dip. 30x monitors have port on the backside. An intereference null cannot be fixed with EQ, but a resonance or baffle edge interference will react better even if its a dip, because proponents don't have equal spl.

Sound&Recording measurement shows sharper dip, because it is not a summed/averaged measurement.