JBL 708i Monitor Review (Passive: Part 1)

[Music1969]

making a correction which is adequate for a flat frequency response under steady state or a certain sweep speed does not convince, me at least, it would be always correct on music.

^^^

Most interesting comment in the thread so far

Profound implications

 

[Puddingbuks]

Yes but factor in Maximum SPL.
Port turbulence increases very quickly in small diameter ports as SPL starts to reach loud. I guarantee you that is an important consideration is a speaker like this which is obviously meant to be/designed to be used very loudly at times.

I'd MUCH rather have some midrange pipe resonances vs port turbulence or chuffing. Port turbulence and chuffing are 100% distortion and a 100% go away you are being returned deal breakers for me.

Both speakers can’t produce any real satisfying bass in terms of spl and hitting those really low notes. They both need a subwoofer and that makes your argument less relevant.

 

[ctrl]

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.

Yes, you put the BR port area and woofer Sd (logarithmically) in relation to each other and thus correct the different levels. But since Amir does not make "real" nearfield measurements anyway (the mic distance is too large for that), the measurements are only guidelines.

Amir always performs the measurements the same way, different speakers can be compared as long as the ratio of BR port area to woofer Sd is roughly comparable.

What you should pay attention to is the sound pressure level distance of the intended Helmholtz resonance (BR port tuning) and the resonances with the highest sound level and if the baffle step correction is included or not.

Here is the BR-port near-field measurement of a 2-way bookshelf speaker with 8'' woofer. In yellow is the frequency response without baffle step correction (BSC), in green with.

I didn't bother to damp and optimize the resonances of the BR-Port (simply a pipe without optimization). Since Q of the "loudest" resonance is high (the resonance is therefore relatively narrow), the design is just fine (mediocre).
Between the desired Helmholtz resonance and the undesired BR port resonances is about 11dB sound pressure difference without BSC. Good designs achieve considerably more difference (>15dB). This ensures that the BR port resonances hardly play a role in the frequency response of the speaker.

Now take another look at Amir's BR port measurement of the JBL 708i. There, the sound pressure difference without BSC is just about 2-3dB. This is not a good result for a speaker in this price range.

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 them, 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.

It is good that this has been pointed out. We can discuss the audibility or inaudibility for a long time (as for example with HD measurements).
But the fact is that a well-designed speaker in this price range does not have to show such severe BR port resonances (similar to how a certain SINAD is expected with hifi devices from a certain price range onwards).

 

[MAB]

Yes, you put the BR port area and woofer Sd (logarithmically) in relation to each other and thus correct the different levels. But since Amir does not make "real" nearfield measurements anyway (the mic distance is too large for that), the measurements are only guidelines.

Amir always performs the measurements the same way, different speakers can be compared as long as the ratio of BR port area to woofer Sd is roughly comparable.

What you should pay attention to is the sound pressure level distance of the intended Helmholtz resonance (BR port tuning) and the resonances with the highest sound level and if the baffle step correction is included or not.

Here is the BR-port near-field measurement of a 2-way bookshelf speaker with 8'' woofer. In yellow is the frequency response without baffle step correction (BSC), in green with.
View attachment 253841
I didn't bother to damp and optimize the resonances of the BR-Port (simply a pipe without optimization). Since Q of the "loudest" resonance is high (the resonance is therefore relatively narrow), the design is just fine (mediocre).
Between the desired Helmholtz resonance and the undesired BR port resonances is about 11dB sound pressure difference without BSC. Good designs achieve considerably more difference (>15dB). This ensures that the BR port resonances hardly play a role in the frequency response of the speaker.

Now take another look at Amir's BR port measurement of the JBL 708i. There, the sound pressure difference without BSC is just about 2-3dB. This is not a good result for a speaker in this price range.
View attachment 253843



It is good that this has been pointed out. We can discuss the audibility or inaudibility for a long time (as for example with HD measurements).
But the fact is that a well-designed speaker in this price range does not have to show such severe BR port resonances (similar to how a certain SINAD is expected with hifi devices from a certain price range onwards).

Thanks. Great explanation. Agreed that no matter what, these are rather large resonances, and makes you wonder why they couldn't do better.

 

[beatelund]

I have built a pair of DIY LSR708i.
With spareparts drivers and the front baffel from JBL.
also did the crossover myself with "original" values.

Glad to see that @amirm measurments lines up with mine, looking forward to part 2

For now i use a Lyngdorf Tdai-1120 with convolution filters from bss dsp through ROON, works great!





maybe the nicest looking 708i in the world?

 

[Sancus]

Most interesting comment in the thread so far

Profound implications

I would have thought that would be well known by now? Any non-linear defect obviously cannot be perfectly corrected with a fixed-level change, that's just... math. The defect might be 3dB at 80dB fundamental and 20dB at 100dB. The resonance Amir ran into on the Elac Uni-Fi 2.0 required a -20dB filter to only correct "90% of the problem".

I don't see a lot of evidence that the port resonance here is extremely non-linear, usually those things show up in distortion and impedance tests. How much you can correct it just depends on how badly it deviates from linearity, I think.

It's obviously better to start off with a design that has well-controlled resonances.

 

[Dj7675]

I have built a pair of DIY LSR708i.
With spareparts drivers and the front baffel from JBL.
also did the crossover myself with "original" values.

Glad to see that these measurments lines up perfectly with mine.

For now i use a Lyngdorf Tdai-1120 with Fir filters through ROON, works great!





maybe the nicest looking 708i in the world?

Very clever. I had a thought of doing something similar making an in wall out of a 705i or 708i.

 

[MAB]

I have built a pair of DIY LSR708i.
With spareparts drivers and the front baffel from JBL.
also did the crossover myself with "original" values.

Glad to see that @amirm measurments lines up with mine, looking forward to part 2

For now i use a Lyngdorf Tdai-1120 with Fir filters through ROON, works great!





maybe the nicest looking 708i in the world?

Very nice!
I have looked for the passive crossover network schematic, but can't seem to find it. Did you use JBL's crossover? I am interested.
In any case, beautiful work.

 

[restorer-john]

I have built a pair of DIY LSR708i.
With spareparts drivers and the front baffel from JBL.
also did the crossover myself with "original" values.

Glad to see that @amirm measurments lines up with mine, looking forward to part 2

For now i use a Lyngdorf Tdai-1120 with convolution filters from bss dsp through ROON, works great!





maybe the nicest looking 708i in the world?

I found that missing 4mm allen key you've been searching for:

 

[ROOSKIE]

Both speakers can’t produce any real satisfying bass in terms of spl and hitting those really low notes. They both need a subwoofer and that makes your argument less relevant.

Based on my experience and testing and designing, I do feel my argument is relevant.
Port chuffing and turbulence is a function of overloading the slug of air in the port which can and will happen whether or not the speaker plays ultra low bass. It often has nothing to do with 'hitting those really low notes'. If the port has turbulence/chuffing issues it is usually at the tuning frequency and the worst just below it. So it will happen at different frequencies for different tunings.

Anyway my main point is that from what I have gathered so far in my speaker designing journey, the energy emitted from the port in the midrange (the 'pipe resonace') is simply extra energy - not distortion as people often think of when dealing with HD, IMD, Doppler ect. Reducing excessive frequency output there via PEQ/DSP or passive crossover components should work as long as the port and woofer are near each other due the typical wavelength of mids.

 

[ROOSKIE]

It can, and has been, done but would require much more power and specially designed driver(s)

In my opinion if a speaker is meant to be used with DSP angway just remove the port altogether and add the bass with DSP. Pass.

As @Frank Dernie stated the driver would need MUCH more power applied (every 3db is double the power so if planning for 6-9db of boost to make up for th eloss of the port you need massive power)
Then you might have heat/thermal issue when slamming something like 500watts into the voice coil.
But more importantly the port takes over for the driver to the point that around tuning it is something like 80%+ the work of the port and driver excursion is greatly reduced. This means much, much lower distortion and also should help reduce IMD and Doppler influences.

Maxium SPL before the driver runs out of useful excursion of most ported designs far exceeds typically comparable sealed designs.

Properly designed ported solutions are vastly more efficient and typically have much less distortion across a broad range of bass frequencies. The driver does eventually become unloaded below the tuning frequency but you just use a compatible high pass in the design.

Personally I am disappointed the correction must be being applied to "solve" resonances in this model.
The magnitude of any resonance will depend on for how long it is excited and damping, so making a correction which is adequate for a flat frequency response under steady state or a certain sweep speed does not convince, me at least, it would be always correct on music.

Nearly all speakers have resonances corrected with EQ.
Whether it is PEQ/DSP initiated or through the use of passive components the RAW responses of the drivers are shaped which is exactly the same as 'EQ".

Maybe some guy has a full range driver running with zero passive components and therefore truly not eq'd(though the baffle shape and size could be seen as a type of EQ choice) but any normally designed high performance speaker has loads of shaping. You should see the RAW responses of the drivers in a cabinet pre crossover design. Those beautiful FLAT active designs and passive designs have been EQ'd. All of them.
Heck the very notion of any crossover itself is that is an EQ that merges the drivers responses to the design spec.

 

[Bartl007]

regarding price, only a fool pays full MSRP for JBL gear. I purchased the 708i several years ago from a pro audio retailer for $950/speaker but subsequently sold them to fund my M2 upgrade. Looks like the price has risen some with inflation and other COVID factors to ~$1200/speaker from the same vendor.

This test is interesting as an exercise, but I wouldn't put too much thought into it, the fully DSP'd speaker and how it sounds is all that matters in the end.

What is crazy is that on the residential side, (JBL synthesis/"luxury" audio group) these kind of poor measurements are common place, and what would never past muster on the pro audio side happens every day with speakers such as SCL-3, SCL-4, etc. Below is what you get for scl4 out of the box for MSRP $3,300 per speaker! :

JBL synthesis is well aware of these flaws and when you hear the term "anechoic EQ" you can be sure that the passive speaker design is far from optimal and can only be "fixed" by purchasing the SDP-75 processor (rebadged trinnov) and loading the EQ profiles for those particular speakers from JBL. Here is the same speaker as above (SCL 4) with "anechoic EQ" applied via the proprietary filters from JBL:

 

[Cars-N-Cans]

No, I think this is just a JBL "thing" - every last one I've seen measured here has weird chewed up mid response going on.

As for "hardly as bad as inexpensive [...] speakers", I should hope not considering their cost. It's still not something I would consider acceptable. The price range these compete in ($2000ish per speaker sans amplifier(s) and DSP) has a lot of competition from other manufacturers that don't have these problems.

Whether one finds it acceptable or not is largely irrelevant if we don't have any direct knowledge of the impact on the subjective response. Should it be there? No, of course not. Could they do better? Well, yes, of course. But being intended for pro-audio use some production engineer who is on someone else's payroll could care less if it doesn't have any actual impact on how it sounds. I would suspect it does, and that will be interesting to see in the second part since now Amir can do side-by-side comparisons. It could easily stand out like a sore thumb once the uncorrected response can be used to hear its full effect. But, without that the "ugly measurement" argument doesn't carry much weight on its own. I am not a Harman fan and aren't interested in JBL pro-audio products, but if it works as intended then our concerns over the resonances are largely academic as it shows they know they are there, but also know they are not so overly detrimental that it impacts the performance. On the other hand, if it really does degrade the subjective performance then it really is unacceptable as it shows that they decided to give it a pass, anyway, despite it being flawed. My feeling will be it will fall in the middle somewhere.

People seem to approach speakers like electronics with respect to the measurements, and that I think ignores some of the eventualities with speakers. Even the shittiest measuring electronics can be completely transparent subjectively and sound every bit as good as our best measuring DACs and amps here at ASR. Speakers, however, have so many other variables involved that such direct comparisons can't be made. The output is a complex acoustical sound field that will vary substantially from design to design, for better or worse, and many of those aspects can't be directly defined like they can in electronics where the output is just a wire that goes to something else. An electrical waveform from some garbage Amazon amp will look and sound exactly the same as one from a Topping or a Benchmark, its only our analyzers that will be able to tell the difference. However substituting one studio monitor with some objective flaws measurement-wise with another one that measures "perfect" could end up being a subjective disaster if it falls short somewhere else. Regardless of personal feelings we do need to look at the broader picture rather than simply deeming something to be unacceptable due to one aspect of its design measuring poorly since we can't just directly substitute one speaker for another without broader considerations. I don't think it bodes well, either, but if it doesn't have any real impacts beyond that then I don't think there is really a sound argument to be made as for why this monitor would not be entirely acceptable if it provides good performance everywhere else and works as advertised. This may seem to be pointing out what is already obvious but outside of other information I'm not going to immediately condemn it just based on the measurements alone. On the other hand if constantly has tonality issues during use and ends up flubbing the subjective part of the review and requires Amir to tinker with EQ to fix it then we absolutely need to dock some points and be critical.

 

[pierre]

regarding price, only a fool pays full MSRP for JBL gear. I purchased the 708i several years ago from a pro audio retailer for $950/speaker but subsequently sold them to fund my M2 upgrade. Looks like the price has risen some with inflation and other COVID factors to ~$1200/speaker from the same vendor.

This test is interesting as an exercise, but I wouldn't put too much thought into it, the fully DSP'd speaker and how it sounds is all that matters in the end.

What is crazy is that on the residential side, (JBL synthesis/"luxury" audio group) these kind of poor measurements are common place, and what would never past muster on the pro audio side happens every day with speakers such as SCL-3, SCL-4, etc. Below is what you get for scl4 out of the box for MSRP $3,300 per speaker! :
View attachment 253923

JBL synthesis is well aware of these flaws and when you hear the term "anechoic EQ" you can be sure that the passive speaker design is far from optimal and can only be "fixed" by purchasing the SDP-75 processor (rebadged trinnov) and loading the EQ profiles for those particular speakers from JBL. Here is the same speaker as above (SCL 4) with "anechoic EQ" applied via the proprietary filters from JBL:
View attachment 253924

I am not sure what you think JBL should do? Target market is high end installation. Directivity of the speaker is excellent. 99% of the customers
will use the a trinnov or similar and get a perfect response. If you want to shell 50k+ for a home theather, you will definitively invest in a smart AVR,
right? This speakers are just designed to be active. Sure JBL is trying to force you to buy into their ecosystem but who does not?

 

[Waxx]

That is quiet dissappointing from JBL, they charge a toplevel price for a very mediocore speaker and say you need to correct it with an dsp. The basic design should be good, not with bad designed ports like this and that amount of resonances that disturb the sound. No dsp can fix those disturbances totally.

Like said, there are many better alternatives at this pricepoint, And i would look at Neumann KH150 or KH310's (if i need more volume) also if i needed a box like this, not at this JBL. They should do better for a product like this at this pricepoint.

 

[Toni Mas]

After all those speakers have no pretentions at all to compete in the high end 2 channels hifi speakers market and are not targeted to picky audiophile end users, Stereophile readers, etc...
These are about home cinema in studio or VIP multichannel set ups, and their specs are mainly about brute force, with spl Max over 110db reaching the first octave 20-40hz...
Needless to say that It does not even make sense to compare them with other pro items from Genelec or Klh, more involved in musical sound quality.

It probably does not make sense to try assess their performance as classical 2 ways passive speakers because the maker has clearly other priorities in their designs... But It is good to know that excellence in pro stuff have different standards and requirements than us home audiophiles...

 

[abdo123]

regarding price, only a fool pays full MSRP for JBL gear. I purchased the 708i several years ago from a pro audio retailer for $950/speaker but subsequently sold them to fund my M2 upgrade. Looks like the price has risen some with inflation and other COVID factors to ~$1200/speaker from the same vendor.

This test is interesting as an exercise, but I wouldn't put too much thought into it, the fully DSP'd speaker and how it sounds is all that matters in the end.

What is crazy is that on the residential side, (JBL synthesis/"luxury" audio group) these kind of poor measurements are common place, and what would never past muster on the pro audio side happens every day with speakers such as SCL-3, SCL-4, etc. Below is what you get for scl4 out of the box for MSRP $3,300 per speaker! :
View attachment 253923

JBL synthesis is well aware of these flaws and when you hear the term "anechoic EQ" you can be sure that the passive speaker design is far from optimal and can only be "fixed" by purchasing the SDP-75 processor (rebadged trinnov) and loading the EQ profiles for those particular speakers from JBL. Here is the same speaker as above (SCL 4) with "anechoic EQ" applied via the proprietary filters from JBL:
View attachment 253924

Why is there a signficant directivity differences between the two spins? I thought it was the same speaker.

 

[Ra1zel]

why the base speaker without DSP has a flawned design?

Happens all the time, "manufacturers" somehow concluded that since DSP can solve anything like a magic spell then the accoustic design can be lazy/wrong. Even worse some active speakers makers concluded that power of DSP allows them to have 0 knowledge on speaker design and building, just make crap and then shape the response with gazillion filters.

 

[Toni Mas]

Happens all the time, "manufacturers" somehow concluded that since DSP can solve anything like a magic spell then the accoustic design can be lazy/wrong. Even worse some active speakers makers concluded that power of DSP allows them to have 0 knowledge on speaker design and building, just make crap and then shape the response with gazillion filters.

Yes, with dsp you no longer need expensive drivers from Scanspeak, Seas, etc... 5$ units are ok enough, and btw the only option considering the budget available to market and sell popular enough designs.

 

[Ra1zel]

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.

Also something your ears don't want you to achieve