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JBL 308P MKII Studio Monitor Review

amirm

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#1
This is a review and detailed measurements of the JBL 308P MKII 8-inch Monitor (powered speaker). I purchased this from a member a few months ago. New, they cost US $249.

The 3 series look the same for good or bad:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor.jpg


The large plastic waveguide is really in your face. Wish JBL would provide a matt version of it.

Back panel has the usual controls:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Back Panel XLR Input.jpg


Drivers are powered using dual 56 watt class D amps. Crossover is stated at 1.8 kHz.

Measurements that you are about to see were performed using the Klippel Near-field Scanner (NFS). This is a robotic measurement system that analyzes the speaker all around and is able (using advanced mathematics and dual scan) to subtract room reflections (so where I measure it doesn't matter). It also measures the speaker at close distance ("near-field") which sharply reduces the impact of room noise. Both of these factors enable testing in ordinary rooms yet results that can be more accurate than an anechoic chamber. In a nutshell, the measurements show the actual sound coming out of the speaker independent of the room.

I performed over 800 measurement which resulted in error rate of less than 1% throughout the range.

Temperature was 60 degrees F. Measurement location is at sea level so you compute the pressure.

Measurements are compliant with latest speaker research into what can predict the speaker preference and is standardized in CEA/CTA-2034 ANSI specifications. Likewise listening tests are performed per research that shows mono listening is much more revealing of differences between speakers than stereo or multichannel.

Reference axis was the tweeter center.

JBL 308P MKII Measurements
Acoustic measurements can be grouped in a way that can be perceptually analyzed to determine how good a speaker is and how it can be used in a room. This so called spinorama shows us just about everything we need to know about the speaker with respect to tonality and some flaws:

JBL 308P MkII Spinorama CTA-2034 Monitor Frequency Response Measurements.png


I must say, this is a better response than I expected! On-axis is essentially flat from 45 Hz to above 15 kHz. There is a resonance near 20 kHz but most of us don't hear that high so probably OK. There is a tiny dip around 1.4 kHz. Measuring each radiating element tells us why:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Driver Response.png


As you see, there is a small "dead" region between the woofer and tweeter crossover region. I wonder if this sample variation. Regardless, if the woofer was 100 Hz higher or tweeter was 100 Hz lower, it would cover that gap.

Early window which is more representative of far field listening sums quite nicely as well:

JBL 308P MkII Spinorama CTA-2034 Monito Early Window  Frequency Response Measurements.png


Putting the two together, this is our predicted in-room far-field response:

JBL 308P MkII Spinorama CTA-2034 Monitor Predicted In-room Frequency Response Measurements.png


Man this is good! It is very hard to get this kind of precision in a passive speaker.

Beamwidth and directivity are excellent:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Horizontal Beamwidth Measurements.png


JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Horizontal Directivity Measurements.png


Even vertically it is good compared to most 2-way designs:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Vertical Directivity Measurements.png


You have ±20 degrees vertically before you get in trouble much.

The only downer is distortion:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Relative tHD Distortion Measurements.png

During the sweep even with my ear protection on, I could hear anomalies at 96 dB. There is electronic limiter which when kicks in, creates all kind of noises and squeals.

Here it is in absolute level:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor THD Distortion Measurements.png


I could get it to produce around 105 dBSPL at 1 meter before it would severely limit levels (not shown).

JBL 308P MKII Listening Tests
Ah, what a joy this speaker is to listen to. It has plenty of warm and impactful bass, yet is almost perfectly neutral. I say if I had to listen to it for a long time, I might take down the highs just a bit but that is it.

Gradually turn up the volume with deep bass though and at first, everything sounds wonderful. When you get to pretty loud levels, the sound gets muddy at first before reaching quite distorted levels. It is not distortion you are used to due to limiter. But it is there. Suspecting it was very low frequencies that was giving it trouble, I dialed in this quick filter:

JBL 308P MkII Review Powered 8 inch Two-Way Studio Monitor Equalization.png


This is helped fair bit but also cost me a bit of that wonderful bass.

And oh, yes, there is hiss from the tweeter. It is very audible with your ear at the tweeter level but is gone at about 2/3 of a meter/2 feet or so. Turning down the gain reduces it a bit but note that this speaker does NOT want to have too much driving it. Setting the gain low and them pumping up the source generates severe distortion. Shame as this would be a good way to reduce the impact.

Conclusions
If you want to get a taste of accurate sound production that manages to delight, the JBL 308P MKii is a wonderful entry into this world. You would quickly learn that what research says about preference and accuracy being two sides of the same kind is very much true.

As with many powered speakers, amplification for the woofer is the limiting factor. This speaker with 100 watts or more to power the woofer would be so darn perfect. As it is, it will get quite loud and present ton of bass. Just don't expect miracles in overall loudness.

I am very happy to recommend the JBL 308P MKii.

------------
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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amirm

amirm

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Thread Starter #2
From @MZKM:

Preference Rating
SCORE: 5.6
SCORE w/sub: 7.4


Frequency response: +/-3.2dB 45Hz-20kHz
 
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richard12511

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#3
WOW! Way better than I was expecting, and way better than the 305p.
 

Rockfella

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JBL knows what they are doing. I got the Kalis fearing rear ported JBL might be an issue for my set-up.
 
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richard12511

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I thought this thing was gonna have way more elevated treble, based on my in room measurements.

JBL308p.jpg


Maybe I just have bad room suckout below 1.8kHz? I do see the same 15k rise, which is neat to see.
 
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amirm

amirm

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Thread Starter #8
I thought this thing was gonna have way more elevated treble, based on my in room measurements.
For tonality, you want to highly filter that response, down to 1/3 to 1/6 octave.
 

AnalogSteph

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#9
Maybe I just have bad room suckout below 1.8kHz?
Not impossible - look at your room treatment behind the speakers, if any.

And oh, yes, there is hiss from the tweeter. It is very audible with your ear at the tweeter level but is gone at about 2/3 of a meter/2 feet or so. Turning down the gain reduces it a bit but note that this speaker does NOT want to have too much driving it. Setting the gain low and them pumping up the source generates severe distortion. Shame as this would be a good way to reduce the impact.
Do you get the expected input levels before it clips? Should be about +8 dBu (2 Vrms) and +20 dBu, respectively, depending on input sensitivity selection.
 
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amirm

amirm

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Thread Starter #10
Do you get the expected input levels before it clips? Should be about +8 dBu (2 Vrms) and +20 dBu, respectively, depending on input sensitivity selection.
Well, there is that gain control in the back so I don't have absolute levels. I set it to 0 dBu for the 96 dBSPL with the gain setting near what you see in the picture.
 

richard12511

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Moral of my story, I should have listened to my ears. When I first got this speaker, I thought it sounded amazing. I compared it to my Revels and JTRs in my main room and thought it sounded as good as those speakers did. I took it into my office and thought it sounded wonderful in there, too. I even tested all the treble settings and found that I preferred the default(+0) treble setting. Then...I measured the response in my office, and it was tilted upwards(not downwards like I expected). After that, I started thinking it was too bright, so I flipped the -2 treble switch on the back, but the placebo was too much, and I ended up relegating them to storage. In some sense I'm happy, as it led me to the Genelec 8030c for my office, but my initial impression was correct, these are great speakers :facepalm:

Second moral of my story, don't trust in room measurements.
 
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amirm

amirm

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Thread Starter #13
Is it supposed to say JBL 305P MKII Measurements above the first measurements or 308?
No, I keep typing 305 when I mean 308. Corrected.
 
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amirm

amirm

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Any Preference on listening or loudness levels compared to the T8V's?
I just sent back the T8V so no chance to compare. The T8V does have more powerful amplifiers and I want to say it played more cleanly until it abrupted cut out. Both play quite loud for desktop monitoring.
 

richard12511

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JBL 308P MKI was a bit harsh to my taste in my room. Sold it
You have great high frequency hearing for a 97 year old!!!
 

Vasr

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#17
View attachment 91939

There is a resonance near 20 kHz but most of us don't hear that high so probably OK.
Actually, having had to fight with some equipment recently with a very similar elevated response in that region, it would be a red flag personally for me. But it can be corrected with EQ at the expense of some high treble using a shelf filter that I had to do by trial and error but the correction will be localized to a listening position. I measured it because I didn't like what I was hearing not the other way around!

It is not where the peak is that is the problem. The rise to that peak can create artifacts. In my chain, it was a very annoying tizziness. It was a similar 6db peak around 18hz rising from about 12khz.

A lot of musical instruments have natural harmonics in that region (e.g., cymbals). So, it is not some specific note or instrument that you hear in that region but the harmonics to what is playing in the mid to mid-highs. When these gets elevated, the fundamental itself suffers from tizziness. Because those elevated harmonics decay out proportionately higher than natural, you hear them for a bit longer. That can feel like you have lost some "blackness" in the background. For example, cymbal strikes may sound like longer TSSSSSSSS which fills up the background instead of a shorter TSHHHH because the higher harmonics dominate the harmonics that are lower. If vocals have reverb added in the recording, you may hear some sibilance because of it especially with female vocals.

In a speaker, the phase better be perfect between the tweeter with that elevation and the mids otherwise it will exacerbate the problem.

The above is obviously very hearing dependent and not universal for that reason but I would personally consider that kind of a response a deal-breaker personally. YMMV.
 
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