This is a review and detailed measurements of the JBL 125C home theater center speaker. It is on kind loan from a member and costs US $120 on Amazon currently.
The 125C really looks nice with the symmetrical what woofers:
Typical of some center speakers, it doesn't have a port (i.e. they think people will put them in cabinets):
NOTE: our company, Madrona Digital is a dealer for Harman which includes JBL line. So feel free to read whatever level of bias you like in my subjective remarks.
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.
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 center of the tweeter (aligned by eye). It is getting colder with the measurement room temp at 16 degrees C. Accuracy is better than 1% for most of the range but drops to 2% for part of the spectrum.
JBL 125C 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:
On axis response looks flat and good other than the sloping down woofer response. Lot of resonances are visible as is the directivity error. The latter messes up the early reflection measurements:
Combining the two we get our predicted in-room response which shows fair amount of coloration:
Near-field response is not directly revealing of the design problem:
But the horizontal beam width is:
The two woofers fight with each other causing sharp narrowing of the response between 500 Hz and 3 kHz until tweeter takes over. For a center speaker, this is really bad as the coverage angle is as low as just 20 degrees.
Contour plot shows the same thing:
These "MTM" designs are optimized for vertical usage and we see that in that orientation:
On the other hand, the two woofers provide ton of dynamics and power handling as seen in our distortion graphs:
Worst case impedance is 4.4 ohm which is not too bad:
For the fans of timing analysis, here are the waterfall and impulse responses:
JBL 125C Listening Tests and Equalization
This section intentionally left blank.
Not feeling that great and can't make noises right now. So no listening results.
Conclusions
As if we needed to drill this message into our head strong and deep, we see that you can't easily build a proper 2-way speaker with symmetrical woofers on each side of the tweeter. Beam width narrows significantly causing issues for a center speaker in home theater which needs to cover a wide seating area. Response is not bad if you use this vertically. It is also better than JBL Stage 135C I reviewed recently.
I can't recommend the JBL Stage 125C based on these measurements. It is the wrong design for the job.
The 125C really looks nice with the symmetrical what woofers:
Typical of some center speakers, it doesn't have a port (i.e. they think people will put them in cabinets):
NOTE: our company, Madrona Digital is a dealer for Harman which includes JBL line. So feel free to read whatever level of bias you like in my subjective remarks.
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.
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 center of the tweeter (aligned by eye). It is getting colder with the measurement room temp at 16 degrees C. Accuracy is better than 1% for most of the range but drops to 2% for part of the spectrum.
JBL 125C 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:
On axis response looks flat and good other than the sloping down woofer response. Lot of resonances are visible as is the directivity error. The latter messes up the early reflection measurements:
Combining the two we get our predicted in-room response which shows fair amount of coloration:
Near-field response is not directly revealing of the design problem:
But the horizontal beam width is:
The two woofers fight with each other causing sharp narrowing of the response between 500 Hz and 3 kHz until tweeter takes over. For a center speaker, this is really bad as the coverage angle is as low as just 20 degrees.
Contour plot shows the same thing:
These "MTM" designs are optimized for vertical usage and we see that in that orientation:
On the other hand, the two woofers provide ton of dynamics and power handling as seen in our distortion graphs:
Worst case impedance is 4.4 ohm which is not too bad:
For the fans of timing analysis, here are the waterfall and impulse responses:
JBL 125C Listening Tests and Equalization
This section intentionally left blank.
Not feeling that great and can't make noises right now. So no listening results.
Conclusions
As if we needed to drill this message into our head strong and deep, we see that you can't easily build a proper 2-way speaker with symmetrical woofers on each side of the tweeter. Beam width narrows significantly causing issues for a center speaker in home theater which needs to cover a wide seating area. Response is not bad if you use this vertically. It is also better than JBL Stage 135C I reviewed recently.
I can't recommend the JBL Stage 125C based on these measurements. It is the wrong design for the job.