This is a review and detailed measurements of the JBL 708P studio monitor (active speaker). It is on kind loan from a member and costs US $1,799
each.
Unlike the lower-end in the series, the 708P exudes seriousness both in look, feel and controls:
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I appreciated the handles on each side as this is a heavy bookshelf speaker. The white LED stands out a bit much. Hopefully there is a way to turn it off your can put some tape on it.
As expected in this price, you have both analog and digital inputs with a bevy of features:
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Signal processing is at 24-bit/192 kHz and there are provisions for multi-band room EQ and such. Alas, the same primitive LCD interface is provided that is slow to respond and quite grainy. It does the job though. For my measurements I set the input to +4 dBu. For listening tests, I only had unbalanced so selected -10 dBu for that.
I left all the controls off/as you see them both for measurements and listening tests.
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 1000 measurement which resulted in error rate of around 1%.
Temperature was 59 degrees F at sea level. I kept the speaker indoor at 70 degrees prior to starting the measurements.
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 708P 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:
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Other than a slight issue around 600 to 900 Hz, this is extremely good frequency response, not only on-axis and off-axis. The cause of the disturbance is easy to identify when we measure each radiating surface up close:
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If you follow the orange curve which is the port response, we see that instead of continuing to decline, it starts to rise up (resonate) and that winds up disturbing the otherwise good response of the woofer. The woofer itself also gets a bit wiggly above 2 kHz but levels are pretty low there so impact is small (you can see a few notches in the spin graph before).
Early window reflections are good sans a dip which is caused by vertical bounce:
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Putting the two together, our far-field response is such:
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As noted, there is less tilt here than we like to see for hi-fi speakers but for professional use, you want flatter response and that is what the 708P delivers. You can always tailor the response either inside the speaker or outside with EQ.
As noted, directivity is good but check out how good it is when we look at the beam width at constant SPL drop:
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Wow, that is nice! It is also confirmed when we look at contour map:
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Vertical response is not as good so stay a few degrees above or below the tweeter axis:
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Waterfall display shows the port and woofer resonances:
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Distortion is quite low at 86 dBSPL but then rises at 96:
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I was surprised to see the tweeter complaining at the higher level:
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JBL 708P Speaker Listening Test and Equalization
The 708P is too large for my desktop so I used my far field listening setup. I was incredibly impressed by the fidelity from 10 foot distance. It produced the sound and tonality that I expect from a perfect speaker! OK, it got a bit better when I took out the port resonance:
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The tonality didn't change much but there was a perception of more clarity and more open sound (could be placebo but I feel good saying otherwise).
The 708P could play loud with excellent dynamics. I was NOT able to find its limit even when playing music with sub-bass frequencies. Mind you, it did not play those tones loudly but neither did it get distorted. My listening space is open and massive and despite using just one speaker, I had no trouble filling the entire space. Pure pleasure is all I can say about the sound of the 708P.
Conclusions
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. Distortion is excellent at low levels but becomes objectively an issue at elevated level but it was not something I noticed when listening. Speaking of listening, if you have $3,600, you can buy a pair of these and be done with it as far as superbly sounding system. This applies whether you are listening for enjoyment or work. Pervious JBL series I have tested had power limitations which are completely removed here. As such, subjectively I had nothing to complain about.
It is my pleasure to highly recommend the JBL 708P.
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